diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 196b8b9..44a2c66 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -6,11 +6,36 @@
   <bookinfo>
     <title>Linux DRM Developer's Guide</title>
 
+    <authorgroup>
+      <author>
+	<firstname>Jesse</firstname>
+	<surname>Barnes</surname>
+	<contrib>Initial version</contrib>
+	<affiliation>
+	  <orgname>Intel Corporation</orgname>
+	  <address>
+	    <email>jesse.barnes@intel.com</email>
+	  </address>
+	</affiliation>
+      </author>
+      <author>
+	<firstname>Laurent</firstname>
+	<surname>Pinchart</surname>
+	<contrib>Driver internals</contrib>
+	<affiliation>
+	  <orgname>Ideas on board SPRL</orgname>
+	  <address>
+	    <email>laurent.pinchart@ideasonboard.com</email>
+	  </address>
+	</affiliation>
+      </author>
+    </authorgroup>
+
     <copyright>
       <year>2008-2009</year>
-      <holder>
-	Intel Corporation (Jesse Barnes &lt;jesse.barnes@intel.com&gt;)
-      </holder>
+      <year>2012</year>
+      <holder>Intel Corporation</holder>
+      <holder>Laurent Pinchart</holder>
     </copyright>
 
     <legalnotice>
@@ -20,6 +45,17 @@
 	the kernel source COPYING file.
       </para>
     </legalnotice>
+
+    <revhistory>
+      <!-- Put document revisions here, newest first. -->
+      <revision>
+	<revnumber>1.0</revnumber>
+	<date>2012-07-13</date>
+	<authorinitials>LP</authorinitials>
+	<revremark>Added extensive documentation about driver internals.
+	</revremark>
+      </revision>
+    </revhistory>
   </bookinfo>
 
 <toc></toc>
@@ -72,342 +108,361 @@
       submission &amp; fencing, suspend/resume support, and DMA
       services.
     </para>
-    <para>
-      The core of every DRM driver is struct drm_driver.  Drivers
-      typically statically initialize a drm_driver structure,
-      then pass it to drm_init() at load time.
-    </para>
 
   <!-- Internals: driver init -->
 
   <sect1>
-    <title>Driver initialization</title>
-    <para>
-      Before calling the DRM initialization routines, the driver must
-      first create and fill out a struct drm_driver structure.
-    </para>
-    <programlisting>
-      static struct drm_driver driver = {
-	/* Don't use MTRRs here; the Xserver or userspace app should
-	 * deal with them for Intel hardware.
-	 */
-	.driver_features =
-	    DRIVER_USE_AGP | DRIVER_REQUIRE_AGP |
-	    DRIVER_HAVE_IRQ | DRIVER_IRQ_SHARED | DRIVER_MODESET,
-	.load = i915_driver_load,
-	.unload = i915_driver_unload,
-	.firstopen = i915_driver_firstopen,
-	.lastclose = i915_driver_lastclose,
-	.preclose = i915_driver_preclose,
-	.save = i915_save,
-	.restore = i915_restore,
-	.device_is_agp = i915_driver_device_is_agp,
-	.get_vblank_counter = i915_get_vblank_counter,
-	.enable_vblank = i915_enable_vblank,
-	.disable_vblank = i915_disable_vblank,
-	.irq_preinstall = i915_driver_irq_preinstall,
-	.irq_postinstall = i915_driver_irq_postinstall,
-	.irq_uninstall = i915_driver_irq_uninstall,
-	.irq_handler = i915_driver_irq_handler,
-	.reclaim_buffers = drm_core_reclaim_buffers,
-	.get_map_ofs = drm_core_get_map_ofs,
-	.get_reg_ofs = drm_core_get_reg_ofs,
-	.fb_probe = intelfb_probe,
-	.fb_remove = intelfb_remove,
-	.fb_resize = intelfb_resize,
-	.master_create = i915_master_create,
-	.master_destroy = i915_master_destroy,
-#if defined(CONFIG_DEBUG_FS)
-	.debugfs_init = i915_debugfs_init,
-	.debugfs_cleanup = i915_debugfs_cleanup,
-#endif
-	.gem_init_object = i915_gem_init_object,
-	.gem_free_object = i915_gem_free_object,
-	.gem_vm_ops = &amp;i915_gem_vm_ops,
-	.ioctls = i915_ioctls,
-	.fops = {
-		.owner = THIS_MODULE,
-		.open = drm_open,
-		.release = drm_release,
-		.ioctl = drm_ioctl,
-		.mmap = drm_mmap,
-		.poll = drm_poll,
-		.fasync = drm_fasync,
-#ifdef CONFIG_COMPAT
-		.compat_ioctl = i915_compat_ioctl,
-#endif
-		.llseek = noop_llseek,
-		},
-	.pci_driver = {
-		.name = DRIVER_NAME,
-		.id_table = pciidlist,
-		.probe = probe,
-		.remove = __devexit_p(drm_cleanup_pci),
-		},
-	.name = DRIVER_NAME,
-	.desc = DRIVER_DESC,
-	.date = DRIVER_DATE,
-	.major = DRIVER_MAJOR,
-	.minor = DRIVER_MINOR,
-	.patchlevel = DRIVER_PATCHLEVEL,
-      };
-    </programlisting>
-    <para>
-      In the example above, taken from the i915 DRM driver, the driver
-      sets several flags indicating what core features it supports;
-      we go over the individual callbacks in later sections.  Since
-      flags indicate which features your driver supports to the DRM
-      core, you need to set most of them prior to calling drm_init().  Some,
-      like DRIVER_MODESET can be set later based on user supplied parameters,
-      but that's the exception rather than the rule.
-    </para>
-    <variablelist>
-      <title>Driver flags</title>
-      <varlistentry>
-	<term>DRIVER_USE_AGP</term>
-	<listitem><para>
-	    Driver uses AGP interface
-	</para></listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_REQUIRE_AGP</term>
-	<listitem><para>
-	    Driver needs AGP interface to function.
-	</para></listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_USE_MTRR</term>
-	<listitem>
-	  <para>
-	    Driver uses MTRR interface for mapping memory.  Deprecated.
-	  </para>
-	</listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_PCI_DMA</term>
-	<listitem><para>
-	    Driver is capable of PCI DMA.  Deprecated.
-	</para></listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_SG</term>
-	<listitem><para>
-	    Driver can perform scatter/gather DMA.  Deprecated.
-	</para></listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_HAVE_DMA</term>
-	<listitem><para>Driver supports DMA.  Deprecated.</para></listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term>
-	<listitem>
-	  <para>
-	    DRIVER_HAVE_IRQ indicates whether the driver has an IRQ
-	    handler.  DRIVER_IRQ_SHARED indicates whether the device &amp;
-	    handler support shared IRQs (note that this is required of
-	    PCI drivers).
-	  </para>
-	</listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_DMA_QUEUE</term>
-	<listitem>
-	  <para>
-	    Should be set if the driver queues DMA requests and completes them
-	    asynchronously.  Deprecated.
-	  </para>
-	</listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_FB_DMA</term>
-	<listitem>
-	  <para>
-	    Driver supports DMA to/from the framebuffer.  Deprecated.
-	  </para>
-	</listitem>
-      </varlistentry>
-      <varlistentry>
-	<term>DRIVER_MODESET</term>
-	<listitem>
-	  <para>
-	    Driver supports mode setting interfaces.
-	  </para>
-	</listitem>
-      </varlistentry>
-    </variablelist>
-    <para>
-      In this specific case, the driver requires AGP and supports
-      IRQs.  DMA, as discussed later, is handled by device-specific ioctls
-      in this case.  It also supports the kernel mode setting APIs, though
-      unlike in the actual i915 driver source, this example unconditionally
-      exports KMS capability.
+    <title>Driver Initialization</title>
+    <para>
+      At the core of every DRM driver is a <structname>drm_driver</structname>
+      structure. Drivers typically statically initialize a drm_driver structure,
+      and then pass it to one of the <function>drm_*_init()</function> functions
+      to register it with the DRM subsystem.
     </para>
-  </sect1>
-
-  <!-- Internals: driver load -->
-
-  <sect1>
-    <title>Driver load</title>
-    <para>
-      In the previous section, we saw what a typical drm_driver
-      structure might look like.  One of the more important fields in
-      the structure is the hook for the load function.
-    </para>
-    <programlisting>
-      static struct drm_driver driver = {
-      	...
-      	.load = i915_driver_load,
-        ...
-      };
-    </programlisting>
-    <para>
-      The load function has many responsibilities: allocating a driver
-      private structure, specifying supported performance counters,
-      configuring the device (e.g. mapping registers &amp; command
-      buffers), initializing the memory manager, and setting up the
-      initial output configuration.
-    </para>
-    <para>
-      If compatibility is a concern (e.g. with drivers converted over
-      to the new interfaces from the old ones), 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 &amp; 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.  The i915 driver supports the "modeset"
-      module parameter to control whether advanced features are
-      enabled at load time or in legacy fashion.
+    <para>
+      The <structname>drm_driver</structname> structure contains static
+      information that describe 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 <structname>drm_driver</structname> static
+      information fields, and will then describe individual operations in
+      details as they get used in later sections.
     </para>
-
     <sect2>
-      <title>Driver private &amp; performance counters</title>
-      <para>
-	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.
-      </para>
+      <title>Driver Information</title>
+      <sect3>
+        <title>Driver Features</title>
+        <para>
+          Drivers inform the DRM core about their requirements and supported
+          features by setting appropriate flags in the
+          <structfield>driver_features</structfield> field. Since those flags
+          influence the DRM core behaviour since registration time, most of them
+          must be set to registering the <structname>drm_driver</structname>
+          instance.
+        </para>
+        <synopsis>u32 driver_features;</synopsis>
+        <variablelist>
+          <title>Driver Feature Flags</title>
+          <varlistentry>
+            <term>DRIVER_USE_AGP</term>
+            <listitem><para>
+              Driver uses AGP interface, the DRM core will manage AGP resources.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_REQUIRE_AGP</term>
+            <listitem><para>
+              Driver needs AGP interface to function. AGP initialization failure
+              will become a fatal error.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_USE_MTRR</term>
+            <listitem><para>
+              Driver uses MTRR interface for mapping memory, the DRM core will
+              manage MTRR resources. Deprecated.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_PCI_DMA</term>
+            <listitem><para>
+              Driver is capable of PCI DMA, mapping of PCI DMA buffers to
+              userspace will be enabled. Deprecated.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_SG</term>
+            <listitem><para>
+              Driver can perform scatter/gather DMA, allocation and mapping of
+              scatter/gather buffers will be enabled. Deprecated.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_HAVE_DMA</term>
+            <listitem><para>
+              Driver supports DMA, the userspace DMA API will be supported.
+              Deprecated.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term>
+            <listitem><para>
+              DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler. The
+              DRM core will automatically register an interrupt handler when the
+              flag is set. DRIVER_IRQ_SHARED indicates whether the device &amp;
+              handler support shared IRQs (note that this is required of PCI
+              drivers).
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_IRQ_VBL</term>
+            <listitem><para>Unused. Deprecated.</para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_DMA_QUEUE</term>
+            <listitem><para>
+              Should be set if the driver queues DMA requests and completes them
+              asynchronously.  Deprecated.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_FB_DMA</term>
+            <listitem><para>
+              Driver supports DMA to/from the framebuffer, mapping of frambuffer
+              DMA buffers to userspace will be supported. Deprecated.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_IRQ_VBL2</term>
+            <listitem><para>Unused. Deprecated.</para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_GEM</term>
+            <listitem><para>
+              Driver use the GEM memory manager.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_MODESET</term>
+            <listitem><para>
+              Driver supports mode setting interfaces (KMS).
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRIVER_PRIME</term>
+            <listitem><para>
+              Driver implements DRM PRIME buffer sharing.
+            </para></listitem>
+          </varlistentry>
+        </variablelist>
+      </sect3>
+      <sect3>
+        <title>Major, Minor and Patchlevel</title>
+        <synopsis>int major;
+  int minor;
+  int patchlevel;</synopsis>
+        <para>
+          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.
+        </para>
+        <para>
+          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.
+        </para>
+      </sect3>
+      <sect3>
+        <title>Name, Description and Date</title>
+        <synopsis>char *name;
+  char *desc;
+  char *date;</synopsis>
+        <para>
+          The driver name is printed to the kernel log at initialization time,
+          used for IRQ registration and passed to userspace through
+          DRM_IOCTL_VERSION.
+        </para>
+        <para>
+          The driver description is a purely informative string passed to
+          userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by
+          the kernel.
+        </para>
+        <para>
+          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.
+        </para>
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Driver Load</title>
       <para>
-	The DRM supports several counters which may be used for rough
-	performance characterization.  Note that the DRM stat counter
-	system is not often used by applications, and supporting
-	additional counters is completely optional.
+        The <methodname>load</methodname> method is the driver and device
+        initialization entry point. The method is responsible for allocating and
+        initializing driver private data, specifying supported performance
+        counters, performing resource allocation and mapping (e.g. acquiring
+        clocks, mapping registers or allocating command buffers), initializing
+        the memory manager (<xref linkend="drm-memory-management"/>), installing
+        the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up
+        vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode
+	setting (<xref linkend="drm-mode-setting"/>) and initial output
+	configuration (<xref linkend="drm-kms-init"/>).
       </para>
+      <note><para>
+        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
+        &amp; 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.
+      </para></note>
+      <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis>
       <para>
-	These interfaces are deprecated and should not be used.  If performance
-	monitoring is desired, the developer should investigate and
-	potentially enhance the kernel perf and tracing infrastructure to export
-	GPU related performance information for consumption by performance
-	monitoring tools and applications.
+        The method takes two arguments, a pointer to the newly created
+	<structname>drm_device</structname> and flags. The flags are used to
+	pass the <structfield>driver_data</structfield> field of the device id
+	corresponding to the device passed to <function>drm_*_init()</function>.
+	Only PCI devices currently use this, USB and platform DRM drivers have
+	their <methodname>load</methodname> method called with flags to 0.
       </para>
+      <sect3>
+        <title>Driver Private &amp; Performance Counters</title>
+        <para>
+          The driver private hangs off the main
+          <structname>drm_device</structname> 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
+          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
+          appropriately; it should be freed and
+          <structname>drm_device</structname>.<structfield>dev_priv</structfield>
+          set to NULL when the driver is unloaded.
+        </para>
+        <para>
+          DRM supports several counters which were used for rough performance
+          characterization. This stat counter system is deprecated and should not
+          be used. If performance monitoring is desired, the developer should
+          investigate and potentially enhance the kernel perf and tracing
+          infrastructure to export GPU related performance information for
+          consumption by performance monitoring tools and applications.
+        </para>
+      </sect3>
+      <sect3 id="drm-irq-registration">
+        <title>IRQ Registration</title>
+        <para>
+          The DRM core tries to facilitate IRQ handler registration and
+          unregistration by providing <function>drm_irq_install</function> and
+          <function>drm_irq_uninstall</function> functions. Those functions only
+          support a single interrupt per device.
+        </para>
+  <!--!Fdrivers/char/drm/drm_irq.c drm_irq_install-->
+        <para>
+          Both functions get the device IRQ by calling
+          <function>drm_dev_to_irq</function>. This inline function will call a
+          bus-specific operation to retrieve the IRQ number. For platform devices,
+          <function>platform_get_irq</function>(..., 0) is used to retrieve the
+          IRQ number.
+        </para>
+        <para>
+          <function>drm_irq_install</function> starts by calling the
+          <methodname>irq_preinstall</methodname> 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.
+        </para>
+        <para>
+          The IRQ will then be requested by a call to
+          <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
+          feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
+          requested.
+        </para>
+        <para>
+          The IRQ handler function must be provided as the mandatory irq_handler
+          driver operation. It will get passed directly to
+          <function>request_irq</function> 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.
+        </para>
+        <para>
+          Finally the function calls the optional
+          <methodname>irq_postinstall</methodname> 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.
+        </para>
+        <para>
+          <function>drm_irq_uninstall</function> 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
+          <methodname>irq_uninstall</methodname> driver operation. The operation
+          must disable all hardware interrupts. Finally the function frees the IRQ
+          by calling <function>free_irq</function>.
+        </para>
+      </sect3>
+      <sect3>
+        <title>Memory Manager Initialization</title>
+        <para>
+          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
+          <xref linkend="drm-memory-management"/> for details.
+        </para>
+      </sect3>
+      <sect3>
+        <title>Miscellaneous Device Configuration</title>
+        <para>
+          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 behavior like
+          hangs or memory corruption.
+  <!--!Fdrivers/pci/rom.c pci_map_rom-->
+        </para>
+      </sect3>
     </sect2>
+  </sect1>
 
