From patchwork Wed Oct 7 07:55:28 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Lukas Wunner X-Patchwork-Id: 7381221 Return-Path: X-Original-To: patchwork-dri-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id ACB44BEEA4 for ; Tue, 13 Oct 2015 02:21:16 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 4923920629 for ; Tue, 13 Oct 2015 02:20:54 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id 0A08620990 for ; Tue, 13 Oct 2015 02:20:28 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B80088A43E; Mon, 12 Oct 2015 19:19:58 -0700 (PDT) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mailout2.hostsharing.net (mailout2.hostsharing.net [83.223.90.233]) by gabe.freedesktop.org (Postfix) with ESMTPS id 749416E91B for ; Mon, 12 Oct 2015 06:37:57 -0700 (PDT) Received: from h08.hostsharing.net (h08.hostsharing.net [83.223.95.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mailout2.hostsharing.net (Postfix) with ESMTPS id 230A51033F63B; Mon, 12 Oct 2015 15:37:56 +0200 (CEST) Received: from localhost (6-38-90-81.adsl.cmo.de [81.90.38.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by h08.hostsharing.net (Postfix) with ESMTPSA id CD2DA603E04D; Mon, 12 Oct 2015 15:36:03 +0200 (CEST) X-Mailbox-Line: From 3058401e19f5406640bdb8acfea6238e61851ae3 Mon Sep 17 00:00:00 2001 Message-Id: <3058401e19f5406640bdb8acfea6238e61851ae3.1444655697.git.lukas@wunner.de> In-Reply-To: References: <1444204528-7870-1-git-send-email-daniel.vetter@ffwll.ch> From: Lukas Wunner Date: Wed, 7 Oct 2015 09:55:28 +0200 Subject: [PATCH RFC 2/5] drm/doc: Rename docbook to gpu.tmpl To: Daniel Vetter , DRI Development X-Mailman-Approved-At: Mon, 12 Oct 2015 19:19:40 -0700 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Spam-Status: No, score=-0.8 required=5.0 tests=BAYES_00, DATE_IN_PAST_96_XX, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Daniel Vetter DRM is a lot more than a direct rendering manager nowadays, and there's also a bunch of things worth documenting for gpu driver developers outside of drivers/gpu/drm, like vgaarb, vga_switcheroo or the various hardware buses like host1x and ipu-v3. To avoid further confusion let's rename the top-level to reflect reality. And yes I'm already looking forward to when we need to replace the G in GPU with a * ;-) Inspired by a thread with Lukas since he refused to include the vga_switcheroo docs into the drm docs because it's not drm. Cc: Lukas Wunner Signed-off-by: Daniel Vetter [Lukas: Drop BUG() easter egg in i915_gem_execbuffer.c spotted by Jani and fix typos in commit message.] Signed-off-by: Lukas Wunner --- Documentation/DocBook/Makefile | 4 +- Documentation/DocBook/drm.tmpl | 4189 ---------------------------------------- Documentation/DocBook/gpu.tmpl | 4189 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 4191 insertions(+), 4191 deletions(-) delete mode 100644 Documentation/DocBook/drm.tmpl create mode 100644 Documentation/DocBook/gpu.tmpl diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index 75b7d9b..2088200 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -14,10 +14,10 @@ DOCBOOKS := z8530book.xml device-drivers.xml \ genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \ 80211.xml debugobjects.xml sh.xml regulator.xml \ alsa-driver-api.xml writing-an-alsa-driver.xml \ - tracepoint.xml drm.xml media_api.xml w1.xml \ + tracepoint.xml gpu.xml media_api.xml w1.xml \ writing_musb_glue_layer.xml crypto-API.xml iio.xml -MARKDOWNREADY := drm.xml +MARKDOWNREADY := gpu.xml include Documentation/DocBook/media/Makefile diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl deleted file mode 100644 index da1060c..0000000 --- a/Documentation/DocBook/drm.tmpl +++ /dev/null @@ -1,4189 +0,0 @@ - - - - - - Linux DRM Developer's Guide - - - - Jesse - Barnes - Initial version - - Intel Corporation -
- jesse.barnes@intel.com -
- - - - Laurent - Pinchart - Driver internals - - Ideas on board SPRL -
- laurent.pinchart@ideasonboard.com -
- - - - Daniel - Vetter - Contributions all over the place - - Intel Corporation -
- daniel.vetter@ffwll.ch -
- - - - - - 2008-2009 - 2013-2014 - Intel Corporation - - - 2012 - Laurent Pinchart - - - - - The contents of this file may be used under the terms of the GNU - General Public License version 2 (the "GPL") as distributed in - the kernel source COPYING file. - - - - - - - 1.0 - 2012-07-13 - LP - Added extensive documentation about driver internals. - - - - - - - - - DRM Core - - - This first part of the DRM Developer's Guide documents core DRM code, - helper libraries for writing drivers and generic userspace interfaces - exposed by DRM drivers. - - - - - Introduction - - The Linux DRM layer contains code intended to support the needs - of complex graphics devices, usually containing programmable - pipelines well suited to 3D graphics acceleration. Graphics - drivers in the kernel may make use of DRM functions to make - tasks like memory management, interrupt handling and DMA easier, - and provide a uniform interface to applications. - - - A note on versions: this guide covers features found in the DRM - tree, including the TTM memory manager, output configuration and - mode setting, and the new vblank internals, in addition to all - the regular features found in current kernels. - - - [Insert diagram of typical DRM stack here] - - - - - - - DRM Internals - - This chapter documents DRM internals relevant to driver authors - and developers working to add support for the latest features to - existing drivers. - - - First, we go over some typical driver initialization - requirements, like setting up command buffers, creating an - initial output configuration, and initializing core services. - Subsequent sections cover core internals in more detail, - providing implementation notes and examples. - - - The DRM layer provides several services to graphics drivers, - many of them driven by the application interfaces it provides - through libdrm, the library that wraps most of the DRM ioctls. - These include vblank event handling, memory - management, output management, framebuffer management, command - submission & fencing, suspend/resume support, and DMA - services. - - - - - - Driver Initialization - - At the core of every DRM driver is a drm_driver - structure. Drivers typically statically initialize a drm_driver structure, - and then pass it to one of the drm_*_init() functions - to register it with the DRM subsystem. - - - Newer drivers that no longer require a drm_bus - structure can alternatively use the low-level device initialization and - registration functions such as drm_dev_alloc() and - drm_dev_register() directly. - - - The drm_driver structure contains static - information that describes the driver and features it supports, and - pointers to methods that the DRM core will call to implement the DRM API. - We will first go through the drm_driver static - information fields, and will then describe individual operations in - details as they get used in later sections. - - - Driver Information - - Driver Features - - Drivers inform the DRM core about their requirements and supported - features by setting appropriate flags in the - driver_features field. Since those flags - influence the DRM core behaviour since registration time, most of them - must be set to registering the drm_driver - instance. - - u32 driver_features; - - Driver Feature Flags - - DRIVER_USE_AGP - - Driver uses AGP interface, the DRM core will manage AGP resources. - - - - DRIVER_REQUIRE_AGP - - Driver needs AGP interface to function. AGP initialization failure - will become a fatal error. - - - - DRIVER_PCI_DMA - - Driver is capable of PCI DMA, mapping of PCI DMA buffers to - userspace will be enabled. Deprecated. - - - - DRIVER_SG - - Driver can perform scatter/gather DMA, allocation and mapping of - scatter/gather buffers will be enabled. Deprecated. - - - - DRIVER_HAVE_DMA - - Driver supports DMA, the userspace DMA API will be supported. - Deprecated. - - - - DRIVER_HAVE_IRQDRIVER_IRQ_SHARED - - DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler - managed by the DRM Core. The core will support simple IRQ handler - installation when the flag is set. The installation process is - described in . - DRIVER_IRQ_SHARED indicates whether the device & handler - support shared IRQs (note that this is required of PCI drivers). - - - - DRIVER_GEM - - Driver use the GEM memory manager. - - - - DRIVER_MODESET - - Driver supports mode setting interfaces (KMS). - - - - DRIVER_PRIME - - Driver implements DRM PRIME buffer sharing. - - - - DRIVER_RENDER - - Driver supports dedicated render nodes. - - - - DRIVER_ATOMIC - - Driver supports atomic properties. In this case the driver - must implement appropriate obj->atomic_get_property() vfuncs - for any modeset objects with driver specific properties. - - - - - - Major, Minor and Patchlevel - int major; -int minor; -int patchlevel; - - The DRM core identifies driver versions by a major, minor and patch - level triplet. The information is printed to the kernel log at - initialization time and passed to userspace through the - DRM_IOCTL_VERSION ioctl. - - - The major and minor numbers are also used to verify the requested driver - API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes - between minor versions, applications can call DRM_IOCTL_SET_VERSION to - select a specific version of the API. If the requested major isn't equal - to the driver major, or the requested minor is larger than the driver - minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise - the driver's set_version() method will be called with the requested - version. - - - - Name, Description and Date - char *name; -char *desc; -char *date; - - The driver name is printed to the kernel log at initialization time, - used for IRQ registration and passed to userspace through - DRM_IOCTL_VERSION. - - - The driver description is a purely informative string passed to - userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by - the kernel. - - - The driver date, formatted as YYYYMMDD, is meant to identify the date of - the latest modification to the driver. However, as most drivers fail to - update it, its value is mostly useless. The DRM core prints it to the - kernel log at initialization time and passes it to userspace through the - DRM_IOCTL_VERSION ioctl. - - - - - Device Registration - - A number of functions are provided to help with device registration. - The functions deal with PCI and platform devices, respectively. - -!Edrivers/gpu/drm/drm_pci.c -!Edrivers/gpu/drm/drm_platform.c - - New drivers that no longer rely on the services provided by the - drm_bus structure can call the low-level - device registration functions directly. The - drm_dev_alloc() function can be used to allocate - and initialize a new drm_device structure. - Drivers will typically want to perform some additional setup on this - structure, such as allocating driver-specific data and storing a - pointer to it in the DRM device's dev_private - field. Drivers should also set the device's unique name using the - drm_dev_set_unique() function. After it has been - set up a device can be registered with the DRM subsystem by calling - drm_dev_register(). This will cause the device to - be exposed to userspace and will call the driver's - .load() implementation. When a device is - removed, the DRM device can safely be unregistered and freed by calling - drm_dev_unregister() followed by a call to - drm_dev_unref(). - -!Edrivers/gpu/drm/drm_drv.c - - - Driver Load - - The load method is the driver and device - initialization entry point. The method is responsible for allocating and - initializing driver private data, performing resource allocation and - mapping (e.g. acquiring - clocks, mapping registers or allocating command buffers), initializing - the memory manager (), installing - the IRQ handler (), setting up - vertical blanking handling (), mode - setting () and initial output - configuration (). - - - If compatibility is a concern (e.g. with drivers converted over from - User Mode Setting to Kernel Mode Setting), care must be taken to prevent - device initialization and control that is incompatible with currently - active userspace drivers. For instance, if user level mode setting - drivers are in use, it would be problematic to perform output discovery - & configuration at load time. Likewise, if user-level drivers - unaware of memory management are in use, memory management and command - buffer setup may need to be omitted. These requirements are - driver-specific, and care needs to be taken to keep both old and new - applications and libraries working. - - int (*load) (struct drm_device *, unsigned long flags); - - The method takes two arguments, a pointer to the newly created - drm_device and flags. The flags are used to - pass the driver_data field of the device id - corresponding to the device passed to drm_*_init(). - Only PCI devices currently use this, USB and platform DRM drivers have - their load method called with flags to 0. - - - Driver Private Data - - The driver private hangs off the main - drm_device structure and can be used for - tracking various device-specific bits of information, like register - offsets, command buffer status, register state for suspend/resume, etc. - At load time, a driver may simply allocate one and set - drm_device.dev_priv - appropriately; it should be freed and - drm_device.dev_priv - set to NULL when the driver is unloaded. - - - - IRQ Registration - - The DRM core tries to facilitate IRQ handler registration and - unregistration by providing drm_irq_install and - drm_irq_uninstall functions. Those functions only - support a single interrupt per device, devices that use more than one - IRQs need to be handled manually. - - - Managed IRQ Registration - - drm_irq_install starts by calling the - irq_preinstall driver operation. The operation - is optional and must make sure that the interrupt will not get fired by - clearing all pending interrupt flags or disabling the interrupt. - - - The passed-in IRQ will then be requested by a call to - request_irq. If the DRIVER_IRQ_SHARED driver - feature flag is set, a shared (IRQF_SHARED) IRQ handler will be - requested. - - - The IRQ handler function must be provided as the mandatory irq_handler - driver operation. It will get passed directly to - request_irq and thus has the same prototype as all - IRQ handlers. It will get called with a pointer to the DRM device as the - second argument. - - - Finally the function calls the optional - irq_postinstall driver operation. The operation - usually enables interrupts (excluding the vblank interrupt, which is - enabled separately), but drivers may choose to enable/disable interrupts - at a different time. - - - drm_irq_uninstall is similarly used to uninstall an - IRQ handler. It starts by waking up all processes waiting on a vblank - interrupt to make sure they don't hang, and then calls the optional - irq_uninstall driver operation. The operation - must disable all hardware interrupts. Finally the function frees the IRQ - by calling free_irq. - - - - Manual IRQ Registration - - Drivers that require multiple interrupt handlers can't use the managed - IRQ registration functions. In that case IRQs must be registered and - unregistered manually (usually with the request_irq - and free_irq functions, or their devm_* equivalent). - - - When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ - driver feature flag, and must not provide the - irq_handler driver operation. They must set the - drm_device irq_enabled - field to 1 upon registration of the IRQs, and clear it to 0 after - unregistering the IRQs. - - - - - Memory Manager Initialization - - Every DRM driver requires a memory manager which must be initialized at - load time. DRM currently contains two memory managers, the Translation - Table Manager (TTM) and the Graphics Execution Manager (GEM). - This document describes the use of the GEM memory manager only. See - for details. - - - - Miscellaneous Device Configuration - - Another task that may be necessary for PCI devices during configuration - is mapping the video BIOS. On many devices, the VBIOS describes device - configuration, LCD panel timings (if any), and contains flags indicating - device state. Mapping the BIOS can be done using the pci_map_rom() call, - a convenience function that takes care of mapping the actual ROM, - whether it has been shadowed into memory (typically at address 0xc0000) - or exists on the PCI device in the ROM BAR. Note that after the ROM has - been mapped and any necessary information has been extracted, it should - be unmapped; on many devices, the ROM address decoder is shared with - other BARs, so leaving it mapped could cause undesired behaviour like - hangs or memory corruption. - - - - - - - - - - Memory management - - Modern Linux systems require large amount of graphics memory to store - frame buffers, textures, vertices and other graphics-related data. Given - the very dynamic nature of many of that data, managing graphics memory - efficiently is thus crucial for the graphics stack and plays a central - role in the DRM infrastructure. - - - The DRM core includes two memory managers, namely Translation Table Maps - (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory - manager to be developed and tried to be a one-size-fits-them all - solution. It provides a single userspace API to accommodate the need of - all hardware, supporting both Unified Memory Architecture (UMA) devices - and devices with dedicated video RAM (i.e. most discrete video cards). - This resulted in a large, complex piece of code that turned out to be - hard to use for driver development. - - - GEM started as an Intel-sponsored project in reaction to TTM's - complexity. Its design philosophy is completely different: instead of - providing a solution to every graphics memory-related problems, GEM - identified common code between drivers and created a support library to - share it. GEM has simpler initialization and execution requirements than - TTM, but has no video RAM management capabilities and is thus limited to - UMA devices. - - - The Translation Table Manager (TTM) - - TTM design background and information belongs here. - - - TTM initialization - This section is outdated. - - Drivers wishing to support TTM must fill out a drm_bo_driver - structure. The structure contains several fields with function - pointers for initializing the TTM, allocating and freeing memory, - waiting for command completion and fence synchronization, and memory - migration. See the radeon_ttm.c file for an example of usage. - - - The ttm_global_reference structure is made up of several fields: - - - struct ttm_global_reference { - enum ttm_global_types global_type; - size_t size; - void *object; - int (*init) (struct ttm_global_reference *); - void (*release) (struct ttm_global_reference *); - }; - - - There should be one global reference structure for your memory - manager as a whole, and there will be others for each object - created by the memory manager at runtime. Your global TTM should - have a type of TTM_GLOBAL_TTM_MEM. The size field for the global - object should be sizeof(struct ttm_mem_global), and the init and - release hooks should point at your driver-specific init and - release routines, which probably eventually call - ttm_mem_global_init and ttm_mem_global_release, respectively. - - - Once your global TTM accounting structure is set up and initialized - by calling ttm_global_item_ref() on it, - you need to create a buffer object TTM to - provide a pool for buffer object allocation by clients and the - kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO, - and its size should be sizeof(struct ttm_bo_global). Again, - driver-specific init and release functions may be provided, - likely eventually calling ttm_bo_global_init() and - ttm_bo_global_release(), respectively. Also, like the previous - object, ttm_global_item_ref() is used to create an initial reference - count for the TTM, which will call your initialization function. - - - - - The Graphics Execution Manager (GEM) - - The GEM design approach has resulted in a memory manager that doesn't - provide full coverage of all (or even all common) use cases in its - userspace or kernel API. GEM exposes a set of standard memory-related - operations to userspace and a set of helper functions to drivers, and let - drivers implement hardware-specific operations with their own private API. - - - The GEM userspace API is described in the - GEM - the Graphics - Execution Manager article on LWN. While slightly - outdated, the document provides a good overview of the GEM API principles. - Buffer allocation and read and write operations, described as part of the - common GEM API, are currently implemented using driver-specific ioctls. - - - GEM is data-agnostic. It manages abstract buffer objects without knowing - what individual buffers contain. APIs that require knowledge of buffer - contents or purpose, such as buffer allocation or synchronization - primitives, are thus outside of the scope of GEM and must be implemented - using driver-specific ioctls. - - - On a fundamental level, GEM involves several operations: - - Memory allocation and freeing - Command execution - Aperture management at command execution time - - Buffer object allocation is relatively straightforward and largely - provided by Linux's shmem layer, which provides memory to back each - object. - - - Device-specific operations, such as command execution, pinning, buffer - read & write, mapping, and domain ownership transfers are left to - driver-specific ioctls. - - - GEM Initialization - - Drivers that use GEM must set the DRIVER_GEM bit in the struct - drm_driver - driver_features field. The DRM core will - then automatically initialize the GEM core before calling the - load operation. Behind the scene, this will - create a DRM Memory Manager object which provides an address space - pool for object allocation. - - - In a KMS configuration, drivers need to allocate and initialize a - command ring buffer following core GEM initialization if required by - the hardware. UMA devices usually have what is called a "stolen" - memory region, which provides space for the initial framebuffer and - large, contiguous memory regions required by the device. This space is - typically not managed by GEM, and must be initialized separately into - its own DRM MM object. - - - - GEM Objects Creation - - GEM splits creation of GEM objects and allocation of the memory that - backs them in two distinct operations. - - - GEM objects are represented by an instance of struct - drm_gem_object. Drivers usually need to extend - GEM objects with private information and thus create a driver-specific - GEM object structure type that embeds an instance of struct - drm_gem_object. - - - To create a GEM object, a driver allocates memory for an instance of its - specific GEM object type and initializes the embedded struct - drm_gem_object with a call to - drm_gem_object_init. The function takes a pointer to - the DRM device, a pointer to the GEM object and the buffer object size - in bytes. - - - GEM uses shmem to allocate anonymous pageable memory. - drm_gem_object_init will create an shmfs file of - the requested size and store it into the struct - drm_gem_object filp - field. The memory is used as either main storage for the object when the - graphics hardware uses system memory directly or as a backing store - otherwise. - - - Drivers are responsible for the actual physical pages allocation by - calling shmem_read_mapping_page_gfp for each page. - Note that they can decide to allocate pages when initializing the GEM - object, or to delay allocation until the memory is needed (for instance - when a page fault occurs as a result of a userspace memory access or - when the driver needs to start a DMA transfer involving the memory). - - - Anonymous pageable memory allocation is not always desired, for instance - when the hardware requires physically contiguous system memory as is - often the case in embedded devices. Drivers can create GEM objects with - no shmfs backing (called private GEM objects) by initializing them with - a call to drm_gem_private_object_init instead of - drm_gem_object_init. Storage for private GEM - objects must be managed by drivers. - - - Drivers that do not need to extend GEM objects with private information - can call the drm_gem_object_alloc function to - allocate and initialize a struct drm_gem_object - instance. The GEM core will call the optional driver - gem_init_object operation after initializing - the GEM object with drm_gem_object_init. - int (*gem_init_object) (struct drm_gem_object *obj); - - - No alloc-and-init function exists for private GEM objects. - - - - GEM Objects Lifetime - - All GEM objects are reference-counted by the GEM core. References can be - acquired and release by calling drm_gem_object_reference - and drm_gem_object_unreference respectively. The - caller must hold the drm_device - struct_mutex lock. As a convenience, GEM - provides the drm_gem_object_reference_unlocked and - drm_gem_object_unreference_unlocked functions that - can be called without holding the lock. - - - When the last reference to a GEM object is released the GEM core calls - the drm_driver - gem_free_object operation. That operation is - mandatory for GEM-enabled drivers and must free the GEM object and all - associated resources. - - - void (*gem_free_object) (struct drm_gem_object *obj); - Drivers are responsible for freeing all GEM object resources, including - the resources created by the GEM core. If an mmap offset has been - created for the object (in which case - drm_gem_object::map_list::map - is not NULL) it must be freed by a call to - drm_gem_free_mmap_offset. The shmfs backing store - must be released by calling drm_gem_object_release - (that function can safely be called if no shmfs backing store has been - created). - - - - GEM Objects Naming - - Communication between userspace and the kernel refers to GEM objects - using local handles, global names or, more recently, file descriptors. - All of those are 32-bit integer values; the usual Linux kernel limits - apply to the file descriptors. - - - GEM handles are local to a DRM file. Applications get a handle to a GEM - object through a driver-specific ioctl, and can use that handle to refer - to the GEM object in other standard or driver-specific ioctls. Closing a - DRM file handle frees all its GEM handles and dereferences the - associated GEM objects. - - - To create a handle for a GEM object drivers call - drm_gem_handle_create. The function takes a pointer - to the DRM file and the GEM object and returns a locally unique handle. - When the handle is no longer needed drivers delete it with a call to - drm_gem_handle_delete. Finally the GEM object - associated with a handle can be retrieved by a call to - drm_gem_object_lookup. - - - Handles don't take ownership of GEM objects, they only take a reference - to the object that will be dropped when the handle is destroyed. To - avoid leaking GEM objects, drivers must make sure they drop the - reference(s) they own (such as the initial reference taken at object - creation time) as appropriate, without any special consideration for the - handle. For example, in the particular case of combined GEM object and - handle creation in the implementation of the - dumb_create operation, drivers must drop the - initial reference to the GEM object before returning the handle. - - - GEM