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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
+
+<book id="drmDevelopersGuide">
+ <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>
+ <author>
+ <firstname>Daniel</firstname>
+ <surname>Vetter</surname>
+ <contrib>Contributions all over the place</contrib>
+ <affiliation>
+ <orgname>Intel Corporation</orgname>
+ <address>
+ <email>daniel.vetter@ffwll.ch</email>
+ </address>
+ </affiliation>
+ </author>
+ </authorgroup>
+
+ <copyright>
+ <year>2008-2009</year>
+ <year>2013-2014</year>
+ <holder>Intel Corporation</holder>
+ </copyright>
+ <copyright>
+ <year>2012</year>
+ <holder>Laurent Pinchart</holder>
+ </copyright>
+
+ <legalnotice>
+ <para>
+ The contents of this file may be used under the terms of the GNU
+ General Public License version 2 (the "GPL") as distributed in
+ the kernel source COPYING file.
+ </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>
+
+<part id="drmCore">
+ <title>DRM Core</title>
+ <partintro>
+ <para>
+ This first part of the DRM Developer's Guide documents core DRM code,
+ helper libraries for writing drivers and generic userspace interfaces
+ exposed by DRM drivers.
+ </para>
+ </partintro>
+
+ <chapter id="drmIntroduction">
+ <title>Introduction</title>
+ <para>
+ The Linux DRM layer contains code intended to support the needs
+ of complex graphics devices, usually containing programmable
+ pipelines well suited to 3D graphics acceleration. Graphics
+ drivers in the kernel may make use of DRM functions to make
+ tasks like memory management, interrupt handling and DMA easier,
+ and provide a uniform interface to applications.
+ </para>
+ <para>
+ A note on versions: this guide covers features found in the DRM
+ tree, including the TTM memory manager, output configuration and
+ mode setting, and the new vblank internals, in addition to all
+ the regular features found in current kernels.
+ </para>
+ <para>
+ [Insert diagram of typical DRM stack here]
+ </para>
+ </chapter>
+
+ <!-- Internals -->
+
+ <chapter id="drmInternals">
+ <title>DRM Internals</title>
+ <para>
+ This chapter documents DRM internals relevant to driver authors
+ and developers working to add support for the latest features to
+ existing drivers.
+ </para>
+ <para>
+ First, we go over some typical driver initialization
+ requirements, like setting up command buffers, creating an
+ initial output configuration, and initializing core services.
+ Subsequent sections cover core internals in more detail,
+ providing implementation notes and examples.
+ </para>
+ <para>
+ The DRM layer provides several services to graphics drivers,
+ many of them driven by the application interfaces it provides
+ through libdrm, the library that wraps most of the DRM ioctls.
+ These include vblank event handling, memory
+ management, output management, framebuffer management, command
+ submission &amp; fencing, suspend/resume support, and DMA
+ services.
+ </para>
+
+ <!-- Internals: driver init -->
+
+ <sect1>
+ <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>
+ <para>
+ Newer drivers that no longer require a <structname>drm_bus</structname>
+ structure can alternatively use the low-level device initialization and
+ registration functions such as <function>drm_dev_alloc()</function> and
+ <function>drm_dev_register()</function> directly.
+ </para>
+ <para>
+ The <structname>drm_driver</structname> structure contains static
+ information that describes the driver and features it supports, and
+ pointers to methods that the DRM core will call to implement the DRM API.
+ We will first go through the <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 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_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
+ managed by the DRM Core. The core will support simple IRQ handler
+ installation when the flag is set. The installation process is
+ described in <xref linkend="drm-irq-registration"/>.</para>
+ <para>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_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>
+ <varlistentry>
+ <term>DRIVER_RENDER</term>
+ <listitem><para>
+ Driver supports dedicated render nodes.
+ </para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>DRIVER_ATOMIC</term>
+ <listitem><para>
+ Driver supports atomic properties. In this case the driver
+ must implement appropriate obj->atomic_get_property() vfuncs
+ for any modeset objects with driver specific properties.
+ </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>Device Registration</title>
+ <para>
+ A number of functions are provided to help with device registration.
+ The functions deal with PCI and platform devices, respectively.
+ </para>
+!Edrivers/gpu/drm/drm_pci.c
+!Edrivers/gpu/drm/drm_platform.c
+ <para>
+ New drivers that no longer rely on the services provided by the
+ <structname>drm_bus</structname> structure can call the low-level
+ device registration functions directly. The
+ <function>drm_dev_alloc()</function> function can be used to allocate
+ and initialize a new <structname>drm_device</structname> structure.
+ Drivers will typically want to perform some additional setup on this
+ structure, such as allocating driver-specific data and storing a
+ pointer to it in the DRM device's <structfield>dev_private</structfield>
+ field. Drivers should also set the device's unique name using the
+ <function>drm_dev_set_unique()</function> function. After it has been
+ set up a device can be registered with the DRM subsystem by calling
+ <function>drm_dev_register()</function>. This will cause the device to
+ be exposed to userspace and will call the driver's
+ <structfield>.load()</structfield> implementation. When a device is
+ removed, the DRM device can safely be unregistered and freed by calling
+ <function>drm_dev_unregister()</function> followed by a call to
+ <function>drm_dev_unref()</function>.
+ </para>
+!Edrivers/gpu/drm/drm_drv.c
+ </sect2>
+ <sect2>
+ <title>Driver Load</title>
+ <para>
+ The <methodname>load</methodname> method is the driver and device
+ initialization entry point. The method is responsible for allocating and
+ initializing driver private data, performing resource allocation and
+ mapping (e.g. acquiring
+ clocks, mapping registers or allocating command buffers), initializing
+ the memory manager (<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>
+ 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 Data</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>
+ </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, devices that use more than one
+ IRQs need to be handled manually.
+ </para>
+ <sect4>
+ <title>Managed IRQ Registration</title>
+ <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 passed-in 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>
+ </sect4>
+ <sect4>
+ <title>Manual IRQ Registration</title>
+ <para>
+ Drivers that require multiple interrupt handlers can't use the managed
+ IRQ registration functions. In that case IRQs must be registered and
+ unregistered manually (usually with the <function>request_irq</function>
+ and <function>free_irq</function> functions, or their devm_* equivalent).
+ </para>
+ <para>
+ When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ
+ driver feature flag, and must not provide the
+ <methodname>irq_handler</methodname> driver operation. They must set the
+ <structname>drm_device</structname> <structfield>irq_enabled</structfield>
+ field to 1 upon registration of the IRQs, and clear it to 0 after
+ unregistering the IRQs.
+ </para>
+ </sect4>
+ </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 behaviour like
+ hangs or memory corruption.
+ <!--!Fdrivers/pci/rom.c pci_map_rom-->
+ </para>
+ </sect3>
+ </sect2>
+ </sect1>
+
+ <!-- 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 accommodate the need of
+ all hardware, supporting both Unified Memory Architecture (UMA) devices
+ and devices with dedicated video RAM (i.e. most discrete video cards).
+ This resulted in a large, complex piece of code that turned out to be
+ hard to use for driver development.
+ </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 capabilities and is thus limited to
+ UMA devices.
+ </para>
+ <sect2>
+ <title>The Translation Table Manager (TTM)</title>
+ <para>
+ TTM design background and information belongs here.