-    <sect2>
-      <title>Configuring the device</title>
-      <para>
-	Obviously, device configuration is device-specific.
-	However, there are several common operations: finding a
-	device's PCI resources, mapping them, and potentially setting
-	up an IRQ handler.
-      </para>
-      <para>
-	Finding &amp; mapping resources is fairly straightforward.  The
-	DRM wrapper functions, drm_get_resource_start() and
-	drm_get_resource_len(), may be used to find BARs on the given
-	drm_device struct.  Once those values have been retrieved, the
-	driver load function can call drm_addmap() to create a new
-	mapping for the BAR in question.  Note that you probably want a
-	drm_local_map_t in your driver private structure to track any
-	mappings you create.
-<!-- !Fdrivers/gpu/drm/drm_bufs.c drm_get_resource_* -->
-<!-- !Finclude/drm/drmP.h drm_local_map_t -->
-      </para>
-      <para>
-	if compatibility with other operating systems isn't a concern
-	(DRM drivers can run under various BSD variants and OpenSolaris),
-	native Linux calls may be used for the above, e.g. pci_resource_*
-	and iomap*/iounmap.  See the Linux device driver book for more
-	info.
-      </para>
-      <para>
-	Once you have a register map, you may use the DRM_READn() and
-	DRM_WRITEn() macros to access the registers on your device, or
-	use driver-specific versions to offset into your MMIO space
-	relative to a driver-specific base pointer (see I915_READ for
-	an example).
-      </para>
-      <para>
-	If your device supports interrupt generation, you may want to
-	set up an interrupt handler when the driver is loaded.  This
-	is done using the drm_irq_install() function.  If your device
-	supports vertical blank interrupts, it should call
-	drm_vblank_init() to initialize the core vblank handling code before
-	enabling interrupts on your device.  This ensures the vblank related
-	structures are allocated and allows the core to handle vblank events.
-      </para>
-<!--!Fdrivers/char/drm/drm_irq.c drm_irq_install-->
-      <para>
-	Once your interrupt handler is registered (it uses your
-	drm_driver.irq_handler as the actual interrupt handling
-	function), you can safely enable interrupts on your device,
-	assuming any other state your interrupt handler uses is also
-	initialized.
-      </para>
-      <para>
-	Another task that may be necessary 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 behavior like hangs or memory corruption.
-<!--!Fdrivers/pci/rom.c pci_map_rom-->
-      </para>
-    </sect2>
+  <!-- Internals: memory management -->
 