names are similar in purpose to handles but are not local to DRM - files. They can be passed between processes to reference a GEM object - globally. Names can't be used directly to refer to objects in the DRM - API, applications must convert handles to names and names to handles - using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls - respectively. The conversion is handled by the DRM core without any - driver-specific support. - - - GEM also supports buffer sharing with dma-buf file descriptors through - PRIME. GEM-based drivers must use the provided helpers functions to - implement the exporting and importing correctly. See . - Since sharing file descriptors is inherently more secure than the - easily guessable and global GEM names it is the preferred buffer - sharing mechanism. Sharing buffers through GEM names is only supported - for legacy userspace. Furthermore PRIME also allows cross-device - buffer sharing since it is based on dma-bufs. - - - - GEM Objects Mapping - - Because mapping operations are fairly heavyweight GEM favours - read/write-like access to buffers, implemented through driver-specific - ioctls, over mapping buffers to userspace. However, when random access - to the buffer is needed (to perform software rendering for instance), - direct access to the object can be more efficient. - - - The mmap system call can't be used directly to map GEM objects, as they - don't have their own file handle. Two alternative methods currently - co-exist to map GEM objects to userspace. The first method uses a - driver-specific ioctl to perform the mapping operation, calling - do_mmap under the hood. This is often considered - dubious, seems to be discouraged for new GEM-enabled drivers, and will - thus not be described here. - - - The second method uses the mmap system call on the DRM file handle. - void *mmap(void *addr, size_t length, int prot, int flags, int fd, - off_t offset); - DRM identifies the GEM object to be mapped by a fake offset passed - through the mmap offset argument. Prior to being mapped, a GEM object - must thus be associated with a fake offset. To do so, drivers must call - drm_gem_create_mmap_offset on the object. The - function allocates a fake offset range from a pool and stores the - offset divided by PAGE_SIZE in - obj->map_list.hash.key. Care must be taken not to - call drm_gem_create_mmap_offset if a fake offset - has already been allocated for the object. This can be tested by - obj->map_list.map being non-NULL. - - - Once allocated, the fake offset value - (obj->map_list.hash.key << PAGE_SHIFT) - must be passed to the application in a driver-specific way and can then - be used as the mmap offset argument. - - - The GEM core provides a helper method drm_gem_mmap - to handle object mapping. The method can be set directly as the mmap - file operation handler. It will look up the GEM object based on the - offset value and set the VMA operations to the - drm_driver gem_vm_ops - field. Note that drm_gem_mmap doesn't map memory to - userspace, but relies on the driver-provided fault handler to map pages - individually. - - - To use drm_gem_mmap, drivers must fill the struct - drm_driver gem_vm_ops - field with a pointer to VM operations. - - - struct vm_operations_struct *gem_vm_ops - - struct vm_operations_struct { - void (*open)(struct vm_area_struct * area); - void (*close)(struct vm_area_struct * area); - int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf); - }; - - - The open and close - operations must update the GEM object reference count. Drivers can use - the drm_gem_vm_open and - drm_gem_vm_close helper functions directly as open - and close handlers. - - - The fault operation handler is responsible for mapping individual pages - to userspace when a page fault occurs. Depending on the memory - allocation scheme, drivers can allocate pages at fault time, or can - decide to allocate memory for the GEM object at the time the object is - created. - - - Drivers that want to map the GEM object upfront instead of handling page - faults can implement their own mmap file operation handler. - - - - Memory Coherency - - When mapped to the device or used in a command buffer, backing pages - for an object are flushed to memory and marked write combined so as to - be coherent with the GPU. Likewise, if the CPU accesses an object - after the GPU has finished rendering to the object, then the object - must be made coherent with the CPU's view of memory, usually involving - GPU cache flushing of various kinds. This core CPU<->GPU - coherency management is provided by a device-specific ioctl, which - evaluates an object's current domain and performs any necessary - flushing or synchronization to put the object into the desired - coherency domain (note that the object may be busy, i.e. an active - render target; in that case, setting the domain blocks the client and - waits for rendering to complete before performing any necessary - flushing operations). - - - - Command Execution - - Perhaps the most important GEM function for GPU devices is providing a - command execution interface to clients. Client programs construct - command buffers containing references to previously allocated memory - objects, and then submit them to GEM. At that point, GEM takes care to - bind all the objects into the GTT, execute the buffer, and provide - necessary synchronization between clients accessing the same buffers. - This often involves evicting some objects from the GTT and re-binding - others (a fairly expensive operation), and providing relocation - support which hides fixed GTT offsets from clients. Clients must take - care not to submit command buffers that reference more objects than - can fit in the GTT; otherwise, GEM will reject them and no rendering - will occur. Similarly, if several objects in the buffer require fence - registers to be allocated for correct rendering (e.g. 2D blits on - pre-965 chips), care must be taken not to require more fence registers - than are available to the client. Such resource management should be - abstracted from the client in libdrm. - - - - GEM Function Reference -!Edrivers/gpu/drm/drm_gem.c - - - - VMA Offset Manager -!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager -!Edrivers/gpu/drm/drm_vma_manager.c -!Iinclude/drm/drm_vma_manager.h - - - PRIME Buffer Sharing - - PRIME is the cross device buffer sharing framework in drm, originally - created for the OPTIMUS range of multi-gpu platforms. To userspace - PRIME buffers are dma-buf based file descriptors. - - - Overview and Driver Interface - - Similar to GEM global names, PRIME file descriptors are - also used to share buffer objects across processes. They offer - additional security: as file descriptors must be explicitly sent over - UNIX domain sockets to be shared between applications, they can't be - guessed like the globally unique GEM names. - - - Drivers that support the PRIME - API must set the DRIVER_PRIME bit in the struct - drm_driver - driver_features field, and implement the - prime_handle_to_fd and - prime_fd_to_handle operations. - - - int (*prime_handle_to_fd)(struct drm_device *dev, - struct drm_file *file_priv, uint32_t handle, - uint32_t flags, int *prime_fd); -int (*prime_fd_to_handle)(struct drm_device *dev, - struct drm_file *file_priv, int prime_fd, - uint32_t *handle); - Those two operations convert a handle to a PRIME file descriptor and - vice versa. Drivers must use the kernel dma-buf buffer sharing framework - to manage the PRIME file descriptors. Similar to the mode setting - API PRIME is agnostic to the underlying buffer object manager, as - long as handles are 32bit unsigned integers. - - - While non-GEM drivers must implement the operations themselves, GEM - drivers must use the drm_gem_prime_handle_to_fd - and drm_gem_prime_fd_to_handle helper functions. - Those helpers rely on the driver - gem_prime_export and - gem_prime_import operations to create a dma-buf - instance from a GEM object (dma-buf exporter role) and to create a GEM - object from a dma-buf instance (dma-buf importer role). - - - struct dma_buf * (*gem_prime_export)(struct drm_device *dev, - struct drm_gem_object *obj, - int flags); -struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev, - struct dma_buf *dma_buf); - These two operations are mandatory for GEM drivers that support - PRIME. - - - - PRIME Helper Functions -!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers - - - - PRIME Function References -!Edrivers/gpu/drm/drm_prime.c - - - DRM MM Range Allocator - - Overview -!Pdrivers/gpu/drm/drm_mm.c Overview - - - LRU Scan/Eviction Support -!Pdrivers/gpu/drm/drm_mm.c lru scan roaster - - - - DRM MM Range Allocator Function References -!Edrivers/gpu/drm/drm_mm.c -!Iinclude/drm/drm_mm.h - - - CMA Helper Functions Reference -!Pdrivers/gpu/drm/drm_gem_cma_helper.c cma helpers -!Edrivers/gpu/drm/drm_gem_cma_helper.c -!Iinclude/drm/drm_gem_cma_helper.h - - - - - - - Mode Setting - - Drivers must initialize the mode setting core by calling - drm_mode_config_init on the DRM device. The function - initializes the drm_device - mode_config field and never fails. Once done, - mode configuration must be setup by initializing the following fields. - - - - int min_width, min_height; -int max_width, max_height; - - Minimum and maximum width and height of the frame buffers in pixel - units. - - - - struct drm_mode_config_funcs *funcs; - Mode setting functions. - - - - Display Modes Function Reference -!Iinclude/drm/drm_modes.h -!Edrivers/gpu/drm/drm_modes.c - - - Atomic Mode Setting Function Reference -!Edrivers/gpu/drm/drm_atomic.c - - - Frame Buffer Creation - struct drm_framebuffer *(*fb_create)(struct drm_device *dev, - struct drm_file *file_priv, - struct drm_mode_fb_cmd2 *mode_cmd); - - Frame buffers are abstract memory objects that provide a source of - pixels to scanout to a CRTC. Applications explicitly request the - creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and - receive an opaque handle that can be passed to the KMS CRTC control, - plane configuration and page flip functions. - - - Frame buffers rely on the underneath memory manager for low-level memory - operations. When creating a frame buffer applications pass a memory - handle (or a list of memory handles for multi-planar formats) through - the drm_mode_fb_cmd2 argument. For drivers using - GEM as their userspace buffer management interface this would be a GEM - handle. Drivers are however free to use their own backing storage object - handles, e.g. vmwgfx directly exposes special TTM handles to userspace - and so expects TTM handles in the create ioctl and not GEM handles. - - - Drivers must first validate the requested frame buffer parameters passed - through the mode_cmd argument. In particular this is where invalid - sizes, pixel formats or pitches can be caught. - - - If the parameters are deemed valid, drivers then create, initialize and - return an instance of struct drm_framebuffer. - If desired the instance can be embedded in a larger driver-specific - structure. Drivers must fill its width, - height, pitches, - offsets, depth, - bits_per_pixel and - pixel_format fields from the values passed - through the drm_mode_fb_cmd2 argument. They - should call the drm_helper_mode_fill_fb_struct - helper function to do so. - - - - The initialization of the new framebuffer instance is finalized with a - call to drm_framebuffer_init which takes a pointer - to DRM frame buffer operations (struct - drm_framebuffer_funcs). Note that this function - publishes the framebuffer and so from this point on it can be accessed - concurrently from other threads. Hence it must be the last step in the - driver's framebuffer initialization sequence. Frame buffer operations - are - - - int (*create_handle)(struct drm_framebuffer *fb, - struct drm_file *file_priv, unsigned int *handle); - - Create a handle to the frame buffer underlying memory object. If - the frame buffer uses a multi-plane format, the handle will - reference the memory object associated with the first plane. - - - Drivers call drm_gem_handle_create to create - the handle. - - - - void (*destroy)(struct drm_framebuffer *framebuffer); - - Destroy the frame buffer object and frees all associated - resources. Drivers must call - drm_framebuffer_cleanup to free resources - allocated by the DRM core for the frame buffer object, and must - make sure to unreference all memory objects associated with the - frame buffer. Handles created by the - create_handle operation are released by - the DRM core. - - - - int (*dirty)(struct drm_framebuffer *framebuffer, - struct drm_file *file_priv, unsigned flags, unsigned color, - struct drm_clip_rect *clips, unsigned num_clips); - - This optional operation notifies the driver that a region of the - frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB - ioctl call. - - - - - - The lifetime of a drm framebuffer is controlled with a reference count, - drivers can grab additional references with - drm_framebuffer_referenceand drop them - again with drm_framebuffer_unreference. For - driver-private framebuffers for which the last reference is never - dropped (e.g. for the fbdev framebuffer when the struct - drm_framebuffer is embedded into the fbdev - helper struct) drivers can manually clean up a framebuffer at module - unload time with - drm_framebuffer_unregister_private. - - - - Dumb Buffer Objects - - The KMS API doesn't standardize backing storage object creation and - leaves it to driver-specific ioctls. Furthermore actually creating a - buffer object even for GEM-based drivers is done through a - driver-specific ioctl - GEM only has a common userspace interface for - sharing and destroying objects. While not an issue for full-fledged - graphics stacks that include device-specific userspace components (in - libdrm for instance), this limit makes DRM-based early boot graphics - unnecessarily complex. - - - Dumb objects partly alleviate the problem by providing a standard - API to create dumb buffers suitable for scanout, which can then be used - to create KMS frame buffers. - - - To support dumb objects drivers must implement the - dumb_create, - dumb_destroy and - dumb_map_offset operations. - - - - int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, - struct drm_mode_create_dumb *args); - - The dumb_create operation creates a driver - object (GEM or TTM handle) suitable for scanout based on the - width, height and depth from the struct - drm_mode_create_dumb argument. It fills the - argument's handle, - pitch and size - fields with a handle for the newly created object and its line - pitch and size in bytes. - - - - int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, - uint32_t handle); - - The dumb_destroy operation destroys a dumb - object created by dumb_create. - - - - int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, - uint32_t handle, uint64_t *offset); - - The dumb_map_offset operation associates an - mmap fake offset with the object given by the handle and returns - it. Drivers must use the - drm_gem_create_mmap_offset function to - associate the fake offset as described in - . - - - - - Note that dumb objects may not be used for gpu acceleration, as has been - attempted on some ARM embedded platforms. Such drivers really must have - a hardware-specific ioctl to allocate suitable buffer objects. - - - - Output Polling - void (*output_poll_changed)(struct drm_device *dev); - - This operation notifies the driver that the status of one or more - connectors has changed. Drivers that use the fb helper can just call the - drm_fb_helper_hotplug_event function to handle this - operation. - - - - Locking - - Beside some lookup structures with their own locking (which is hidden - behind the interface functions) most of the modeset state is protected - by the dev-<mode_config.lock mutex and additionally - per-crtc locks to allow cursor updates, pageflips and similar operations - to occur concurrently with background tasks like output detection. - Operations which cross domains like a full modeset always grab all - locks. Drivers there need to protect resources shared between crtcs with - additional locking. They also need to be careful to always grab the - relevant crtc locks if a modset functions touches crtc state, e.g. for - load detection (which does only grab the mode_config.lock - to allow concurrent screen updates on live crtcs). - - - - - - - - KMS Initialization and Cleanup - - A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders - and connectors. KMS drivers must thus create and initialize all those - objects at load time after initializing mode setting. - - - CRTCs (struct <structname>drm_crtc</structname>) - - A CRTC is an abstraction representing a part of the chip that contains a - pointer to a scanout buffer. Therefore, the number of CRTCs available - determines how many independent scanout buffers can be active at any - given time. The CRTC structure contains several fields to support this: - a pointer to some video memory (abstracted as a frame buffer object), a - display mode, and an (x, y) offset into the video memory to support - panning or configurations where one piece of video memory spans multiple - CRTCs. - - - CRTC Initialization - - A KMS device must create and register at least one struct - drm_crtc instance. The instance is allocated - and zeroed by the driver, possibly as part of a larger structure, and - registered with a call to drm_crtc_init with a - pointer to CRTC functions. - - - - CRTC Operations - - Set Configuration - int (*set_config)(struct drm_mode_set *set); - - Apply a new CRTC configuration to the device. The configuration - specifies a CRTC, a frame buffer to scan out from, a (x,y) position in - the frame buffer, a display mode and an array of connectors to drive - with the CRTC if possible. - - - If the frame buffer specified in the configuration is NULL, the driver - must detach all encoders connected to the CRTC and all connectors - attached to those encoders and disable them. - - - This operation is called with the mode config lock held. - - - Note that the drm core has no notion of restoring the mode setting - state after resume, since all resume handling is in the full - responsibility of the driver. The common mode setting helper library - though provides a helper which can be used for this: - drm_helper_resume_force_mode. - - - - Page Flipping - int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb, - struct drm_pending_vblank_event *event); - - Schedule a page flip to the given frame buffer for the CRTC. This - operation is called with the mode config mutex held. - - - Page flipping is a synchronization mechanism that replaces the frame - buffer being scanned out by the CRTC with a new frame buffer during - vertical blanking, avoiding tearing. When an application requests a page - flip the DRM core verifies that the new frame buffer is large enough to - be scanned out by the CRTC in the currently configured mode and then - calls the CRTC page_flip operation with a - pointer to the new frame buffer. - - - The page_flip operation schedules a page flip. - Once any pending rendering targeting the new frame buffer has - completed, the CRTC will be reprogrammed to display that frame buffer - after the next vertical refresh. The operation must return immediately - without waiting for rendering or page flip to complete and must block - any new rendering to the frame buffer until the page flip completes. - - - If a page flip can be successfully scheduled the driver must set the - drm_crtc->fb field to the new framebuffer pointed to - by fb. This is important so that the reference counting - on framebuffers stays balanced. - - - If a page flip is already pending, the - page_flip operation must return - -EBUSY. - - - To synchronize page flip to vertical blanking the driver will likely - need to enable vertical blanking interrupts. It should call - drm_vblank_get for that purpose, and call - drm_vblank_put after the page flip completes. - - - If the application has requested to be notified when page flip completes - the page_flip operation will be called with a - non-NULL event argument pointing to a - drm_pending_vblank_event instance. Upon page - flip completion the driver must call drm_send_vblank_event - to fill in the event and send to wake up any waiting processes. - This can be performed with - event_lock, flags); - ... - drm_send_vblank_event(dev, pipe, event); - spin_unlock_irqrestore(&dev->event_lock, flags); - ]]> - - - FIXME: Could drivers that don't need to wait for rendering to complete - just add the event to dev->vblank_event_list and - let the DRM core handle everything, as for "normal" vertical blanking - events? - - - While waiting for the page flip to complete, the - event->base.link list head can be used freely by - the driver to store the pending event in a driver-specific list. - - - If the file handle is closed before the event is signaled, drivers must - take care to destroy the event in their - preclose operation (and, if needed, call - drm_vblank_put). - - - - Miscellaneous - - - void (*set_property)(struct drm_crtc *crtc, - struct drm_property *property, uint64_t value); - - Set the value of the given CRTC property to - value. See - for more information about properties. - - - - void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b, - uint32_t start, uint32_t size); - - Apply a gamma table to the device. The operation is optional. - - - - void (*destroy)(struct drm_crtc *crtc); - - Destroy the CRTC when not needed anymore. See - . - - - - - - - - Planes (struct <structname>drm_plane</structname>) - - A plane represents an image source that can be blended with or overlayed - on top of a CRTC during the scanout process. Planes are associated with - a frame buffer to crop a portion of the image memory (source) and - optionally scale it to a destination size. The result is then blended - with or overlayed on top of a CRTC. - - - The DRM core recognizes three types of planes: - - - DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. Primary - planes are the planes operated upon by CRTC modesetting and flipping - operations described in . - - - DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. Cursor - planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and - DRM_IOCTL_MODE_CURSOR2 ioctls. - - - DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes. - Some drivers refer to these types of planes as "sprites" internally. - - - For compatibility with legacy userspace, only overlay planes are made - available to userspace by default. Userspace clients may set the - DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that - they wish to receive a universal plane list containing all plane types. - - - Plane Initialization - - To create a plane, a KMS drivers allocates and - zeroes an instances of struct drm_plane - (possibly as part of a larger structure) and registers it with a call - to drm_universal_plane_init. The function takes a bitmask - of the CRTCs that can be associated with the plane, a pointer to the - plane functions, a list of format supported formats, and the type of - plane (primary, cursor, or overlay) being initialized. - - - Cursor and overlay planes are optional. All drivers should provide - one primary plane per CRTC (although this requirement may change in - the future); drivers that do not wish to provide special handling for - primary planes may make use of the helper functions described in - to create and register a - primary plane with standard capabilities. - - - - Plane Operations - - - int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc, - struct drm_framebuffer *fb, int crtc_x, int crtc_y, - unsigned int crtc_w, unsigned int crtc_h, - uint32_t src_x, uint32_t src_y, - uint32_t src_w, uint32_t src_h); - - Enable and configure the plane to use the given CRTC and frame buffer. - - - The source rectangle in frame buffer memory coordinates is given by - the src_x, src_y, - src_w and src_h - parameters (as 16.16 fixed point values). Devices that don't support - subpixel plane coordinates can ignore the fractional part. - - - The destination rectangle in CRTC coordinates is given by the - crtc_x, crtc_y, - crtc_w and crtc_h - parameters (as integer values). Devices scale the source rectangle to - the destination rectangle. If scaling is not supported, and the source - rectangle size doesn't match the destination rectangle size, the - driver must return a -EINVAL error. - - - - int (*disable_plane)(struct drm_plane *plane); - - Disable the plane. The DRM core calls this method in response to a - DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0. - Disabled planes must not be processed by the CRTC. - - - - void (*destroy)(struct drm_plane *plane); - - Destroy the plane when not needed anymore. See - . - - - - - - - Encoders (struct <structname>drm_encoder</structname>) - - An encoder takes pixel data from a CRTC and converts it to a format - suitable for any attached connectors. On some devices, it may be - possible to have a CRTC send data to more than one encoder. In that - case, both encoders would receive data from the same scanout buffer, - resulting in a "cloned" display configuration across the connectors - attached to each encoder. - - - Encoder Initialization - - As for CRTCs, a KMS driver must create, initialize and register at - least one struct drm_encoder instance. The - instance is allocated and zeroed by the driver, possibly as part of a - larger structure. - - - Drivers must initialize the struct drm_encoder - possible_crtcs and - possible_clones fields before registering the - encoder. Both fields are bitmasks of respectively the CRTCs that the - encoder can be connected to, and sibling encoders candidate for cloning. - - - After being initialized, the encoder must be registered with a call to - drm_encoder_init. The function takes a pointer to - the encoder functions and an encoder type. Supported types are - - - DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A - - - DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort - - - DRM_MODE_ENCODER_LVDS for display panels - - - DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component, - SCART) - - - DRM_MODE_ENCODER_VIRTUAL for virtual machine displays - - - - - Encoders must be attached to a CRTC to be used. DRM drivers leave - encoders unattached at initialization time. Applications (or the fbdev - compatibility layer when implemented) are responsible for attaching the - encoders they want to use to a CRTC. - - - - Encoder Operations - - - void (*destroy)(struct drm_encoder *encoder); - - Called to destroy the encoder when not needed anymore. See - . - - - - void (*set_property)(struct drm_plane *plane, - struct drm_property *property, uint64_t value); - - Set the value of the given plane property to - value. See - for more information about properties. - - - - - - - Connectors (struct <structname>drm_connector</structname>) - - A connector is the final destination for pixel data on a device, and - usually connects directly to an external display device like a monitor - or laptop panel. A connector can only be attached to one encoder at a - time. The connector is also the structure where information about the - attached display is kept, so it contains fields for display data, EDID - data, DPMS & connection status, and information about modes - supported on the attached displays. - - - Connector Initialization - - Finally a KMS driver must create, initialize, register and