1 <?xml version="1.0" encoding="UTF-8"?>
2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
5 <book id="drmDevelopersGuide">
7 <title>Linux DRM Developer's Guide</title>
11 <firstname>Jesse</firstname>
12 <surname>Barnes</surname>
13 <contrib>Initial version</contrib>
15 <orgname>Intel Corporation</orgname>
17 <email>jesse.barnes@intel.com</email>
22 <firstname>Laurent</firstname>
23 <surname>Pinchart</surname>
24 <contrib>Driver internals</contrib>
26 <orgname>Ideas on board SPRL</orgname>
28 <email>laurent.pinchart@ideasonboard.com</email>
33 <firstname>Daniel</firstname>
34 <surname>Vetter</surname>
35 <contrib>Contributions all over the place</contrib>
37 <orgname>Intel Corporation</orgname>
39 <email>daniel.vetter@ffwll.ch</email>
46 <year>2008-2009</year>
47 <year>2013-2014</year>
48 <holder>Intel Corporation</holder>
52 <holder>Laurent Pinchart</holder>
57 The contents of this file may be used under the terms of the GNU
58 General Public License version 2 (the "GPL") as distributed in
59 the kernel source COPYING file.
64 <!-- Put document revisions here, newest first. -->
66 <revnumber>1.0</revnumber>
67 <date>2012-07-13</date>
68 <authorinitials>LP</authorinitials>
69 <revremark>Added extensive documentation about driver internals.
78 <title>DRM Core</title>
81 This first part of the DRM Developer's Guide documents core DRM code,
82 helper libraries for writing drivers and generic userspace interfaces
83 exposed by DRM drivers.
87 <chapter id="drmIntroduction">
88 <title>Introduction</title>
90 The Linux DRM layer contains code intended to support the needs
91 of complex graphics devices, usually containing programmable
92 pipelines well suited to 3D graphics acceleration. Graphics
93 drivers in the kernel may make use of DRM functions to make
94 tasks like memory management, interrupt handling and DMA easier,
95 and provide a uniform interface to applications.
98 A note on versions: this guide covers features found in the DRM
99 tree, including the TTM memory manager, output configuration and
100 mode setting, and the new vblank internals, in addition to all
101 the regular features found in current kernels.
104 [Insert diagram of typical DRM stack here]
110 <chapter id="drmInternals">
111 <title>DRM Internals</title>
113 This chapter documents DRM internals relevant to driver authors
114 and developers working to add support for the latest features to
118 First, we go over some typical driver initialization
119 requirements, like setting up command buffers, creating an
120 initial output configuration, and initializing core services.
121 Subsequent sections cover core internals in more detail,
122 providing implementation notes and examples.
125 The DRM layer provides several services to graphics drivers,
126 many of them driven by the application interfaces it provides
127 through libdrm, the library that wraps most of the DRM ioctls.
128 These include vblank event handling, memory
129 management, output management, framebuffer management, command
130 submission & fencing, suspend/resume support, and DMA
134 <!-- Internals: driver init -->
137 <title>Driver Initialization</title>
139 At the core of every DRM driver is a <structname>drm_driver</structname>
140 structure. Drivers typically statically initialize a drm_driver structure,
141 and then pass it to one of the <function>drm_*_init()</function> functions
142 to register it with the DRM subsystem.
145 The <structname>drm_driver</structname> structure contains static
146 information that describes the driver and features it supports, and
147 pointers to methods that the DRM core will call to implement the DRM API.
148 We will first go through the <structname>drm_driver</structname> static
149 information fields, and will then describe individual operations in
150 details as they get used in later sections.
153 <title>Driver Information</title>
155 <title>Driver Features</title>
157 Drivers inform the DRM core about their requirements and supported
158 features by setting appropriate flags in the
159 <structfield>driver_features</structfield> field. Since those flags
160 influence the DRM core behaviour since registration time, most of them
161 must be set to registering the <structname>drm_driver</structname>
164 <synopsis>u32 driver_features;</synopsis>
166 <title>Driver Feature Flags</title>
168 <term>DRIVER_USE_AGP</term>
170 Driver uses AGP interface, the DRM core will manage AGP resources.
174 <term>DRIVER_REQUIRE_AGP</term>
176 Driver needs AGP interface to function. AGP initialization failure
177 will become a fatal error.
181 <term>DRIVER_PCI_DMA</term>
183 Driver is capable of PCI DMA, mapping of PCI DMA buffers to
184 userspace will be enabled. Deprecated.
188 <term>DRIVER_SG</term>
190 Driver can perform scatter/gather DMA, allocation and mapping of
191 scatter/gather buffers will be enabled. Deprecated.
195 <term>DRIVER_HAVE_DMA</term>
197 Driver supports DMA, the userspace DMA API will be supported.
202 <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term>
204 DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler
205 managed by the DRM Core. The core will support simple IRQ handler
206 installation when the flag is set. The installation process is
207 described in <xref linkend="drm-irq-registration"/>.</para>
208 <para>DRIVER_IRQ_SHARED indicates whether the device & handler
209 support shared IRQs (note that this is required of PCI drivers).