+  <sect1 id="drm-memory-management">
+    <title>Memory management</title>
+    <para>
+      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.
+    </para>
+    <para>
+      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 accomodate 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.
+    </para>
+    <para>
+      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 capabitilies and is thus limited to
+      UMA devices.
+    </para>
     <sect2>
-      <title>Memory manager initialization</title>
-      <para>
-	In order to allocate command buffers, cursor memory, scanout
-	buffers, etc., as well as support the latest features provided
-	by packages like Mesa and the X.Org X server, your driver
-	should support a memory manager.
-      </para>
+      <title>The Translation Table Manager (TTM)</title>
       <para>
-	If your driver supports memory management (it should!), you
-	need to set that up at load time as well.  How you initialize
-	it depends on which memory manager you're using: TTM or GEM.
+	TTM design background and information belongs here.
       </para>
       <sect3>
 	<title>TTM initialization</title>
-	<para>
-	  TTM (for Translation Table Manager) manages video memory and
-	  aperture space for graphics devices. TTM supports both UMA devices
-	  and devices with dedicated video RAM (VRAM), i.e. most discrete
-	  graphics devices.  If your device has dedicated RAM, supporting
-	  TTM is desirable.  TTM also integrates tightly with your
-	  driver-specific buffer execution function.  See the radeon
-	  driver for examples.
-	</para>
-	<para>
-	  The core TTM structure is the ttm_bo_driver struct.  It 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.
+        <warning><para>This section is outdated.</para></warning>
+        <para>
+          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.
 	</para>
 	<para>
 	  The ttm_global_reference structure is made up of several fields:
@@ -445,82 +500,1081 @@
 	  count for the TTM, which will call your initialization function.
 	</para>
       </sect3>
+    </sect2>
+    <sect2 id="drm-gem">
+      <title>The Graphics Execution Manager (GEM)</title>
+      <para>
+        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.
+      </para>
+      <para>
+        The GEM userspace API is described in the
+        <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics
+        Execution Manager</citetitle></ulink> 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.
+      </para>
+      <para>
+        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.
+      </para>
+      <para>
+	On a fundamental level, GEM involves several operations:
+	<itemizedlist>
+	  <listitem>Memory allocation and freeing</listitem>
+	  <listitem>Command execution</listitem>
+	  <listitem>Aperture management at command execution time</listitem>
+	</itemizedlist>
+	Buffer object allocation is relatively straightforward and largely
+        provided by Linux's shmem layer, which provides memory to back each
+        object.
+      </para>
+      <para>
+        Device-specific operations, such as command execution, pinning, buffer
+	read &amp; write, mapping, and domain ownership transfers are left to
+        driver-specific ioctls.
+      </para>
+      <sect3>
+        <title>GEM Initialization</title>
+        <para>
+          Drivers that use GEM must set the DRIVER_GEM bit in the struct
+          <structname>drm_driver</structname>
+          <structfield>driver_features</structfield> field. The DRM core will
+          then automatically initialize the GEM core before calling the
+          <methodname>load</methodname> operation. Behind the scene, this will
+          create a DRM Memory Manager object which provides an address space
+          pool for object allocation.
+        </para>
+        <para>
+          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.
+        </para>
+      </sect3>
       <sect3>
-	<title>GEM initialization</title>
-	<para>
-	  GEM is an alternative to TTM, designed specifically for UMA
-	  devices.  It has simpler initialization and execution requirements
-	  than TTM, but has no VRAM management capability.  Core GEM
-	  is initialized by calling drm_mm_init() to create
-	  a GTT DRM MM object, which provides an address space pool for
-	  object allocation.  In a KMS configuration, the driver
-	  needs to allocate and initialize a command ring buffer following
-	  core GEM initialization.  A UMA device usually has 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 not typically managed by GEM, and it must
-	  be initialized separately into its own DRM MM object.
-	</para>
-	<para>
-	  Initialization is driver-specific. In the case of Intel
-	  integrated graphics chips like 965GM, GEM initialization can
-	  be done by calling the internal GEM init function,
-	  i915_gem_do_init().  Since the 965GM is a UMA device
-	  (i.e. it doesn't have dedicated VRAM), GEM manages
-	  making regular RAM available for GPU operations.  Memory set
-	  aside by the BIOS (called "stolen" memory by the i915
-	  driver) is managed by the DRM memrange allocator; the
-	  rest of the aperture is managed by GEM.
-	  <programlisting>
-	    /* Basic memrange allocator for stolen space (aka vram) */
-	    drm_memrange_init(&amp;dev_priv->vram, 0, prealloc_size);
-	    /* Let GEM Manage from end of prealloc space to end of aperture */
-	    i915_gem_do_init(dev, prealloc_size, agp_size);
-	  </programlisting>
-<!--!Edrivers/char/drm/drm_memrange.c-->
-	</para>
-	<para>
-	  Once the memory manager has been set up, we may allocate the
-	  command buffer.  In the i915 case, this is also done with a
-	  GEM function, i915_gem_init_ringbuffer().
-	</para>
+        <title>GEM Objects Creation</title>
+        <para>
+          GEM splits creation of GEM objects and allocation of the memory that
+          backs them in two distinct operations.
+        </para>
+        <para>
+          GEM objects are represented by an instance of struct
+          <structname>drm_gem_object</structname>. 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
+          <structname>drm_gem_object</structname>.
+        </para>
+        <para>
+          To create a GEM object, a driver allocates memory for an instance of its
+          specific GEM object type and initializes the embedded struct
+          <structname>drm_gem_object</structname> with a call to
+          <function>drm_gem_object_init</function>. The function takes a pointer to
+          the DRM device, a pointer to the GEM object and the buffer object size
+          in bytes.
+        </para>
+        <para>
+          GEM uses shmem to allocate anonymous pageable memory.
+          <function>drm_gem_object_init</function> will create an shmfs file of
+          the requested size and store it into the struct
+          <structname>drm_gem_object</structname> <structfield>filp</structfield>
+          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.
+        </para>
+        <para>
+          Drivers are responsible for the actual physical pages allocation by
+          calling <function>shmem_read_mapping_page_gfp</function> 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).
+        </para>
+        <para>
+          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 <function>drm_gem_private_object_init</function> instead of
+          <function>drm_gem_object_init</function>. Storage for private GEM
+          objects must be managed by drivers.
+        </para>
+        <para>
+          Drivers that do not need to extend GEM objects with private information
+          can call the <function>drm_gem_object_alloc</function> function to
+          allocate and initialize a struct <structname>drm_gem_object</structname>
+          instance. The GEM core will call the optional driver
+          <methodname>gem_init_object</methodname> operation after initializing
+          the GEM object with <function>drm_gem_object_init</function>.
+          <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis>
+        </para>
+        <para>
+          No alloc-and-init function exists for private GEM objects.
+        </para>
+      </sect3>
+      <sect3>
+        <title>GEM Objects Lifetime</title>
+        <para>
+          All GEM objects are reference-counted by the GEM core. References can be
+          acquired and release by <function>calling drm_gem_object_reference</function>
+          and <function>drm_gem_object_unreference</function> respectively. The
+          caller must hold the <structname>drm_device</structname>
+          <structfield>struct_mutex</structfield> lock. As a convenience, GEM
+          provides the <function>drm_gem_object_reference_unlocked</function> and
+          <function>drm_gem_object_unreference_unlocked</function> functions that
+          can be called without holding the lock.
+        </para>
+        <para>
+          When the last reference to a GEM object is released the GEM core calls
+          the <structname>drm_driver</structname>
+          <methodname>gem_free_object</methodname> operation. That operation is
+          mandatory for GEM-enabled drivers and must free the GEM object and all
+          associated resources.
+        </para>
+        <para>
+          <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis>
+          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
+          <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield>
+          is not NULL) it must be freed by a call to
+          <function>drm_gem_free_mmap_offset</function>. The shmfs backing store
+          must be released by calling <function>drm_gem_object_release</function>
+          (that function can safely be called if no shmfs backing store has been
+          created).
+        </para>
+      </sect3>
+      <sect3>
+        <title>GEM Objects Naming</title>
+        <para>
+          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.
+        </para>
+        <para>
+          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.
+        </para>
+        <para>
+          To create a handle for a GEM object drivers call
+          <function>drm_gem_handle_create</function>. 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
+          <function>drm_gem_handle_delete</function>. Finally the GEM object
+          associated with a handle can be retrieved by a call to
+          <function>drm_gem_object_lookup</function>.
+        </para>
+        <para>
+          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
+          <methodname>dumb_create</methodname> operation, drivers must drop the
+          initial reference to the GEM object before returning the handle.
+        </para>
+        <para>
+          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.
+        </para>
+        <para>
+          Similar to global names, GEM file descriptors are also used to share GEM
+          objects across processes. They offer additional security: as file
+          descriptors must be explictly sent over UNIX domain sockets to be shared
+          between applications, they can't be guessed like the globally unique GEM
+          names.
+        </para>
+        <para>
+          Drivers that support GEM file descriptors, also known as the DRM PRIME
+          API, must set the DRIVER_PRIME bit in the struct
+          <structname>drm_driver</structname>
+          <structfield>driver_features</structfield> field, and implement the
+          <methodname>prime_handle_to_fd</methodname> and
+          <methodname>prime_fd_to_handle</methodname> operations.
+        </para>
+        <para>
+          <synopsis>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);</synopsis>
+          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.
+        </para>
+        <para>
+          While non-GEM drivers must implement the operations themselves, GEM
+          drivers must use the <function>drm_gem_prime_handle_to_fd</function>
+          and <function>drm_gem_prime_fd_to_handle</function> helper functions.
+          Those helpers rely on the driver
+          <methodname>gem_prime_export</methodname> and
+          <methodname>gem_prime_import</methodname> 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).
+        </para>
+        <para>
+          <synopsis>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);</synopsis>
+          These two operations are mandatory for GEM drivers that support DRM
+          PRIME.
+        </para>
+      </sect3>
+      <sect3 id="drm-gem-objects-mapping">
+        <title>GEM Objects Mapping</title>
+        <para>
+          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.
+        </para>
+        <para>
+          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
+          <function>do_mmap</function> under the hood. This is often considered
+          dubious, seems to be discouraged for new GEM-enabled drivers, and will
+          thus not be described here.
+        </para>
+        <para>
+          The second method uses the mmap system call on the DRM file handle.
+          <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd,
+             off_t offset);</synopsis>
+          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
+          <function>drm_gem_create_mmap_offset</function> on the object. The
+          function allocates a fake offset range from a pool and stores the
+          offset divided by PAGE_SIZE in
+          <literal>obj-&gt;map_list.hash.key</literal>. Care must be taken not to
+          call <function>drm_gem_create_mmap_offset</function> if a fake offset
+          has already been allocated for the object. This can be tested by
+          <literal>obj-&gt;map_list.map</literal> being non-NULL.
+        </para>
+        <para>
+          Once allocated, the fake offset value
+          (<literal>obj-&gt;map_list.hash.key &lt;&lt; PAGE_SHIFT</literal>)
+          must be passed to the application in a driver-specific way and can then
+          be used as the mmap offset argument.
+        </para>
+        <para>
+          The GEM core provides a helper method <function>drm_gem_mmap</function>
+          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
+          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
+          field. Note that <function>drm_gem_mmap</function> doesn't map memory to
+          userspace, but relies on the driver-provided fault handler to map pages
+          individually.
+        </para>
+        <para>
+          To use <function>drm_gem_mmap</function>, drivers must fill the struct
+          <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
+          field with a pointer to VM operations.
+        </para>
+        <para>
+          <synopsis>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);
+  };</synopsis>
+        </para>
+        <para>
+          The <methodname>open</methodname> and <methodname>close</methodname>
+          operations must update the GEM object reference count. Drivers can use
+          the <function>drm_gem_vm_open</function> and
+          <function>drm_gem_vm_close</function> helper functions directly as open
+          and close handlers.
+        </para>
+        <para>
+          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.
+        </para>
+        <para>
+          Drivers that want to map the GEM object upfront instead of handling page
+          faults can implement their own mmap file operation handler.
+        </para>
+      </sect3>
+      <sect3>
+        <title>Dumb GEM Objects</title>
+        <para>
+          The GEM API doesn't standardize GEM objects creation and leaves it to
+          driver-specific ioctls. 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.
+        </para>
+        <para>
+          Dumb GEM 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.
+        </para>
+        <para>
+          To support dumb GEM objects drivers must implement the
+          <methodname>dumb_create</methodname>,
+          <methodname>dumb_destroy</methodname> and
+          <methodname>dumb_map_offset</methodname> operations.
+        </para>
+        <itemizedlist>
+          <listitem>
+            <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev,
+                     struct drm_mode_create_dumb *args);</synopsis>
+            <para>
+              The <methodname>dumb_create</methodname> operation creates a GEM
+              object suitable for scanout based on the width, height and depth
+              from the struct <structname>drm_mode_create_dumb</structname>
+              argument. It fills the argument's <structfield>handle</structfield>,
+              <structfield>pitch</structfield> and <structfield>size</structfield>
+              fields with a handle for the newly created GEM object and its line
+              pitch and size in bytes.
+            </para>
+          </listitem>
+          <listitem>
+            <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev,
+                      uint32_t handle);</synopsis>
+            <para>
+              The <methodname>dumb_destroy</methodname> operation destroys a dumb
+              GEM object created by <methodname>dumb_create</methodname>.
+            </para>
+          </listitem>
+          <listitem>
+            <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev,
+                         uint32_t handle, uint64_t *offset);</synopsis>
+            <para>
+              The <methodname>dumb_map_offset</methodname> operation associates an
+              mmap fake offset with the GEM object given by the handle and returns
+              it. Drivers must use the
+              <function>drm_gem_create_mmap_offset</function> function to
+              associate the fake offset as described in
+              <xref linkend="drm-gem-objects-mapping"/>.
+            </para>
+          </listitem>
+        </itemizedlist>
+      </sect3>
+      <sect3>
+        <title>Memory Coherency</title>
+        <para>
+          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&lt;-&gt;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).
+        </para>
+      </sect3>
+      <sect3>
+        <title>Command Execution</title>
+        <para>
+	  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.
+        </para>
       </sect3>
     </sect2>
+  </sect1>
+
+  <!-- Internals: mode setting -->
 