attach at - least one struct drm_connector instance. The - instance is created as other KMS objects and initialized by setting the - following fields. - - - - interlace_allowed - - Whether the connector can handle interlaced modes. - - - - doublescan_allowed - - Whether the connector can handle doublescan. - - - - display_info - - - Display information is filled from EDID information when a display - is detected. For non hot-pluggable displays such as flat panels in - embedded systems, the driver should initialize the - display_info.width_mm - and - display_info.height_mm - fields with the physical size of the display. - - - - polled - - Connector polling mode, a combination of - - - DRM_CONNECTOR_POLL_HPD - - The connector generates hotplug events and doesn't need to be - periodically polled. The CONNECT and DISCONNECT flags must not - be set together with the HPD flag. - - - - DRM_CONNECTOR_POLL_CONNECT - - Periodically poll the connector for connection. - - - - DRM_CONNECTOR_POLL_DISCONNECT - - Periodically poll the connector for disconnection. - - - - Set to 0 for connectors that don't support connection status - discovery. - - - - - The connector is then registered with a call to - drm_connector_init with a pointer to the connector - functions and a connector type, and exposed through sysfs with a call to - drm_connector_register. - - - Supported connector types are - - DRM_MODE_CONNECTOR_VGA - DRM_MODE_CONNECTOR_DVII - DRM_MODE_CONNECTOR_DVID - DRM_MODE_CONNECTOR_DVIA - DRM_MODE_CONNECTOR_Composite - DRM_MODE_CONNECTOR_SVIDEO - DRM_MODE_CONNECTOR_LVDS - DRM_MODE_CONNECTOR_Component - DRM_MODE_CONNECTOR_9PinDIN - DRM_MODE_CONNECTOR_DisplayPort - DRM_MODE_CONNECTOR_HDMIA - DRM_MODE_CONNECTOR_HDMIB - DRM_MODE_CONNECTOR_TV - DRM_MODE_CONNECTOR_eDP - DRM_MODE_CONNECTOR_VIRTUAL - - - - Connectors must be attached to an encoder to be used. For devices that - map connectors to encoders 1:1, the connector should be attached at - initialization time with a call to - drm_mode_connector_attach_encoder. The driver must - also set the drm_connector - encoder field to point to the attached - encoder. - - - Finally, drivers must initialize the connectors state change detection - with a call to drm_kms_helper_poll_init. If at - least one connector is pollable but can't generate hotplug interrupts - (indicated by the DRM_CONNECTOR_POLL_CONNECT and - DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will - automatically be queued to periodically poll for changes. Connectors - that can generate hotplug interrupts must be marked with the - DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must - call drm_helper_hpd_irq_event. The function will - queue a delayed work to check the state of all connectors, but no - periodic polling will be done. - - - - Connector Operations - - Unless otherwise state, all operations are mandatory. - - - DPMS - void (*dpms)(struct drm_connector *connector, int mode); - - The DPMS operation sets the power state of a connector. The mode - argument is one of - - DRM_MODE_DPMS_ON - DRM_MODE_DPMS_STANDBY - DRM_MODE_DPMS_SUSPEND - DRM_MODE_DPMS_OFF - - - - In all but DPMS_ON mode the encoder to which the connector is attached - should put the display in low-power mode by driving its signals - appropriately. If more than one connector is attached to the encoder - care should be taken not to change the power state of other displays as - a side effect. Low-power mode should be propagated to the encoders and - CRTCs when all related connectors are put in low-power mode. - - - - Modes - int (*fill_modes)(struct drm_connector *connector, uint32_t max_width, - uint32_t max_height); - - Fill the mode list with all supported modes for the connector. If the - max_width and max_height - arguments are non-zero, the implementation must ignore all modes wider - than max_width or higher than - max_height. - - - The connector must also fill in this operation its - display_info - width_mm and - height_mm fields with the connected display - physical size in millimeters. The fields should be set to 0 if the value - isn't known or is not applicable (for instance for projector devices). - - - - Connection Status - - The connection status is updated through polling or hotplug events when - supported (see ). The status - value is reported to userspace through ioctls and must not be used - inside the driver, as it only gets initialized by a call to - drm_mode_getconnector from userspace. - - enum drm_connector_status (*detect)(struct drm_connector *connector, - bool force); - - Check to see if anything is attached to the connector. The - force parameter is set to false whilst polling or - to true when checking the connector due to user request. - force can be used by the driver to avoid - expensive, destructive operations during automated probing. - - - Return connector_status_connected if something is connected to the - connector, connector_status_disconnected if nothing is connected and - connector_status_unknown if the connection state isn't known. - - - Drivers should only return connector_status_connected if the connection - status has really been probed as connected. Connectors that can't detect - the connection status, or failed connection status probes, should return - connector_status_unknown. - - - - Miscellaneous - - - void (*set_property)(struct drm_connector *connector, - struct drm_property *property, uint64_t value); - - Set the value of the given connector property to - value. See - for more information about properties. - - - - void (*destroy)(struct drm_connector *connector); - - Destroy the connector when not needed anymore. See - . - - - - - - - - Cleanup - - The DRM core manages its objects' lifetime. When an object is not needed - anymore the core calls its destroy function, which must clean up and - free every resource allocated for the object. Every - drm_*_init call must be matched with a - corresponding drm_*_cleanup call to cleanup CRTCs - (drm_crtc_cleanup), planes - (drm_plane_cleanup), encoders - (drm_encoder_cleanup) and connectors - (drm_connector_cleanup). Furthermore, connectors - that have been added to sysfs must be removed by a call to - drm_connector_unregister before calling - drm_connector_cleanup. - - - Connectors state change detection must be cleanup up with a call to - drm_kms_helper_poll_fini. - - - - Output discovery and initialization example - base; - drm_connector_init(dev, &intel_output->base, - &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA); - - drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs, - DRM_MODE_ENCODER_DAC); - - drm_mode_connector_attach_encoder(&intel_output->base, - &intel_output->enc); - - /* Set up the DDC bus. */ - intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A"); - if (!intel_output->ddc_bus) { - dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration " - "failed.\n"); - return; - } - - intel_output->type = INTEL_OUTPUT_ANALOG; - connector->interlace_allowed = 0; - connector->doublescan_allowed = 0; - - drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs); - drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); - - drm_connector_register(connector); -}]]> - - In the example above (taken from the i915 driver), a CRTC, connector and - encoder combination is created. A device-specific i2c bus is also - created for fetching EDID data and performing monitor detection. Once - the process is complete, the new connector is registered with sysfs to - make its properties available to applications. - - - - KMS API Functions -!Edrivers/gpu/drm/drm_crtc.c - - - KMS Data Structures -!Iinclude/drm/drm_crtc.h - - - KMS Locking -!Pdrivers/gpu/drm/drm_modeset_lock.c kms locking -!Iinclude/drm/drm_modeset_lock.h -!Edrivers/gpu/drm/drm_modeset_lock.c - - - - - - - Mode Setting Helper Functions - - The plane, CRTC, encoder and connector functions provided by the drivers - implement the DRM API. They're called by the DRM core and ioctl handlers - to handle device state changes and configuration request. As implementing - those functions often requires logic not specific to drivers, mid-layer - helper functions are available to avoid duplicating boilerplate code. - - - The DRM core contains one mid-layer implementation. The mid-layer provides - implementations of several plane, CRTC, encoder and connector functions - (called from the top of the mid-layer) that pre-process requests and call - lower-level functions provided by the driver (at the bottom of the - mid-layer). For instance, the - drm_crtc_helper_set_config function can be used to - fill the struct drm_crtc_funcs - set_config field. When called, it will split - the set_config operation in smaller, simpler - operations and call the driver to handle them. - - - To use the mid-layer, drivers call drm_crtc_helper_add, - drm_encoder_helper_add and - drm_connector_helper_add functions to install their - mid-layer bottom operations handlers, and fill the - drm_crtc_funcs, - drm_encoder_funcs and - drm_connector_funcs structures with pointers to - the mid-layer top API functions. Installing the mid-layer bottom operation - handlers is best done right after registering the corresponding KMS object. - - - The mid-layer is not split between CRTC, encoder and connector operations. - To use it, a driver must provide bottom functions for all of the three KMS - entities. - - - Helper Functions - - - int drm_crtc_helper_set_config(struct drm_mode_set *set); - - The drm_crtc_helper_set_config helper function - is a CRTC set_config implementation. It - first tries to locate the best encoder for each connector by calling - the connector best_encoder helper - operation. - - - After locating the appropriate encoders, the helper function will - call the mode_fixup encoder and CRTC helper - operations to adjust the requested mode, or reject it completely in - which case an error will be returned to the application. If the new - configuration after mode adjustment is identical to the current - configuration the helper function will return without performing any - other operation. - - - If the adjusted mode is identical to the current mode but changes to - the frame buffer need to be applied, the - drm_crtc_helper_set_config function will call - the CRTC mode_set_base helper operation. If - the adjusted mode differs from the current mode, or if the - mode_set_base helper operation is not - provided, the helper function performs a full mode set sequence by - calling the prepare, - mode_set and - commit CRTC and encoder helper operations, - in that order. - - - - void drm_helper_connector_dpms(struct drm_connector *connector, int mode); - - The drm_helper_connector_dpms helper function - is a connector dpms implementation that - tracks power state of connectors. To use the function, drivers must - provide dpms helper operations for CRTCs - and encoders to apply the DPMS state to the device. - - - The mid-layer doesn't track the power state of CRTCs and encoders. - The dpms helper operations can thus be - called with a mode identical to the currently active mode. - - - - int drm_helper_probe_single_connector_modes(struct drm_connector *connector, - uint32_t maxX, uint32_t maxY); - - The drm_helper_probe_single_connector_modes helper - function is a connector fill_modes - implementation that updates the connection status for the connector - and then retrieves a list of modes by calling the connector - get_modes helper operation. - - - If the helper operation returns no mode, and if the connector status - is connector_status_connected, standard VESA DMT modes up to - 1024x768 are automatically added to the modes list by a call to - drm_add_modes_noedid. - - - The function then filters out modes larger than - max_width and max_height - if specified. It finally calls the optional connector - mode_valid helper operation for each mode in - the probed list to check whether the mode is valid for the connector. - - - - - - CRTC Helper Operations - - - bool (*mode_fixup)(struct drm_crtc *crtc, - const struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode); - - Let CRTCs adjust the requested mode or reject it completely. This - operation returns true if the mode is accepted (possibly after being - adjusted) or false if it is rejected. - - - The mode_fixup operation should reject the - mode if it can't reasonably use it. The definition of "reasonable" - is currently fuzzy in this context. One possible behaviour would be - to set the adjusted mode to the panel timings when a fixed-mode - panel is used with hardware capable of scaling. Another behaviour - would be to accept any input mode and adjust it to the closest mode - supported by the hardware (FIXME: This needs to be clarified). - - - - int (*mode_set_base)(struct drm_crtc *crtc, int x, int y, - struct drm_framebuffer *old_fb) - - Move the CRTC on the current frame buffer (stored in - crtc->fb) to position (x,y). Any of the frame - buffer, x position or y position may have been modified. - - - This helper operation is optional. If not provided, the - drm_crtc_helper_set_config function will fall - back to the mode_set helper operation. - - - FIXME: Why are x and y passed as arguments, as they can be accessed - through crtc->x and - crtc->y? - - - - void (*prepare)(struct drm_crtc *crtc); - - Prepare the CRTC for mode setting. This operation is called after - validating the requested mode. Drivers use it to perform - device-specific operations required before setting the new mode. - - - - int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode, int x, int y, - struct drm_framebuffer *old_fb); - - Set a new mode, position and frame buffer. Depending on the device - requirements, the mode can be stored internally by the driver and - applied in the commit operation, or - programmed to the hardware immediately. - - - The mode_set operation returns 0 on success - or a negative error code if an error occurs. - - - - void (*commit)(struct drm_crtc *crtc); - - Commit a mode. This operation is called after setting the new mode. - Upon return the device must use the new mode and be fully - operational. - - - - - - Encoder Helper Operations - - - bool (*mode_fixup)(struct drm_encoder *encoder, - const struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode); - - Let encoders adjust the requested mode or reject it completely. This - operation returns true if the mode is accepted (possibly after being - adjusted) or false if it is rejected. See the - mode_fixup CRTC helper - operation for an explanation of the allowed adjustments. - - - - void (*prepare)(struct drm_encoder *encoder); - - Prepare the encoder for mode setting. This operation is called after - validating the requested mode. Drivers use it to perform - device-specific operations required before setting the new mode. - - - - void (*mode_set)(struct drm_encoder *encoder, - struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode); - - Set a new mode. Depending on the device requirements, the mode can - be stored internally by the driver and applied in the - commit operation, or programmed to the - hardware immediately. - - - - void (*commit)(struct drm_encoder *encoder); - - Commit a mode. This operation is called after setting the new mode. - Upon return the device must use the new mode and be fully - operational. - - - - - - Connector Helper Operations - - - struct drm_encoder *(*best_encoder)(struct drm_connector *connector); - - Return a pointer to the best encoder for the connecter. Device that - map connectors to encoders 1:1 simply return the pointer to the - associated encoder. This operation is mandatory. - - - - int (*get_modes)(struct drm_connector *connector); - - Fill the connector's probed_modes list - by parsing EDID data with drm_add_edid_modes, - adding standard VESA DMT modes with drm_add_modes_noedid, - or calling drm_mode_probed_add directly for every - supported mode and return the number of modes it has detected. This - operation is mandatory. - - - Note that the caller function will automatically add standard VESA - DMT modes up to 1024x768 if the get_modes - helper operation returns no mode and if the connector status is - connector_status_connected. There is no need to call - drm_add_edid_modes manually in that case. - - - When adding modes manually the driver creates each mode with a call to - drm_mode_create and must fill the following fields. - - - __u32 type; - - Mode type bitmask, a combination of - - - DRM_MODE_TYPE_BUILTIN - not used? - - - DRM_MODE_TYPE_CLOCK_C - not used? - - - DRM_MODE_TYPE_CRTC_C - not used? - - - - DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector - - - not used? - - - - DRM_MODE_TYPE_DEFAULT - not used? - - - DRM_MODE_TYPE_USERDEF - not used? - - - DRM_MODE_TYPE_DRIVER - - - The mode has been created by the driver (as opposed to - to user-created modes). - - - - - Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they - create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred - mode. - - - - __u32 clock; - Pixel clock frequency in kHz unit - - - __u16 hdisplay, hsync_start, hsync_end, htotal; - __u16 vdisplay, vsync_start, vsync_end, vtotal; - Horizontal and vertical timing information - <----------------><-------------><--------------> - - //////////////////////| - ////////////////////// | - ////////////////////// |.................. ................ - _______________ - - <----- [hv]display -----> - <------------- [hv]sync_start ------------> - <--------------------- [hv]sync_end ---------------------> - <-------------------------------- [hv]total -----------------------------> -]]> - - - __u16 hskew; - __u16 vscan; - Unknown - - - __u32 flags; - - Mode flags, a combination of - - - DRM_MODE_FLAG_PHSYNC - - Horizontal sync is active high - - - - DRM_MODE_FLAG_NHSYNC - - Horizontal sync is active low - - - - DRM_MODE_FLAG_PVSYNC - - Vertical sync is active high - - - - DRM_MODE_FLAG_NVSYNC - - Vertical sync is active low - - - - DRM_MODE_FLAG_INTERLACE - - Mode is interlaced - - - - DRM_MODE_FLAG_DBLSCAN - - Mode uses doublescan - - - - DRM_MODE_FLAG_CSYNC - - Mode uses composite sync - - - - DRM_MODE_FLAG_PCSYNC - - Composite sync is active high - - - - DRM_MODE_FLAG_NCSYNC - - Composite sync is active low - - - - DRM_MODE_FLAG_HSKEW - - hskew provided (not used?) - - - - DRM_MODE_FLAG_BCAST - - not used? - - - - DRM_MODE_FLAG_PIXMUX - - not used? - - - - DRM_MODE_FLAG_DBLCLK - - not used? - - - - DRM_MODE_FLAG_CLKDIV2 - - ? - - - - - - Note that modes marked with the INTERLACE or DBLSCAN flags will be - filtered out by - drm_helper_probe_single_connector_modes if - the connector's interlace_allowed or - doublescan_allowed field is set to 0. - - - - char name[DRM_DISPLAY_MODE_LEN]; - - Mode name. The driver must call - drm_mode_set_name to fill the mode name from - hdisplay, - vdisplay and interlace flag after - filling the corresponding fields. - - - - - - The vrefresh value is computed by - drm_helper_probe_single_connector_modes. - - - When parsing EDID data, drm_add_edid_modes fills the - connector display_info - width_mm and - height_mm fields. When creating modes - manually the get_modes helper operation must - set the display_info - width_mm and - height_mm fields if they haven't been set - already (for instance at initialization time when a fixed-size panel is - attached to the connector). The mode width_mm - and height_mm fields are only used internally - during EDID parsing and should not be set when creating modes manually. - - - - int (*mode_valid)(struct drm_connector *connector, - struct drm_display_mode *mode); - - Verify whether a mode is valid for the connector. Return MODE_OK for - supported modes and one of the enum drm_mode_status values (MODE_*) - for unsupported modes. This operation is optional. - - - As the mode rejection reason is currently not used beside for - immediately removing the unsupported mode, an implementation can - return MODE_BAD regardless of the exact reason why the mode is not - valid. - - - Note that the mode_valid helper operation is - only called for modes detected by the device, and - not for modes set by the user through the CRTC - set_config operation. - - - - - - Atomic Modeset Helper Functions Reference - - Overview -!Pdrivers/gpu/drm/drm_atomic_helper.c overview - - - Implementing Asynchronous Atomic Commit -!Pdrivers/gpu/drm/drm_atomic_helper.c implementing async commit - - - Atomic State Reset and Initialization -!Pdrivers/gpu/drm/drm_atomic_helper.c atomic state reset and initialization - -!Iinclude/drm/drm_atomic_helper.h -!Edrivers/gpu/drm/drm_atomic_helper.c - - - Modeset Helper Functions Reference -!Iinclude/drm/drm_crtc_helper.h -!Edrivers/gpu/drm/drm_crtc_helper.c -!Pdrivers/gpu/drm/drm_crtc_helper.c overview - - - Output Probing Helper Functions Reference -!Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview -!Edrivers/gpu/drm/drm_probe_helper.c - - - fbdev Helper Functions Reference -!Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers -!Edrivers/gpu/drm/drm_fb_helper.c -!Iinclude/drm/drm_fb_helper.h - - - Display Port Helper Functions Reference -!Pdrivers/gpu/drm/drm_dp_helper.c dp helpers -!Iinclude/drm/drm_dp_helper.h -!Edrivers/gpu/drm/drm_dp_helper.c - - - Display Port MST Helper Functions Reference -!Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper -!Iinclude/drm/drm_dp_mst_helper.h -!Edrivers/gpu/drm/drm_dp_mst_topology.c - - - MIPI DSI Helper Functions Reference -!Pdrivers/gpu/drm/drm_mipi_dsi.c dsi helpers -!Iinclude/drm/drm_mipi_dsi.h -!Edrivers/gpu/drm/drm_mipi_dsi.c - - - EDID Helper Functions Reference -!Edrivers/gpu/drm/drm_edid.c - - - Rectangle Utilities Reference -!Pinclude/drm/drm_rect.h rect utils -!Iinclude/drm/drm_rect.h -!Edrivers/gpu/drm/drm_rect.c - - - Flip-work Helper Reference -!Pinclude/drm/drm_flip_work.h flip utils -!Iinclude/drm/drm_flip_work.h -!Edrivers/gpu/drm/drm_flip_work.c - - - HDMI Infoframes Helper Reference - - Strictly speaking this is not a DRM helper library but generally useable - by any driver interfacing with HDMI outputs like v4l or alsa drivers. - But it nicely fits into the overall topic of mode setting helper - libraries and hence is also included here. - -!Iinclude/linux/hdmi.h -!Edrivers/video/hdmi.c - - - Plane Helper Reference -!Edrivers/gpu/drm/drm_plane_helper.c -!Pdrivers/gpu/drm/drm_plane_helper.c overview - - - Tile group -!Pdrivers/gpu/drm/drm_crtc.c Tile group - - - Bridges - - Overview -!Pdrivers/gpu/drm/drm_bridge.c overview - - - Default bridge callback sequence -!Pdrivers/gpu/drm/drm_bridge.c bridge callbacks - -!Edrivers/gpu/drm/drm_bridge.c - - - - - - - KMS Properties - - Drivers may need to expose additional parameters to applications than - those described in the previous sections. KMS supports attaching - properties to CRTCs, connectors and planes and offers a userspace API to - list, get and set the property values. - - - Properties are identified by a name that uniquely defines the property - purpose, and store an associated value. For all property types except blob - properties the value is a 64-bit unsigned integer. - - - KMS differentiates between properties and property instances. Drivers - first create properties and then create and associate individual instances - of those properties to objects. A property can be instantiated multiple - times and associated with different objects. Values are stored in property - instances, and all other property information are stored in the property - and shared between all instances of the property. - - - Every property is created with a type that influences how the KMS core - handles the property. Supported property types are - - - DRM_MODE_PROP_RANGE - Range properties report their minimum and maximum - admissible values. The KMS core verifies that values set by - application fit in that range. - - - DRM_MODE_PROP_ENUM - Enumerated properties take a numerical value that - ranges from 0 to the number of enumerated values defined by the - property minus one, and associate a free-formed string name to each - value. Applications can retrieve the list of defined value-name pairs - and use the numerical value to get and set property instance values. - - - - DRM_MODE_PROP_BITMASK - Bitmask properties are enumeration properties that - additionally restrict all enumerated values to the 0..63 range. - Bitmask property instance values combine one or more of the - enumerated bits defined by the property. - - - DRM_MODE_PROP_BLOB - Blob properties store a binary blob without any format - restriction. The binary blobs are created as KMS standalone objects, - and blob property instance values store the ID of their associated - blob object. - Blob properties are only used for the connector EDID property - and cannot be created by drivers. - - - - - To create a property drivers call one of the following functions depending - on the property type. All property creation functions take property flags - and name, as well as type-specific arguments. - - - struct drm_property *drm_property_create_range(struct drm_device *dev, int flags, - const char *name, - uint64_t min, uint64_t max); - Create a range property with the given minimum and maximum - values. - - - struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags, - const char *name, - const struct drm_prop_enum_list *props, - int num_values); - Create an enumerated property. The props - argument points to an array of num_values - value-name pairs. - - - struct drm_property *drm_property_create_bitmask(struct drm_device *dev, - int flags, const char *name, - const struct drm_prop_enum_list *props, - int num_values); - Create a bitmask property. The props - argument points to an array of num_values - value-name pairs. - - - - - Properties can additionally be created as immutable, in which case they - will be read-only for applications but can be modified by the driver. To - create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE - flag at property creation time. - - - When no array of value-name pairs is readily available at property - creation time for enumerated or range properties, drivers can create - the property using the drm_property_create function - and manually add enumeration value-name pairs by calling the - drm_property_add_enum function. Care must be taken to - properly specify the property type through the flags - argument. - - - After creating properties drivers can attach property instances to CRTC, - connector and plane objects by calling the - drm_object_attach_property. The function takes a - pointer to the target object, a pointer to the previously created property - and an initial instance value. - - - Existing KMS Properties - - The following table gives description of drm properties exposed by various - modules/drivers. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Owner Module/DriversGroupProperty NameTypeProperty ValuesObject attachedDescription/Restrictions
DRMGeneric“rotation”BITMASK{ 0, "rotate-0" }, - { 1, "rotate-90" }, - { 2, "rotate-180" }, - { 3, "rotate-270" }, - { 4, "reflect-x" }, - { 5, "reflect-y" }CRTC, Planerotate-(degrees) rotates the image by the specified amount in degrees - in counter clockwise direction. reflect-x and reflect-y reflects the - image along the specified axis prior to rotation
Connector“EDID”BLOB | IMMUTABLE0ConnectorContains id of edid blob ptr object.
“DPMS”ENUM{ “On”, “Standby”, “Suspend”, “Off” }ConnectorContains DPMS operation mode value.
“PATH”BLOB | IMMUTABLE0ConnectorContains topology path to a connector.
“TILE”BLOB | IMMUTABLE0ConnectorContains tiling information for a connector.
