From patchwork Tue Dec 18 17:59:36 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shuah X-Patchwork-Id: 10736087 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C70406C2 for ; Tue, 18 Dec 2018 17:59:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B28B12AA84 for ; Tue, 18 Dec 2018 17:59:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A67392AA90; Tue, 18 Dec 2018 17:59:51 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9739A2AAA6 for ; Tue, 18 Dec 2018 17:59:50 +0000 (UTC) Received: from alsa0.perex.cz (localhost [127.0.0.1]) by alsa0.perex.cz (Postfix) with ESMTP id D3461267946; Tue, 18 Dec 2018 18:59:48 +0100 (CET) X-Original-To: alsa-devel@alsa-project.org Delivered-To: alsa-devel@alsa-project.org Received: by alsa0.perex.cz (Postfix, from userid 1000) id CB62D267ACB; Tue, 18 Dec 2018 18:59:46 +0100 (CET) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by alsa0.perex.cz (Postfix) with ESMTP id EE48826782E for ; Tue, 18 Dec 2018 18:59:43 +0100 (CET) Received: from localhost.localdomain (c-24-9-64-241.hsd1.co.comcast.net [24.9.64.241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9FCD5218A4; Tue, 18 Dec 2018 17:59:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545155983; bh=pnt6TDP7y5RANK4IplsrjGNjrKbIp1LoT81svnMoqK8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=acNbpPneWtzpCRonHyB7tHpFP8hnx70/e7TPDVX6HylSn6o8gjxhyRFlkslSGURmy wVIKhdcrFN1HM3kRmaVoP/rGA4tDzchkQlYei9lvjWq9iYRlXApS03DetVnfMkk3Cw gm5DqoTVOdh2dIWTisHfm1rZW1f3ntwROvEaa7Ws= From: shuah@kernel.org To: mchehab@kernel.org, perex@perex.cz, tiwai@suse.com, hverkuil@xs4all.nl Date: Tue, 18 Dec 2018 10:59:36 -0700 Message-Id: <33aac16e561f4c685de0d5a77db2ec4dce67c15f.1545154778.git.shuah@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: References: MIME-Version: 1.0 Cc: alsa-devel@alsa-project.org, Shuah Khan , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org Subject: [alsa-devel] [PATCH v9 1/4] media: Media Device Allocator API X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org X-Virus-Scanned: ClamAV using ClamSMTP From: Shuah Khan Media Device Allocator API to allows multiple drivers share a media device. This API solves a very common use-case for media devices where one physical device (an USB stick) provides both audio and video. When such media device exposes a standard USB Audio class, a proprietary Video class, two or more independent drivers will share a single physical USB bridge. In such cases, it is necessary to coordinate access to the shared resource. Using this API, drivers can allocate a media device with the shared struct device as the key. Once the media device is allocated by a driver, other drivers can get a reference to it. The media device is released when all the references are released. Signed-off-by: Shuah Khan --- Documentation/media/kapi/mc-core.rst | 41 +++++++++ drivers/media/Makefile | 4 + drivers/media/media-dev-allocator.c | 132 +++++++++++++++++++++++++++ include/media/media-dev-allocator.h | 53 +++++++++++ 4 files changed, 230 insertions(+) create mode 100644 drivers/media/media-dev-allocator.c create mode 100644 include/media/media-dev-allocator.h diff --git a/Documentation/media/kapi/mc-core.rst b/Documentation/media/kapi/mc-core.rst index 69362b3135c2..022381fc1f66 100644 --- a/Documentation/media/kapi/mc-core.rst +++ b/Documentation/media/kapi/mc-core.rst @@ -257,6 +257,45 @@ Subsystems should facilitate link validation by providing subsystem specific helper functions to provide easy access for commonly needed information, and in the end provide a way to use driver-specific callbacks. +Media Controller Device Allocator API +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +When the media device belongs to more than one driver, the shared media +device is allocated with the shared struct device as the key for look ups. + +The shared media device should stay in registered state until the last +driver unregisters it. In addition, the media device should be released when +all the references are released. Each driver gets a reference to the media +device during probe, when it allocates the media device. If media device is +already allocated, the allocate API bumps up the refcount and returns the +existing media device. The driver puts the reference back in its disconnect +routine when it calls :c:func:`media_device_delete()`. + +The media device is unregistered and cleaned up from the kref put handler to +ensure that the media device stays in registered state until the last driver +unregisters the media device. + +**Driver Usage** + +Drivers should use the appropriate media-core routines to manage the shared +media device life-time handling the two states: +1. allocate -> register -> delete +2. get reference to already registered device -> delete + +call :c:func:`media_device_delete()` routine to make sure the shared media +device delete is handled correctly. + +**driver probe:** +Call :c:func:`media_device_usb_allocate()` to allocate or get a reference +Call :c:func:`media_device_register()`, if media devnode isn't registered + +**driver disconnect:** +Call :c:func:`media_device_delete()` to free the media_device. Freeing is +handled by the kref put handler. + +API Definitions +^^^^^^^^^^^^^^^ + .. kernel-doc:: include/media/media-device.h .. kernel-doc:: include/media/media-devnode.h @@ -264,3 +303,5 @@ in the end provide a way to use driver-specific callbacks. .. kernel-doc:: include/media/media-entity.h .. kernel-doc:: include/media/media-request.h + +.. kernel-doc:: include/media/media-dev-allocator.h diff --git a/drivers/media/Makefile b/drivers/media/Makefile index 985d35ec6b29..1d7653318af6 100644 --- a/drivers/media/Makefile +++ b/drivers/media/Makefile @@ -6,6 +6,10 @@ media-objs := media-device.o media-devnode.o media-entity.o \ media-request.o +ifeq ($(CONFIG_USB),y) + media-objs += media-dev-allocator.o +endif + # # I2C drivers should come before other drivers, otherwise they'll fail # when compiled as builtin drivers diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c new file mode 100644 index 000000000000..82b450cbc998 --- /dev/null +++ b/drivers/media/media-dev-allocator.c @@ -0,0 +1,132 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * media-dev-allocator.c - Media Controller Device Allocator API + * + * Copyright (c) 2018 Shuah Khan + * + * Credits: Suggested by Laurent Pinchart + */ + +/* + * This file adds a global refcounted Media Controller Device Instance API. + * A system wide global media device list is managed and each media device + * includes a kref count. The last put on the media device releases the media + * device instance. + * + */ + +#include +#include +#include +#include + +#include + +static LIST_HEAD(media_device_list); +static DEFINE_MUTEX(media_device_lock); + +struct media_device_instance { + struct media_device mdev; + struct module *owner; + struct list_head list; + struct kref refcount; +}; + +static inline struct media_device_instance * +to_media_device_instance(struct media_device *mdev) +{ + return container_of(mdev, struct media_device_instance, mdev); +} + +static void media_device_instance_release(struct kref *kref) +{ + struct media_device_instance *mdi = + container_of(kref, struct media_device_instance, refcount); + + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); + + mutex_lock(&media_device_lock); + + media_device_unregister(&mdi->mdev); + media_device_cleanup(&mdi->mdev); + + list_del(&mdi->list); + mutex_unlock(&media_device_lock); + + kfree(mdi); +} + +/* Callers should hold media_device_lock when calling this function */ +static struct media_device *__media_device_get(struct device *dev, + const char *module_name) +{ + struct media_device_instance *mdi; + + list_for_each_entry(mdi, &media_device_list, list) { + if (mdi->mdev.dev != dev) + continue; + + kref_get(&mdi->refcount); + /* get module reference for the media_device owner */ + if (find_module(module_name) != mdi->owner && + !try_module_get(mdi->owner)) + dev_err(dev, "%s: try_module_get() error\n", __func__); + dev_dbg(dev, "%s: get mdev=%p module_name %s\n", + __func__, &mdi->mdev, module_name); + return &mdi->mdev; + } + + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); + if (!mdi) + return NULL; + + mdi->owner = find_module(module_name); + kref_init(&mdi->refcount); + list_add_tail(&mdi->list, &media_device_list); + + dev_dbg(dev, "%s: alloc mdev=%p module_name %s\n", __func__, + &mdi->mdev, module_name); + return &mdi->mdev; +} + +#if IS_ENABLED(CONFIG_USB) +struct media_device *media_device_usb_allocate(struct usb_device *udev, + const char *module_name) +{ + struct media_device *mdev; + + mutex_lock(&media_device_lock); + mdev = __media_device_get(&udev->dev, module_name); + if (!mdev) { + mutex_unlock(&media_device_lock); + return ERR_PTR(-ENOMEM); + } + + /* check if media device is already initialized */ + if (!mdev->dev) + __media_device_usb_init(mdev, udev, udev->product, + module_name); + mutex_unlock(&media_device_lock); + return mdev; +} +EXPORT_SYMBOL_GPL(media_device_usb_allocate); +#endif + +void media_device_delete(struct media_device *mdev, const char *module_name) +{ + struct media_device_instance *mdi = to_media_device_instance(mdev); + + dev_dbg(mdi->mdev.dev, "%s: mdev=%p module_name %s\n", + __func__, &mdi->mdev, module_name); + + mutex_lock(&media_device_lock); + /* put module reference if media_device owner is not THIS_MODULE */ + if (mdi->owner != find_module(module_name)) { + module_put(mdi->owner); + dev_dbg(mdi->mdev.dev, + "%s decremented owner module reference\n", __func__); + } + mutex_unlock(&media_device_lock); + kref_put(&mdi->refcount, media_device_instance_release); +} +EXPORT_SYMBOL_GPL(media_device_delete); diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h new file mode 100644 index 000000000000..9164795e911c --- /dev/null +++ b/include/media/media-dev-allocator.h @@ -0,0 +1,53 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * media-dev-allocator.h - Media Controller Device Allocator API + * + * Copyright (c) 2018 Shuah Khan + * + * Credits: Suggested by Laurent Pinchart + */ + +/* + * This file adds a global ref-counted Media Controller Device Instance API. + * A system wide global media device list is managed and each media device + * includes a kref count. The last put on the media device releases the media + * device instance. + */ + +#ifndef _MEDIA_DEV_ALLOCTOR_H +#define _MEDIA_DEV_ALLOCTOR_H + +struct usb_device; + +#if defined(CONFIG_MEDIA_CONTROLLER) && defined(CONFIG_USB) +/** + * media_device_usb_allocate() - Allocate and return struct &media device + * + * @udev: struct &usb_device pointer + * @module_name: should be filled with %KBUILD_MODNAME + * + * This interface should be called to allocate a Media Device when multiple + * drivers share usb_device and the media device. This interface allocates + * &media_device structure and calls media_device_usb_init() to initialize + * it. + * + */ +struct media_device *media_device_usb_allocate(struct usb_device *udev, + char *module_name); +/** + * media_device_delete() - Release media device. Calls kref_put(). + * + * @mdev: struct &media_device pointer + * @module_name: should be filled with %KBUILD_MODNAME + * + * This interface should be called to put Media Device Instance kref. + */ +void media_device_delete(struct media_device *mdev, char *module_name); +#else +static inline struct media_device *media_device_usb_allocate( + struct usb_device *udev, char *module_name) + { return NULL; } +static inline void media_device_delete( + struct media_device *mdev, char *module_name) { } +#endif /* CONFIG_MEDIA_CONTROLLER */ +#endif