+  <sect1 id="drm-mode-setting">
+    <title>Mode Setting</title>
+    <para>
+      Drivers must initialize the mode setting core by calling
+      <function>drm_mode_config_init</function> on the DRM device. The function
+      initializes the <structname>drm_device</structname>
+      <structfield>mode_config</structfield> field and never fails. Once done,
+      mode configuration must be setup by initializing the following fields.
+    </para>
+    <itemizedlist>
+      <listitem>
+        <synopsis>int min_width, min_height;
+int max_width, max_height;</synopsis>
+        <para>
+	  Minimum and maximum width and height of the frame buffers in pixel
+	  units.
+	</para>
+      </listitem>
+      <listitem>
+        <synopsis>struct drm_mode_config_funcs *funcs;</synopsis>
+	<para>Mode setting functions.</para>
+      </listitem>
+    </itemizedlist>
     <sect2>
-      <title>Output configuration</title>
+      <title>Frame Buffer Creation</title>
+      <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev,
+				     struct drm_file *file_priv,
+				     struct drm_mode_fb_cmd2 *mode_cmd);</synopsis>
       <para>
-	The final initialization task is output configuration.  This involves:
-	<itemizedlist>
-	  <listitem>
-	    Finding and initializing the CRTCs, encoders, and connectors
-	    for the device.
-	  </listitem>
-	  <listitem>
-	    Creating an initial configuration.
-	  </listitem>
-	  <listitem>
-	    Registering a framebuffer console driver.
-	  </listitem>
-	</itemizedlist>
+        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.
+      </para>
+      <para>
+        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 <parameter>drm_mode_fb_cmd2</parameter> argument. This document
+        assumes that the driver uses GEM, those handles thus reference GEM
+        objects.
+      </para>
+      <para>
+        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.
+      </para>
+      <para>
+        If the parameters are deemed valid, drivers then create, initialize and
+        return an instance of struct <structname>drm_framebuffer</structname>.
+        If desired the instance can be embedded in a larger driver-specific
+        structure. The new instance is initialized with a call to
+        <function>drm_framebuffer_init</function> which takes a pointer to DRM
+        frame buffer operations (struct
+        <structname>drm_framebuffer_funcs</structname>). Frame buffer operations are
+        <itemizedlist>
+          <listitem>
+            <synopsis>int (*create_handle)(struct drm_framebuffer *fb,
+		     struct drm_file *file_priv, unsigned int *handle);</synopsis>
+            <para>
+              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.
+            </para>
+            <para>
+              Drivers call <function>drm_gem_handle_create</function> to create
+              the handle.
+            </para>
+          </listitem>
+          <listitem>
+            <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis>
+            <para>
+              Destroy the frame buffer object and frees all associated
+              resources. Drivers must call
+              <function>drm_framebuffer_cleanup</function> 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
+              <methodname>create_handle</methodname> operation are released by
+              the DRM core.
+            </para>
+          </listitem>
+          <listitem>
+            <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer,
+	     struct drm_file *file_priv, unsigned flags, unsigned color,
+	     struct drm_clip_rect *clips, unsigned num_clips);</synopsis>
+            <para>
+              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.
+            </para>
+          </listitem>
+        </itemizedlist>
+      </para>
+      <para>
+        After initializing the <structname>drm_framebuffer</structname>
+        instance drivers must fill its <structfield>width</structfield>,
+        <structfield>height</structfield>, <structfield>pitches</structfield>,
+        <structfield>offsets</structfield>, <structfield>depth</structfield>,
+        <structfield>bits_per_pixel</structfield> and
+        <structfield>pixel_format</structfield> fields from the values passed
+        through the <parameter>drm_mode_fb_cmd2</parameter> argument. They
+        should call the <function>drm_helper_mode_fill_fb_struct</function>
+        helper function to do so.
+      </para>
+    </sect2>
+    <sect2>
+      <title>Output Polling</title>
+      <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis>
+      <para>
+        This operation notifies the driver that the status of one or more
+        connectors has changed. Drivers that use the fbdev helper can just call
+        the <function>drm_fb_helper_hotplug_event</function> function to handle
+        this operation.
+      </para>
+    </sect2>
+  </sect1>
+
+  <!-- Internals: kms initialization and cleanup -->
+
+  <sect1 id="drm-kms-init">
+    <title>KMS Initialization and Cleanup</title>
+    <para>
+      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.
+    </para>
+    <sect2>
+      <title>CRTCs (struct <structname>drm_crtc</structname>)</title>
+      <para>
+        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.
       </para>
       <sect3>
-	<title>Output discovery and initialization</title>
-	<para>
-	  Several core functions exist to create CRTCs, encoders, and
-	  connectors, namely: drm_crtc_init(), drm_connector_init(), and
-	  drm_encoder_init(), along with several "helper" functions to
-	  perform common tasks.
-	</para>
-	<para>
-	  Connectors should be registered with sysfs once they've been
-	  detected and initialized, using the
-	  drm_sysfs_connector_add() function.  Likewise, when they're
-	  removed from the system, they should be destroyed with
-	  drm_sysfs_connector_remove().
-	</para>
-	<programlisting>
-<![CDATA[
+        <title>CRTC Initialization</title>
+        <para>
+          A KMS device must create and register at least one struct
+          <structname>drm_crtc</structname> instance. The instance is allocated
+          and zeroed by the driver, possibly as part of a larger structure, and
+          registered with a call to <function>drm_crtc_init</function> with a
+          pointer to CRTC functions.
+        </para>
+      </sect3>
+      <sect3>
+        <title>CRTC Operations</title>
+        <sect4>
+          <title>Set Configuration</title>
+          <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis>
+          <para>
+            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.
+          </para>
+          <para>
+            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.
+          </para>
+          <para>
+            This operation is called with the mode config lock held.
+          </para>
+          <note><para>
+            FIXME: How should set_config interact with DPMS? If the CRTC is
+            suspended, should it be resumed?
+          </para></note>
+        </sect4>
+        <sect4>
+          <title>Page Flipping</title>
+          <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb,
+                   struct drm_pending_vblank_event *event);</synopsis>
+          <para>
+            Schedule a page flip to the given frame buffer for the CRTC. This
+            operation is called with the mode config mutex held.
+          </para>
+          <para>
+            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 <methodname>page_flip</methodname> operation with a
+            pointer to the new frame buffer.
+          </para>
+          <para>
+            The <methodname>page_flip</methodname> operation schedules a page flip.
+            Once any pending rendering targetting 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.
+          </para>
+          <para>
+            If a page flip is already pending, the
+            <methodname>page_flip</methodname> operation must return
+            -<errorname>EBUSY</errorname>.
+          </para>
+          <para>
+            To synchronize page flip to vertical blanking the driver will likely
+            need to enable vertical blanking interrupts. It should call
+            <function>drm_vblank_get</function> for that purpose, and call
+            <function>drm_vblank_put</function> after the page flip completes.
+          </para>
+          <para>
+            If the application has requested to be notified when page flip completes
+            the <methodname>page_flip</methodname> operation will be called with a
+            non-NULL <parameter>event</parameter> argument pointing to a
+            <structname>drm_pending_vblank_event</structname> instance. Upon page
+            flip completion the driver must fill the
+            <parameter>event</parameter>::<structfield>event</structfield>
+            <structfield>sequence</structfield>, <structfield>tv_sec</structfield>
+            and <structfield>tv_usec</structfield> fields with the associated
+            vertical blanking count and timestamp, add the event to the
+            <parameter>drm_file</parameter> list of events to be signaled, and wake
+            up any waiting process. This can be performed with
+            <programlisting><![CDATA[
+            struct timeval now;
+
+            event->event.sequence = drm_vblank_count_and_time(..., &now);
+            event->event.tv_sec = now.tv_sec;
+            event->event.tv_usec = now.tv_usec;
+
+            spin_lock_irqsave(&dev->event_lock, flags);
+            list_add_tail(&event->base.link, &event->base.file_priv->event_list);
+            wake_up_interruptible(&event->base.file_priv->event_wait);
+            spin_unlock_irqrestore(&dev->event_lock, flags);
+            ]]></programlisting>
+          </para>
+          <note><para>
+            FIXME: Could drivers that don't need to wait for rendering to complete
+            just add the event to <literal>dev-&gt;vblank_event_list</literal> and
+            let the DRM core handle everything, as for "normal" vertical blanking
+            events?
+          </para></note>
+          <para>
+            While waiting for the page flip to complete, the
+            <literal>event-&gt;base.link</literal> list head can be used freely by
+            the driver to store the pending event in a driver-specific list.
+          </para>
+          <para>
+            If the file handle is closed before the event is signaled, drivers must
+            take care to destroy the event in their
+            <methodname>preclose</methodname> operation (and, if needed, call
+            <function>drm_vblank_put</function>).
+          </para>
+        </sect4>
+        <sect4>
+          <title>Miscellaneous</title>
+          <itemizedlist>
+            <listitem>
+              <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
+                        uint32_t start, uint32_t size);</synopsis>
+              <para>
+                Apply a gamma table to the device. The operation is optional.
+              </para>
+            </listitem>
+            <listitem>
+              <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis>
+              <para>
+                Destroy the CRTC when not needed anymore. See
+                <xref linkend="drm-kms-init"/>.
+              </para>
+            </listitem>
+          </itemizedlist>
+        </sect4>
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Planes (struct <structname>drm_plane</structname>)</title>
+      <para>
+        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.
+      </para>
+      <sect3>
+        <title>Plane Initialization</title>
+        <para>
+          Planes are optional. To create a plane, a KMS drivers allocates and
+          zeroes an instances of struct <structname>drm_plane</structname>
+          (possibly as part of a larger structure) and registers it with a call
+          to <function>drm_plane_init</function>. The function takes a bitmask
+          of the CRTCs that can be associated with the plane, a pointer to the
+          plane functions and a list of format supported formats.
+        </para>
+      </sect3>
+      <sect3>
+        <title>Plane Operations</title>
+        <itemizedlist>
+          <listitem>
+            <synopsis>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);</synopsis>
+            <para>
+              Enable and configure the plane to use the given CRTC and frame buffer.
+            </para>
+            <para>
+              The source rectangle in frame buffer memory coordinates is given by
+              the <parameter>src_x</parameter>, <parameter>src_y</parameter>,
+              <parameter>src_w</parameter> and <parameter>src_h</parameter>
+              parameters (as 16.16 fixed point values). Devices that don't support