+ </para>
+ <sect3>
+ <title>TTM initialization</title>
+ <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:
+ </para>
+ <programlisting>
+ struct ttm_global_reference {
+ enum ttm_global_types global_type;
+ size_t size;
+ void *object;
+ int (*init) (struct ttm_global_reference *);
+ void (*release) (struct ttm_global_reference *);
+ };
+ </programlisting>
+ <para>
+ There should be one global reference structure for your memory
+ manager as a whole, and there will be others for each object
+ created by the memory manager at runtime. Your global TTM should
+ have a type of TTM_GLOBAL_TTM_MEM. The size field for the global
+ object should be sizeof(struct ttm_mem_global), and the init and
+ release hooks should point at your driver-specific init and
+ release routines, which probably eventually call
+ ttm_mem_global_init and ttm_mem_global_release, respectively.
+ </para>
+ <para>
+ Once your global TTM accounting structure is set up and initialized
+ by calling ttm_global_item_ref() on it,
+ you need to create a buffer object TTM to
+ provide a pool for buffer object allocation by clients and the
+ kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO,
+ and its size should be sizeof(struct ttm_bo_global). Again,
+ driver-specific init and release functions may be provided,
+ likely eventually calling ttm_bo_global_init() and
+ ttm_bo_global_release(), respectively. Also, like the previous
+ object, ttm_global_item_ref() is used to create an initial reference
+ count for the TTM, which will call your initialization function.
+ </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 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>
+ GEM also supports buffer sharing with dma-buf file descriptors through
+ PRIME. GEM-based drivers must use the provided helpers functions to
+ implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />.
+ Since sharing file descriptors is inherently more secure than the
+ easily guessable and global GEM names it is the preferred buffer
+ sharing mechanism. Sharing buffers through GEM names is only supported
+ for legacy userspace. Furthermore PRIME also allows cross-device
+ buffer sharing since it is based on dma-bufs.
+ </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>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>
+ <sect3>
+ <title>GEM Function Reference</title>
+!Edrivers/gpu/drm/drm_gem.c
+ </sect3>
+ </sect2>
+ <sect2>
+ <title>VMA Offset Manager</title>
+!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager
+!Edrivers/gpu/drm/drm_vma_manager.c
+!Iinclude/drm/drm_vma_manager.h
+ </sect2>
+ <sect2 id="drm-prime-support">
+ <title>PRIME Buffer Sharing</title>
+ <para>
+ PRIME is the cross device buffer sharing framework in drm, originally
+ created for the OPTIMUS range of multi-gpu platforms. To userspace
+ PRIME buffers are dma-buf based file descriptors.
+ </para>
+ <sect3>
+ <title>Overview and Driver Interface</title>
+ <para>
+ Similar to GEM global names, PRIME file descriptors are
+ also used to share buffer objects across processes. They offer
+ additional security: as file descriptors must be explicitly sent over
+ UNIX domain sockets to be shared between applications, they can't be
+ guessed like the globally unique GEM names.
+ </para>
+ <para>
+ Drivers that support the 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. Similar to the mode setting
+ API PRIME is agnostic to the underlying buffer object manager, as
+ long as handles are 32bit unsigned integers.
+ </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
+ PRIME.
+ </para>
+ </sect3>
+ <sect3>
+ <title>PRIME Helper Functions</title>
+!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers
+ </sect3>
+ </sect2>
+ <sect2>
+ <title>PRIME Function References</title>
+!Edrivers/gpu/drm/drm_prime.c
+ </sect2>
+ <sect2>
+ <title>DRM MM Range Allocator</title>
+ <sect3>
+ <title>Overview</title>
+!Pdrivers/gpu/drm/drm_mm.c Overview
+ </sect3>
+ <sect3>
+ <title>LRU Scan/Eviction Support</title>
+!Pdrivers/gpu/drm/drm_mm.c lru scan roaster
+ </sect3>
+ </sect2>
+ <sect2>
+ <title>DRM MM Range Allocator Function References</title>
+!Edrivers/gpu/drm/drm_mm.c
+!Iinclude/drm/drm_mm.h
+ </sect2>
+ <sect2>
+ <title>CMA Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_gem_cma_helper.c cma helpers
+!Edrivers/gpu/drm/drm_gem_cma_helper.c
+!Iinclude/drm/drm_gem_cma_helper.h
+ </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>Display Modes Function Reference</title>
+!Iinclude/drm/drm_modes.h
+!Edrivers/gpu/drm/drm_modes.c
+ </sect2>
+ <sect2>
+ <title>Atomic Mode Setting Function Reference</title>
+!Edrivers/gpu/drm/drm_atomic.c
+ </sect2>
+ <sect2>
+ <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>
+ 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. For drivers using
+ GEM as their userspace buffer management interface this would be a GEM
+ handle. Drivers are however free to use their own backing storage object
+ handles, e.g. vmwgfx directly exposes special TTM handles to userspace
+ and so expects TTM handles in the create ioctl and not GEM handles.
+ </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. 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>
+
+ <para>
+ The initialization of the new framebuffer instance is finalized with a
+ call to <function>drm_framebuffer_init</function> which takes a pointer
+ to DRM frame buffer operations (struct
+ <structname>drm_framebuffer_funcs</structname>). Note that this function
+ publishes the framebuffer and so from this point on it can be accessed
+ concurrently from other threads. Hence it must be the last step in the
+ driver's framebuffer initialization sequence. Frame buffer operations
+ are
+ <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>
+ The lifetime of a drm framebuffer is controlled with a reference count,
+ drivers can grab additional references with
+ <function>drm_framebuffer_reference</function>and drop them
+ again with <function>drm_framebuffer_unreference</function>. For
+ driver-private framebuffers for which the last reference is never
+ dropped (e.g. for the fbdev framebuffer when the struct
+ <structname>drm_framebuffer</structname> is embedded into the fbdev
+ helper struct) drivers can manually clean up a framebuffer at module
+ unload time with
+ <function>drm_framebuffer_unregister_private</function>.
+ </para>
+ </sect2>
+ <sect2>
+ <title>Dumb Buffer Objects</title>
+ <para>
+ The KMS API doesn't standardize backing storage object creation and
+ leaves it to driver-specific ioctls. Furthermore actually creating a
+ buffer object even for GEM-based drivers is done through a
+ driver-specific ioctl - GEM only has a common userspace interface for
+ sharing and destroying objects. While not an issue for full-fledged
+ graphics stacks that include device-specific userspace components (in
+ libdrm for instance), this limit makes DRM-based early boot graphics
+ unnecessarily complex.
+ </para>
+ <para>
+ Dumb objects partly alleviate the problem by providing a standard
+ API to create dumb buffers suitable for scanout, which can then be used
+ to create KMS frame buffers.
+ </para>
+ <para>
+ To support dumb 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 driver
+ object (GEM or TTM handle) 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 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
+ 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 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>
+ <para>
+ Note that dumb objects may not be used for gpu acceleration, as has been
+ attempted on some ARM embedded platforms. Such drivers really must have
+ a hardware-specific ioctl to allocate suitable buffer objects.
+ </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 fb helper can just call the
+ <function>drm_fb_helper_hotplug_event</function> function to handle this
+ operation.