“CRTC_ID”OBJECTDRM_MODE_OBJECT_CRTCConnectorCRTC that connector is attached to (atomic)
Plane“type”ENUM | IMMUTABLE{ "Overlay", "Primary", "Cursor" }PlanePlane type
“SRC_X”RANGEMin=0, Max=UINT_MAXPlaneScanout source x coordinate in 16.16 fixed point (atomic)
“SRC_Y”RANGEMin=0, Max=UINT_MAXPlaneScanout source y coordinate in 16.16 fixed point (atomic)
“SRC_W”RANGEMin=0, Max=UINT_MAXPlaneScanout source width in 16.16 fixed point (atomic)
“SRC_H”RANGEMin=0, Max=UINT_MAXPlaneScanout source height in 16.16 fixed point (atomic)
“CRTC_X”SIGNED_RANGEMin=INT_MIN, Max=INT_MAXPlaneScanout CRTC (destination) x coordinate (atomic)
“CRTC_Y”SIGNED_RANGEMin=INT_MIN, Max=INT_MAXPlaneScanout CRTC (destination) y coordinate (atomic)
“CRTC_W”RANGEMin=0, Max=UINT_MAXPlaneScanout CRTC (destination) width (atomic)
“CRTC_H”RANGEMin=0, Max=UINT_MAXPlaneScanout CRTC (destination) height (atomic)
“FB_ID”OBJECTDRM_MODE_OBJECT_FBPlaneScanout framebuffer (atomic)
“CRTC_ID”OBJECTDRM_MODE_OBJECT_CRTCPlaneCRTC that plane is attached to (atomic)
DVI-I“subconnector”ENUM{ “Unknown”, “DVI-D”, “DVI-A” }ConnectorTBD
“select subconnector”ENUM{ “Automatic”, “DVI-D”, “DVI-A” }ConnectorTBD
TV“subconnector”ENUM{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }ConnectorTBD
“select subconnector”ENUM{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }ConnectorTBD
“mode”ENUM{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.ConnectorTBD
“left margin”RANGEMin=0, Max=100ConnectorTBD
“right margin”RANGEMin=0, Max=100ConnectorTBD
“top margin”RANGEMin=0, Max=100ConnectorTBD
“bottom margin”RANGEMin=0, Max=100ConnectorTBD
“brightness”RANGEMin=0, Max=100ConnectorTBD
“contrast”RANGEMin=0, Max=100ConnectorTBD
“flicker reduction”RANGEMin=0, Max=100ConnectorTBD
“overscan”RANGEMin=0, Max=100ConnectorTBD
“saturation”RANGEMin=0, Max=100ConnectorTBD
“hue”RANGEMin=0, Max=100ConnectorTBD
Virtual GPU“suggested X”RANGEMin=0, Max=0xffffffffConnectorproperty to suggest an X offset for a connector
“suggested Y”RANGEMin=0, Max=0xffffffffConnectorproperty to suggest an Y offset for a connector
Optional“scaling mode”ENUM{ "None", "Full", "Center", "Full aspect" }ConnectorTBD
"aspect ratio"ENUM{ "None", "4:3", "16:9" }ConnectorDRM property to set aspect ratio from user space app. - This enum is made generic to allow addition of custom aspect - ratios.
“dirty”ENUM | IMMUTABLE{ "Off", "On", "Annotate" }ConnectorTBD
i915Generic"Broadcast RGB"ENUM{ "Automatic", "Full", "Limited 16:235" }ConnectorTBD
“audio”ENUM{ "force-dvi", "off", "auto", "on" }ConnectorTBD
SDVO-TV“mode”ENUM{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.ConnectorTBD
"left_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"right_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"top_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"bottom_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
“hpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“vpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“contrast”RANGEMin=0, Max= SDVO dependentConnectorTBD
“saturation”RANGEMin=0, Max= SDVO dependentConnectorTBD
“hue”RANGEMin=0, Max= SDVO dependentConnectorTBD
“sharpness”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_adaptive”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_2d”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_chroma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_luma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“dot_crawl”RANGEMin=0, Max=1ConnectorTBD
SDVO-TV/LVDS“brightness”RANGEMin=0, Max= SDVO dependentConnectorTBD
CDV gma-500Generic"Broadcast RGB"ENUM{ “Full”, “Limited 16:235” }ConnectorTBD
"Broadcast RGB"ENUM{ “off”, “auto”, “on” }ConnectorTBD
PoulsboGeneric“backlight”RANGEMin=0, Max=100ConnectorTBD
SDVO-TV“mode”ENUM{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.ConnectorTBD
"left_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"right_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"top_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"bottom_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
“hpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“vpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“contrast”RANGEMin=0, Max= SDVO dependentConnectorTBD
“saturation”RANGEMin=0, Max= SDVO dependentConnectorTBD
“hue”RANGEMin=0, Max= SDVO dependentConnectorTBD
“sharpness”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_adaptive”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_2d”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_chroma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_luma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“dot_crawl”RANGEMin=0, Max=1ConnectorTBD
SDVO-TV/LVDS“brightness”RANGEMin=0, Max= SDVO dependentConnectorTBD
armadaCRTC"CSC_YUV"ENUM{ "Auto" , "CCIR601", "CCIR709" }CRTCTBD
"CSC_RGB"ENUM{ "Auto", "Computer system", "Studio" }CRTCTBD
Overlay"colorkey"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_min"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_max"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_val"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_alpha"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_mode"ENUM{ "disabled", "Y component", "U component" - , "V component", "RGB", “R component", "G component", "B component" }PlaneTBD
"brightness"RANGEMin=0, Max=256 + 255PlaneTBD
"contrast"RANGEMin=0, Max=0x7fffPlaneTBD
"saturation"RANGEMin=0, Max=0x7fffPlaneTBD
exynosCRTC“mode”ENUM{ "normal", "blank" }CRTCTBD
Overlay“zpos”RANGEMin=0, Max=MAX_PLANE-1PlaneTBD
i2c/ch7006_drvGeneric“scale”RANGEMin=0, Max=2ConnectorTBD
TV“mode”ENUM{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc" - , "PAL-60", "NTSC-M", "NTSC-J" }ConnectorTBD
nouveauNV10 Overlay"colorkey"RANGEMin=0, Max=0x01ffffffPlaneTBD
“contrast”RANGEMin=0, Max=8192-1PlaneTBD
“brightness”RANGEMin=0, Max=1024PlaneTBD
“hue”RANGEMin=0, Max=359PlaneTBD
“saturation”RANGEMin=0, Max=8192-1PlaneTBD
“iturbt_709”RANGEMin=0, Max=1PlaneTBD
Nv04 Overlay“colorkey”RANGEMin=0, Max=0x01ffffffPlaneTBD
“brightness”RANGEMin=0, Max=1024PlaneTBD
Display“dithering mode”ENUM{ "auto", "off", "on" }ConnectorTBD
“dithering depth”ENUM{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }ConnectorTBD
“underscan”ENUM{ "auto", "6 bpc", "8 bpc" }ConnectorTBD
“underscan hborder”RANGEMin=0, Max=128ConnectorTBD
“underscan vborder”RANGEMin=0, Max=128ConnectorTBD
“vibrant hue”RANGEMin=0, Max=180ConnectorTBD
“color vibrance”RANGEMin=0, Max=200ConnectorTBD
omapGeneric“zorder”RANGEMin=0, Max=3CRTC, PlaneTBD
qxlGeneric“hotplug_mode_update"RANGEMin=0, Max=1ConnectorTBD
radeonDVI-I“coherent”RANGEMin=0, Max=1ConnectorTBD
DAC enable load detect“load detection”RANGEMin=0, Max=1ConnectorTBD
TV Standard"tv standard"ENUM{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j" - , "scart-pal", "pal-cn", "secam" }ConnectorTBD
legacy TMDS PLL detect"tmds_pll"ENUM{ "driver", "bios" }-TBD
Underscan"underscan"ENUM{ "off", "on", "auto" }ConnectorTBD
"underscan hborder"RANGEMin=0, Max=128ConnectorTBD
"underscan vborder"RANGEMin=0, Max=128ConnectorTBD
Audio“audio”ENUM{ "off", "on", "auto" }ConnectorTBD
FMT Dithering“dither”ENUM{ "off", "on" }ConnectorTBD
rcar-duGeneric"alpha"RANGEMin=0, Max=255PlaneTBD
"colorkey"RANGEMin=0, Max=0x01ffffffPlaneTBD
"zpos"RANGEMin=1, Max=7PlaneTBD
- - - - - - - Vertical Blanking - - Vertical blanking plays a major role in graphics rendering. To achieve - tear-free display, users must synchronize page flips and/or rendering to - vertical blanking. The DRM API offers ioctls to perform page flips - synchronized to vertical blanking and wait for vertical blanking. - - - The DRM core handles most of the vertical blanking management logic, which - involves filtering out spurious interrupts, keeping race-free blanking - counters, coping with counter wrap-around and resets and keeping use - counts. It relies on the driver to generate vertical blanking interrupts - and optionally provide a hardware vertical blanking counter. Drivers must - implement the following operations. - - - - int (*enable_vblank) (struct drm_device *dev, int crtc); -void (*disable_vblank) (struct drm_device *dev, int crtc); - - Enable or disable vertical blanking interrupts for the given CRTC. - - - - u32 (*get_vblank_counter) (struct drm_device *dev, int crtc); - - Retrieve the value of the vertical blanking counter for the given - CRTC. If the hardware maintains a vertical blanking counter its value - should be returned. Otherwise drivers can use the - drm_vblank_count helper function to handle this - operation. - - - - - Drivers must initialize the vertical blanking handling core with a call to - drm_vblank_init in their - load operation. The function will set the struct - drm_device - vblank_disable_allowed field to 0. This will - keep vertical blanking interrupts enabled permanently until the first mode - set operation, where vblank_disable_allowed is - set to 1. The reason behind this is not clear. Drivers can set the field - to 1 after calling drm_vblank_init to make vertical - blanking interrupts dynamically managed from the beginning. - - - Vertical blanking interrupts can be enabled by the DRM core or by drivers - themselves (for instance to handle page flipping operations). The DRM core - maintains a vertical blanking use count to ensure that the interrupts are - not disabled while a user still needs them. To increment the use count, - drivers call drm_vblank_get. Upon return vertical - blanking interrupts are guaranteed to be enabled. - - - To decrement the use count drivers call - drm_vblank_put. Only when the use count drops to zero - will the DRM core disable the vertical blanking interrupts after a delay - by scheduling a timer. The delay is accessible through the vblankoffdelay - module parameter or the drm_vblank_offdelay global - variable and expressed in milliseconds. Its default value is 5000 ms. - Zero means never disable, and a negative value means disable immediately. - Drivers may override the behaviour by setting the - drm_device - vblank_disable_immediate flag, which when set - causes vblank interrupts to be disabled immediately regardless of the - drm_vblank_offdelay value. The flag should only be set if there's a - properly working hardware vblank counter present. - - - When a vertical blanking interrupt occurs drivers only need to call the - drm_handle_vblank function to account for the - interrupt. - - - Resources allocated by drm_vblank_init must be freed - with a call to drm_vblank_cleanup in the driver - unload operation handler. - - - Vertical Blanking and Interrupt Handling Functions Reference -!Edrivers/gpu/drm/drm_irq.c -!Finclude/drm/drmP.h drm_crtc_vblank_waitqueue - - - - - - - Open/Close, File Operations and IOCTLs - - Open and Close - int (*firstopen) (struct drm_device *); -void (*lastclose) (struct drm_device *); -int (*open) (struct drm_device *, struct drm_file *); -void (*preclose) (struct drm_device *, struct drm_file *); -void (*postclose) (struct drm_device *, struct drm_file *); - Open and close handlers. None of those methods are mandatory. - - - The firstopen method is called by the DRM core - for legacy UMS (User Mode Setting) drivers only when an application - opens a device that has no other opened file handle. UMS drivers can - implement it to acquire device resources. KMS drivers can't use the - method and must acquire resources in the load - method instead. - - - Similarly the lastclose method is called when - the last application holding a file handle opened on the device closes - it, for both UMS and KMS drivers. Additionally, the method is also - called at module unload time or, for hot-pluggable devices, when the - device is unplugged. The firstopen and - lastclose calls can thus be unbalanced. - - - The open method is called every time the device - is opened by an application. Drivers can allocate per-file private data - in this method and store them in the struct - drm_file driver_priv - field. Note that the open method is called - before firstopen. - - - The close operation is split into preclose and - postclose methods. Drivers must stop and - cleanup all per-file operations in the preclose - method. For instance pending vertical blanking and page flip events must - be cancelled. No per-file operation is allowed on the file handle after - returning from the preclose method. - - - Finally the postclose method is called as the - last step of the close operation, right before calling the - lastclose method if no other open file handle - exists for the device. Drivers that have allocated per-file private data - in the open method should free it here. - - - The lastclose method should restore CRTC and - plane properties to default value, so that a subsequent open of the - device will not inherit state from the previous user. It can also be - used to execute delayed power switching state changes, e.g. in - conjunction with the vga_switcheroo infrastructure. Beyond that KMS - drivers should not do any further cleanup. Only legacy UMS drivers might - need to clean up device state so that the vga console or an independent - fbdev driver could take over. - - - - File Operations - const struct file_operations *fops - File operations for the DRM device node. - - Drivers must define the file operations structure that forms the DRM - userspace API entry point, even though most of those operations are - implemented in the DRM core. The open, - release and ioctl - operations are handled by - - .owner = THIS_MODULE, - .open = drm_open, - .release = drm_release, - .unlocked_ioctl = drm_ioctl, - #ifdef CONFIG_COMPAT - .compat_ioctl = drm_compat_ioctl, - #endif - - - - Drivers that implement private ioctls that requires 32/64bit - compatibility support must provide their own - compat_ioctl handler that processes private - ioctls and calls drm_compat_ioctl for core ioctls. - - - The read and poll - operations provide support for reading DRM events and polling them. They - are implemented by - - .poll = drm_poll, - .read = drm_read, - .llseek = no_llseek, - - - - The memory mapping implementation varies depending on how the driver - manages memory. Pre-GEM drivers will use drm_mmap, - while GEM-aware drivers will use drm_gem_mmap. See - . - - .mmap = drm_gem_mmap, - - - - No other file operation is supported by the DRM API. - - - - IOCTLs - struct drm_ioctl_desc *ioctls; -int num_ioctls; - Driver-specific ioctls descriptors table. - - Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls - descriptors table is indexed by the ioctl number offset from the base - value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the - table entries. - - - DRM_IOCTL_DEF_DRV(ioctl, func, flags) - - ioctl is the ioctl name. Drivers must define - the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number - offset from DRM_COMMAND_BASE and the ioctl number respectively. The - first macro is private to the device while the second must be exposed - to userspace in a public header. - - - func is a pointer to the ioctl handler function - compatible with the drm_ioctl_t type. - typedef int drm_ioctl_t(struct drm_device *dev, void *data, - struct drm_file *file_priv); - - - flags is a bitmask combination of the following - values. It restricts how the ioctl is allowed to be called. - - - DRM_AUTH - Only authenticated callers allowed - - - DRM_MASTER - The ioctl can only be called on the master file - handle - - - DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed - - - DRM_CONTROL_ALLOW - The ioctl can only be called on a control - device - - - DRM_UNLOCKED - The ioctl handler will be called without locking - the DRM global mutex - - - - - - - - Legacy Support Code - - The section very briefly covers some of the old legacy support code which - is only used by old DRM drivers which have done a so-called shadow-attach - to the underlying device instead of registering as a real driver. This - also includes some of the old generic buffer management and command - submission code. Do not use any of this in new and modern drivers. - - - - Legacy Suspend/Resume - - The DRM core provides some suspend/resume code, but drivers wanting full - suspend/resume support should provide save() and restore() functions. - These are called at suspend, hibernate, or resume time, and should perform - any state save or restore required by your device across suspend or - hibernate states. - - int (*suspend) (struct drm_device *, pm_message_t state); - int (*resume) (struct drm_device *); - - Those are legacy suspend and resume methods which - only work with the legacy shadow-attach driver - registration functions. New driver should use the power management - interface provided by their bus type (usually through - the struct device_driver dev_pm_ops) and set - these methods to NULL. - - - - - Legacy DMA Services - - This should cover how DMA mapping etc. is supported by the core. - These functions are deprecated and should not be used. - - - - - - - - - - - Userland interfaces - - The DRM core exports several interfaces to applications, - generally intended to be used through corresponding libdrm - wrapper functions. In addition, drivers export device-specific - interfaces for use by userspace drivers & device-aware - applications through ioctls and sysfs files. - - - External interfaces include: memory mapping, context management, - DMA operations, AGP management, vblank control, fence - management, memory management, and output management. - - - Cover generic ioctls and sysfs layout here. We only need high-level - info, since man pages should cover the rest. - - - - - - Render nodes - - DRM core provides multiple character-devices for user-space to use. - Depending on which device is opened, user-space can perform a different - set of operations (mainly ioctls). The primary node is always created - and called card<num>. Additionally, a currently - unused control node, called controlD<num> is also - created. The primary node provides all legacy operations and - historically was the only interface used by userspace. With KMS, the - control node was introduced. However, the planned KMS control interface - has never been written and so the control node stays unused to date. - - - With the increased use of offscreen renderers and GPGPU applications, - clients no longer require running compositors or graphics servers to - make use of a GPU. But the DRM API required unprivileged clients to - authenticate to a DRM-Master prior to getting GPU access. To avoid this - step and to grant clients GPU access without authenticating, render - nodes were introduced. Render nodes solely serve render clients, that - is, no modesetting or privileged ioctls can be issued on render nodes. - Only non-global rendering commands are allowed. If a driver supports - render nodes, it must advertise it via the DRIVER_RENDER - DRM driver capability. If not supported, the primary node must be used - for render clients together with the legacy drmAuth authentication - procedure. - - - If a driver advertises render node support, DRM core will create a - separate render node called renderD<num>. There will - be one render node per device. No ioctls except PRIME-related ioctls - will be allowed on this node. Especially GEM_OPEN will be - explicitly prohibited. Render nodes are designed to avoid the - buffer-leaks, which occur if clients guess the flink names or mmap - offsets on the legacy interface. Additionally to this basic interface, - drivers must mark their driver-dependent render-only ioctls as - DRM_RENDER_ALLOW so render clients can use them. Driver - authors must be careful not to allow any privileged ioctls on render - nodes. - - - With render nodes, user-space can now control access to the render node - via basic file-system access-modes. A running graphics server which - authenticates clients on the privileged primary/legacy node is no longer - required. Instead, a client can open the render node and is immediately - granted GPU access. Communication between clients (or servers) is done - via PRIME. FLINK from render node to legacy node is not supported. New - clients must not use the insecure FLINK interface. - - - Besides dropping all modeset/global ioctls, render nodes also drop the - DRM-Master concept. There is no reason to associate render clients with - a DRM-Master as they are independent of any graphics server. Besides, - they must work without any running master, anyway. - Drivers must be able to run without a master object if they support - render nodes. If, on the other hand, a driver requires shared state - between clients which is visible to user-space and accessible beyond - open-file boundaries, they cannot support render nodes. - - - - - - - VBlank event handling - - The DRM core exposes two vertical blank related ioctls: - - - DRM_IOCTL_WAIT_VBLANK - - - This takes a struct drm_wait_vblank structure as its argument, - and it is used to block or request a signal when a specified - vblank event occurs. - - - - - DRM_IOCTL_MODESET_CTL - - - This was only used for user-mode-settind drivers around - modesetting changes to allow the kernel to update the vblank - interrupt after mode setting, since on many devices the vertical - blank counter is reset to 0 at some point during modeset. Modern - drivers should not call this any more since with kernel mode - setting it is a no-op. - - - - - - - - - - - DRM Drivers - - - - This second part of the DRM Developer's Guide documents driver code, - implementation details and also all the driver-specific userspace - interfaces. Especially since all hardware-acceleration interfaces to - userspace are driver specific for efficiency and other reasons these - interfaces can be rather substantial. Hence every driver has its own - chapter. - - - - - drm/i915 Intel GFX Driver - - The drm/i915 driver supports all (with the exception of some very early - models) integrated GFX chipsets with both Intel display and rendering - blocks. This excludes a set of SoC platforms with an SGX rendering unit, - those have basic support through the gma500 drm driver. - - - Core Driver Infrastructure - - This section covers core driver infrastructure used by both the display - and the GEM parts of the driver. - - - Runtime Power Management -!Pdrivers/gpu/drm/i915/intel_runtime_pm.c runtime pm -!Idrivers/gpu/drm/i915/intel_runtime_pm.c -!Idrivers/gpu/drm/i915/intel_uncore.c - - - Interrupt Handling -!Pdrivers/gpu/drm/i915/i915_irq.c interrupt handling -!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_init intel_irq_init_hw intel_hpd_init -!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_disable_interrupts -!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_enable_interrupts - - - Intel GVT-g Guest Support(vGPU) -!Pdrivers/gpu/drm/i915/i915_vgpu.c Intel GVT-g guest support -!Idrivers/gpu/drm/i915/i915_vgpu.c - - - - Display Hardware Handling - - This section covers everything related to the display hardware including - the mode setting infrastructure, plane, sprite and cursor handling and - display, output probing and related topics. - - - Mode Setting Infrastructure - - The i915 driver is thus far the only DRM driver which doesn't use the - common DRM helper code to implement mode setting sequences. Thus it - has its own tailor-made infrastructure for executing a display - configuration change. - - - - Frontbuffer Tracking -!Pdrivers/gpu/drm/i915/intel_frontbuffer.c frontbuffer tracking -!Idrivers/gpu/drm/i915/intel_frontbuffer.c -!Fdrivers/gpu/drm/i915/i915_gem.c i915_gem_track_fb - - - Display FIFO Underrun Reporting -!Pdrivers/gpu/drm/i915/intel_fifo_underrun.c fifo underrun handling -!Idrivers/gpu/drm/i915/intel_fifo_underrun.c - - - Plane Configuration - - This section covers plane configuration and composition with the - primary plane, sprites, cursors and overlays. This includes the - infrastructure to do atomic vsync'ed updates of all this state and - also tightly coupled topics like watermark setup and computation, - framebuffer compression and panel self refresh. - - - - Atomic Plane Helpers -!Pdrivers/gpu/drm/i915/intel_atomic_plane.c atomic plane helpers -!Idrivers/gpu/drm/i915/intel_atomic_plane.c - - - Output Probing - - This section covers output probing and related infrastructure like the - hotplug interrupt storm detection and mitigation code. Note that the - i915 driver still uses most of the common DRM helper code for output - probing, so those sections fully apply. - - - - Hotplug -!Pdrivers/gpu/drm/i915/intel_hotplug.c Hotplug -!Idrivers/gpu/drm/i915/intel_hotplug.c - - - High Definition Audio -!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port -!Idrivers/gpu/drm/i915/intel_audio.c - - - Panel Self Refresh PSR (PSR/SRD) -!Pdrivers/gpu/drm/i915/intel_psr.c Panel Self Refresh (PSR/SRD) -!Idrivers/gpu/drm/i915/intel_psr.c - - - Frame Buffer Compression (FBC) -!Pdrivers/gpu/drm/i915/intel_fbc.c Frame Buffer Compression (FBC) -!Idrivers/gpu/drm/i915/intel_fbc.c - - - Display Refresh Rate Switching (DRRS) -!Pdrivers/gpu/drm/i915/intel_dp.c Display Refresh Rate Switching (DRRS) -!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_set_drrs_state -!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_enable -!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_disable -!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_invalidate -!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_flush -!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_drrs_init - - - - DPIO -!Pdrivers/gpu/drm/i915/i915_reg.h DPIO - - - - CSR firmware support for DMC -!Pdrivers/gpu/drm/i915/intel_csr.c csr support for dmc -!Idrivers/gpu/drm/i915/intel_csr.c - - - - - Memory Management and Command Submission - - This sections covers all things related to the GEM implementation in the - i915 driver. - - - Batchbuffer Parsing -!Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser -!Idrivers/gpu/drm/i915/i915_cmd_parser.c - - - Batchbuffer Pools -!Pdrivers/gpu/drm/i915/i915_gem_batch_pool.c batch pool -!Idrivers/gpu/drm/i915/i915_gem_batch_pool.c - - - Logical Rings, Logical Ring Contexts and Execlists -!Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists -!Idrivers/gpu/drm/i915/intel_lrc.c - - - Global GTT views -!Pdrivers/gpu/drm/i915/i915_gem_gtt.c Global GTT views -!Idrivers/gpu/drm/i915/i915_gem_gtt.c - - - GTT Fences and Swizzling -!Idrivers/gpu/drm/i915/i915_gem_fence.c - - Global GTT Fence Handling -!Pdrivers/gpu/drm/i915/i915_gem_fence.c fence register handling - - - Hardware Tiling and Swizzling Details -!Pdrivers/gpu/drm/i915/i915_gem_fence.c tiling swizzling details - - - - Object Tiling IOCTLs -!Idrivers/gpu/drm/i915/i915_gem_tiling.c -!Pdrivers/gpu/drm/i915/i915_gem_tiling.c buffer object tiling - - - Buffer Object Eviction - - This section documents the interface functions for evicting buffer - objects to make space available in the virtual gpu address spaces. - Note that this is mostly orthogonal to shrinking buffer objects - caches, which has the goal to make main memory (shared with the gpu - through the unified memory architecture) available. - -!Idrivers/gpu/drm/i915/i915_gem_evict.c - - - Buffer Object Memory Shrinking - - This section documents the interface function for shrinking memory - usage of buffer object caches. Shrinking is used to make main memory - available. Note that this is mostly orthogonal to evicting buffer - objects, which has the goal to make space in gpu virtual address - spaces. - -!Idrivers/gpu/drm/i915/i915_gem_shrinker.c - - - - GuC-based Command Submission - - GuC -!Pdrivers/gpu/drm/i915/intel_guc_loader.c GuC-specific firmware loader -!Idrivers/gpu/drm/i915/intel_guc_loader.c - - - GuC Client -!Pdrivers/gpu/drm/i915/i915_guc_submission.c GuC-based command submissison -!Idrivers/gpu/drm/i915/i915_guc_submission.c - - - - - Tracing - - This sections covers all things related to the tracepoints implemented in - the i915 driver. - - - i915_ppgtt_create and i915_ppgtt_release -!Pdrivers/gpu/drm/i915/i915_trace.h i915_ppgtt_create and i915_ppgtt_release tracepoints - - - i915_context_create and i915_context_free -!Pdrivers/gpu/drm/i915/i915_trace.h i915_context_create and i915_context_free tracepoints - - - switch_mm -!Pdrivers/gpu/drm/i915/i915_trace.h switch_mm tracepoint - - - - -!Cdrivers/gpu/drm/i915/i915_irq.c - - diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl new file mode 100644 index 0000000..94c600c --- /dev/null +++ b/Documentation/DocBook/gpu.tmpl @@ -0,0 +1,4189 @@ + + + + + + Linux GPU Driver Developer's Guide + + + + Jesse + Barnes + Initial version + + Intel Corporation +