+              subpixel plane coordinates can ignore the fractional part.
+            </para>
+            <para>
+              The destination rectangle in CRTC coordinates is given by the
+              <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>,
+              <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter>
+              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 -<errorname>EINVAL</errorname> error.
+            </para>
+          </listitem>
+          <listitem>
+            <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis>
+            <para>
+              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.
+            </para>
+          </listitem>
+          <listitem>
+            <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis>
+            <para>
+              Destroy the plane when not needed anymore. See
+              <xref linkend="drm-kms-init"/>.
+            </para>
+          </listitem>
+        </itemizedlist>
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Encoders (struct <structname>drm_encoder</structname>)</title>
+      <para>
+        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.
+      </para>
+      <sect3>
+        <title>Encoder Initialization</title>
+        <para>
+          As for CRTCs, a KMS driver must create, initialize and register at
+          least one struct <structname>drm_encoder</structname> instance. The
+          instance is allocated and zeroed by the driver, possibly as part of a
+          larger structure.
+        </para>
+        <para>
+          Drivers must initialize the struct <structname>drm_encoder</structname>
+          <structfield>possible_crtcs</structfield> and
+          <structfield>possible_clones</structfield> 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.
+        </para>
+        <para>
+          After being initialized, the encoder must be registered with a call to
+          <function>drm_encoder_init</function>. The function takes a pointer to
+          the encoder functions and an encoder type. Supported types are
+          <itemizedlist>
+            <listitem>
+              DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A
+              </listitem>
+            <listitem>
+              DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort
+            </listitem>
+            <listitem>
+              DRM_MODE_ENCODER_LVDS for display panels
+            </listitem>
+            <listitem>
+              DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component,
+              SCART)
+            </listitem>
+            <listitem>
+              DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
+            </listitem>
+          </itemizedlist>
+        </para>
+        <para>
+          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.
+        </para>
+      </sect3>
+      <sect3>
+        <title>Encoder Operations</title>
+        <itemizedlist>
+          <listitem>
+            <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis>
+            <para>
+              Called to destroy the encoder when not needed anymore. See
+              <xref linkend="drm-kms-init"/>.
+            </para>
+          </listitem>
+        </itemizedlist>
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Connectors (struct <structname>drm_connector</structname>)</title>
+      <para>
+        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 &amp; connection status, and information about modes
+	supported on the attached displays.
+      </para>
+      <sect3>
+        <title>Connector Initialization</title>
+        <para>
+          Finally a KMS driver must create, initialize, register and attach at
+          least one struct <structname>drm_connector</structname> instance. The
+          instance is created as other KMS objects and initialized by setting the
+          following fields.
+        </para>
+        <variablelist>
+          <varlistentry>
+            <term><structfield>interlace_allowed</structfield></term>
+            <listitem><para>
+              Whether the connector can handle interlaced modes.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term><structfield>doublescan_allowed</structfield></term>
+            <listitem><para>
+              Whether the connector can handle doublescan.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term><structfield>display_info
+            </structfield></term>
+            <listitem><para>
+              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
+              <structfield>display_info</structfield>.<structfield>width_mm</structfield>
+              and
+              <structfield>display_info</structfield>.<structfield>height_mm</structfield>
+              fields with the physical size of the display.
+            </para></listitem>
+          </varlistentry>
+          <varlistentry>
+            <term id="drm-kms-connector-polled"><structfield>polled</structfield></term>
+            <listitem><para>
+              Connector polling mode, a combination of
+              <variablelist>
+                <varlistentry>
+                  <term>DRM_CONNECTOR_POLL_HPD</term>
+                  <listitem><para>
+                    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.
+                  </para></listitem>
+                </varlistentry>
+                <varlistentry>
+                  <term>DRM_CONNECTOR_POLL_CONNECT</term>
+                  <listitem><para>
+                    Periodically poll the connector for connection.
+                  </para></listitem>
+                </varlistentry>
+                <varlistentry>
+                  <term>DRM_CONNECTOR_POLL_DISCONNECT</term>
+                  <listitem><para>
+                    Periodically poll the connector for disconnection.
+                  </para></listitem>
+                </varlistentry>
+              </variablelist>
+              Set to 0 for connectors that don't support connection status
+              discovery.
+            </para></listitem>
+          </varlistentry>
+        </variablelist>
+        <para>
+          The connector is then registered with a call to
+          <function>drm_connector_init</function> with a pointer to the connector
+          functions and a connector type, and exposed through sysfs with a call to
+          <function>drm_sysfs_connector_add</function>.
+        </para>
+        <para>
+          Supported connector types are
+          <itemizedlist>
+            <listitem>DRM_MODE_CONNECTOR_VGA</listitem>
+            <listitem>DRM_MODE_CONNECTOR_DVII</listitem>
+            <listitem>DRM_MODE_CONNECTOR_DVID</listitem>
+            <listitem>DRM_MODE_CONNECTOR_DVIA</listitem>
+            <listitem>DRM_MODE_CONNECTOR_Composite</listitem>
+            <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem>
+            <listitem>DRM_MODE_CONNECTOR_LVDS</listitem>
+            <listitem>DRM_MODE_CONNECTOR_Component</listitem>
+            <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem>
+            <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem>
+            <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem>
+            <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem>
+            <listitem>DRM_MODE_CONNECTOR_TV</listitem>
+            <listitem>DRM_MODE_CONNECTOR_eDP</listitem>
+            <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem>
+          </itemizedlist>
+        </para>
+        <para>
+          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
+          <function>drm_mode_connector_attach_encoder</function>. The driver must
+          also set the <structname>drm_connector</structname>
+          <structfield>encoder</structfield> field to point to the attached
+          encoder.
+        </para>
+        <para>
+          Finally, drivers must initialize the connectors state change detection
+          with a call to <function>drm_kms_helper_poll_init</function>. 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 <function>drm_helper_hpd_irq_event</function>. The function will
+          queue a delayed work to check the state of all connectors, but no
+          periodic polling will be done.
+        </para>
+      </sect3>
+      <sect3>
+        <title>Connector Operations</title>
+        <note><para>
+          Unless otherwise state, all operations are mandatory.
+        </para></note>
+        <sect4>
+          <title>DPMS</title>
+          <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis>
+          <para>
+            The DPMS operation sets the power state of a connector. The mode
+            argument is one of
+            <itemizedlist>
+              <listitem><para>DRM_MODE_DPMS_ON</para></listitem>
+              <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem>
+              <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem>
+              <listitem><para>DRM_MODE_DPMS_OFF</para></listitem>
+            </itemizedlist>
+          </para>
+          <para>
+            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.
+          </para>
+        </sect4>
+        <sect4>
+          <title>Modes</title>
+          <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width,
+                      uint32_t max_height);</synopsis>
+          <para>
+            Fill the mode list with all supported modes for the connector. If the
+            <parameter>max_width</parameter> and <parameter>max_height</parameter>
+            arguments are non-zero, the implementation must ignore all modes wider
+            than <parameter>max_width</parameter> or higher than
+            <parameter>max_height</parameter>.
+          </para>
+          <para>
+            The connector must also fill in this operation its
+            <structfield>display_info</structfield>
+            <structfield>width_mm</structfield> and
+            <structfield>height_mm</structfield> 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).
+          </para>
+        </sect4>
+        <sect4>
+          <title>Connection Status</title>
+          <para>
+            The connection status is updated through polling or hotplug events when
+            supported (see <xref linkend="drm-kms-connector-polled"/>). 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
+            <function>drm_mode_getconnector</function> from userspace.
+          </para>
+          <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector,
+                                        bool force);</synopsis>
+          <para>
+            Check to see if anything is attached to the connector. The
+            <parameter>force</parameter> parameter is set to false whilst polling or
+            to true when checking the connector due to user request.
+            <parameter>force</parameter> can be used by the driver to avoid
+            expensive, destructive operations during automated probing.
+          </para>
+          <para>
+            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.
+          </para>
+          <para>
+            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.
+          </para>
+        </sect4>
+        <sect4>
+          <title>Miscellaneous</title>
+          <itemizedlist>
+            <listitem>
+              <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
+              <para>
+                Destroy the connector when not needed anymore. See
+                <xref linkend="drm-kms-init"/>.
+              </para>
+            </listitem>
+          </itemizedlist>
+        </sect4>
+      </sect3>
+    </sect2>
+    <sect2>
+      <title>Cleanup</title>
+      <para>
+        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
+	<function>drm_*_init</function> call must be matched with a
+	corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs
+	(<function>drm_crtc_cleanup</function>), planes
+	(<function>drm_plane_cleanup</function>), encoders
+	(<function>drm_encoder_cleanup</function>) and connectors
+	(<function>drm_connector_cleanup</function>). Furthermore, connectors
+	that have been added to sysfs must be removed by a call to
+	<function>drm_sysfs_connector_remove</function> before calling
+	<function>drm_connector_cleanup</function>.
+      </para>
+      <para>
+        Connectors state change detection must be cleanup up with a call to
+	<function>drm_kms_helper_poll_fini</function>.
+      </para>
+    </sect2>
+    <sect2>
+      <title>Output discovery and initialization example</title>
+      <programlisting><![CDATA[
 void intel_crt_init(struct drm_device *dev)
 {
 	struct drm_connector *connector;
@@ -556,252 +1610,741 @@ void intel_crt_init(struct drm_device *dev)
 	drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
 