+ </para>
+ </sect2>
+ <sect2>
+ <title>Locking</title>
+ <para>
+ Beside some lookup structures with their own locking (which is hidden
+ behind the interface functions) most of the modeset state is protected
+ by the <code>dev-&lt;mode_config.lock</code> mutex and additionally
+ per-crtc locks to allow cursor updates, pageflips and similar operations
+ to occur concurrently with background tasks like output detection.
+ Operations which cross domains like a full modeset always grab all
+ locks. Drivers there need to protect resources shared between crtcs with
+ additional locking. They also need to be careful to always grab the
+ relevant crtc locks if a modset functions touches crtc state, e.g. for
+ load detection (which does only grab the <code>mode_config.lock</code>
+ to allow concurrent screen updates on live crtcs).
+ </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>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 id="drm-kms-crtcops">
+ <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>
+ Note that the drm core has no notion of restoring the mode setting
+ state after resume, since all resume handling is in the full
+ responsibility of the driver. The common mode setting helper library
+ though provides a helper which can be used for this:
+ <function>drm_helper_resume_force_mode</function>.
+ </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 targeting the new frame buffer has
+ completed, the CRTC will be reprogrammed to display that frame buffer
+ after the next vertical refresh. The operation must return immediately
+ without waiting for rendering or page flip to complete and must block
+ any new rendering to the frame buffer until the page flip completes.
+ </para>
+ <para>
+ If a page flip can be successfully scheduled the driver must set the
+ <code>drm_crtc-&gt;fb</code> field to the new framebuffer pointed to
+ by <code>fb</code>. This is important so that the reference counting
+ on framebuffers stays balanced.
+ </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 call <methodname>drm_send_vblank_event</methodname>
+ to fill in the event and send to wake up any waiting processes.
+ This can be performed with
+ <programlisting><![CDATA[
+ spin_lock_irqsave(&dev->event_lock, flags);
+ ...
+ drm_send_vblank_event(dev, pipe, event);
+ 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 (*set_property)(struct drm_crtc *crtc,
+ struct drm_property *property, uint64_t value);</synopsis>
+ <para>
+ Set the value of the given CRTC property to
+ <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
+ for more information about properties.
+ </para>
+ </listitem>
+ <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>
+ <para>
+ The DRM core recognizes three types of planes:
+ <itemizedlist>
+ <listitem>
+ DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. Primary
+ planes are the planes operated upon by CRTC modesetting and flipping
+ operations described in <xref linkend="drm-kms-crtcops"/>.
+ </listitem>
+ <listitem>
+ DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. Cursor
+ planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
+ DRM_IOCTL_MODE_CURSOR2 ioctls.
+ </listitem>
+ <listitem>
+ DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes.
+ Some drivers refer to these types of planes as "sprites" internally.
+ </listitem>
+ </itemizedlist>
+ For compatibility with legacy userspace, only overlay planes are made
+ available to userspace by default. Userspace clients may set the
+ DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that
+ they wish to receive a universal plane list containing all plane types.
+ </para>
+ <sect3>
+ <title>Plane Initialization</title>
+ <para>
+ 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_universal_plane_init</function>. The function takes a bitmask
+ of the CRTCs that can be associated with the plane, a pointer to the
+ plane functions, a list of format supported formats, and the type of
+ plane (primary, cursor, or overlay) being initialized.
+ </para>
+ <para>
+ Cursor and overlay planes are optional. All drivers should provide
+ one primary plane per CRTC (although this requirement may change in
+ the future); drivers that do not wish to provide special handling for
+ primary planes may make use of the helper functions described in
+ <xref linkend="drm-kms-planehelpers"/> to create and register a
+ primary plane with standard capabilities.
+ </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>
+ <listitem>
+ <synopsis>void (*set_property)(struct drm_plane *plane,
+ struct drm_property *property, uint64_t value);</synopsis>
+ <para>
+ Set the value of the given plane property to
+ <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
+ for more information about properties.
+ </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_connector_register</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 (*set_property)(struct drm_connector *connector,
+ struct drm_property *property, uint64_t value);</synopsis>
+ <para>
+ Set the value of the given connector property to
+ <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
+ for more information about properties.
+ </para>
+ </listitem>
+ <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_connector_unregister</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;
+ struct intel_output *intel_output;
+
+ intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
+ if (!intel_output)
+ return;
+
+ connector = &intel_output->base;
+ drm_connector_init(dev, &intel_output->base,
+ &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
+
+ drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
+ DRM_MODE_ENCODER_DAC);
+
+ drm_mode_connector_attach_encoder(&intel_output->base,
+ &intel_output->enc);
+
+ /* Set up the DDC bus. */
+ intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
+ if (!intel_output->ddc_bus) {
+ dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
+ "failed.\n");
+ return;
+ }
+
+ intel_output->type = INTEL_OUTPUT_ANALOG;
+ connector->interlace_allowed = 0;
+ connector->doublescan_allowed = 0;
+
+ drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
+ drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
+
+ drm_connector_register(connector);
+}]]></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>
+ <sect2>
+ <title>KMS API Functions</title>
+!Edrivers/gpu/drm/drm_crtc.c
+ </sect2>
+ <sect2>
+ <title>KMS Data Structures</title>
+!Iinclude/drm/drm_crtc.h
+ </sect2>
+ <sect2>
+ <title>KMS Locking</title>
+!Pdrivers/gpu/drm/drm_modeset_lock.c kms locking
+!Iinclude/drm/drm_modeset_lock.h
+!Edrivers/gpu/drm/drm_modeset_lock.c
+ </sect2>
+ </sect1>
+
+ <!-- Internals: kms helper functions -->
+
+ <sect1>
+ <title>Mode Setting Helper Functions</title>
+ <para>
+ The plane, CRTC, encoder and connector functions provided by the drivers
+ implement the DRM API. They're called by the DRM core and ioctl handlers
+ to handle device state changes and configuration request. As implementing
+ those functions often requires logic not specific to drivers, mid-layer
+ helper functions are available to avoid duplicating boilerplate code.
+ </para>
+ <para>
+ The DRM core contains one mid-layer implementation. The mid-layer provides
+ implementations of several plane, CRTC, encoder and connector functions
+ (called from the top of the mid-layer) that pre-process requests and call
+ lower-level functions provided by the driver (at the bottom of the
+ mid-layer). For instance, the
+ <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 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>
+ 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>
+ If the helper operation returns no mode, and if the connector status
+ is connector_status_connected, standard VESA DMT modes up to
+ 1024x768 are automatically added to the modes list by a call to
+ <function>drm_add_modes_noedid</function>.
+ </para>
+ <para>
+ The function then filters out modes larger than
+ <parameter>max_width</parameter> and <parameter>max_height</parameter>
+ if specified. It finally calls the optional 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>
+ <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>,
+ adding standard VESA DMT modes with <function>drm_add_modes_noedid</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>
+ Note that the caller function will automatically add standard VESA
+ DMT modes up to 1024x768 if the <methodname>get_modes</methodname>
+ helper operation returns no mode and if the connector status is
+ connector_status_connected. There is no need to call
+ <function>drm_add_edid_modes</function> manually in that case.
+ </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> fills 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 initialization 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 optional.