+ jesse.barnes@intel.com +
+ + + + Laurent + Pinchart + Driver internals + + Ideas on board SPRL +
+ laurent.pinchart@ideasonboard.com +
+ + + + Daniel + Vetter + Contributions all over the place + + Intel Corporation +
+ daniel.vetter@ffwll.ch +
+ + + + + + 2008-2009 + 2013-2014 + Intel Corporation + + + 2012 + Laurent Pinchart + + + + + The contents of this file may be used under the terms of the GNU + General Public License version 2 (the "GPL") as distributed in + the kernel source COPYING file. + + + + + + + 1.0 + 2012-07-13 + LP + Added extensive documentation about driver internals. + + + + + + + + + DRM Core + + + This first part of the DRM Developer's Guide documents core DRM code, + helper libraries for writing drivers and generic userspace interfaces + exposed by DRM drivers. + + + + + Introduction + + The Linux DRM layer contains code intended to support the needs + of complex graphics devices, usually containing programmable + pipelines well suited to 3D graphics acceleration. Graphics + drivers in the kernel may make use of DRM functions to make + tasks like memory management, interrupt handling and DMA easier, + and provide a uniform interface to applications. + + + A note on versions: this guide covers features found in the DRM + tree, including the TTM memory manager, output configuration and + mode setting, and the new vblank internals, in addition to all + the regular features found in current kernels. + + + [Insert diagram of typical DRM stack here] + + + + + + + DRM Internals + + This chapter documents DRM internals relevant to driver authors + and developers working to add support for the latest features to + existing drivers. + + + First, we go over some typical driver initialization + requirements, like setting up command buffers, creating an + initial output configuration, and initializing core services. + Subsequent sections cover core internals in more detail, + providing implementation notes and examples. + + + The DRM layer provides several services to graphics drivers, + many of them driven by the application interfaces it provides + through libdrm, the library that wraps most of the DRM ioctls. + These include vblank event handling, memory + management, output management, framebuffer management, command + submission & fencing, suspend/resume support, and DMA + services. + + + + + + Driver Initialization + + At the core of every DRM driver is a drm_driver + structure. Drivers typically statically initialize a drm_driver structure, + and then pass it to one of the drm_*_init() functions + to register it with the DRM subsystem. + + + Newer drivers that no longer require a drm_bus + structure can alternatively use the low-level device initialization and + registration functions such as drm_dev_alloc() and + drm_dev_register() directly. + + + The drm_driver structure contains static + information that describes the driver and features it supports, and + pointers to methods that the DRM core will call to implement the DRM API. + We will first go through the drm_driver static + information fields, and will then describe individual operations in + details as they get used in later sections. + + + Driver Information + + Driver Features + + Drivers inform the DRM core about their requirements and supported + features by setting appropriate flags in the + driver_features field. Since those flags + influence the DRM core behaviour since registration time, most of them + must be set to registering the drm_driver + instance. + + u32 driver_features; + + Driver Feature Flags + + DRIVER_USE_AGP + + Driver uses AGP interface, the DRM core will manage AGP resources. + + + + DRIVER_REQUIRE_AGP + + Driver needs AGP interface to function. AGP initialization failure + will become a fatal error. + + + + DRIVER_PCI_DMA + + Driver is capable of PCI DMA, mapping of PCI DMA buffers to + userspace will be enabled. Deprecated. + + + + DRIVER_SG + + Driver can perform scatter/gather DMA, allocation and mapping of + scatter/gather buffers will be enabled. Deprecated. + + + + DRIVER_HAVE_DMA + + Driver supports DMA, the userspace DMA API will be supported. + Deprecated. + + + + DRIVER_HAVE_IRQDRIVER_IRQ_SHARED + + DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler + managed by the DRM Core. The core will support simple IRQ handler + installation when the flag is set. The installation process is + described in . + DRIVER_IRQ_SHARED indicates whether the device & handler + support shared IRQs (note that this is required of PCI drivers). + + + + DRIVER_GEM + + Driver use the GEM memory manager. + + + + DRIVER_MODESET + + Driver supports mode setting interfaces (KMS). + + + + DRIVER_PRIME + + Driver implements DRM PRIME buffer sharing. + + + + DRIVER_RENDER + + Driver supports dedicated render nodes. + + + + DRIVER_ATOMIC + + Driver supports atomic properties. In this case the driver + must implement appropriate obj->atomic_get_property() vfuncs + for any modeset objects with driver specific properties. + + + + + + Major, Minor and Patchlevel + int major; +int minor; +int patchlevel; + + The DRM core identifies driver versions by a major, minor and patch + level triplet. The information is printed to the kernel log at + initialization time and passed to userspace through the + DRM_IOCTL_VERSION ioctl. + + + The major and minor numbers are also used to verify the requested driver + API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes + between minor versions, applications can call DRM_IOCTL_SET_VERSION to + select a specific version of the API. If the requested major isn't equal + to the driver major, or the requested minor is larger than the driver + minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise + the driver's set_version() method will be called with the requested + version. + + + + Name, Description and Date + char *name; +char *desc; +char *date; + + The driver name is printed to the kernel log at initialization time, + used for IRQ registration and passed to userspace through + DRM_IOCTL_VERSION. + + + The driver description is a purely informative string passed to + userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by + the kernel. + + + The driver date, formatted as YYYYMMDD, is meant to identify the date of + the latest modification to the driver. However, as most drivers fail to + update it, its value is mostly useless. The DRM core prints it to the + kernel log at initialization time and passes it to userspace through the + DRM_IOCTL_VERSION ioctl. + + + + + Device Registration + + A number of functions are provided to help with device registration. + The functions deal with PCI and platform devices, respectively. + +!Edrivers/gpu/drm/drm_pci.c +!Edrivers/gpu/drm/drm_platform.c + + New drivers that no longer rely on the services provided by the + drm_bus structure can call the low-level + device registration functions directly. The + drm_dev_alloc() function can be used to allocate + and initialize a new drm_device structure. + Drivers will typically want to perform some additional setup on this + structure, such as allocating driver-specific data and storing a + pointer to it in the DRM device's dev_private + field. Drivers should also set the device's unique name using the + drm_dev_set_unique() function. After it has been + set up a device can be registered with the DRM subsystem by calling + drm_dev_register(). This will cause the device to + be exposed to userspace and will call the driver's + .load() implementation. When a device is + removed, the DRM device can safely be unregistered and freed by calling + drm_dev_unregister() followed by a call to + drm_dev_unref(). + +!Edrivers/gpu/drm/drm_drv.c + + + Driver Load + + The load method is the driver and device + initialization entry point. The method is responsible for allocating and + initializing driver private data, performing resource allocation and + mapping (e.g. acquiring + clocks, mapping registers or allocating command buffers), initializing + the memory manager (), installing + the IRQ handler (), setting up + vertical blanking handling (), mode + setting () and initial output + configuration (). + + + If compatibility is a concern (e.g. with drivers converted over from + User Mode Setting to Kernel Mode Setting), care must be taken to prevent + device initialization and control that is incompatible with currently + active userspace drivers. For instance, if user level mode setting + drivers are in use, it would be problematic to perform output discovery + & configuration at load time. Likewise, if user-level drivers + unaware of memory management are in use, memory management and command + buffer setup may need to be omitted. These requirements are + driver-specific, and care needs to be taken to keep both old and new + applications and libraries working. + + int (*load) (struct drm_device *, unsigned long flags); + + The method takes two arguments, a pointer to the newly created + drm_device and flags. The flags are used to + pass the driver_data field of the device id + corresponding to the device passed to drm_*_init(). + Only PCI devices currently use this, USB and platform DRM drivers have + their load method called with flags to 0. + + + Driver Private Data + + The driver private hangs off the main + drm_device structure and can be used for + tracking various device-specific bits of information, like register + offsets, command buffer status, register state for suspend/resume, etc. + At load time, a driver may simply allocate one and set + drm_device.dev_priv + appropriately; it should be freed and + drm_device.dev_priv + set to NULL when the driver is unloaded. + + + + IRQ Registration + + The DRM core tries to facilitate IRQ handler registration and + unregistration by providing drm_irq_install and + drm_irq_uninstall functions. Those functions only + support a single interrupt per device, devices that use more than one + IRQs need to be handled manually. + + + Managed IRQ Registration + + drm_irq_install starts by calling the + irq_preinstall driver operation. The operation + is optional and must make sure that the interrupt will not get fired by + clearing all pending interrupt flags or disabling the interrupt. + + + The passed-in IRQ will then be requested by a call to + request_irq. If the DRIVER_IRQ_SHARED driver + feature flag is set, a shared (IRQF_SHARED) IRQ handler will be + requested. + + + The IRQ handler function must be provided as the mandatory irq_handler + driver operation. It will get passed directly to + request_irq and thus has the same prototype as all + IRQ handlers. It will get called with a pointer to the DRM device as the + second argument. + + + Finally the function calls the optional + irq_postinstall driver operation. The operation + usually enables interrupts (excluding the vblank interrupt, which is + enabled separately), but drivers may choose to enable/disable interrupts + at a different time. + + + drm_irq_uninstall is similarly used to uninstall an + IRQ handler. It starts by waking up all processes waiting on a vblank + interrupt to make sure they don't hang, and then calls the optional + irq_uninstall driver operation. The operation + must disable all hardware interrupts. Finally the function frees the IRQ + by calling free_irq. + + + + Manual IRQ Registration + + Drivers that require multiple interrupt handlers can't use the managed + IRQ registration functions. In that case IRQs must be registered and + unregistered manually (usually with the request_irq + and free_irq functions, or their devm_* equivalent). + + + When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ + driver feature flag, and must not provide the + irq_handler driver operation. They must set the + drm_device irq_enabled + field to 1 upon registration of the IRQs, and clear it to 0 after + unregistering the IRQs. + + + + + Memory Manager Initialization + + Every DRM driver requires a memory manager which must be initialized at + load time. DRM currently contains two memory managers, the Translation + Table Manager (TTM) and the Graphics Execution Manager (GEM). + This document describes the use of the GEM memory manager only. See + for details. + + + + Miscellaneous Device Configuration + + Another task that may be necessary for PCI devices during configuration + is mapping the video BIOS. On many devices, the VBIOS describes device + configuration, LCD panel timings (if any), and contains flags indicating + device state. Mapping the BIOS can be done using the pci_map_rom() call, + a convenience function that takes care of mapping the actual ROM, + whether it has been shadowed into memory (typically at address 0xc0000) + or exists on the PCI device in the ROM BAR. Note that after the ROM has + been mapped and any necessary information has been extracted, it should + be unmapped; on many devices, the ROM address decoder is shared with + other BARs, so leaving it mapped could cause undesired behaviour like + hangs or memory corruption. + + + + + + + + + + Memory management + + Modern Linux systems require large amount of graphics memory to store + frame buffers, textures, vertices and other graphics-related data. Given + the very dynamic nature of many of that data, managing graphics memory + efficiently is thus crucial for the graphics stack and plays a central + role in the DRM infrastructure. + + + The DRM core includes two memory managers, namely Translation Table Maps + (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory + manager to be developed and tried to be a one-size-fits-them all + solution. It provides a single userspace API to accommodate the need of + all hardware, supporting both Unified Memory Architecture (UMA) devices + and devices with dedicated video RAM (i.e. most discrete video cards). + This resulted in a large, complex piece of code that turned out to be + hard to use for driver development. + + + GEM started as an Intel-sponsored project in reaction to TTM's + complexity. Its design philosophy is completely different: instead of + providing a solution to every graphics memory-related problems, GEM + identified common code between drivers and created a support library to + share it. GEM has simpler initialization and execution requirements than + TTM, but has no video RAM management capabilities and is thus limited to + UMA devices. + + + The Translation Table Manager (TTM) + + TTM design background and information belongs here. + + + TTM initialization + This section is outdated. + + Drivers wishing to support TTM must fill out a drm_bo_driver + structure. The structure contains several fields with function + pointers for initializing the TTM, allocating and freeing memory, + waiting for command completion and fence synchronization, and memory + migration. See the radeon_ttm.c file for an example of usage. + + + The ttm_global_reference structure is made up of several fields: + + + struct ttm_global_reference { + enum ttm_global_types global_type; + size_t size; + void *object; + int (*init) (struct ttm_global_reference *); + void (*release) (struct ttm_global_reference *); + }; + + + There should be one global reference structure for your memory + manager as a whole, and there will be others for each object + created by the memory manager at runtime. Your global TTM should + have a type of TTM_GLOBAL_TTM_MEM. The size field for the global + object should be sizeof(struct ttm_mem_global), and the init and + release hooks should point at your driver-specific init and + release routines, which probably eventually call + ttm_mem_global_init and ttm_mem_global_release, respectively. + + + Once your global TTM accounting structure is set up and initialized + by calling ttm_global_item_ref() on it, + you need to create a buffer object TTM to + provide a pool for buffer object allocation by clients and the + kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO, + and its size should be sizeof(struct ttm_bo_global). Again, + driver-specific init and release functions may be provided, + likely eventually calling ttm_bo_global_init() and + ttm_bo_global_release(), respectively. Also, like the previous + object, ttm_global_item_ref() is used to create an initial reference + count for the TTM, which will call your initialization function. + + + + + The Graphics Execution Manager (GEM) + + The GEM design approach has resulted in a memory manager that doesn't + provide full coverage of all (or even all common) use cases in its + userspace or kernel API. GEM exposes a set of standard memory-related + operations to userspace and a set of helper functions to drivers, and let + drivers implement hardware-specific operations with their own private API. + + + The GEM userspace API is described in the + GEM - the Graphics + Execution Manager article on LWN. While slightly + outdated, the document provides a good overview of the GEM API principles. + Buffer allocation and read and write operations, described as part of the + common GEM API, are currently implemented using driver-specific ioctls. + + + GEM is data-agnostic. It manages abstract buffer objects without knowing + what individual buffers contain. APIs that require knowledge of buffer + contents or purpose, such as buffer allocation or synchronization + primitives, are thus outside of the scope of GEM and must be implemented + using driver-specific ioctls. + + + On a fundamental level, GEM involves several operations: + + Memory allocation and freeing + Command execution + Aperture management at command execution time + + Buffer object allocation is relatively straightforward and largely + provided by Linux's shmem layer, which provides memory to back each + object. + + + Device-specific operations, such as command execution, pinning, buffer + read & write, mapping, and domain ownership transfers are left to + driver-specific ioctls. + + + GEM Initialization + + Drivers that use GEM must set the DRIVER_GEM bit in the struct + drm_driver + driver_features field. The DRM core will + then automatically initialize the GEM core before calling the + load operation. Behind the scene, this will + create a DRM Memory Manager object which provides an address space + pool for object allocation. + + + In a KMS configuration, drivers need to allocate and initialize a + command ring buffer following core GEM initialization if required by + the hardware. UMA devices usually have what is called a "stolen" + memory region, which provides space for the initial framebuffer and + large, contiguous memory regions required by the device. This space is + typically not managed by GEM, and must be initialized separately into + its own DRM MM object. + + + + GEM Objects Creation + + GEM splits creation of GEM objects and allocation of the memory that + backs them in two distinct operations. + + + GEM objects are represented by an instance of struct + drm_gem_object. Drivers usually need to extend + GEM objects with private information and thus create a driver-specific + GEM object structure type that embeds an instance of struct + drm_gem_object. + + + To create a GEM object, a driver allocates memory for an instance of its + specific GEM object type and initializes the embedded struct + drm_gem_object with a call to + drm_gem_object_init. The function takes a pointer to + the DRM device, a pointer to the GEM object and the buffer object size + in bytes. + + + GEM uses shmem to allocate anonymous pageable memory. + drm_gem_object_init will create an shmfs file of + the requested size and store it into the struct + drm_gem_object filp + field. The memory is used as either main storage for the object when the + graphics hardware uses system memory directly or as a backing store + otherwise. + + + Drivers are responsible for the actual physical pages allocation by + calling shmem_read_mapping_page_gfp for each page. + Note that they can decide to allocate pages when initializing the GEM + object, or to delay allocation until the memory is needed (for instance + when a page fault occurs as a result of a userspace memory access or + when the driver needs to start a DMA transfer involving the memory). + + + Anonymous pageable memory allocation is not always desired, for instance + when the hardware requires physically contiguous system memory as is + often the case in embedded devices. Drivers can create GEM objects with + no shmfs backing (called private GEM objects) by initializing them with + a call to drm_gem_private_object_init instead of + drm_gem_object_init. Storage for private GEM + objects must be managed by drivers. + + + Drivers that do not need to extend GEM objects with private information + can call the drm_gem_object_alloc function to + allocate and initialize a struct drm_gem_object + instance. The GEM core will call the optional driver + gem_init_object operation after initializing + the GEM object with drm_gem_object_init. + int (*gem_init_object) (struct drm_gem_object *obj); + + + No alloc-and-init function exists for private GEM objects. + + + + GEM Objects Lifetime + + All GEM objects are reference-counted by the GEM core. References can be + acquired and release by calling drm_gem_object_reference + and drm_gem_object_unreference respectively. The + caller must hold the drm_device + struct_mutex lock. As a convenience, GEM + provides the drm_gem_object_reference_unlocked and + drm_gem_object_unreference_unlocked functions that + can be called without holding the lock. + + + When the last reference to a GEM object is released the GEM core calls + the drm_driver + gem_free_object operation. That operation is + mandatory for GEM-enabled drivers and must free the GEM object and all + associated resources. + + + void (*gem_free_object) (struct drm_gem_object *obj); + Drivers are responsible for freeing all GEM object resources, including + the resources created by the GEM core. If an mmap offset has been + created for the object (in which case + drm_gem_object::map_list::map + is not NULL) it must be freed by a call to + drm_gem_free_mmap_offset. The shmfs backing store + must be released by calling drm_gem_object_release + (that function can safely be called if no shmfs backing store has been + created). + + + + GEM Objects Naming + + Communication between userspace and the kernel refers to GEM objects + using local handles, global names or, more recently, file descriptors. + All of those are 32-bit integer values; the usual Linux kernel limits + apply to the file descriptors. + + + GEM handles are local to a DRM file. Applications get a handle to a GEM + object through a driver-specific ioctl, and can use that handle to refer + to the GEM object in other standard or driver-specific ioctls. Closing a + DRM file handle frees all its GEM handles and dereferences the + associated GEM objects. + + + To create a handle for a GEM object drivers call + drm_gem_handle_create. The function takes a pointer + to the DRM file and the GEM object and returns a locally unique handle. + When the handle is no longer needed drivers delete it with a call to + drm_gem_handle_delete. Finally the GEM object + associated with a handle can be retrieved by a call to + drm_gem_object_lookup. + + + Handles don't take ownership of GEM objects, they only take a reference + to the object that will be dropped when the handle is destroyed. To + avoid leaking GEM objects, drivers must make sure they drop the + reference(s) they own (such as the initial reference taken at object + creation time) as appropriate, without any special consideration for the + handle. For example, in the particular case of combined GEM object and + handle creation in the implementation of the + dumb_create operation, drivers must drop the + initial reference to the GEM object before returning the handle. + + + GEM names are similar in purpose to handles but are not local to DRM + files. They can be passed between processes to reference a GEM object + globally. Names can't be used directly to refer to objects in the DRM + API, applications must convert handles to names and names to handles + using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls + respectively. The conversion is handled by the DRM core without any + driver-specific support. + + + GEM also supports buffer sharing with dma-buf file descriptors through + PRIME. GEM-based drivers must use the provided helpers functions to + implement the exporting and importing correctly. See . + Since sharing file descriptors is inherently more secure than the + easily guessable and global GEM names it is the preferred buffer + sharing mechanism. Sharing buffers through GEM names is only supported + for legacy userspace. Furthermore PRIME also allows cross-device + buffer sharing since it is based on dma-bufs. + + + + GEM Objects Mapping + + Because mapping operations are fairly heavyweight GEM favours + read/write-like access to buffers, implemented through driver-specific + ioctls, over mapping buffers to userspace. However, when random access + to the buffer is needed (to perform software rendering for instance), + direct access to the object can be more efficient. + + + The mmap system call can't be used directly to map GEM objects, as they + don't have their own file handle. Two alternative methods currently + co-exist to map GEM objects to userspace. The first method uses a + driver-specific ioctl to perform the mapping operation, calling + do_mmap under the hood. This is often considered + dubious, seems to be discouraged for new GEM-enabled drivers, and will + thus not be described here. + + + The second method uses the mmap system call on the DRM file handle. + void *mmap(void *addr, size_t length, int prot, int flags, int fd, + off_t offset); + DRM identifies the GEM object to be mapped by a fake offset passed + through the mmap offset argument. Prior to being mapped, a GEM object + must thus be associated with a fake offset. To do so, drivers must call + drm_gem_create_mmap_offset on the object. The + function allocates a fake offset range from a pool and stores the + offset divided by PAGE_SIZE in + obj->map_list.hash.key. Care must be taken not to + call drm_gem_create_mmap_offset if a fake offset + has already been allocated for the object. This can be tested by + obj->map_list.map being non-NULL. + + + Once allocated, the fake offset value + (obj->map_list.hash.key << PAGE_SHIFT) + must be passed to the application in a driver-specific way and can then + be used as the mmap offset argument. + + + The GEM core provides a helper method drm_gem_mmap + to handle object mapping. The method can be set directly as the mmap + file operation handler. It will look up the GEM object based on the + offset value and set the VMA operations to the + drm_driver gem_vm_ops + field. Note that drm_gem_mmap doesn't map memory to + userspace, but relies on the driver-provided fault handler to map pages + individually. + + + To use drm_gem_mmap, drivers must fill the struct + drm_driver gem_vm_ops + field with a pointer to VM operations. + + + struct vm_operations_struct *gem_vm_ops + + struct vm_operations_struct { + void (*open)(struct vm_area_struct * area); + void (*close)(struct vm_area_struct * area); + int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf); + }; + + + The open and close + operations must update the GEM object reference count. Drivers can use + the drm_gem_vm_open and + drm_gem_vm_close helper functions directly as open + and close handlers. + + + The fault operation handler is responsible for mapping individual pages + to userspace when a page fault occurs. Depending on the memory + allocation scheme, drivers can allocate pages at fault time, or can + decide to allocate memory for the GEM object at the time the object is + created. + + + Drivers that want to map the GEM object upfront instead of handling page + faults can implement their own mmap file operation handler. + + + + Memory Coherency + + When mapped to the device or used in a command buffer, backing pages + for an object are flushed to memory and marked write combined so as to + be coherent with the GPU. Likewise, if the CPU accesses an object + after the GPU has finished rendering to the object, then the object + must be made coherent with the CPU's view of memory, usually involving + GPU cache flushing of various kinds. This core CPU<->GPU + coherency management is provided by a device-specific ioctl, which + evaluates an object's current domain and performs any necessary + flushing or synchronization to put the object into the desired + coherency domain (note that the object may be busy, i.e. an active + render target; in that case, setting the domain blocks the client and + waits for rendering to complete before performing any necessary + flushing operations). + + + + Command Execution + + Perhaps the most important GEM function for GPU devices is providing a + command execution interface to clients. Client programs construct + command buffers containing references to previously allocated memory + objects, and then submit them to GEM. At that point, GEM takes care to + bind all the objects into the GTT, execute the buffer, and provide + necessary synchronization between clients accessing the same buffers. + This often involves evicting some objects from the GTT and re-binding + others (a fairly expensive operation), and providing relocation + support which hides fixed GTT offsets from clients. Clients must take + care not to submit command buffers that reference more objects than + can fit in the GTT; otherwise, GEM will reject them and no rendering + will occur. Similarly, if several objects in the buffer require fence + registers to be allocated for correct rendering (e.g. 2D blits on + pre-965 chips), care must be taken not to require more fence registers + than are available to the client. Such resource management should be + abstracted from the client in libdrm. + + + + GEM Function Reference +!Edrivers/gpu/drm/drm_gem.c + + + + VMA Offset Manager +!