 	drm_sysfs_connector_add(connector);
-}
-]]>
-	</programlisting>
-	<para>
-	  In the example above (again, taken from the i915 driver), a
-	  CRT 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.
-	</para>
-	<sect4>
-	  <title>Helper functions and core functions</title>
-	  <para>
-	    Since many PC-class graphics devices have similar display output
-	    designs, the DRM provides a set of helper functions to make
-	    output management easier.  The core helper routines handle
-	    encoder re-routing and the disabling of unused functions following
-	    mode setting.  Using the helpers is optional, but recommended for
-	    devices with PC-style architectures (i.e. a set of display planes
-	    for feeding pixels to encoders which are in turn routed to
-	    connectors).  Devices with more complex requirements needing
-	    finer grained management may opt to use the core callbacks
-	    directly.
-	  </para>
-	  <para>
-	    [Insert typical diagram here.]  [Insert OMAP style config here.]
-	  </para>
-	</sect4>
-	<para>
-	  Each encoder object needs to provide:
-	  <itemizedlist>
-	    <listitem>
-	      A DPMS (basically on/off) function.
-	    </listitem>
-	    <listitem>
-	      A mode-fixup function (for converting requested modes into
-	      native hardware timings).
-	    </listitem>
-	    <listitem>
-	      Functions (prepare, set, and commit) for use by the core DRM
-	      helper functions.
-	    </listitem>
-	  </itemizedlist>
-	  Connector helpers need to provide functions (mode-fetch, validity,
-	  and encoder-matching) for returning an ideal encoder for a given
-	  connector.  The core connector functions include a DPMS callback,
-	  save/restore routines (deprecated), detection, mode probing,
-	  property handling, and cleanup functions.
-	</para>
-<!--!Edrivers/char/drm/drm_crtc.h-->
-<!--!Edrivers/char/drm/drm_crtc.c-->
-<!--!Edrivers/char/drm/drm_crtc_helper.c-->
-      </sect3>
+}]]></programlisting>
+      <para>
+        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.
+      </para>
     </sect2>
   </sect1>
 