+ </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>
+ <sect2>
+ <title>Atomic Modeset Helper Functions Reference</title>
+ <sect3>
+ <title>Overview</title>
+!Pdrivers/gpu/drm/drm_atomic_helper.c overview
+ </sect3>
+ <sect3>
+ <title>Implementing Asynchronous Atomic Commit</title>
+!Pdrivers/gpu/drm/drm_atomic_helper.c implementing async commit
+ </sect3>
+ <sect3>
+ <title>Atomic State Reset and Initialization</title>
+!Pdrivers/gpu/drm/drm_atomic_helper.c atomic state reset and initialization
+ </sect3>
+!Iinclude/drm/drm_atomic_helper.h
+!Edrivers/gpu/drm/drm_atomic_helper.c
+ </sect2>
+ <sect2>
+ <title>Modeset Helper Functions Reference</title>
+!Iinclude/drm/drm_crtc_helper.h
+!Edrivers/gpu/drm/drm_crtc_helper.c
+!Pdrivers/gpu/drm/drm_crtc_helper.c overview
+ </sect2>
+ <sect2>
+ <title>Output Probing Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview
+!Edrivers/gpu/drm/drm_probe_helper.c
+ </sect2>
+ <sect2>
+ <title>fbdev Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers
+!Edrivers/gpu/drm/drm_fb_helper.c
+!Iinclude/drm/drm_fb_helper.h
+ </sect2>
+ <sect2>
+ <title>Display Port Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
+!Iinclude/drm/drm_dp_helper.h
+!Edrivers/gpu/drm/drm_dp_helper.c
+ </sect2>
+ <sect2>
+ <title>Display Port MST Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper
+!Iinclude/drm/drm_dp_mst_helper.h
+!Edrivers/gpu/drm/drm_dp_mst_topology.c
+ </sect2>
+ <sect2>
+ <title>MIPI DSI Helper Functions Reference</title>
+!Pdrivers/gpu/drm/drm_mipi_dsi.c dsi helpers
+!Iinclude/drm/drm_mipi_dsi.h
+!Edrivers/gpu/drm/drm_mipi_dsi.c
+ </sect2>
+ <sect2>
+ <title>EDID Helper Functions Reference</title>
+!Edrivers/gpu/drm/drm_edid.c
+ </sect2>
+ <sect2>
+ <title>Rectangle Utilities Reference</title>
+!Pinclude/drm/drm_rect.h rect utils
+!Iinclude/drm/drm_rect.h
+!Edrivers/gpu/drm/drm_rect.c
+ </sect2>
+ <sect2>
+ <title>Flip-work Helper Reference</title>
+!Pinclude/drm/drm_flip_work.h flip utils
+!Iinclude/drm/drm_flip_work.h
+!Edrivers/gpu/drm/drm_flip_work.c
+ </sect2>
+ <sect2>
+ <title>HDMI Infoframes Helper Reference</title>
+ <para>
+ Strictly speaking this is not a DRM helper library but generally useable
+ by any driver interfacing with HDMI outputs like v4l or alsa drivers.
+ But it nicely fits into the overall topic of mode setting helper
+ libraries and hence is also included here.
+ </para>
+!Iinclude/linux/hdmi.h
+!Edrivers/video/hdmi.c
+ </sect2>
+ <sect2>
+ <title id="drm-kms-planehelpers">Plane Helper Reference</title>
+!Edrivers/gpu/drm/drm_plane_helper.c
+!Pdrivers/gpu/drm/drm_plane_helper.c overview
+ </sect2>
+ <sect2>
+ <title>Tile group</title>
+!Pdrivers/gpu/drm/drm_crtc.c Tile group
+ </sect2>
+ </sect1>
+
+ <!-- Internals: kms properties -->
+
+ <sect1 id="drm-kms-properties">
+ <title>KMS Properties</title>
+ <para>
+ Drivers may need to expose additional parameters to applications than
+ those described in the previous sections. KMS supports attaching
+ properties to CRTCs, connectors and planes and offers a userspace API to
+ list, get and set the property values.
+ </para>
+ <para>
+ Properties are identified by a name that uniquely defines the property
+ purpose, and store an associated value. For all property types except blob
+ properties the value is a 64-bit unsigned integer.
+ </para>
+ <para>
+ KMS differentiates between properties and property instances. Drivers
+ first create properties and then create and associate individual instances
+ of those properties to objects. A property can be instantiated multiple
+ times and associated with different objects. Values are stored in property
+ instances, and all other property information are stored in the property
+ and shared between all instances of the property.
+ </para>
+ <para>
+ Every property is created with a type that influences how the KMS core
+ handles the property. Supported property types are
+ <variablelist>
+ <varlistentry>
+ <term>DRM_MODE_PROP_RANGE</term>
+ <listitem><para>Range properties report their minimum and maximum
+ admissible values. The KMS core verifies that values set by
+ application fit in that range.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>DRM_MODE_PROP_ENUM</term>
+ <listitem><para>Enumerated properties take a numerical value that
+ ranges from 0 to the number of enumerated values defined by the
+ property minus one, and associate a free-formed string name to each
+ value. Applications can retrieve the list of defined value-name pairs
+ and use the numerical value to get and set property instance values.
+ </para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>DRM_MODE_PROP_BITMASK</term>
+ <listitem><para>Bitmask properties are enumeration properties that
+ additionally restrict all enumerated values to the 0..63 range.
+ Bitmask property instance values combine one or more of the
+ enumerated bits defined by the property.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>DRM_MODE_PROP_BLOB</term>
+ <listitem><para>Blob properties store a binary blob without any format
+ restriction. The binary blobs are created as KMS standalone objects,
+ and blob property instance values store the ID of their associated
+ blob object.</para>
+ <para>Blob properties are only used for the connector EDID property
+ and cannot be created by drivers.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ <para>
+ To create a property drivers call one of the following functions depending
+ on the property type. All property creation functions take property flags
+ and name, as well as type-specific arguments.
+ <itemizedlist>
+ <listitem>
+ <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
+ const char *name,
+ uint64_t min, uint64_t max);</synopsis>
+ <para>Create a range property with the given minimum and maximum
+ values.</para>
+ </listitem>
+ <listitem>
+ <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
+ const char *name,
+ const struct drm_prop_enum_list *props,
+ int num_values);</synopsis>
+ <para>Create an enumerated property. The <parameter>props</parameter>
+ argument points to an array of <parameter>num_values</parameter>
+ value-name pairs.</para>
+ </listitem>
+ <listitem>
+ <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
+ int flags, const char *name,
+ const struct drm_prop_enum_list *props,
+ int num_values);</synopsis>
+ <para>Create a bitmask property. The <parameter>props</parameter>
+ argument points to an array of <parameter>num_values</parameter>
+ value-name pairs.</para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ Properties can additionally be created as immutable, in which case they
+ will be read-only for applications but can be modified by the driver. To
+ create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE
+ flag at property creation time.
+ </para>
+ <para>
+ When no array of value-name pairs is readily available at property
+ creation time for enumerated or range properties, drivers can create
+ the property using the <function>drm_property_create</function> function
+ and manually add enumeration value-name pairs by calling the
+ <function>drm_property_add_enum</function> function. Care must be taken to
+ properly specify the property type through the <parameter>flags</parameter>
+ argument.
+ </para>
+ <para>
+ After creating properties drivers can attach property instances to CRTC,
+ connector and plane objects by calling the
+ <function>drm_object_attach_property</function>. The function takes a
+ pointer to the target object, a pointer to the previously created property
+ and an initial instance value.
+ </para>
+ <sect2>
+ <title>Existing KMS Properties</title>
+ <para>
+ The following table gives description of drm properties exposed by various
+ modules/drivers.