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager +!Edrivers/gpu/drm/drm_vma_manager.c +!Iinclude/drm/drm_vma_manager.h + + + PRIME Buffer Sharing + + PRIME is the cross device buffer sharing framework in drm, originally + created for the OPTIMUS range of multi-gpu platforms. To userspace + PRIME buffers are dma-buf based file descriptors. + + + Overview and Driver Interface + + Similar to GEM global names, PRIME file descriptors are + also used to share buffer objects across processes. They offer + additional security: as file descriptors must be explicitly sent over + UNIX domain sockets to be shared between applications, they can't be + guessed like the globally unique GEM names. + + + Drivers that support the PRIME + API must set the DRIVER_PRIME bit in the struct + drm_driver + driver_features field, and implement the + prime_handle_to_fd and + prime_fd_to_handle operations. + + + int (*prime_handle_to_fd)(struct drm_device *dev, + struct drm_file *file_priv, uint32_t handle, + uint32_t flags, int *prime_fd); +int (*prime_fd_to_handle)(struct drm_device *dev, + struct drm_file *file_priv, int prime_fd, + uint32_t *handle); + Those two operations convert a handle to a PRIME file descriptor and + vice versa. Drivers must use the kernel dma-buf buffer sharing framework + to manage the PRIME file descriptors. Similar to the mode setting + API PRIME is agnostic to the underlying buffer object manager, as + long as handles are 32bit unsigned integers. + + + While non-GEM drivers must implement the operations themselves, GEM + drivers must use the drm_gem_prime_handle_to_fd + and drm_gem_prime_fd_to_handle helper functions. + Those helpers rely on the driver + gem_prime_export and + gem_prime_import operations to create a dma-buf + instance from a GEM object (dma-buf exporter role) and to create a GEM + object from a dma-buf instance (dma-buf importer role). + + + struct dma_buf * (*gem_prime_export)(struct drm_device *dev, + struct drm_gem_object *obj, + int flags); +struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev, + struct dma_buf *dma_buf); + These two operations are mandatory for GEM drivers that support + PRIME. + + + + PRIME Helper Functions +!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers + + + + PRIME Function References +!Edrivers/gpu/drm/drm_prime.c + + + DRM MM Range Allocator + + Overview +!Pdrivers/gpu/drm/drm_mm.c Overview + + + LRU Scan/Eviction Support +!Pdrivers/gpu/drm/drm_mm.c lru scan roaster + + + + DRM MM Range Allocator Function References +!Edrivers/gpu/drm/drm_mm.c +!Iinclude/drm/drm_mm.h + + + CMA Helper Functions Reference +!Pdrivers/gpu/drm/drm_gem_cma_helper.c cma helpers +!Edrivers/gpu/drm/drm_gem_cma_helper.c +!Iinclude/drm/drm_gem_cma_helper.h + + + + + + + Mode Setting + + Drivers must initialize the mode setting core by calling + drm_mode_config_init on the DRM device. The function + initializes the drm_device + mode_config field and never fails. Once done, + mode configuration must be setup by initializing the following fields. + + + + int min_width, min_height; +int max_width, max_height; + + Minimum and maximum width and height of the frame buffers in pixel + units. + + + + struct drm_mode_config_funcs *funcs; + Mode setting functions. + + + + Display Modes Function Reference +!Iinclude/drm/drm_modes.h +!Edrivers/gpu/drm/drm_modes.c + + + Atomic Mode Setting Function Reference +!Edrivers/gpu/drm/drm_atomic.c + + + Frame Buffer Creation + struct drm_framebuffer *(*fb_create)(struct drm_device *dev, + struct drm_file *file_priv, + struct drm_mode_fb_cmd2 *mode_cmd); + + Frame buffers are abstract memory objects that provide a source of + pixels to scanout to a CRTC. Applications explicitly request the + creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and + receive an opaque handle that can be passed to the KMS CRTC control, + plane configuration and page flip functions. + + + Frame buffers rely on the underneath memory manager for low-level memory + operations. When creating a frame buffer applications pass a memory + handle (or a list of memory handles for multi-planar formats) through + the drm_mode_fb_cmd2 argument. For drivers using + GEM as their userspace buffer management interface this would be a GEM + handle. Drivers are however free to use their own backing storage object + handles, e.g. vmwgfx directly exposes special TTM handles to userspace + and so expects TTM handles in the create ioctl and not GEM handles. + + + Drivers must first validate the requested frame buffer parameters passed + through the mode_cmd argument. In particular this is where invalid + sizes, pixel formats or pitches can be caught. + + + If the parameters are deemed valid, drivers then create, initialize and + return an instance of struct drm_framebuffer. + If desired the instance can be embedded in a larger driver-specific + structure. Drivers must fill its width, + height, pitches, + offsets, depth, + bits_per_pixel and + pixel_format fields from the values passed + through the drm_mode_fb_cmd2 argument. They + should call the drm_helper_mode_fill_fb_struct + helper function to do so. + + + + The initialization of the new framebuffer instance is finalized with a + call to drm_framebuffer_init which takes a pointer + to DRM frame buffer operations (struct + drm_framebuffer_funcs). Note that this function + publishes the framebuffer and so from this point on it can be accessed + concurrently from other threads. Hence it must be the last step in the + driver's framebuffer initialization sequence. Frame buffer operations + are + + + int (*create_handle)(struct drm_framebuffer *fb, + struct drm_file *file_priv, unsigned int *handle); + + Create a handle to the frame buffer underlying memory object. If + the frame buffer uses a multi-plane format, the handle will + reference the memory object associated with the first plane. + + + Drivers call drm_gem_handle_create to create + the handle. + + + + void (*destroy)(struct drm_framebuffer *framebuffer); + + Destroy the frame buffer object and frees all associated + resources. Drivers must call + drm_framebuffer_cleanup to free resources + allocated by the DRM core for the frame buffer object, and must + make sure to unreference all memory objects associated with the + frame buffer. Handles created by the + create_handle operation are released by + the DRM core. + + + + int (*dirty)(struct drm_framebuffer *framebuffer, + struct drm_file *file_priv, unsigned flags, unsigned color, + struct drm_clip_rect *clips, unsigned num_clips); + + This optional operation notifies the driver that a region of the + frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB + ioctl call. + + + + + + The lifetime of a drm framebuffer is controlled with a reference count, + drivers can grab additional references with + drm_framebuffer_referenceand drop them + again with drm_framebuffer_unreference. For + driver-private framebuffers for which the last reference is never + dropped (e.g. for the fbdev framebuffer when the struct + drm_framebuffer is embedded into the fbdev + helper struct) drivers can manually clean up a framebuffer at module + unload time with + drm_framebuffer_unregister_private. + + + + Dumb Buffer Objects + + The KMS API doesn't standardize backing storage object creation and + leaves it to driver-specific ioctls. Furthermore actually creating a + buffer object even for GEM-based drivers is done through a + driver-specific ioctl - GEM only has a common userspace interface for + sharing and destroying objects. While not an issue for full-fledged + graphics stacks that include device-specific userspace components (in + libdrm for instance), this limit makes DRM-based early boot graphics + unnecessarily complex. + + + Dumb objects partly alleviate the problem by providing a standard + API to create dumb buffers suitable for scanout, which can then be used + to create KMS frame buffers. + + + To support dumb objects drivers must implement the + dumb_create, + dumb_destroy and + dumb_map_offset operations. + + + + int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, + struct drm_mode_create_dumb *args); + + The dumb_create operation creates a driver + object (GEM or TTM handle) suitable for scanout based on the + width, height and depth from the struct + drm_mode_create_dumb argument. It fills the + argument's handle, + pitch and size + fields with a handle for the newly created object and its line + pitch and size in bytes. + + + + int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle); + + The dumb_destroy operation destroys a dumb + object created by dumb_create. + + + + int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle, uint64_t *offset); + + The dumb_map_offset operation associates an + mmap fake offset with the object given by the handle and returns + it. Drivers must use the + drm_gem_create_mmap_offset function to + associate the fake offset as described in + . + + + + + Note that dumb objects may not be used for gpu acceleration, as has been + attempted on some ARM embedded platforms. Such drivers really must have + a hardware-specific ioctl to allocate suitable buffer objects. + + + + Output Polling + void (*output_poll_changed)(struct drm_device *dev); + + This operation notifies the driver that the status of one or more + connectors has changed. Drivers that use the fb helper can just call the + drm_fb_helper_hotplug_event function to handle this + operation. + + + + Locking + + Beside some lookup structures with their own locking (which is hidden + behind the interface functions) most of the modeset state is protected + by the dev-<mode_config.lock mutex and additionally + per-crtc locks to allow cursor updates, pageflips and similar operations + to occur concurrently with background tasks like output detection. + Operations which cross domains like a full modeset always grab all + locks. Drivers there need to protect resources shared between crtcs with + additional locking. They also need to be careful to always grab the + relevant crtc locks if a modset functions touches crtc state, e.g. for + load detection (which does only grab the mode_config.lock + to allow concurrent screen updates on live crtcs). + + + + + + + + KMS Initialization and Cleanup + + A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders + and connectors. KMS drivers must thus create and initialize all those + objects at load time after initializing mode setting. + + + CRTCs (struct <structname>drm_crtc</structname>) + + A CRTC is an abstraction representing a part of the chip that contains a + pointer to a scanout buffer. Therefore, the number of CRTCs available + determines how many independent scanout buffers can be active at any + given time. The CRTC structure contains several fields to support this: + a pointer to some video memory (abstracted as a frame buffer object), a + display mode, and an (x, y) offset into the video memory to support + panning or configurations where one piece of video memory spans multiple + CRTCs. + + + CRTC Initialization + + A KMS device must create and register at least one struct + drm_crtc instance. The instance is allocated + and zeroed by the driver, possibly as part of a larger structure, and + registered with a call to drm_crtc_init with a + pointer to CRTC functions. + + + + CRTC Operations + + Set Configuration + int (*set_config)(struct drm_mode_set *set); + + Apply a new CRTC configuration to the device. The configuration + specifies a CRTC, a frame buffer to scan out from, a (x,y) position in + the frame buffer, a display mode and an array of connectors to drive + with the CRTC if possible. + + + If the frame buffer specified in the configuration is NULL, the driver + must detach all encoders connected to the CRTC and all connectors + attached to those encoders and disable them. + + + This operation is called with the mode config lock held. + + + Note that the drm core has no notion of restoring the mode setting + state after resume, since all resume handling is in the full + responsibility of the driver. The common mode setting helper library + though provides a helper which can be used for this: + drm_helper_resume_force_mode. + + + + Page Flipping + int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb, + struct drm_pending_vblank_event *event); + + Schedule a page flip to the given frame buffer for the CRTC. This + operation is called with the mode config mutex held. + + + Page flipping is a synchronization mechanism that replaces the frame + buffer being scanned out by the CRTC with a new frame buffer during + vertical blanking, avoiding tearing. When an application requests a page + flip the DRM core verifies that the new frame buffer is large enough to + be scanned out by the CRTC in the currently configured mode and then + calls the CRTC page_flip operation with a + pointer to the new frame buffer. + + + The page_flip operation schedules a page flip. + Once any pending rendering targeting the new frame buffer has + completed, the CRTC will be reprogrammed to display that frame buffer + after the next vertical refresh. The operation must return immediately + without waiting for rendering or page flip to complete and must block + any new rendering to the frame buffer until the page flip completes. + + + If a page flip can be successfully scheduled the driver must set the + drm_crtc->fb field to the new framebuffer pointed to + by fb. This is important so that the reference counting + on framebuffers stays balanced. + + + If a page flip is already pending, the + page_flip operation must return + -EBUSY. + + + To synchronize page flip to vertical blanking the driver will likely + need to enable vertical blanking interrupts. It should call + drm_vblank_get for that purpose, and call + drm_vblank_put after the page flip completes. + + + If the application has requested to be notified when page flip completes + the page_flip operation will be called with a + non-NULL event argument pointing to a + drm_pending_vblank_event instance. Upon page + flip completion the driver must call drm_send_vblank_event + to fill in the event and send to wake up any waiting processes. + This can be performed with + event_lock, flags); + ... + drm_send_vblank_event(dev, pipe, event); + spin_unlock_irqrestore(&dev->event_lock, flags); + ]]> + + + FIXME: Could drivers that don't need to wait for rendering to complete + just add the event to dev->vblank_event_list and + let the DRM core handle everything, as for "normal" vertical blanking + events? + + + While waiting for the page flip to complete, the + event->base.link list head can be used freely by + the driver to store the pending event in a driver-specific list. + + + If the file handle is closed before the event is signaled, drivers must + take care to destroy the event in their + preclose operation (and, if needed, call + drm_vblank_put). + + + + Miscellaneous + + + void (*set_property)(struct drm_crtc *crtc, + struct drm_property *property, uint64_t value); + + Set the value of the given CRTC property to + value. See + for more information about properties. + + + + void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b, + uint32_t start, uint32_t size); + + Apply a gamma table to the device. The operation is optional. + + + + void (*destroy)(struct drm_crtc *crtc); + + Destroy the CRTC when not needed anymore. See + . + + + + + + + + Planes (struct <structname>drm_plane</structname>) + + A plane represents an image source that can be blended with or overlayed + on top of a CRTC during the scanout process. Planes are associated with + a frame buffer to crop a portion of the image memory (source) and + optionally scale it to a destination size. The result is then blended + with or overlayed on top of a CRTC. + + + The DRM core recognizes three types of planes: + + + DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. Primary + planes are the planes operated upon by CRTC modesetting and flipping + operations described in . + + + DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. Cursor + planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and + DRM_IOCTL_MODE_CURSOR2 ioctls. + + + DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes. + Some drivers refer to these types of planes as "sprites" internally. + + + For compatibility with legacy userspace, only overlay planes are made + available to userspace by default. Userspace clients may set the + DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that + they wish to receive a universal plane list containing all plane types. + + + Plane Initialization + + To create a plane, a KMS drivers allocates and + zeroes an instances of struct drm_plane + (possibly as part of a larger structure) and registers it with a call + to drm_universal_plane_init. The function takes a bitmask + of the CRTCs that can be associated with the plane, a pointer to the + plane functions, a list of format supported formats, and the type of + plane (primary, cursor, or overlay) being initialized. + + + Cursor and overlay planes are optional. All drivers should provide + one primary plane per CRTC (although this requirement may change in + the future); drivers that do not wish to provide special handling for + primary planes may make use of the helper functions described in + to create and register a + primary plane with standard capabilities. + + + + Plane Operations + + + int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc, + struct drm_framebuffer *fb, int crtc_x, int crtc_y, + unsigned int crtc_w, unsigned int crtc_h, + uint32_t src_x, uint32_t src_y, + uint32_t src_w, uint32_t src_h); + + Enable and configure the plane to use the given CRTC and frame buffer. + + + The source rectangle in frame buffer memory coordinates is given by + the src_x, src_y, + src_w and src_h + parameters (as 16.16 fixed point values). Devices that don't support + subpixel plane coordinates can ignore the fractional part. + + + The destination rectangle in CRTC coordinates is given by the + crtc_x, crtc_y, + crtc_w and crtc_h + parameters (as integer values). Devices scale the source rectangle to + the destination rectangle. If scaling is not supported, and the source + rectangle size doesn't match the destination rectangle size, the + driver must return a -EINVAL error. + + + + int (*disable_plane)(struct drm_plane *plane); + + Disable the plane. The DRM core calls this method in response to a + DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0. + Disabled planes must not be processed by the CRTC. + + + + void (*destroy)(struct drm_plane *plane); + + Destroy the plane when not needed anymore. See + . + + + + + + + Encoders (struct <structname>drm_encoder</structname>) + + An encoder takes pixel data from a CRTC and converts it to a format + suitable for any attached connectors. On some devices, it may be + possible to have a CRTC send data to more than one encoder. In that + case, both encoders would receive data from the same scanout buffer, + resulting in a "cloned" display configuration across the connectors + attached to each encoder. + + + Encoder Initialization + + As for CRTCs, a KMS driver must create, initialize and register at + least one struct drm_encoder instance. The + instance is allocated and zeroed by the driver, possibly as part of a + larger structure. + + + Drivers must initialize the struct drm_encoder + possible_crtcs and + possible_clones fields before registering the + encoder. Both fields are bitmasks of respectively the CRTCs that the + encoder can be connected to, and sibling encoders candidate for cloning. + + + After being initialized, the encoder must be registered with a call to + drm_encoder_init. The function takes a pointer to + the encoder functions and an encoder type. Supported types are + + + DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A + + + DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort + + + DRM_MODE_ENCODER_LVDS for display panels + + + DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component, + SCART) + + + DRM_MODE_ENCODER_VIRTUAL for virtual machine displays + + + + + Encoders must be attached to a CRTC to be used. DRM drivers leave + encoders unattached at initialization time. Applications (or the fbdev + compatibility layer when implemented) are responsible for attaching the + encoders they want to use to a CRTC. + + + + Encoder Operations + + + void (*destroy)(struct drm_encoder *encoder); + + Called to destroy the encoder when not needed anymore. See + . + + + + void (*set_property)(struct drm_plane *plane, + struct drm_property *property, uint64_t value); + + Set the value of the given plane property to + value. See + for more information about properties. + + + + + + + Connectors (struct <structname>drm_connector</structname>) + + A connector is the final destination for pixel data on a device, and + usually connects directly to an external display device like a monitor + or laptop panel. A connector can only be attached to one encoder at a + time. The connector is also the structure where information about the + attached display is kept, so it contains fields for display data, EDID + data, DPMS & connection status, and information about modes + supported on the attached displays. + + + Connector Initialization + + Finally a KMS driver must create, initialize, register and attach at + least one struct drm_connector instance. The + instance is created as other KMS objects and initialized by setting the + following fields. + + + + interlace_allowed + + Whether the connector can handle interlaced modes. + + + + doublescan_allowed + + Whether the connector can handle doublescan. + + + + display_info + + + Display information is filled from EDID information when a display + is detected. For non hot-pluggable displays such as flat panels in + embedded systems, the driver should initialize the + display_info.width_mm + and + display_info.height_mm + fields with the physical size of the display. + + + + polled + + Connector polling mode, a combination of + + + DRM_CONNECTOR_POLL_HPD + + The connector generates hotplug events and doesn't need to be + periodically polled. The CONNECT and DISCONNECT flags must not + be set together with the HPD flag. + + + + DRM_CONNECTOR_POLL_CONNECT + + Periodically poll the connector for connection. + + + + DRM_CONNECTOR_POLL_DISCONNECT + + Periodically poll the connector for disconnection. + + + + Set to 0 for connectors that don't support connection status + discovery. + + + + + The connector is then registered with a call to + drm_connector_init with a pointer to the connector + functions and a connector type, and exposed through sysfs with a call to + drm_connector_register. + + + Supported connector types are + + DRM_MODE_CONNECTOR_VGA + DRM_MODE_CONNECTOR_DVII + DRM_MODE_CONNECTOR_DVID + DRM_MODE_CONNECTOR_DVIA + DRM_MODE_CONNECTOR_Composite + DRM_MODE_CONNECTOR_SVIDEO + DRM_MODE_CONNECTOR_LVDS + DRM_MODE_CONNECTOR_Component + DRM_MODE_CONNECTOR_9PinDIN + DRM_MODE_CONNECTOR_DisplayPort + DRM_MODE_CONNECTOR_HDMIA + DRM_MODE_CONNECTOR_HDMIB + DRM_MODE_CONNECTOR_TV + DRM_MODE_CONNECTOR_eDP + DRM_MODE_CONNECTOR_VIRTUAL + + + + Connectors must be attached to an encoder to be used. For devices that + map connectors to encoders 1:1, the connector should be attached at + initialization time with a call to + drm_mode_connector_attach_encoder. The driver must + also set the drm_connector + encoder field to point to the attached + encoder. + + + Finally, drivers must initialize the connectors state change detection + with a call to drm_kms_helper_poll_init. If at + least one connector is pollable but can't generate hotplug interrupts + (indicated by the DRM_CONNECTOR_POLL_CONNECT and + DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will + automatically be queued to