-  <!-- Internals: vblank handling -->
+  <!-- Internals: mid-layer helper functions -->
 
   <sect1>
-    <title>VBlank event handling</title>
+    <title>Mid-layer Helper Functions</title>
     <para>
-      The DRM core exposes two vertical blank related ioctls:
-      <variablelist>
-        <varlistentry>
-          <term>DRM_IOCTL_WAIT_VBLANK</term>
-          <listitem>
-            <para>
-              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.
-            </para>
-          </listitem>
-        </varlistentry>
-        <varlistentry>
-          <term>DRM_IOCTL_MODESET_CTL</term>
-          <listitem>
-            <para>
-              This should be called by application level drivers before and
-              after mode setting, since on many devices the vertical blank
-              counter is reset at that time.  Internally, the DRM snapshots
-              the last vblank count when the ioctl is called with the
-              _DRM_PRE_MODESET command, so that the counter won't go backwards
-              (which is dealt with when _DRM_POST_MODESET is used).
-            </para>
-          </listitem>
-        </varlistentry>
-      </variablelist>
-<!--!Edrivers/char/drm/drm_irq.c-->
+      The 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.
+    </para>
+    <para>
+      The DRM core contains one mid-layer implementation. The mid-layer provides
+      implementations of several 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
+      <function>drm_crtc_helper_set_config</function> function can be used to
+      fill the struct <structname>drm_crtc_funcs</structname>
+      <structfield>set_config</structfield> field. When called, it will split
+      the <methodname>set_config</methodname> operation in smaller, simpler
+      operations and call the driver to handle them.
     </para>
     <para>
-      To support the functions above, the DRM core provides several
-      helper functions for tracking vertical blank counters, and
-      requires drivers to provide several callbacks:
-      get_vblank_counter(), enable_vblank() and disable_vblank().  The
-      core uses get_vblank_counter() to keep the counter accurate
-      across interrupt disable periods.  It should return the current
-      vertical blank event count, which is often tracked in a device
-      register.  The enable and disable vblank callbacks should enable
-      and disable vertical blank interrupts, respectively.  In the
-      absence of DRM clients waiting on vblank events, the core DRM
-      code uses the disable_vblank() function to disable
-      interrupts, which saves power.  They are re-enabled again when
-      a client calls the vblank wait ioctl above.
+      To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>,
+      <function>drm_encoder_helper_add</function> and
+      <function>drm_connector_helper_add</function> functions to install their
+      mid-layer bottom operations handlers, and fill the
+      <structname>drm_crtc_funcs</structname>,
+      <structname>drm_encoder_funcs</structname> and
+      <structname>drm_connector_funcs</structname> 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.
     </para>
     <para>
-      A device that doesn't provide a count register may simply use an
-      internal atomic counter incremented on every vertical blank
-      interrupt (and then treat the enable_vblank() and disable_vblank()
-      callbacks as no-ops).
+      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.
     </para>
+    <sect2>
+      <title>Helper Functions</title>
+      <itemizedlist>
+        <listitem>
+          <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis>
+          <para>
+            The <function>drm_crtc_helper_set_config</function> helper function
+            is a CRTC <methodname>set_config</methodname> implementation. It
+            first tries to locate the best encoder for each connector by calling
+            the connector <methodname>best_encoder</methodname> helper
+            operation.
+          </para>
+          <para>
+            After locating the appropriate encoders, the helper function will
+            call the <methodname>mode_fixup</methodname> 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.
+          </para>
+          <para>
+            If the adjusted mode is identical to the current mode but changes to
+            the frame buffer need to be applied, the
+            <function>drm_crtc_helper_set_config</function> function will call
+            the CRTC <methodname>mode_set_base</methodname> helper operation. If
+            the adjusted mode differs from the current mode, or if the
+            <methodname>mode_set_base</methodname> helper operation is not
+            provided, the helper function performs a full mode set sequence by
+            calling the <methodname>prepare</methodname>,
+            <methodname>mode_set</methodname> and
+            <methodname>commit</methodname> CRTC and encoder helper operations,
+            in that order.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis>
+          <para>
+            The <function>drm_helper_connector_dpms</function> helper function
+            is a connector <methodname>dpms</methodname> implementation that
+            tracks power state of connectors. To use the function, drivers must
+            provide <methodname>dpms</methodname> helper operations for CRTCs
+            and encoders to apply the DPMS state to the device.
+          </para>
+          <para>
+            The mid-layer doesn't track the power state of CRTCs and encoders.
+            The <methodname>dpms</methodname> helper operations can thus be
+            called with a mode identical to the currently active mode.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
+                                            uint32_t maxX, uint32_t maxY);</synopsis>
+          <para>
+            The <function>drm_helper_probe_single_connector_modes</function> helper
+            function is a connector <methodname>fill_modes</methodname>
+            implementation that updates the connection status for the connector
+            and then retrieves a list of modes by calling the connector
+            <methodname>get_modes</methodname> helper operation.
+          </para>
+          <para>
+            The function filters out modes larger than
+            <parameter>max_width</parameter> and <parameter>max_height</parameter>
+            if specified. It then calls the connector
+            <methodname>mode_valid</methodname> helper operation for  each mode in
+            the probed list to check whether the mode is valid for the connector.
+          </para>
+        </listitem>
+      </itemizedlist>
+    </sect2>
+    <sect2>
+      <title>CRTC Helper Operations</title>
+      <itemizedlist>
+        <listitem id="drm-helper-crtc-mode-fixup">
+          <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc,
+                       const struct drm_display_mode *mode,
+                       struct drm_display_mode *adjusted_mode);</synopsis>
+          <para>
+            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.
+          </para>
+          <para>
+            The <methodname>mode_fixup</methodname> 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).
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
+                     struct drm_framebuffer *old_fb)</synopsis>
+          <para>
+            Move the CRTC on the current frame buffer (stored in
+            <literal>crtc-&gt;fb</literal>) to position (x,y). Any of the frame
+            buffer, x position or y position may have been modified.
+          </para>
+          <para>
+            This helper operation is optional. If not provided, the
+            <function>drm_crtc_helper_set_config</function> function will fall
+            back to the <methodname>mode_set</methodname> helper operation.
+          </para>
+          <note><para>
+            FIXME: Why are x and y passed as arguments, as they can be accessed
+            through <literal>crtc-&gt;x</literal> and
+            <literal>crtc-&gt;y</literal>?
+          </para></note>
+        </listitem>
+        <listitem>
+          <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis>
+          <para>
+            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.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>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);</synopsis>
+          <para>
+            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 <methodname>commit</methodname> operation, or
+            programmed to the hardware immediately.
+          </para>
+          <para>
+            The <methodname>mode_set</methodname> operation returns 0 on success
+	    or a negative error code if an error occurs.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis>
+          <para>
+            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.
+          </para>
+        </listitem>
+      </itemizedlist>
+    </sect2>
+    <sect2>
+      <title>Encoder Helper Operations</title>
+      <itemizedlist>
+        <listitem>
+          <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder,
+                       const struct drm_display_mode *mode,
+                       struct drm_display_mode *adjusted_mode);</synopsis>
+          <note><para>
+            FIXME: The mode argument be const, but the i915 driver modifies
+            mode-&gt;clock in <function>intel_dp_mode_fixup</function>.
+          </para></note>
+          <para>
+            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
+            <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper
+            operation</link> for an explanation of the allowed adjustments.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis>
+          <para>
+            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.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>void (*mode_set)(struct drm_encoder *encoder,
+                 struct drm_display_mode *mode,
+                 struct drm_display_mode *adjusted_mode);</synopsis>
+          <para>
+            Set a new mode. Depending on the device requirements, the mode can
+            be stored internally by the driver and applied in the
+            <methodname>commit</methodname> operation, or programmed to the
+            hardware immediately.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis>
+          <para>
+            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.
+          </para>
+        </listitem>
+      </itemizedlist>
+    </sect2>
+    <sect2>
+      <title>Connector Helper Operations</title>
+      <itemizedlist>
+        <listitem>
+          <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis>
+          <para>
+            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.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis>
+          <para>
+            Fill the connector's <structfield>probed_modes</structfield> list
+            by parsing EDID data with <function>drm_add_edid_modes</function> or
+            calling <function>drm_mode_probed_add</function> directly for every
+            supported mode and return the number of modes it has detected. This
+            operation is mandatory.
+          </para>
+          <para>
+            When adding modes manually the driver creates each mode with a call to
+            <function>drm_mode_create</function> and must fill the following fields.
+            <itemizedlist>
+              <listitem>
+                <synopsis>__u32 type;</synopsis>
+                <para>
+                  Mode type bitmask, a combination of
+                  <variablelist>
+                    <varlistentry>
+                      <term>DRM_MODE_TYPE_BUILTIN</term>
+                      <listitem><para>not used?</para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_TYPE_CLOCK_C</term>
+                      <listitem><para>not used?</para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_TYPE_CRTC_C</term>
+                      <listitem><para>not used?</para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>
+        DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector
+                      </term>
+                      <listitem>
+                        <para>not used?</para>
+                      </listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_TYPE_DEFAULT</term>
+                      <listitem><para>not used?</para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_TYPE_USERDEF</term>
+                      <listitem><para>not used?</para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_TYPE_DRIVER</term>
+                      <listitem>
+                        <para>
+                          The mode has been created by the driver (as opposed to
+                          to user-created modes).
+                        </para>
+                      </listitem>
+                    </varlistentry>
+                  </variablelist>
+                  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.
+                </para>
+              </listitem>
+              <listitem>
+                <synopsis>__u32 clock;</synopsis>
+                <para>Pixel clock frequency in kHz unit</para>
+              </listitem>
+              <listitem>
+                <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal;
+    __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis>
+                <para>Horizontal and vertical timing information</para>
+                <screen><![CDATA[
+             Active                 Front           Sync           Back
+             Region                 Porch                          Porch
+    <-----------------------><----------------><-------------><-------------->
+
+      //////////////////////|
+     ////////////////////// |
+    //////////////////////  |..................               ................
+                                               _______________
+
+    <----- [hv]display ----->
+    <------------- [hv]sync_start ------------>
+    <--------------------- [hv]sync_end --------------------->
+    <-------------------------------- [hv]total ----------------------------->
+]]></screen>
+              </listitem>
+              <listitem>
+                <synopsis>__u16 hskew;
+    __u16 vscan;</synopsis>
+                <para>Unknown</para>
+              </listitem>
+              <listitem>
+                <synopsis>__u32 flags;</synopsis>
+                <para>
+                  Mode flags, a combination of
+                  <variablelist>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_PHSYNC</term>
+                      <listitem><para>
+                        Horizontal sync is active high
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_NHSYNC</term>
+                      <listitem><para>
+                        Horizontal sync is active low
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_PVSYNC</term>
+                      <listitem><para>
+                        Vertical sync is active high
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_NVSYNC</term>
+                      <listitem><para>
+                        Vertical sync is active low
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_INTERLACE</term>
+                      <listitem><para>
+                        Mode is interlaced
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_DBLSCAN</term>
+                      <listitem><para>
+                        Mode uses doublescan
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_CSYNC</term>
+                      <listitem><para>
+                        Mode uses composite sync
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_PCSYNC</term>
+                      <listitem><para>
+                        Composite sync is active high
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_NCSYNC</term>
+                      <listitem><para>
+                        Composite sync is active low
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_HSKEW</term>
+                      <listitem><para>
+                        hskew provided (not used?)
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_BCAST</term>
+                      <listitem><para>
+                        not used?
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_PIXMUX</term>
+                      <listitem><para>
+                        not used?
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_DBLCLK</term>
+                      <listitem><para>
+                        not used?
+                      </para></listitem>
+                    </varlistentry>
+                    <varlistentry>
+                      <term>DRM_MODE_FLAG_CLKDIV2</term>
+                      <listitem><para>
+                        ?
+                      </para></listitem>
+                    </varlistentry>
+                  </variablelist>
+                </para>
+                <para>
+                  Note that modes marked with the INTERLACE or DBLSCAN flags will be
+                  filtered out by
+                  <function>drm_helper_probe_single_connector_modes</function> if
+                  the connector's <structfield>interlace_allowed</structfield> or
+                  <structfield>doublescan_allowed</structfield> field is set to 0.
+                </para>
+              </listitem>
+              <listitem>
+                <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis>
+                <para>
+                  Mode name. The driver must call
+                  <function>drm_mode_set_name</function> to fill the mode name from
+                  <structfield>hdisplay</structfield>,
+                  <structfield>vdisplay</structfield> and interlace flag after
+                  filling the corresponding fields.
+                </para>
+              </listitem>
+            </itemizedlist>
+          </para>
+          <para>
+            The <structfield>vrefresh</structfield> value is computed by
+            <function>drm_helper_probe_single_connector_modes</function>.
+          </para>
+          <para>
+            When parsing EDID data, <function>drm_add_edid_modes</function> fill the
+            connector <structfield>display_info</structfield>
+            <structfield>width_mm</structfield> and
+            <structfield>height_mm</structfield> fields. When creating modes
+            manually the <methodname>get_modes</methodname> helper operation must
+            set the <structfield>display_info</structfield>
+            <structfield>width_mm</structfield> and
+            <structfield>height_mm</structfield> fields if they haven't been set
+            already (for instance at initilization time when a fixed-size panel is
+            attached to the connector). The mode <structfield>width_mm</structfield>
+            and <structfield>height_mm</structfield> fields are only used internally
+            during EDID parsing and should not be set when creating modes manually.
+          </para>
+        </listitem>
+        <listitem>
+          <synopsis>int (*mode_valid)(struct drm_connector *connector,
+		  struct drm_display_mode *mode);</synopsis>
+          <para>
+            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 mandatory.
+          </para>
+          <para>
+            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.
+          </para>
+          <note><para>
+            Note that the <methodname>mode_valid</methodname> helper operation is
+            only called for modes detected by the device, and
+            <emphasis>not</emphasis> for modes set by the user through the CRTC
+            <methodname>set_config</methodname> operation.
+          </para></note>
+        </listitem>
+      </itemizedlist>
+    </sect2>
   </sect1>
 
-  <sect1>
-    <title>Memory management</title>
+  <!-- Internals: vertical blanking -->
+
+  <sect1 id="drm-vertical-blank">
+    <title>Vertical Blanking</title>
+    <para>
+      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.
+    </para>
+    <para>
+      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.
+    </para>
+    <itemizedlist>
+      <listitem>
+        <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc);
+void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
+        <para>
+	  Enable or disable vertical blanking interrupts for the given CRTC.
+	</para>
+      </listitem>
+      <listitem>
+        <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis>
+        <para>
+	  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
+	  <function>drm_vblank_count</function> helper function to handle this
+	  operation.
+	</para>
+      </listitem>
+    </itemizedlist>
     <para>
-      The memory manager lies at the heart of many DRM operations; it
-      is required to support advanced client features like OpenGL
-      pbuffers.  The DRM currently contains two memory managers: TTM
-      and GEM.
+      Drivers must initialize the vertical blanking handling core with a call to
+      <function>drm_vblank_init</function> in their
+      <methodname>load</methodname> operation. The function will set the struct
+      <structname>drm_device</structname>
+      <structfield>vblank_disable_allowed</structfield> field to 0. This will
+      keep vertical blanking interrupts enabled permanently until the first mode
+      set operation, where <structfield>vblank_disable_allowed</structfield> is
+      set to 1. The reason behind this is not clear. Drivers can set the field
+      to 1 after <function>calling drm_vblank_init</function> to make vertical
+      blanking interrupts dynamically managed from the beginning.
     </para>
+    <para>
+      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 <function>drm_vblank_get</function>. Upon return vertical
+      blanking interrupts are guaranteed to be enabled.
+    </para>
+    <para>
+      To decrement the use count drivers call
+      <function>drm_vblank_put</function>. 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 <varname>drm_vblank_offdelay</varname> global
+      variable and expressed in milliseconds. Its default value is 5000 ms.
+    </para>
+    <para>
+      When a vertical blanking interrupt occurs drivers only need to call the
+      <function>drm_handle_vblank</function> function to account for the
+      interrupt.
+    </para>
+    <para>
+      Resources allocated by <function>drm_vblank_init</function> must be freed
+      with a call to <function>drm_vblank_cleanup</function> in the driver
+      <methodname>unload</methodname> operation handler.
+    </para>
+  </sect1>
+
+  <!-- Internals: open/close, file operations and ioctls -->
 