+ </para>
+ <table border="1" cellpadding="0" cellspacing="0">
+ <tbody>
+ <tr style="font-weight: bold;">
+ <td valign="top" >Owner Module/Drivers</td>
+ <td valign="top" >Group</td>
+ <td valign="top" >Property Name</td>
+ <td valign="top" >Type</td>
+ <td valign="top" >Property Values</td>
+ <td valign="top" >Object attached</td>
+ <td valign="top" >Description/Restrictions</td>
+ </tr>
+ <tr>
+ <td rowspan="36" valign="top" >DRM</td>
+ <td rowspan="5" valign="top" >Connector</td>
+ <td valign="top" >“EDID”</td>
+ <td valign="top" >BLOB | IMMUTABLE</td>
+ <td valign="top" >0</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >Contains id of edid blob ptr object.</td>
+ </tr>
+ <tr>
+ <td valign="top" >“DPMS”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ “On”, “Standby”, “Suspend”, “Off” }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >Contains DPMS operation mode value.</td>
+ </tr>
+ <tr>
+ <td valign="top" >“PATH”</td>
+ <td valign="top" >BLOB | IMMUTABLE</td>
+ <td valign="top" >0</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >Contains topology path to a connector.</td>
+ </tr>
+ <tr>
+ <td valign="top" >“TILE”</td>
+ <td valign="top" >BLOB | IMMUTABLE</td>
+ <td valign="top" >0</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >Contains tiling information for a connector.</td>
+ </tr>
+ <tr>
+ <td valign="top" >“CRTC_ID”</td>
+ <td valign="top" >OBJECT</td>
+ <td valign="top" >DRM_MODE_OBJECT_CRTC</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >CRTC that connector is attached to (atomic)</td>
+ </tr>
+ <tr>
+ <td rowspan="11" valign="top" >Plane</td>
+ <td valign="top" >“type”</td>
+ <td valign="top" >ENUM | IMMUTABLE</td>
+ <td valign="top" >{ "Overlay", "Primary", "Cursor" }</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Plane type</td>
+ </tr>
+ <tr>
+ <td valign="top" >“SRC_X”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=UINT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout source x coordinate in 16.16 fixed point (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“SRC_Y”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=UINT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout source y coordinate in 16.16 fixed point (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“SRC_W”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=UINT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout source width in 16.16 fixed point (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“SRC_H”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=UINT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout source height in 16.16 fixed point (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“CRTC_X”</td>
+ <td valign="top" >SIGNED_RANGE</td>
+ <td valign="top" >Min=INT_MIN, Max=INT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout CRTC (destination) x coordinate (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“CRTC_Y”</td>
+ <td valign="top" >SIGNED_RANGE</td>
+ <td valign="top" >Min=INT_MIN, Max=INT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout CRTC (destination) y coordinate (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“CRTC_W”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=UINT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout CRTC (destination) width (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“CRTC_H”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=UINT_MAX</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout CRTC (destination) height (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“FB_ID”</td>
+ <td valign="top" >OBJECT</td>
+ <td valign="top" >DRM_MODE_OBJECT_FB</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >Scanout framebuffer (atomic)</td>
+ </tr>
+ <tr>
+ <td valign="top" >“CRTC_ID”</td>
+ <td valign="top" >OBJECT</td>
+ <td valign="top" >DRM_MODE_OBJECT_CRTC</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >CRTC that plane is attached to (atomic)</td>
+ </tr>
+ <tr>
+ <td rowspan="2" valign="top" >DVI-I</td>
+ <td valign="top" >“subconnector”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ “Unknown”, “DVI-D”, “DVI-A” }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“select subconnector”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ “Automatic”, “DVI-D”, “DVI-A” }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="13" valign="top" >TV</td>
+ <td valign="top" >“subconnector”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“select subconnector”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“mode”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“left margin”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“right margin”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“top margin”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“bottom margin”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“brightness”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“contrast”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“flicker reduction”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“overscan”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“saturation”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“hue”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="2" valign="top" >Virtual GPU</td>
+ <td valign="top" >“suggested X”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0xffffffff</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >property to suggest an X offset for a connector</td>
+ </tr>
+ <tr>
+ <td valign="top" >“suggested Y”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0xffffffff</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >property to suggest an Y offset for a connector</td>
+ </tr>
+ <tr>
+ <td rowspan="3" valign="top" >Optional</td>
+ <td valign="top" >“scaling mode”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"aspect ratio"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "None", "4:3", "16:9" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >DRM property to set aspect ratio from user space app.
+ This enum is made generic to allow addition of custom aspect
+ ratios.</td>
+ </tr>
+ <tr>
+ <td valign="top" >“dirty”</td>
+ <td valign="top" >ENUM | IMMUTABLE</td>
+ <td valign="top" >{ "Off", "On", "Annotate" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="21" valign="top" >i915</td>
+ <td rowspan="2" valign="top" >Generic</td>
+ <td valign="top" >"Broadcast RGB"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“audio”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "force-dvi", "off", "auto", "on" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="1" valign="top" >Plane</td>
+ <td valign="top" >“rotation”</td>
+ <td valign="top" >BITMASK</td>
+ <td valign="top" >{ 0, "rotate-0" }, { 2, "rotate-180" }</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="17" valign="top" >SDVO-TV</td>
+ <td valign="top" >“mode”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"left_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"right_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"top_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"bottom_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“hpos”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“vpos”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“contrast”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“saturation”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“hue”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“sharpness”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“flicker_filter”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“flicker_filter_adaptive”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“flicker_filter_2d”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“tv_chroma_filter”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“tv_luma_filter”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“dot_crawl”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >SDVO-TV/LVDS</td>
+ <td valign="top" >“brightness”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="2" valign="top" >CDV gma-500</td>
+ <td rowspan="2" valign="top" >Generic</td>
+ <td valign="top" >"Broadcast RGB"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ “Full”, “Limited 16:235” }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"Broadcast RGB"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ “off”, “auto”, “on” }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="19" valign="top" >Poulsbo</td>
+ <td rowspan="1" valign="top" >Generic</td>
+ <td valign="top" >“backlight”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=100</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="17" valign="top" >SDVO-TV</td>
+ <td valign="top" >“mode”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"left_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"right_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"top_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"bottom_margin"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“hpos”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“vpos”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“contrast”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“saturation”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“hue”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“sharpness”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“flicker_filter”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“flicker_filter_adaptive”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“flicker_filter_2d”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“tv_chroma_filter”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“tv_luma_filter”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“dot_crawl”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >SDVO-TV/LVDS</td>
+ <td valign="top" >“brightness”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max= SDVO dependent</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="11" valign="top" >armada</td>
+ <td rowspan="2" valign="top" >CRTC</td>
+ <td valign="top" >"CSC_YUV"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td>
+ <td valign="top" >CRTC</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"CSC_RGB"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "Auto", "Computer system", "Studio" }</td>
+ <td valign="top" >CRTC</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="9" valign="top" >Overlay</td>