periodically poll for changes. Connectors + that can generate hotplug interrupts must be marked with the + DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must + call drm_helper_hpd_irq_event. The function will + queue a delayed work to check the state of all connectors, but no + periodic polling will be done. + + + + Connector Operations + + Unless otherwise state, all operations are mandatory. + + + DPMS + void (*dpms)(struct drm_connector *connector, int mode); + + The DPMS operation sets the power state of a connector. The mode + argument is one of + + DRM_MODE_DPMS_ON + DRM_MODE_DPMS_STANDBY + DRM_MODE_DPMS_SUSPEND + DRM_MODE_DPMS_OFF + + + + In all but DPMS_ON mode the encoder to which the connector is attached + should put the display in low-power mode by driving its signals + appropriately. If more than one connector is attached to the encoder + care should be taken not to change the power state of other displays as + a side effect. Low-power mode should be propagated to the encoders and + CRTCs when all related connectors are put in low-power mode. + + + + Modes + int (*fill_modes)(struct drm_connector *connector, uint32_t max_width, + uint32_t max_height); + + Fill the mode list with all supported modes for the connector. If the + max_width and max_height + arguments are non-zero, the implementation must ignore all modes wider + than max_width or higher than + max_height. + + + The connector must also fill in this operation its + display_info + width_mm and + height_mm fields with the connected display + physical size in millimeters. The fields should be set to 0 if the value + isn't known or is not applicable (for instance for projector devices). + + + + Connection Status + + The connection status is updated through polling or hotplug events when + supported (see ). The status + value is reported to userspace through ioctls and must not be used + inside the driver, as it only gets initialized by a call to + drm_mode_getconnector from userspace. + + enum drm_connector_status (*detect)(struct drm_connector *connector, + bool force); + + Check to see if anything is attached to the connector. The + force parameter is set to false whilst polling or + to true when checking the connector due to user request. + force can be used by the driver to avoid + expensive, destructive operations during automated probing. + + + Return connector_status_connected if something is connected to the + connector, connector_status_disconnected if nothing is connected and + connector_status_unknown if the connection state isn't known. + + + Drivers should only return connector_status_connected if the connection + status has really been probed as connected. Connectors that can't detect + the connection status, or failed connection status probes, should return + connector_status_unknown. + + + + Miscellaneous + + + void (*set_property)(struct drm_connector *connector, + struct drm_property *property, uint64_t value); + + Set the value of the given connector property to + value. See + for more information about properties. + + + + void (*destroy)(struct drm_connector *connector); + + Destroy the connector when not needed anymore. See + . + + + + + + + + Cleanup + + The DRM core manages its objects' lifetime. When an object is not needed + anymore the core calls its destroy function, which must clean up and + free every resource allocated for the object. Every + drm_*_init call must be matched with a + corresponding drm_*_cleanup call to cleanup CRTCs + (drm_crtc_cleanup), planes + (drm_plane_cleanup), encoders + (drm_encoder_cleanup) and connectors + (drm_connector_cleanup). Furthermore, connectors + that have been added to sysfs must be removed by a call to + drm_connector_unregister before calling + drm_connector_cleanup. + + + Connectors state change detection must be cleanup up with a call to + drm_kms_helper_poll_fini. + + + + Output discovery and initialization example + base; + drm_connector_init(dev, &intel_output->base, + &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA); + + drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs, + DRM_MODE_ENCODER_DAC); + + drm_mode_connector_attach_encoder(&intel_output->base, + &intel_output->enc); + + /* Set up the DDC bus. */ + intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A"); + if (!intel_output->ddc_bus) { + dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration " + "failed.\n"); + return; + } + + intel_output->type = INTEL_OUTPUT_ANALOG; + connector->interlace_allowed = 0; + connector->doublescan_allowed = 0; + + drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs); + drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); + + drm_connector_register(connector); +}]]> + + In the example above (taken from the i915 driver), a CRTC, connector and + encoder combination is created. A device-specific i2c bus is also + created for fetching EDID data and performing monitor detection. Once + the process is complete, the new connector is registered with sysfs to + make its properties available to applications. + + + + KMS API Functions +!Edrivers/gpu/drm/drm_crtc.c + + + KMS Data Structures +!Iinclude/drm/drm_crtc.h + + + KMS Locking +!Pdrivers/gpu/drm/drm_modeset_lock.c kms locking +!Iinclude/drm/drm_modeset_lock.h +!Edrivers/gpu/drm/drm_modeset_lock.c + + + + + + + Mode Setting Helper Functions + + The plane, CRTC, encoder and connector functions provided by the drivers + implement the DRM API. They're called by the DRM core and ioctl handlers + to handle device state changes and configuration request. As implementing + those functions often requires logic not specific to drivers, mid-layer + helper functions are available to avoid duplicating boilerplate code. + + + The DRM core contains one mid-layer implementation. The mid-layer provides + implementations of several plane, CRTC, encoder and connector functions + (called from the top of the mid-layer) that pre-process requests and call + lower-level functions provided by the driver (at the bottom of the + mid-layer). For instance, the + drm_crtc_helper_set_config function can be used to + fill the struct drm_crtc_funcs + set_config field. When called, it will split + the set_config operation in smaller, simpler + operations and call the driver to handle them. + + + To use the mid-layer, drivers call drm_crtc_helper_add, + drm_encoder_helper_add and + drm_connector_helper_add functions to install their + mid-layer bottom operations handlers, and fill the + drm_crtc_funcs, + drm_encoder_funcs and + drm_connector_funcs structures with pointers to + the mid-layer top API functions. Installing the mid-layer bottom operation + handlers is best done right after registering the corresponding KMS object. + + + The mid-layer is not split between CRTC, encoder and connector operations. + To use it, a driver must provide bottom functions for all of the three KMS + entities. + + + Helper Functions + + + int drm_crtc_helper_set_config(struct drm_mode_set *set); + + The drm_crtc_helper_set_config helper function + is a CRTC set_config implementation. It + first tries to locate the best encoder for each connector by calling + the connector best_encoder helper + operation. + + + After locating the appropriate encoders, the helper function will + call the mode_fixup encoder and CRTC helper + operations to adjust the requested mode, or reject it completely in + which case an error will be returned to the application. If the new + configuration after mode adjustment is identical to the current + configuration the helper function will return without performing any + other operation. + + + If the adjusted mode is identical to the current mode but changes to + the frame buffer need to be applied, the + drm_crtc_helper_set_config function will call + the CRTC mode_set_base helper operation. If + the adjusted mode differs from the current mode, or if the + mode_set_base helper operation is not + provided, the helper function performs a full mode set sequence by + calling the prepare, + mode_set and + commit CRTC and encoder helper operations, + in that order. + + + + void drm_helper_connector_dpms(struct drm_connector *connector, int mode); + + The drm_helper_connector_dpms helper function + is a connector dpms implementation that + tracks power state of connectors. To use the function, drivers must + provide dpms helper operations for CRTCs + and encoders to apply the DPMS state to the device. + + + The mid-layer doesn't track the power state of CRTCs and encoders. + The dpms helper operations can thus be + called with a mode identical to the currently active mode. + + + + int drm_helper_probe_single_connector_modes(struct drm_connector *connector, + uint32_t maxX, uint32_t maxY); + + The drm_helper_probe_single_connector_modes helper + function is a connector fill_modes + implementation that updates the connection status for the connector + and then retrieves a list of modes by calling the connector + get_modes helper operation. + + + If the helper operation returns no mode, and if the connector status + is connector_status_connected, standard VESA DMT modes up to + 1024x768 are automatically added to the modes list by a call to + drm_add_modes_noedid. + + + The function then filters out modes larger than + max_width and max_height + if specified. It finally calls the optional connector + mode_valid helper operation for each mode in + the probed list to check whether the mode is valid for the connector. + + + + + + CRTC Helper Operations + + + bool (*mode_fixup)(struct drm_crtc *crtc, + const struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode); + + Let CRTCs adjust the requested mode or reject it completely. This + operation returns true if the mode is accepted (possibly after being + adjusted) or false if it is rejected. + + + The mode_fixup operation should reject the + mode if it can't reasonably use it. The definition of "reasonable" + is currently fuzzy in this context. One possible behaviour would be + to set the adjusted mode to the panel timings when a fixed-mode + panel is used with hardware capable of scaling. Another behaviour + would be to accept any input mode and adjust it to the closest mode + supported by the hardware (FIXME: This needs to be clarified). + + + + int (*mode_set_base)(struct drm_crtc *crtc, int x, int y, + struct drm_framebuffer *old_fb) + + Move the CRTC on the current frame buffer (stored in + crtc->fb) to position (x,y). Any of the frame + buffer, x position or y position may have been modified. + + + This helper operation is optional. If not provided, the + drm_crtc_helper_set_config function will fall + back to the mode_set helper operation. + + + FIXME: Why are x and y passed as arguments, as they can be accessed + through crtc->x and + crtc->y? + + + + void (*prepare)(struct drm_crtc *crtc); + + Prepare the CRTC for mode setting. This operation is called after + validating the requested mode. Drivers use it to perform + device-specific operations required before setting the new mode. + + + + int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode, int x, int y, + struct drm_framebuffer *old_fb); + + Set a new mode, position and frame buffer. Depending on the device + requirements, the mode can be stored internally by the driver and + applied in the commit operation, or + programmed to the hardware immediately. + + + The mode_set operation returns 0 on success + or a negative error code if an error occurs. + + + + void (*commit)(struct drm_crtc *crtc); + + Commit a mode. This operation is called after setting the new mode. + Upon return the device must use the new mode and be fully + operational. + + + + + + Encoder Helper Operations + + + bool (*mode_fixup)(struct drm_encoder *encoder, + const struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode); + + Let encoders adjust the requested mode or reject it completely. This + operation returns true if the mode is accepted (possibly after being + adjusted) or false if it is rejected. See the + mode_fixup CRTC helper + operation for an explanation of the allowed adjustments. + + + + void (*prepare)(struct drm_encoder *encoder); + + Prepare the encoder for mode setting. This operation is called after + validating the requested mode. Drivers use it to perform + device-specific operations required before setting the new mode. + + + + void (*mode_set)(struct drm_encoder *encoder, + struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode); + + Set a new mode. Depending on the device requirements, the mode can + be stored internally by the driver and applied in the + commit operation, or programmed to the + hardware immediately. + + + + void (*commit)(struct drm_encoder *encoder); + + Commit a mode. This operation is called after setting the new mode. + Upon return the device must use the new mode and be fully + operational. + + + + + + Connector Helper Operations + + + struct drm_encoder *(*best_encoder)(struct drm_connector *connector); + + Return a pointer to the best encoder for the connecter. Device that + map connectors to encoders 1:1 simply return the pointer to the + associated encoder. This operation is mandatory. + + + + int (*get_modes)(struct drm_connector *connector); + + Fill the connector's probed_modes list + by parsing EDID data with drm_add_edid_modes, + adding standard VESA DMT modes with drm_add_modes_noedid, + or calling drm_mode_probed_add directly for every + supported mode and return the number of modes it has detected. This + operation is mandatory. + + + Note that the caller function will automatically add standard VESA + DMT modes up to 1024x768 if the get_modes + helper operation returns no mode and if the connector status is + connector_status_connected. There is no need to call + drm_add_edid_modes manually in that case. + + + When adding modes manually the driver creates each mode with a call to + drm_mode_create and must fill the following fields. + + + __u32 type; + + Mode type bitmask, a combination of + + + DRM_MODE_TYPE_BUILTIN + not used? + + + DRM_MODE_TYPE_CLOCK_C + not used? + + + DRM_MODE_TYPE_CRTC_C + not used? + + + + DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector + + + not used? + + + + DRM_MODE_TYPE_DEFAULT + not used? + + + DRM_MODE_TYPE_USERDEF + not used? + + + DRM_MODE_TYPE_DRIVER + + + The mode has been created by the driver (as opposed to + to user-created modes). + + + + + Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they + create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred + mode. + + + + __u32 clock; + Pixel clock frequency in kHz unit + + + __u16 hdisplay, hsync_start, hsync_end, htotal; + __u16 vdisplay, vsync_start, vsync_end, vtotal; + Horizontal and vertical timing information + <----------------><-------------><--------------> + + //////////////////////| + ////////////////////// | + ////////////////////// |.................. ................ + _______________ + + <----- [hv]display -----> + <------------- [hv]sync_start ------------> + <--------------------- [hv]sync_end ---------------------> + <-------------------------------- [hv]total -----------------------------> +]]> + + + __u16 hskew; + __u16 vscan; + Unknown + + + __u32 flags; + + Mode flags, a combination of + + + DRM_MODE_FLAG_PHSYNC + + Horizontal sync is active high + + + + DRM_MODE_FLAG_NHSYNC + + Horizontal sync is active low + + + + DRM_MODE_FLAG_PVSYNC + + Vertical sync is active high + + + + DRM_MODE_FLAG_NVSYNC + + Vertical sync is active low + + + + DRM_MODE_FLAG_INTERLACE + + Mode is interlaced + + + + DRM_MODE_FLAG_DBLSCAN + + Mode uses doublescan + + + + DRM_MODE_FLAG_CSYNC + + Mode uses composite sync + + + + DRM_MODE_FLAG_PCSYNC + + Composite sync is active high + + + + DRM_MODE_FLAG_NCSYNC + + Composite sync is active low + + + + DRM_MODE_FLAG_HSKEW + + hskew provided (not used?) + + + + DRM_MODE_FLAG_BCAST + + not used? + + + + DRM_MODE_FLAG_PIXMUX + + not used? + + + + DRM_MODE_FLAG_DBLCLK + + not used? + + + + DRM_MODE_FLAG_CLKDIV2 + + ? + + + + + + Note that modes marked with the INTERLACE or DBLSCAN flags will be + filtered out by + drm_helper_probe_single_connector_modes if + the connector's interlace_allowed or + doublescan_allowed field is set to 0. + + + + char name[DRM_DISPLAY_MODE_LEN]; + + Mode name. The driver must call + drm_mode_set_name to fill the mode name from + hdisplay, + vdisplay and interlace flag after + filling the corresponding fields. + + + + + + The vrefresh value is computed by + drm_helper_probe_single_connector_modes. + + + When parsing EDID data, drm_add_edid_modes fills the + connector display_info + width_mm and + height_mm fields. When creating modes + manually the get_modes helper operation must + set the display_info + width_mm and + height_mm fields if they haven't been set + already (for instance at initialization time when a fixed-size panel is + attached to the connector). The mode width_mm + and height_mm fields are only used internally + during EDID parsing and should not be set when creating modes manually. + + + + int (*mode_valid)(struct drm_connector *connector, + struct drm_display_mode *mode); + + Verify whether a mode is valid for the connector. Return MODE_OK for + supported modes and one of the enum drm_mode_status values (MODE_*) + for unsupported modes. This operation is optional. + + + As the mode rejection reason is currently not used beside for + immediately removing the unsupported mode, an implementation can + return MODE_BAD regardless of the exact reason why the mode is not + valid. + + + Note that the mode_valid helper operation is + only called for modes detected by the device, and + not for modes set by the user through the CRTC + set_config operation. + + + + + + Atomic Modeset Helper Functions Reference + + Overview +!Pdrivers/gpu/drm/drm_atomic_helper.c overview + + + Implementing Asynchronous Atomic Commit +!Pdrivers/gpu/drm/drm_atomic_helper.c implementing async commit + + + Atomic State Reset and Initialization +!Pdrivers/gpu/drm/drm_atomic_helper.c atomic state reset and initialization + +!Iinclude/drm/drm_atomic_helper.h +!Edrivers/gpu/drm/drm_atomic_helper.c + + + Modeset Helper Functions Reference +!Iinclude/drm/drm_crtc_helper.h +!Edrivers/gpu/drm/drm_crtc_helper.c +!Pdrivers/gpu/drm/drm_crtc_helper.c overview + + + Output Probing Helper Functions Reference +!Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview +!Edrivers/gpu/drm/drm_probe_helper.c + + + fbdev Helper Functions Reference +!Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers +!Edrivers/gpu/drm/drm_fb_helper.c +!Iinclude/drm/drm_fb_helper.h + + + Display Port Helper Functions Reference +!Pdrivers/gpu/drm/drm_dp_helper.c dp helpers +!Iinclude/drm/drm_dp_helper.h +!Edrivers/gpu/drm/drm_dp_helper.c + + + Display Port MST Helper Functions Reference +!Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper +!Iinclude/drm/drm_dp_mst_helper.h +!Edrivers/gpu/drm/drm_dp_mst_topology.c + + + MIPI DSI Helper Functions Reference +!Pdrivers/gpu/drm/drm_mipi_dsi.c dsi helpers +!Iinclude/drm/drm_mipi_dsi.h +!Edrivers/gpu/drm/drm_mipi_dsi.c + + + EDID Helper Functions Reference +!Edrivers/gpu/drm/drm_edid.c + + + Rectangle Utilities Reference +!Pinclude/drm/drm_rect.h rect utils +!Iinclude/drm/drm_rect.h +!Edrivers/gpu/drm/drm_rect.c + + + Flip-work Helper Reference +!Pinclude/drm/drm_flip_work.h flip utils +!Iinclude/drm/drm_flip_work.h +!Edrivers/gpu/drm/drm_flip_work.c + + + HDMI Infoframes Helper Reference + + Strictly speaking this is not a DRM helper library but generally useable + by any driver interfacing with HDMI outputs like v4l or alsa drivers. + But it nicely fits into the overall topic of mode setting helper + libraries and hence is also included here. + +!Iinclude/linux/hdmi.h +!Edrivers/video/hdmi.c + + + Plane Helper Reference +!Edrivers/gpu/drm/drm_plane_helper.c +!Pdrivers/gpu/drm/drm_plane_helper.c overview + + + Tile group +!Pdrivers/gpu/drm/drm_crtc.c Tile group + + + Bridges + + Overview +!Pdrivers/gpu/drm/drm_bridge.c overview + + + Default bridge callback sequence +!Pdrivers/gpu/drm/drm_bridge.c bridge callbacks + +!Edrivers/gpu/drm/drm_bridge.c + + + + + + + KMS Properties + + Drivers may need to expose additional parameters to applications than + those described in the previous sections. KMS supports attaching + properties to CRTCs, connectors and planes and offers a userspace API to + list, get and set the property values. + + + Properties are identified by a name that uniquely defines the property + purpose, and store an associated value. For all property types except blob + properties the value is a 64-bit unsigned integer. + + + KMS differentiates between properties and property instances. Drivers + first create properties and then create and associate individual instances + of those properties to objects. A property can be instantiated multiple + times and associated with different objects. Values are stored in property + instances, and all other property information are stored in the property + and shared between all instances of the property. + + + Every property is created with a type that influences how the KMS core + handles the property. Supported property types are + + + DRM_MODE_PROP_RANGE + Range properties report their minimum and maximum + admissible values. The KMS core verifies that values set by + application fit in that range. + + + DRM_MODE_PROP_ENUM + Enumerated properties take a numerical value that + ranges from 0 to the number of enumerated values defined by the + property minus one, and associate a free-formed string name to each + value. Applications can retrieve the list of defined value-name pairs + and use the numerical value to get and set property instance values. + + + + DRM_MODE_PROP_BITMASK + Bitmask properties are enumeration properties that + additionally restrict all enumerated values to the 0..63 range. + Bitmask property instance values combine one or more of the + enumerated bits defined by the property. + + + DRM_MODE_PROP_BLOB + Blob properties store a binary blob without any format + restriction. The binary blobs are created as KMS standalone objects, + and blob property instance values store the ID of their associated + blob object. + Blob properties are only used for the connector EDID property + and cannot be created by drivers. + + + + + To create a property drivers call one of the following functions depending + on the property type. All property creation functions take property flags + and name, as well as type-specific arguments. + + + struct drm_property *drm_property_create_range(struct drm_device *dev, int flags, + const char *name, + uint64_t min, uint64_t max); + Create a range property with the given minimum and maximum + values. + + + struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags, + const char *name, + const struct drm_prop_enum_list *props, + int num_values); + Create an enumerated property. The props + argument points to an array of num_values + value-name pairs. + + + struct drm_property *drm_property_create_bitmask(struct drm_device *dev, + int flags, const char *name, + const struct drm_prop_enum_list *props, + int num_values); + Create a bitmask property. The props + argument points to an array of num_values + value-name pairs. + + + + + Properties can additionally be created as immutable, in which case they + will be read-only for applications but can be modified by the driver. To + create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE + flag at property creation time. + + + When no array of value-name pairs is readily available at property + creation time for enumerated or range properties, drivers can create + the property using the drm_property_create function + and manually add enumeration value-name pairs by calling the + drm_property_add_enum function. Care must be taken to + properly specify the property type through the flags + argument. + + + After creating properties drivers can attach property instances to CRTC, + connector and plane objects by calling the + drm_object_attach_property. The function takes a + pointer to the target object, a pointer to the previously created property + and an initial instance value. + + + Existing KMS Properties + + The following table gives description of drm properties exposed by various + modules/drivers. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
Owner Module/DriversGroupProperty NameTypeProperty ValuesObject attachedDescription/Restrictions
DRMGeneric“rotation”BITMASK{ 0, "rotate-0" }, + { 1, "rotate-90" }, + { 2, "rotate-180" }, + { 3, "rotate-270" }, + { 4, "reflect-x" }, + { 5, "reflect-y" }CRTC, Planerotate-(degrees) rotates the image by the specified amount in degrees + in counter clockwise direction. reflect-x and reflect-y reflects the + image along the specified axis prior to rotation
Connector“EDID”BLOB | IMMUTABLE0ConnectorContains id of edid blob ptr object.
“DPMS”ENUM{ “On”, “Standby”, “Suspend”, “Off” }ConnectorContains DPMS operation mode value.
“PATH”BLOB | IMMUTABLE0ConnectorContains topology path to a connector.
“TILE”BLOB | IMMUTABLE0ConnectorContains tiling information for a connector.
“CRTC_ID”OBJECTDRM_MODE_OBJECT_CRTCConnectorCRTC that connector is attached to (atomic)
Plane“type”ENUM | IMMUTABLE{ "Overlay", "Primary", "Cursor" }PlanePlane type
“SRC_X”RANGEMin=0, Max=UINT_MAXPlaneScanout source x coordinate in 16.16 fixed point (atomic)
“SRC_Y”RANGEMin=0, Max=UINT_MAXPlaneScanout source y coordinate in 16.16 fixed point (atomic)
“SRC_W”RANGEMin=0, Max=UINT_MAXPlaneScanout source width in 16.16 fixed point (atomic)
“SRC_H”RANGEMin=0, Max=UINT_MAXPlaneScanout source height in 16.16 fixed point (atomic)
“CRTC_X”SIGNED_RANGEMin=INT_MIN, Max=INT_MAXPlaneScanout CRTC (destination) x coordinate (atomic)
“CRTC_Y”SIGNED_RANGEMin=INT_MIN, Max=INT_MAXPlaneScanout CRTC (destination) y coordinate (atomic)
“CRTC_W”RANGEMin=0, Max=UINT_MAXPlaneScanout CRTC (destination) width (atomic)
“CRTC_H”RANGEMin=0, Max=UINT_MAXPlaneScanout CRTC (destination) height (atomic)
“FB_ID”OBJECTDRM_MODE_OBJECT_FBPlaneScanout framebuffer (atomic)
“CRTC_ID”OBJECTDRM_MODE_OBJECT_CRTCPlaneCRTC that plane is attached to (atomic)
DVI-I“subconnector”ENUM{ “Unknown”, “DVI-D”, “DVI-A” }ConnectorTBD
“select subconnector”ENUM{ “Automatic”, “DVI-D”, “DVI-A” }ConnectorTBD
TV“subconnector”ENUM{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }ConnectorTBD
“select subconnector”ENUM{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }ConnectorTBD
“mode”ENUM{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.ConnectorTBD
“left margin”RANGEMin=0, Max=100ConnectorTBD
“right margin”RANGEMin=0, Max=100ConnectorTBD
“top margin”RANGEMin=0, Max=100ConnectorTBD
“bottom margin”RANGEMin=0, Max=100ConnectorTBD
“brightness”RANGEMin=0, Max=100ConnectorTBD
“contrast”RANGEMin=0, Max=100ConnectorTBD
“flicker reduction”RANGEMin=0, Max=100ConnectorTBD
“overscan”RANGEMin=0, Max=100ConnectorTBD
“saturation”RANGEMin=0, Max=100ConnectorTBD
“hue”RANGEMin=0, Max=100ConnectorTBD
Virtual GPU“suggested X”RANGEMin=0, Max=0xffffffffConnectorproperty to suggest an X offset for a connector
“suggested Y”RANGEMin=0, Max=0xffffffffConnectorproperty to suggest an Y offset for a connector
Optional“scaling mode”ENUM{ "None", "Full", "Center", "Full aspect" }ConnectorTBD
"aspect ratio"ENUM{ "None", "4:3", "16:9" }ConnectorDRM property to set aspect ratio from user space app. + This enum is made generic to allow addition of custom aspect + ratios.