+  <sect1>
+    <title>Open/Close, File Operations and IOCTLs</title>
     <sect2>
-      <title>The Translation Table Manager (TTM)</title>
+      <title>Open and Close</title>
+      <synopsis>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 *);</synopsis>
+      <abstract>Open and close handlers. None of those methods are mandatory.
+      </abstract>
       <para>
-	TTM was developed by Tungsten Graphics, primarily by Thomas
-	Hellström, and is intended to be a flexible, high performance
-	graphics memory manager.
+        The <methodname>firstopen</methodname> method is called by the DRM core
+	when an application opens a device that has no other opened file handle.
+	Similarly the <methodname>lastclose</methodname> method is called when
+	the last application holding a file handle opened on the device closes
+	it. Both methods are mostly used for UMS (User Mode Setting) drivers to
+	acquire and release device resources which should be done in the
+	<methodname>load</methodname> and <methodname>unload</methodname>
+	methods for KMS drivers.
       </para>
       <para>
-	Drivers wishing to support TTM must fill out a drm_bo_driver
-	structure.
+        Note that the <methodname>lastclose</methodname> method is also called
+	at module unload time or, for hot-pluggable devices, when the device is
+	unplugged. The <methodname>firstopen</methodname> and
+	<methodname>lastclose</methodname> calls can thus be unbalanced.
       </para>
       <para>
-	TTM design background and information belongs here.
+        The <methodname>open</methodname> 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
+	<structname>drm_file</structname> <structfield>driver_priv</structfield>
+	field. Note that the <methodname>open</methodname> method is called
+	before <methodname>firstopen</methodname>.
+      </para>
+      <para>
+        The close operation is split into <methodname>preclose</methodname> and
+	<methodname>postclose</methodname> methods. Drivers must stop and
+	cleanup all per-file operations in the <methodname>preclose</methodname>
+	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 <methodname>preclose</methodname> method.
+      </para>
+      <para>
+        Finally the <methodname>postclose</methodname> method is called as the
+	last step of the close operation, right before calling the
+	<methodname>lastclose</methodname> method if no other open file handle
+	exists for the device. Drivers that have allocated per-file private data
+	in the <methodname>open</methodname> method should free it here.
+      </para>
+      <para>
+        The <methodname>lastclose</methodname> 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.
       </para>
     </sect2>
-
     <sect2>
-      <title>The Graphics Execution Manager (GEM)</title>
+      <title>File Operations</title>
+      <synopsis>const struct file_operations *fops</synopsis>
+      <abstract>File operations for the DRM device node.</abstract>
       <para>
-	GEM is an Intel project, authored by Eric Anholt and Keith
-	Packard.  It provides simpler interfaces than TTM, and is well
-	suited for UMA devices.
+        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 <methodname>open</methodname>,
+	<methodname>release</methodname> and <methodname>ioctl</methodname>
+	operations are handled by
+	<programlisting>
+	.owner = THIS_MODULE,
+	.open = drm_open,
+	.release = drm_release,
+	.unlocked_ioctl = drm_ioctl,
+  #ifdef CONFIG_COMPAT
+	.compat_ioctl = drm_compat_ioctl,
+  #endif
+        </programlisting>
       </para>
       <para>
-	GEM-enabled drivers must provide gem_init_object() and
-	gem_free_object() callbacks to support the core memory
-	allocation routines.  They should also provide several driver-specific
-	ioctls to support command execution, pinning, buffer
-	read &amp; write, mapping, and domain ownership transfers.
+        Drivers that implement private ioctls that requires 32/64bit
+	compatibility support must provide their own
+	<methodname>compat_ioctl</methodname> handler that processes private
+	ioctls and calls <function>drm_compat_ioctl</function> for core ioctls.
       </para>
       <para>
-	On a fundamental level, GEM involves several operations:
-	<itemizedlist>
-	  <listitem>Memory allocation and freeing</listitem>
-	  <listitem>Command execution</listitem>
-	  <listitem>Aperture management at command execution time</listitem>
-	</itemizedlist>
-	Buffer object allocation is relatively
-	straightforward and largely provided by Linux's shmem layer, which
-	provides memory to back each object.  When mapped into the GTT
-	or used in a command buffer, the 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&lt;-&gt;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).
-      </para>
-      <para>
-	Perhaps the most important GEM function 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.
+        The <methodname>read</methodname> and <methodname>poll</methodname>
+	operations provide support for reading DRM events and polling them. They
+	are implemented by
+	<programlisting>
+	.poll = drm_poll,
+	.read = drm_read,
+	.fasync = drm_fasync,
+	.llseek = no_llseek,
+	</programlisting>
+      </para>
+      <para>
+        The memory mapping implementation varies depending on how the driver
+	manages memory. Pre-GEM drivers will use <function>drm_mmap</function>,
+	while GEM-aware drivers will use <function>drm_gem_mmap</function>. See
+	<xref linkend="drm-gem"/>.
+	<programlisting>
+	.mmap = drm_gem_mmap,
+	</programlisting>
+      </para>
+      <para>
+        No other file operation is supported by the DRM API.
+      </para>
+    </sect2>
+    <sect2>
+      <title>IOCTLs</title>
+      <synopsis>struct drm_ioctl_desc *ioctls;
+int num_ioctls;</synopsis>
+      <abstract>Driver-specific ioctls descriptors table.</abstract>
+      <para>
+        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.
+      </para>
+      <para>
+        <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting>
+	<para>
+	  <parameter>ioctl</parameter> 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.
+	</para>
+	<para>
+	  <parameter>func</parameter> is a pointer to the ioctl handler function
+	  compatible with the <type>drm_ioctl_t</type> type.
+	  <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data,
+		struct drm_file *file_priv);</programlisting>
+	</para>
+	<para>
+	  <parameter>flags</parameter> is a bitmask combination of the following
+	  values. It restricts how the ioctl is allowed to be called.
+	  <itemizedlist>
+	    <listitem><para>
+	      DRM_AUTH - Only authenticated callers allowed
+	    </para></listitem>
+	    <listitem><para>
+	      DRM_MASTER - The ioctl can only be called on the master file
+	      handle
+	    </para></listitem>
+            <listitem><para>
+	      DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed
+	    </para></listitem>
+            <listitem><para>
+	      DRM_CONTROL_ALLOW - The ioctl can only be called on a control
+	      device
+	    </para></listitem>
+            <listitem><para>
+	      DRM_UNLOCKED - The ioctl handler will be called without locking
+	      the DRM global mutex
+	    </para></listitem>
+	  </itemizedlist>
+	</para>
       </para>
     </sect2>
-
-  </sect1>
-
-  <!-- Output management -->
-  <sect1>
-    <title>Output management</title>
-    <para>
-      At the core of the DRM output management code is a set of
-      structures representing CRTCs, encoders, and connectors.
-    </para>
-    <para>
-      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, 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.
-    </para>
-    <para>
-      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.
-    </para>
-    <para>
-      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 &amp;
-      connection status, and information about modes supported on the
-      attached displays.
-    </para>
-<!--!Edrivers/char/drm/drm_crtc.c-->
-  </sect1>
-
-  <sect1>
-    <title>Framebuffer management</title>
-    <para>
-      Clients need to provide a framebuffer object which provides a source
-      of pixels for a CRTC to deliver to the encoder(s) and ultimately the
-      connector(s). A framebuffer is fundamentally a driver-specific memory
-      object, made into an opaque handle by the DRM's addfb() function.
-      Once a framebuffer has been created this way, it may be passed to the
-      KMS mode setting routines for use in a completed configuration.
-    </para>
   </sect1>
 
   <sect1>
@@ -812,15 +2355,24 @@ void intel_crt_init(struct drm_device *dev)
     </para>
   </sect1>
 
+  <!-- Internals: suspend/resume -->
+
   <sect1>
-    <title>Suspend/resume</title>
+    <title>Suspend/Resume</title>
+    <para>
+      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.
+    </para>
+    <synopsis>int (*suspend) (struct drm_device *, pm_message_t state);
+int (*resume) (struct drm_device *);</synopsis>
     <para>
-      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.
+      Those are legacy suspend and resume methods. New driver should use the
+      power management interface provided by their bus type (usually through
+      the struct <structname>device_driver</structname> dev_pm_ops) and set
+      these methods to NULL.
     </para>
   </sect1>
 
@@ -833,6 +2385,35 @@ void intel_crt_init(struct drm_device *dev)
   </sect1>
   </chapter>
 
+<!-- TODO
+
+- Add a glossary
+- Document the struct_mutex catch-all lock
+- Document connector properties
+
+- Why is the load method optional?
+- What are drivers supposed to set the initial display state to, and how?
+  Connector's DPMS states are not initialized and are thus equal to
+  DRM_MODE_DPMS_ON. The fbcon compatibility layer calls
+  drm_helper_disable_unused_functions(), which disables unused encoders and
+  CRTCs, but doesn't touch the connectors' DPMS state, and
+  drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers
+  that don't implement (or just don't use) fbcon compatibility need to call
+  those functions themselves?
+- KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset()
+  around mode setting. Should this be done in the DRM core?
+- vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset()
+  call and never set back to 0. It seems to be safe to permanently set it to 1
+  in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as
+  well. This should be investigated.
+- crtc and connector .save and .restore operations are only used internally in
+  drivers, should they be removed from the core?
+- encoder mid-layer .save and .restore operations are only used internally in
+  drivers, should they be removed from the core?
+- encoder mid-layer .detect operation is only used internally in drivers,
+  should it be removed from the core?
+-->
+
   <!-- External interfaces -->
 
   <chapter id="drmExternals">
@@ -853,6 +2434,42 @@ void intel_crt_init(struct drm_device *dev)
       Cover generic ioctls and sysfs layout here.  We only need high-level
       info, since man pages should cover the rest.
     </para>
+
+  <!-- External: vblank handling -->
+
+    <sect1>
+      <title>VBlank event handling</title>
+      <para>
+        The DRM core exposes two vertical blank related ioctls:
+        <variablelist>
+          <varlistentry>
+            <term>DRM_IOCTL_WAIT_VBLANK</term>
+            <listitem>
+              <para>
+                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.
+              </para>
+            </listitem>
+          </varlistentry>
+          <varlistentry>
+            <term>DRM_IOCTL_MODESET_CTL</term>
+            <listitem>
+              <para>
+                This should be called by application level drivers before and
+                after mode setting, since on many devices the vertical blank
+                counter is reset at that time.  Internally, the DRM snapshots
+                the last vblank count when the ioctl is called with the
+                _DRM_PRE_MODESET command, so that the counter won't go backwards
+                (which is dealt with when _DRM_POST_MODESET is used).
+              </para>
+            </listitem>
+          </varlistentry>
+        </variablelist>
+<!--!Edrivers/char/drm/drm_irq.c-->
+      </para>
+    </sect1>
+
   </chapter>
 
   <!-- API reference -->