+ <td valign="top" >"colorkey"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0xffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"colorkey_min"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0xffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"colorkey_max"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0xffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"colorkey_val"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0xffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"colorkey_alpha"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0xffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"colorkey_mode"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "disabled", "Y component", "U component"
+ , "V component", "RGB", “R component", "G component", "B component" }</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"brightness"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=256 + 255</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"contrast"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0x7fff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"saturation"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0x7fff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="2" valign="top" >exynos</td>
+ <td valign="top" >CRTC</td>
+ <td valign="top" >“mode”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "normal", "blank" }</td>
+ <td valign="top" >CRTC</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >Overlay</td>
+ <td valign="top" >“zpos”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=MAX_PLANE-1</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="2" valign="top" >i2c/ch7006_drv</td>
+ <td valign="top" >Generic</td>
+ <td valign="top" >“scale”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=2</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="1" valign="top" >TV</td>
+ <td valign="top" >“mode”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc"
+ , "PAL-60", "NTSC-M", "NTSC-J" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="15" valign="top" >nouveau</td>
+ <td rowspan="6" valign="top" >NV10 Overlay</td>
+ <td valign="top" >"colorkey"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0x01ffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“contrast”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=8192-1</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“brightness”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1024</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“hue”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=359</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“saturation”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=8192-1</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“iturbt_709”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="2" valign="top" >Nv04 Overlay</td>
+ <td valign="top" >“colorkey”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0x01ffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“brightness”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1024</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="7" valign="top" >Display</td>
+ <td valign="top" >“dithering mode”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "auto", "off", "on" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“dithering depth”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“underscan”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“underscan hborder”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=128</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“underscan vborder”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=128</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“vibrant hue”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=180</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“color vibrance”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=200</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="2" valign="top" >omap</td>
+ <td rowspan="2" valign="top" >Generic</td>
+ <td valign="top" >“rotation”</td>
+ <td valign="top" >BITMASK</td>
+ <td valign="top" >{ 0, "rotate-0" },
+ { 1, "rotate-90" },
+ { 2, "rotate-180" },
+ { 3, "rotate-270" },
+ { 4, "reflect-x" },
+ { 5, "reflect-y" }</td>
+ <td valign="top" >CRTC, Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >“zorder”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=3</td>
+ <td valign="top" >CRTC, Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >qxl</td>
+ <td valign="top" >Generic</td>
+ <td valign="top" >“hotplug_mode_update"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="9" valign="top" >radeon</td>
+ <td valign="top" >DVI-I</td>
+ <td valign="top" >“coherent”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >DAC enable load detect</td>
+ <td valign="top" >“load detection”</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=1</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >TV Standard</td>
+ <td valign="top" >"tv standard"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j"
+ , "scart-pal", "pal-cn", "secam" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >legacy TMDS PLL detect</td>
+ <td valign="top" >"tmds_pll"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "driver", "bios" }</td>
+ <td valign="top" >-</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="3" valign="top" >Underscan</td>
+ <td valign="top" >"underscan"</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "off", "on", "auto" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"underscan hborder"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=128</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"underscan vborder"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=128</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >Audio</td>
+ <td valign="top" >“audio”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "off", "on", "auto" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >FMT Dithering</td>
+ <td valign="top" >“dither”</td>
+ <td valign="top" >ENUM</td>
+ <td valign="top" >{ "off", "on" }</td>
+ <td valign="top" >Connector</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td rowspan="3" valign="top" >rcar-du</td>
+ <td rowspan="3" valign="top" >Generic</td>
+ <td valign="top" >"alpha"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=255</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"colorkey"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=0, Max=0x01ffffff</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ <tr>
+ <td valign="top" >"zpos"</td>
+ <td valign="top" >RANGE</td>
+ <td valign="top" >Min=1, Max=7</td>
+ <td valign="top" >Plane</td>
+ <td valign="top" >TBD</td>
+ </tr>
+ </tbody>
+ </table>
+ </sect2>
+ </sect1>
+
+ <!-- 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>
+ 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.
+ Zero means never disable, and a negative value means disable immediately.
+ Drivers may override the behaviour by setting the
+ <structname>drm_device</structname>
+ <structfield>vblank_disable_immediate</structfield> flag, which when set
+ causes vblank interrupts to be disabled immediately regardless of the
+ drm_vblank_offdelay value. The flag should only be set if there's a
+ properly working hardware vblank counter present.
+ </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>
+ <sect2>
+ <title>Vertical Blanking and Interrupt Handling Functions Reference</title>
+!Edrivers/gpu/drm/drm_irq.c
+!Finclude/drm/drmP.h drm_crtc_vblank_waitqueue
+ </sect2>
+ </sect1>
+
+ <!-- Internals: open/close, file operations and ioctls -->
+
+ <sect1>
+ <title>Open/Close, File Operations and IOCTLs</title>
+ <sect2>
+ <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>
+ The <methodname>firstopen</methodname> method is called by the DRM core
+ for legacy UMS (User Mode Setting) drivers only when an application
+ opens a device that has no other opened file handle. UMS drivers can
+ implement it to acquire device resources. KMS drivers can't use the
+ method and must acquire resources in the <methodname>load</methodname>
+ method instead.
+ </para>
+ <para>
+ Similarly the <methodname>lastclose</methodname> method is called when
+ the last application holding a file handle opened on the device closes
+ it, for both UMS and KMS drivers. Additionally, the method is also
+ called at module unload time or, for hot-pluggable devices, when the
+ device is unplugged. The <methodname>firstopen</methodname> and
+ <methodname>lastclose</methodname> calls can thus be unbalanced.
+ </para>
+ <para>
+ 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. It can also be
+ used to execute delayed power switching state changes, e.g. in
+ conjunction with the vga-switcheroo infrastructure. Beyond that KMS
+ drivers should not do any further cleanup. Only legacy UMS drivers might
+ need to clean up device state so that the vga console or an independent
+ fbdev driver could take over.
+ </para>
+ </sect2>
+ <sect2>
+ <title>File Operations</title>
+ <synopsis>const struct file_operations *fops</synopsis>
+ <abstract>File operations for the DRM device node.</abstract>
+ <para>
+ 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>
+ 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>
+ 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,
+ .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>
+ <sect1>
+ <title>Legacy Support Code</title>
+ <para>
+ The section very briefly covers some of the old legacy support code which
+ is only used by old DRM drivers which have done a so-called shadow-attach
+ to the underlying device instead of registering as a real driver. This
+ also includes some of the old generic buffer management and command
+ submission code. Do not use any of this in new and modern drivers.
+ </para>
+
+ <sect2>
+ <title>Legacy 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>
+ Those are legacy suspend and resume methods which
+ <emphasis>only</emphasis> work with the legacy shadow-attach driver
+ registration functions. New driver should use the power management
+ interface provided by their bus type (usually through
+ the struct <structname>device_driver</structname> dev_pm_ops) and set
+ these methods to NULL.
+ </para>
+ </sect2>
+
+ <sect2>
+ <title>Legacy DMA Services</title>
+ <para>
+ This should cover how DMA mapping etc. is supported by the core.
+ These functions are deprecated and should not be used.
+ </para>
+ </sect2>
+ </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">
+ <title>Userland interfaces</title>
+ <para>
+ The DRM core exports several interfaces to applications,
+ generally intended to be used through corresponding libdrm
+ wrapper functions. In addition, drivers export device-specific
+ interfaces for use by userspace drivers &amp; device-aware
+ applications through ioctls and sysfs files.
+ </para>
+ <para>
+ External interfaces include: memory mapping, context management,
+ DMA operations, AGP management, vblank control, fence
+ management, memory management, and output management.