“dirty”ENUM | IMMUTABLE{ "Off", "On", "Annotate" }ConnectorTBD
i915Generic"Broadcast RGB"ENUM{ "Automatic", "Full", "Limited 16:235" }ConnectorTBD
“audio”ENUM{ "force-dvi", "off", "auto", "on" }ConnectorTBD
SDVO-TV“mode”ENUM{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.ConnectorTBD
"left_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"right_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"top_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"bottom_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
“hpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“vpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“contrast”RANGEMin=0, Max= SDVO dependentConnectorTBD
“saturation”RANGEMin=0, Max= SDVO dependentConnectorTBD
“hue”RANGEMin=0, Max= SDVO dependentConnectorTBD
“sharpness”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_adaptive”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_2d”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_chroma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_luma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“dot_crawl”RANGEMin=0, Max=1ConnectorTBD
SDVO-TV/LVDS“brightness”RANGEMin=0, Max= SDVO dependentConnectorTBD
CDV gma-500Generic"Broadcast RGB"ENUM{ “Full”, “Limited 16:235” }ConnectorTBD
"Broadcast RGB"ENUM{ “off”, “auto”, “on” }ConnectorTBD
PoulsboGeneric“backlight”RANGEMin=0, Max=100ConnectorTBD
SDVO-TV“mode”ENUM{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.ConnectorTBD
"left_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"right_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"top_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
"bottom_margin"RANGEMin=0, Max= SDVO dependentConnectorTBD
“hpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“vpos”RANGEMin=0, Max= SDVO dependentConnectorTBD
“contrast”RANGEMin=0, Max= SDVO dependentConnectorTBD
“saturation”RANGEMin=0, Max= SDVO dependentConnectorTBD
“hue”RANGEMin=0, Max= SDVO dependentConnectorTBD
“sharpness”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_adaptive”RANGEMin=0, Max= SDVO dependentConnectorTBD
“flicker_filter_2d”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_chroma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“tv_luma_filter”RANGEMin=0, Max= SDVO dependentConnectorTBD
“dot_crawl”RANGEMin=0, Max=1ConnectorTBD
SDVO-TV/LVDS“brightness”RANGEMin=0, Max= SDVO dependentConnectorTBD
armadaCRTC"CSC_YUV"ENUM{ "Auto" , "CCIR601", "CCIR709" }CRTCTBD
"CSC_RGB"ENUM{ "Auto", "Computer system", "Studio" }CRTCTBD
Overlay"colorkey"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_min"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_max"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_val"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_alpha"RANGEMin=0, Max=0xffffffPlaneTBD
"colorkey_mode"ENUM{ "disabled", "Y component", "U component" + , "V component", "RGB", “R component", "G component", "B component" }PlaneTBD
"brightness"RANGEMin=0, Max=256 + 255PlaneTBD
"contrast"RANGEMin=0, Max=0x7fffPlaneTBD
"saturation"RANGEMin=0, Max=0x7fffPlaneTBD
exynosCRTC“mode”ENUM{ "normal", "blank" }CRTCTBD
Overlay“zpos”RANGEMin=0, Max=MAX_PLANE-1PlaneTBD
i2c/ch7006_drvGeneric“scale”RANGEMin=0, Max=2ConnectorTBD
TV“mode”ENUM{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc" + , "PAL-60", "NTSC-M", "NTSC-J" }ConnectorTBD
nouveauNV10 Overlay"colorkey"RANGEMin=0, Max=0x01ffffffPlaneTBD
“contrast”RANGEMin=0, Max=8192-1PlaneTBD
“brightness”RANGEMin=0, Max=1024PlaneTBD
“hue”RANGEMin=0, Max=359PlaneTBD
“saturation”RANGEMin=0, Max=8192-1PlaneTBD
“iturbt_709”RANGEMin=0, Max=1PlaneTBD
Nv04 Overlay“colorkey”RANGEMin=0, Max=0x01ffffffPlaneTBD
“brightness”RANGEMin=0, Max=1024PlaneTBD
Display“dithering mode”ENUM{ "auto", "off", "on" }ConnectorTBD
“dithering depth”ENUM{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }ConnectorTBD
“underscan”ENUM{ "auto", "6 bpc", "8 bpc" }ConnectorTBD
“underscan hborder”RANGEMin=0, Max=128ConnectorTBD
“underscan vborder”RANGEMin=0, Max=128ConnectorTBD
“vibrant hue”RANGEMin=0, Max=180ConnectorTBD
“color vibrance”RANGEMin=0, Max=200ConnectorTBD
omapGeneric“zorder”RANGEMin=0, Max=3CRTC, PlaneTBD
qxlGeneric“hotplug_mode_update"RANGEMin=0, Max=1ConnectorTBD
radeonDVI-I“coherent”RANGEMin=0, Max=1ConnectorTBD
DAC enable load detect“load detection”RANGEMin=0, Max=1ConnectorTBD
TV Standard"tv standard"ENUM{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j" + , "scart-pal", "pal-cn", "secam" }ConnectorTBD
legacy TMDS PLL detect"tmds_pll"ENUM{ "driver", "bios" }-TBD
Underscan"underscan"ENUM{ "off", "on", "auto" }ConnectorTBD
"underscan hborder"RANGEMin=0, Max=128ConnectorTBD
"underscan vborder"RANGEMin=0, Max=128ConnectorTBD
Audio“audio”ENUM{ "off", "on", "auto" }ConnectorTBD
FMT Dithering“dither”ENUM{ "off", "on" }ConnectorTBD
rcar-duGeneric"alpha"RANGEMin=0, Max=255PlaneTBD
"colorkey"RANGEMin=0, Max=0x01ffffffPlaneTBD
"zpos"RANGEMin=1, Max=7PlaneTBD
+ + + + + + + Vertical Blanking + + Vertical blanking plays a major role in graphics rendering. To achieve + tear-free display, users must synchronize page flips and/or rendering to + vertical blanking. The DRM API offers ioctls to perform page flips + synchronized to vertical blanking and wait for vertical blanking. + + + The DRM core handles most of the vertical blanking management logic, which + involves filtering out spurious interrupts, keeping race-free blanking + counters, coping with counter wrap-around and resets and keeping use + counts. It relies on the driver to generate vertical blanking interrupts + and optionally provide a hardware vertical blanking counter. Drivers must + implement the following operations. + + + + int (*enable_vblank) (struct drm_device *dev, int crtc); +void (*disable_vblank) (struct drm_device *dev, int crtc); + + Enable or disable vertical blanking interrupts for the given CRTC. + + + + u32 (*get_vblank_counter) (struct drm_device *dev, int crtc); + + Retrieve the value of the vertical blanking counter for the given + CRTC. If the hardware maintains a vertical blanking counter its value + should be returned. Otherwise drivers can use the + drm_vblank_count helper function to handle this + operation. + + + + + Drivers must initialize the vertical blanking handling core with a call to + drm_vblank_init in their + load operation. The function will set the struct + drm_device + vblank_disable_allowed field to 0. This will + keep vertical blanking interrupts enabled permanently until the first mode + set operation, where vblank_disable_allowed is + set to 1. The reason behind this is not clear. Drivers can set the field + to 1 after calling drm_vblank_init to make vertical + blanking interrupts dynamically managed from the beginning. + + + Vertical blanking interrupts can be enabled by the DRM core or by drivers + themselves (for instance to handle page flipping operations). The DRM core + maintains a vertical blanking use count to ensure that the interrupts are + not disabled while a user still needs them. To increment the use count, + drivers call drm_vblank_get. Upon return vertical + blanking interrupts are guaranteed to be enabled. + + + To decrement the use count drivers call + drm_vblank_put. Only when the use count drops to zero + will the DRM core disable the vertical blanking interrupts after a delay + by scheduling a timer. The delay is accessible through the vblankoffdelay + module parameter or the drm_vblank_offdelay global + variable and expressed in milliseconds. Its default value is 5000 ms. + Zero means never disable, and a negative value means disable immediately. + Drivers may override the behaviour by setting the + drm_device + vblank_disable_immediate flag, which when set + causes vblank interrupts to be disabled immediately regardless of the + drm_vblank_offdelay value. The flag should only be set if there's a + properly working hardware vblank counter present. + + + When a vertical blanking interrupt occurs drivers only need to call the + drm_handle_vblank function to account for the + interrupt. + + + Resources allocated by drm_vblank_init must be freed + with a call to drm_vblank_cleanup in the driver + unload operation handler. + + + Vertical Blanking and Interrupt Handling Functions Reference +!Edrivers/gpu/drm/drm_irq.c +!Finclude/drm/drmP.h drm_crtc_vblank_waitqueue + + + + + + + Open/Close, File Operations and IOCTLs + + Open and Close + int (*firstopen) (struct drm_device *); +void (*lastclose) (struct drm_device *); +int (*open) (struct drm_device *, struct drm_file *); +void (*preclose) (struct drm_device *, struct drm_file *); +void (*postclose) (struct drm_device *, struct drm_file *); + Open and close handlers. None of those methods are mandatory. + + + The firstopen method is called by the DRM core + for legacy UMS (User Mode Setting) drivers only when an application + opens a device that has no other opened file handle. UMS drivers can + implement it to acquire device resources. KMS drivers can't use the + method and must acquire resources in the load + method instead. + + + Similarly the lastclose method is called when + the last application holding a file handle opened on the device closes + it, for both UMS and KMS drivers. Additionally, the method is also + called at module unload time or, for hot-pluggable devices, when the + device is unplugged. The firstopen and + lastclose calls can thus be unbalanced. + + + The open method is called every time the device + is opened by an application. Drivers can allocate per-file private data + in this method and store them in the struct + drm_file driver_priv + field. Note that the open method is called + before firstopen. + + + The close operation is split into preclose and + postclose methods. Drivers must stop and + cleanup all per-file operations in the preclose + method. For instance pending vertical blanking and page flip events must + be cancelled. No per-file operation is allowed on the file handle after + returning from the preclose method. + + + Finally the postclose method is called as the + last step of the close operation, right before calling the + lastclose method if no other open file handle + exists for the device. Drivers that have allocated per-file private data + in the open method should free it here. + + + The lastclose method should restore CRTC and + plane properties to default value, so that a subsequent open of the + device will not inherit state from the previous user. It can also be + used to execute delayed power switching state changes, e.g. in + conjunction with the vga_switcheroo infrastructure. Beyond that KMS + drivers should not do any further cleanup. Only legacy UMS drivers might + need to clean up device state so that the vga console or an independent + fbdev driver could take over. + + + + File Operations + const struct file_operations *fops + File operations for the DRM device node. + + Drivers must define the file operations structure that forms the DRM + userspace API entry point, even though most of those operations are + implemented in the DRM core. The open, + release and ioctl + operations are handled by + + .owner = THIS_MODULE, + .open = drm_open, + .release = drm_release, + .unlocked_ioctl = drm_ioctl, + #ifdef CONFIG_COMPAT + .compat_ioctl = drm_compat_ioctl, + #endif + + + + Drivers that implement private ioctls that requires 32/64bit + compatibility support must provide their own + compat_ioctl handler that processes private + ioctls and calls drm_compat_ioctl for core ioctls. + + + The read and poll + operations provide support for reading DRM events and polling them. They + are implemented by + + .poll = drm_poll, + .read = drm_read, + .llseek = no_llseek, + + + + The memory mapping implementation varies depending on how the driver + manages memory. Pre-GEM drivers will use drm_mmap, + while GEM-aware drivers will use drm_gem_mmap. See + . + + .mmap = drm_gem_mmap, + + + + No other file operation is supported by the DRM API. + + + + IOCTLs + struct drm_ioctl_desc *ioctls; +int num_ioctls; + Driver-specific ioctls descriptors table. + + Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls + descriptors table is indexed by the ioctl number offset from the base + value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the + table entries. + + + DRM_IOCTL_DEF_DRV(ioctl, func, flags) + + ioctl is the ioctl name. Drivers must define + the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number + offset from DRM_COMMAND_BASE and the ioctl number respectively. The + first macro is private to the device while the second must be exposed + to userspace in a public header. + + + func is a pointer to the ioctl handler function + compatible with the drm_ioctl_t type. + typedef int drm_ioctl_t(struct drm_device *dev, void *data, + struct drm_file *file_priv); + + + flags is a bitmask combination of the following + values. It restricts how the ioctl is allowed to be called. + + + DRM_AUTH - Only authenticated callers allowed + + + DRM_MASTER - The ioctl can only be called on the master file + handle + + + DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed + + + DRM_CONTROL_ALLOW - The ioctl can only be called on a control + device + + + DRM_UNLOCKED - The ioctl handler will be called without locking + the DRM global mutex + + + + + + + + Legacy Support Code + + The section very briefly covers some of the old legacy support code which + is only used by old DRM drivers which have done a so-called shadow-attach + to the underlying device instead of registering as a real driver. This + also includes some of the old generic buffer management and command + submission code. Do not use any of this in new and modern drivers. + + + + Legacy Suspend/Resume + + The DRM core provides some suspend/resume code, but drivers wanting full + suspend/resume support should provide save() and restore() functions. + These are called at suspend, hibernate, or resume time, and should perform + any state save or restore required by your device across suspend or + hibernate states. + + int (*suspend) (struct drm_device *, pm_message_t state); + int (*resume) (struct drm_device *); + + Those are legacy suspend and resume methods which + only work with the legacy shadow-attach driver + registration functions. New driver should use the power management + interface provided by their bus type (usually through + the struct device_driver dev_pm_ops) and set + these methods to NULL. + + + + + Legacy DMA Services + + This should cover how DMA mapping etc. is supported by the core. + These functions are deprecated and should not be used. + + + + + + + + + + + Userland interfaces + + The DRM core exports several interfaces to applications, + generally intended to be used through corresponding libdrm + wrapper functions. In addition, drivers export device-specific + interfaces for use by userspace drivers & device-aware + applications through ioctls and sysfs files. + + + External interfaces include: memory mapping, context management, + DMA operations, AGP management, vblank control, fence + management, memory management, and output management. + + + Cover generic ioctls and sysfs layout here. We only need high-level + info, since man pages should cover the rest. + + + + + + Render nodes + + DRM core provides multiple character-devices for user-space to use. + Depending on which device is opened, user-space can perform a different + set of operations (mainly ioctls). The primary node is always created + and called card<num>. Additionally, a currently + unused control node, called controlD<num> is also + created. The primary node provides all legacy operations and + historically was the only interface used by userspace. With KMS, the + control node was introduced. However, the planned KMS control interface + has never been written and so the control node stays unused to date. + + + With the increased use of offscreen renderers and GPGPU applications, + clients no longer require running compositors or graphics servers to + make use of a GPU. But the DRM API required unprivileged clients to + authenticate to a DRM-Master prior to getting GPU access. To avoid this + step and to grant clients GPU access without authenticating, render + nodes were introduced. Render nodes solely serve render clients, that + is, no modesetting or privileged ioctls can be issued on render nodes. + Only non-global rendering commands are allowed. If a driver supports + render nodes, it must advertise it via the DRIVER_RENDER + DRM driver capability. If not supported, the primary node must be used + for render clients together with the legacy drmAuth authentication + procedure. + + + If a driver advertises render node support, DRM core will create a + separate render node called renderD<num>. There will + be one render node per device. No ioctls except PRIME-related ioctls + will be allowed on this node. Especially GEM_OPEN will be + explicitly prohibited. Render nodes are designed to avoid the + buffer-leaks, which occur if clients guess the flink names or mmap + offsets on the legacy interface. Additionally to this basic interface, + drivers must mark their driver-dependent render-only ioctls as + DRM_RENDER_ALLOW so render clients can use them. Driver + authors must be careful not to allow any privileged ioctls on render + nodes. + + + With render nodes, user-space can now control access to the render node + via basic file-system access-modes. A running graphics server which + authenticates clients on the privileged primary/legacy node is no longer + required. Instead, a client can open the render node and is immediately + granted GPU access. Communication between clients (or servers) is done + via PRIME. FLINK from render node to legacy node is not supported. New + clients must not use the insecure FLINK interface. + + + Besides dropping all modeset/global ioctls, render nodes also drop the + DRM-Master concept. There is no reason to associate render clients with + a DRM-Master as they are independent of any graphics server. Besides, + they must work without any running master, anyway. + Drivers must be able to run without a master object if they support + render nodes. If, on the other hand, a driver requires shared state + between clients which is visible to user-space and accessible beyond + open-file boundaries, they cannot support render nodes. + + + + + + + VBlank event handling + + The DRM core exposes two vertical blank related ioctls: + + + DRM_IOCTL_WAIT_VBLANK + + + This takes a struct drm_wait_vblank structure as its argument, + and it is used to block or request a signal when a specified + vblank event occurs. + + + + + DRM_IOCTL_MODESET_CTL + + + This was only used for user-mode-settind drivers around + modesetting changes to allow the kernel to update the vblank + interrupt after mode setting, since on many devices the vertical + blank counter is reset to 0 at some point during modeset. Modern + drivers should not call this any more since with kernel mode + setting it is a no-op. + + + + + + + + + + + DRM Drivers + + + + This second part of the DRM Developer's Guide documents driver code, + implementation details and also all the driver-specific userspace + interfaces. Especially since all hardware-acceleration interfaces to + userspace are driver specific for efficiency and other reasons these + interfaces can be rather substantial. Hence every driver has its own + chapter. + + + + + drm/i915 Intel GFX Driver + + The drm/i915 driver supports all (with the exception of some very early + models) integrated GFX chipsets with both Intel display and rendering + blocks. This excludes a set of SoC platforms with an SGX rendering unit, + those have basic support through the gma500 drm driver. + + + Core Driver Infrastructure + + This section covers core driver infrastructure used by both the display + and the GEM parts of the driver. + + + Runtime Power Management +!Pdrivers/gpu/drm/i915/intel_runtime_pm.c runtime pm +!Idrivers/gpu/drm/i915/intel_runtime_pm.c +!Idrivers/gpu/drm/i915/intel_uncore.c + + + Interrupt Handling +!Pdrivers/gpu/drm/i915/i915_irq.c interrupt handling +!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_init intel_irq_init_hw intel_hpd_init +!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_disable_interrupts +!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_enable_interrupts + + + Intel GVT-g Guest Support(vGPU) +!Pdrivers/gpu/drm/i915/i915_vgpu.c Intel GVT-g guest support +!Idrivers/gpu/drm/i915/i915_vgpu.c + + + + Display Hardware Handling + + This section covers everything related to the display hardware including + the mode setting infrastructure, plane, sprite and cursor handling and + display, output probing and related topics. + + + Mode Setting Infrastructure + + The i915 driver is thus far the only DRM driver which doesn't use the + common DRM helper code to implement mode setting sequences. Thus it + has its own tailor-made infrastructure for executing a display + configuration change. + + + + Frontbuffer Tracking +!Pdrivers/gpu/drm/i915/intel_frontbuffer.c frontbuffer tracking +!Idrivers/gpu/drm/i915/intel_frontbuffer.c +!Fdrivers/gpu/drm/i915/i915_gem.c i915_gem_track_fb + + + Display FIFO Underrun Reporting +!Pdrivers/gpu/drm/i915/intel_fifo_underrun.c fifo underrun handling +!Idrivers/gpu/drm/i915/intel_fifo_underrun.c + + + Plane Configuration + + This section covers plane configuration and composition with the + primary plane, sprites, cursors and overlays. This includes the + infrastructure to do atomic vsync'ed updates of all this state and + also tightly coupled topics like watermark setup and computation, + framebuffer compression and panel self refresh. + + + + Atomic Plane Helpers +!Pdrivers/gpu/drm/i915/intel_atomic_plane.c atomic plane helpers +!Idrivers/gpu/drm/i915/intel_atomic_plane.c + + + Output Probing + + This section covers output probing and related infrastructure like the + hotplug interrupt storm detection and mitigation code. Note that the + i915 driver still uses most of the common DRM helper code for output + probing, so those sections fully apply. + + + + Hotplug +!Pdrivers/gpu/drm/i915/intel_hotplug.c Hotplug +!Idrivers/gpu/drm/i915/intel_hotplug.c + + + High Definition Audio +!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port +!Idrivers/gpu/drm/i915/intel_audio.c + + + Panel Self Refresh PSR (PSR/SRD) +!Pdrivers/gpu/drm/i915/intel_psr.c Panel Self Refresh (PSR/SRD) +!Idrivers/gpu/drm/i915/intel_psr.c + + + Frame Buffer Compression (FBC) +!Pdrivers/gpu/drm/i915/intel_fbc.c Frame Buffer Compression (FBC) +!Idrivers/gpu/drm/i915/intel_fbc.c + + + Display Refresh Rate Switching (DRRS) +!Pdrivers/gpu/drm/i915/intel_dp.c Display Refresh Rate Switching (DRRS) +!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_set_drrs_state +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_enable +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_disable +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_invalidate +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_flush +!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_drrs_init + + + + DPIO +!Pdrivers/gpu/drm/i915/i915_reg.h DPIO + + + + CSR firmware support for DMC +!Pdrivers/gpu/drm/i915/intel_csr.c csr support for dmc +!Idrivers/gpu/drm/i915/intel_csr.c + + + + + Memory Management and Command Submission + + This sections covers all things related to the GEM implementation in the + i915 driver. + + + Batchbuffer Parsing +!Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser +!Idrivers/gpu/drm/i915/i915_cmd_parser.c + + + Batchbuffer Pools +!Pdrivers/gpu/drm/i915/i915_gem_batch_pool.c batch pool +!Idrivers/gpu/drm/i915/i915_gem_batch_pool.c + + + Logical Rings, Logical Ring Contexts and Execlists +!Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists +!Idrivers/gpu/drm/i915/intel_lrc.c + + + Global GTT views +!Pdrivers/gpu/drm/i915/i915_gem_gtt.c Global GTT views +!Idrivers/gpu/drm/i915/i915_gem_gtt.c + + + GTT Fences and Swizzling +!Idrivers/gpu/drm/i915/i915_gem_fence.c + + Global GTT Fence Handling +!Pdrivers/gpu/drm/i915/i915_gem_fence.c fence register handling + + + Hardware Tiling and Swizzling Details +!Pdrivers/gpu/drm/i915/i915_gem_fence.c tiling swizzling details + + + + Object Tiling IOCTLs +!Idrivers/gpu/drm/i915/i915_gem_tiling.c +!Pdrivers/gpu/drm/i915/i915_gem_tiling.c buffer object tiling + + + Buffer Object Eviction + + This section documents the interface functions for evicting buffer + objects to make space available in the virtual gpu address spaces. + Note that this is mostly orthogonal to shrinking buffer objects + caches, which has the goal to make main memory (shared with the gpu + through the unified memory architecture) available. + +!Idrivers/gpu/drm/i915/i915_gem_evict.c + + + Buffer Object Memory Shrinking + + This section documents the interface function for shrinking memory + usage of buffer object caches. Shrinking is used to make main memory + available. Note that this is mostly orthogonal to evicting buffer + objects, which has the goal to make space in gpu virtual address + spaces. + +!Idrivers/gpu/drm/i915/i915_gem_shrinker.c + + + + GuC-based Command Submission + + GuC +!Pdrivers/gpu/drm/i915/intel_guc_loader.c GuC-specific firmware loader +!Idrivers/gpu/drm/i915/intel_guc_loader.c + + + GuC Client +!Pdrivers/gpu/drm/i915/i915_guc_submission.c GuC-based command submissison +!Idrivers/gpu/drm/i915/i915_guc_submission.c + + + + + Tracing + + This sections covers all things related to the tracepoints implemented in + the i915 driver. + + + i915_ppgtt_create and i915_ppgtt_release +!Pdrivers/gpu/drm/i915/i915_trace.h i915_ppgtt_create and i915_ppgtt_release tracepoints + + + i915_context_create and i915_context_free +!Pdrivers/gpu/drm/i915/i915_trace.h i915_context_create and i915_context_free tracepoints + + + switch_mm +!Pdrivers/gpu/drm/i915/i915_trace.h switch_mm tracepoint + + + + +!Cdrivers/gpu/drm/i915/i915_irq.c + +