+ </para>
+ <para>
+ Cover generic ioctls and sysfs layout here. We only need high-level
+ info, since man pages should cover the rest.
+ </para>
+
+ <!-- External: render nodes -->
+
+ <sect1>
+ <title>Render nodes</title>
+ <para>
+ DRM core provides multiple character-devices for user-space to use.
+ Depending on which device is opened, user-space can perform a different
+ set of operations (mainly ioctls). The primary node is always created
+ and called card&lt;num&gt;. Additionally, a currently
+ unused control node, called controlD&lt;num&gt; is also
+ created. The primary node provides all legacy operations and
+ historically was the only interface used by userspace. With KMS, the
+ control node was introduced. However, the planned KMS control interface
+ has never been written and so the control node stays unused to date.
+ </para>
+ <para>
+ With the increased use of offscreen renderers and GPGPU applications,
+ clients no longer require running compositors or graphics servers to
+ make use of a GPU. But the DRM API required unprivileged clients to
+ authenticate to a DRM-Master prior to getting GPU access. To avoid this
+ step and to grant clients GPU access without authenticating, render
+ nodes were introduced. Render nodes solely serve render clients, that
+ is, no modesetting or privileged ioctls can be issued on render nodes.
+ Only non-global rendering commands are allowed. If a driver supports
+ render nodes, it must advertise it via the DRIVER_RENDER
+ DRM driver capability. If not supported, the primary node must be used
+ for render clients together with the legacy drmAuth authentication
+ procedure.
+ </para>
+ <para>
+ If a driver advertises render node support, DRM core will create a
+ separate render node called renderD&lt;num&gt;. There will
+ be one render node per device. No ioctls except PRIME-related ioctls
+ will be allowed on this node. Especially GEM_OPEN will be
+ explicitly prohibited. Render nodes are designed to avoid the
+ buffer-leaks, which occur if clients guess the flink names or mmap
+ offsets on the legacy interface. Additionally to this basic interface,
+ drivers must mark their driver-dependent render-only ioctls as
+ DRM_RENDER_ALLOW so render clients can use them. Driver
+ authors must be careful not to allow any privileged ioctls on render
+ nodes.
+ </para>
+ <para>
+ With render nodes, user-space can now control access to the render node
+ via basic file-system access-modes. A running graphics server which
+ authenticates clients on the privileged primary/legacy node is no longer
+ required. Instead, a client can open the render node and is immediately
+ granted GPU access. Communication between clients (or servers) is done
+ via PRIME. FLINK from render node to legacy node is not supported. New
+ clients must not use the insecure FLINK interface.
+ </para>
+ <para>
+ Besides dropping all modeset/global ioctls, render nodes also drop the
+ DRM-Master concept. There is no reason to associate render clients with
+ a DRM-Master as they are independent of any graphics server. Besides,
+ they must work without any running master, anyway.
+ Drivers must be able to run without a master object if they support
+ render nodes. If, on the other hand, a driver requires shared state
+ between clients which is visible to user-space and accessible beyond
+ open-file boundaries, they cannot support render nodes.
+ </para>
+ </sect1>
+
+ <!-- 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 was only used for user-mode-settind drivers around
+ modesetting changes to allow the kernel to update the vblank
+ interrupt after mode setting, since on many devices the vertical
+ blank counter is reset to 0 at some point during modeset. Modern
+ drivers should not call this any more since with kernel mode
+ setting it is a no-op.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </sect1>
+
+ </chapter>
+</part>
+<part id="drmDrivers">
+ <title>DRM Drivers</title>
+
+ <partintro>
+ <para>
+ This second part of the DRM Developer's Guide documents driver code,
+ implementation details and also all the driver-specific userspace
+ interfaces. Especially since all hardware-acceleration interfaces to
+ userspace are driver specific for efficiency and other reasons these
+ interfaces can be rather substantial. Hence every driver has its own
+ chapter.
+ </para>
+ </partintro>
+
+ <chapter id="drmI915">
+ <title>drm/i915 Intel GFX Driver</title>
+ <para>
+ The drm/i915 driver supports all (with the exception of some very early
+ models) integrated GFX chipsets with both Intel display and rendering
+ blocks. This excludes a set of SoC platforms with an SGX rendering unit,
+ those have basic support through the gma500 drm driver.
+ </para>
+ <sect1>
+ <title>Core Driver Infrastructure</title>
+ <para>
+ This section covers core driver infrastructure used by both the display
+ and the GEM parts of the driver.
+ </para>
+ <sect2>
+ <title>Runtime Power Management</title>
+!Pdrivers/gpu/drm/i915/intel_runtime_pm.c runtime pm
+!Idrivers/gpu/drm/i915/intel_runtime_pm.c
+!Idrivers/gpu/drm/i915/intel_uncore.c
+ </sect2>
+ <sect2>
+ <title>Interrupt Handling</title>
+!Pdrivers/gpu/drm/i915/i915_irq.c interrupt handling
+!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_init intel_irq_init_hw intel_hpd_init
+!Fdrivers/gpu/drm/i915/i915_irq.c intel_irq_fini
+!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_disable_interrupts
+!Fdrivers/gpu/drm/i915/i915_irq.c intel_runtime_pm_enable_interrupts
+ </sect2>
+ <sect2>
+ <title>Intel GVT-g Guest Support(vGPU)</title>
+!Pdrivers/gpu/drm/i915/i915_vgpu.c Intel GVT-g guest support
+!Idrivers/gpu/drm/i915/i915_vgpu.c
+ </sect2>
+ </sect1>
+ <sect1>
+ <title>Display Hardware Handling</title>
+ <para>
+ This section covers everything related to the display hardware including
+ the mode setting infrastructure, plane, sprite and cursor handling and
+ display, output probing and related topics.
+ </para>
+ <sect2>
+ <title>Mode Setting Infrastructure</title>
+ <para>
+ The i915 driver is thus far the only DRM driver which doesn't use the
+ common DRM helper code to implement mode setting sequences. Thus it
+ has its own tailor-made infrastructure for executing a display
+ configuration change.
+ </para>
+ </sect2>
+ <sect2>
+ <title>Frontbuffer Tracking</title>
+!Pdrivers/gpu/drm/i915/intel_frontbuffer.c frontbuffer tracking
+!Idrivers/gpu/drm/i915/intel_frontbuffer.c
+!Fdrivers/gpu/drm/i915/intel_drv.h intel_frontbuffer_flip
+!Fdrivers/gpu/drm/i915/i915_gem.c i915_gem_track_fb
+ </sect2>
+ <sect2>
+ <title>Display FIFO Underrun Reporting</title>
+!Pdrivers/gpu/drm/i915/intel_fifo_underrun.c fifo underrun handling
+!Idrivers/gpu/drm/i915/intel_fifo_underrun.c
+ </sect2>
+ <sect2>
+ <title>Plane Configuration</title>
+ <para>
+ This section covers plane configuration and composition with the
+ primary plane, sprites, cursors and overlays. This includes the
+ infrastructure to do atomic vsync'ed updates of all this state and
+ also tightly coupled topics like watermark setup and computation,
+ framebuffer compression and panel self refresh.
+ </para>
+ </sect2>
+ <sect2>
+ <title>Atomic Plane Helpers</title>
+!Pdrivers/gpu/drm/i915/intel_atomic_plane.c atomic plane helpers
+!Idrivers/gpu/drm/i915/intel_atomic_plane.c
+ </sect2>
+ <sect2>
+ <title>Output Probing</title>
+ <para>
+ This section covers output probing and related infrastructure like the
+ hotplug interrupt storm detection and mitigation code. Note that the
+ i915 driver still uses most of the common DRM helper code for output
+ probing, so those sections fully apply.
+ </para>
+ </sect2>
+ <sect2>
+ <title>High Definition Audio</title>
+!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port
+!Idrivers/gpu/drm/i915/intel_audio.c
+ </sect2>
+ <sect2>
+ <title>Panel Self Refresh PSR (PSR/SRD)</title>
+!Pdrivers/gpu/drm/i915/intel_psr.c Panel Self Refresh (PSR/SRD)
+!Idrivers/gpu/drm/i915/intel_psr.c
+ </sect2>
+ <sect2>
+ <title>Frame Buffer Compression (FBC)</title>
+!Pdrivers/gpu/drm/i915/intel_fbc.c Frame Buffer Compression (FBC)
+!Idrivers/gpu/drm/i915/intel_fbc.c
+ </sect2>
+ <sect2>
+ <title>Display Refresh Rate Switching (DRRS)</title>
+!Pdrivers/gpu/drm/i915/intel_dp.c Display Refresh Rate Switching (DRRS)
+!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_set_drrs_state
+!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_enable
+!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_disable
+!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_invalidate
+!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_flush
+!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_drrs_init
+
+ </sect2>
+ <sect2>
+ <title>DPIO</title>
+!Pdrivers/gpu/drm/i915/i915_reg.h DPIO
+ <table id="dpiox2">
+ <title>Dual channel PHY (VLV/CHV)</title>
+ <tgroup cols="8">
+ <colspec colname="c0" />
+ <colspec colname="c1" />
+ <colspec colname="c2" />
+ <colspec colname="c3" />
+ <colspec colname="c4" />
+ <colspec colname="c5" />
+ <colspec colname="c6" />
+ <colspec colname="c7" />
+ <spanspec spanname="ch0" namest="c0" nameend="c3" />
+ <spanspec spanname="ch1" namest="c4" nameend="c7" />
+ <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
+ <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
+ <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" />
+ <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" />
+ <thead>
+ <row>
+ <entry spanname="ch0">CH0</entry>
+ <entry spanname="ch1">CH1</entry>
+ </row>
+ </thead>
+ <tbody valign="top" align="center">
+ <row>
+ <entry spanname="ch0">CMN/PLL/REF</entry>
+ <entry spanname="ch1">CMN/PLL/REF</entry>
+ </row>
+ <row>
+ <entry spanname="ch0pcs01">PCS01</entry>
+ <entry spanname="ch0pcs23">PCS23</entry>
+ <entry spanname="ch1pcs01">PCS01</entry>
+ <entry spanname="ch1pcs23">PCS23</entry>
+ </row>
+ <row>
+ <entry>TX0</entry>
+ <entry>TX1</entry>
+ <entry>TX2</entry>
+ <entry>TX3</entry>
+ <entry>TX0</entry>
+ <entry>TX1</entry>
+ <entry>TX2</entry>
+ <entry>TX3</entry>
+ </row>
+ <row>
+ <entry spanname="ch0">DDI0</entry>
+ <entry spanname="ch1">DDI1</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ <table id="dpiox1">
+ <title>Single channel PHY (CHV)</title>
+ <tgroup cols="4">
+ <colspec colname="c0" />
+ <colspec colname="c1" />
+ <colspec colname="c2" />
+ <colspec colname="c3" />
+ <spanspec spanname="ch0" namest="c0" nameend="c3" />
+ <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
+ <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
+ <thead>
+ <row>
+ <entry spanname="ch0">CH0</entry>
+ </row>
+ </thead>
+ <tbody valign="top" align="center">
+ <row>
+ <entry spanname="ch0">CMN/PLL/REF</entry>
+ </row>
+ <row>
+ <entry spanname="ch0pcs01">PCS01</entry>
+ <entry spanname="ch0pcs23">PCS23</entry>
+ </row>
+ <row>
+ <entry>TX0</entry>
+ <entry>TX1</entry>
+ <entry>TX2</entry>
+ <entry>TX3</entry>
+ </row>
+ <row>
+ <entry spanname="ch0">DDI2</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </sect2>
+ </sect1>
+
+ <sect1>
+ <title>Memory Management and Command Submission</title>
+ <para>
+ This sections covers all things related to the GEM implementation in the
+ i915 driver.
+ </para>
+ <sect2>
+ <title>Batchbuffer Parsing</title>
+!Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser
+!Idrivers/gpu/drm/i915/i915_cmd_parser.c
+ </sect2>
+ <sect2>
+ <title>Batchbuffer Pools</title>
+!Pdrivers/gpu/drm/i915/i915_gem_batch_pool.c batch pool
+!Idrivers/gpu/drm/i915/i915_gem_batch_pool.c
+ </sect2>
+ <sect2>
+ <title>Logical Rings, Logical Ring Contexts and Execlists</title>
+!Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists
+!Idrivers/gpu/drm/i915/intel_lrc.c
+ </sect2>
+ <sect2>
+ <title>Global GTT views</title>
+!Pdrivers/gpu/drm/i915/i915_gem_gtt.c Global GTT views
+!Idrivers/gpu/drm/i915/i915_gem_gtt.c
+ </sect2>
+ <sect2>
+ <title>Buffer Object Eviction</title>
+ <para>
+ This section documents the interface functions for evicting buffer
+ objects to make space available in the virtual gpu address spaces.
+ Note that this is mostly orthogonal to shrinking buffer objects
+ caches, which has the goal to make main memory (shared with the gpu
+ through the unified memory architecture) available.
+ </para>
+!Idrivers/gpu/drm/i915/i915_gem_evict.c
+ </sect2>
+ <sect2>
+ <title>Buffer Object Memory Shrinking</title>
+ <para>
+ This section documents the interface function for shrinking memory
+ usage of buffer object caches. Shrinking is used to make main memory
+ available. Note that this is mostly orthogonal to evicting buffer
+ objects, which has the goal to make space in gpu virtual address
+ spaces.
+ </para>
+!Idrivers/gpu/drm/i915/i915_gem_shrinker.c
+ </sect2>
+ </sect1>
+
+ <sect1>
+ <title> Tracing </title>
+ <para>
+ This sections covers all things related to the tracepoints implemented in
+ the i915 driver.
+ </para>
+ <sect2>
+ <title> i915_ppgtt_create and i915_ppgtt_release </title>
+!Pdrivers/gpu/drm/i915/i915_trace.h i915_ppgtt_create and i915_ppgtt_release tracepoints
+ </sect2>
+ <sect2>
+ <title> i915_context_create and i915_context_free </title>
+!Pdrivers/gpu/drm/i915/i915_trace.h i915_context_create and i915_context_free tracepoints
+ </sect2>
+ <sect2>
+ <title> switch_mm </title>
+!Pdrivers/gpu/drm/i915/i915_trace.h switch_mm tracepoint
+ </sect2>
+ </sect1>
+
+ </chapter>
+!Cdrivers/gpu/drm/i915/i915_irq.c
+</part>
+</book>
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-16 14:58:39 +0000