213 <term>DRIVER_GEM</term>
215 Driver use the GEM memory manager.
219 <term>DRIVER_MODESET</term>
221 Driver supports mode setting interfaces (KMS).
225 <term>DRIVER_PRIME</term>
227 Driver implements DRM PRIME buffer sharing.
231 <term>DRIVER_RENDER</term>
233 Driver supports dedicated render nodes.
239 <title>Major, Minor and Patchlevel</title>
242 int patchlevel;</synopsis>
244 The DRM core identifies driver versions by a major, minor and patch
245 level triplet. The information is printed to the kernel log at
246 initialization time and passed to userspace through the
247 DRM_IOCTL_VERSION ioctl.
250 The major and minor numbers are also used to verify the requested driver
251 API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes
252 between minor versions, applications can call DRM_IOCTL_SET_VERSION to
253 select a specific version of the API. If the requested major isn't equal
254 to the driver major, or the requested minor is larger than the driver
255 minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise
256 the driver's set_version() method will be called with the requested
261 <title>Name, Description and Date</title>
262 <synopsis>char *name;
264 char *date;</synopsis>
266 The driver name is printed to the kernel log at initialization time,
267 used for IRQ registration and passed to userspace through
271 The driver description is a purely informative string passed to
272 userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by
276 The driver date, formatted as YYYYMMDD, is meant to identify the date of
277 the latest modification to the driver. However, as most drivers fail to
278 update it, its value is mostly useless. The DRM core prints it to the
279 kernel log at initialization time and passes it to userspace through the
280 DRM_IOCTL_VERSION ioctl.
285 <title>Device Registration</title>
287 A number of functions are provided to help with device registration.
288 The functions deal with PCI, USB and platform devices, respectively.
290 !Edrivers/gpu/drm/drm_pci.c
291 !Edrivers/gpu/drm/drm_usb.c
292 !Edrivers/gpu/drm/drm_platform.c
295 <title>Driver Load</title>
297 The <methodname>load</methodname> method is the driver and device
298 initialization entry point. The method is responsible for allocating and
299 initializing driver private data, performing resource allocation and
300 mapping (e.g. acquiring
301 clocks, mapping registers or allocating command buffers), initializing
302 the memory manager (<xref linkend="drm-memory-management"/>), installing
303 the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up
304 vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode
305 setting (<xref linkend="drm-mode-setting"/>) and initial output
306 configuration (<xref linkend="drm-kms-init"/>).
309 If compatibility is a concern (e.g. with drivers converted over from
310 User Mode Setting to Kernel Mode Setting), care must be taken to prevent
311 device initialization and control that is incompatible with currently
312 active userspace drivers. For instance, if user level mode setting
313 drivers are in use, it would be problematic to perform output discovery
314 & configuration at load time. Likewise, if user-level drivers
315 unaware of memory management are in use, memory management and command
316 buffer setup may need to be omitted. These requirements are
317 driver-specific, and care needs to be taken to keep both old and new
318 applications and libraries working.
320 <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis>
322 The method takes two arguments, a pointer to the newly created
323 <structname>drm_device</structname> and flags. The flags are used to
324 pass the <structfield>driver_data</structfield> field of the device id
325 corresponding to the device passed to <function>drm_*_init()</function>.
326 Only PCI devices currently use this, USB and platform DRM drivers have
327 their <methodname>load</methodname> method called with flags to 0.
330 <title>Driver Private Data</title>
332 The driver private hangs off the main
333 <structname>drm_device</structname> structure and can be used for
334 tracking various device-specific bits of information, like register
335 offsets, command buffer status, register state for suspend/resume, etc.
336 At load time, a driver may simply allocate one and set
337 <structname>drm_device</structname>.<structfield>dev_priv</structfield>
338 appropriately; it should be freed and
339 <structname>drm_device</structname>.<structfield>dev_priv</structfield>
340 set to NULL when the driver is unloaded.
343 <sect3 id="drm-irq-registration">
344 <title>IRQ Registration</title>
346 The DRM core tries to facilitate IRQ handler registration and
347 unregistration by providing <function>drm_irq_install</function> and
348 <function>drm_irq_uninstall</function> functions. Those functions only
349 support a single interrupt per device, devices that use more than one
350 IRQs need to be handled manually.
353 <title>Managed IRQ Registration</title>
355 <function>drm_irq_install</function> starts by calling the
356 <methodname>irq_preinstall</methodname> driver operation. The operation
357 is optional and must make sure that the interrupt will not get fired by
358 clearing all pending interrupt flags or disabling the interrupt.
361 The passed-in IRQ will then be requested by a call to
362 <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
363 feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
367 The IRQ handler function must be provided as the mandatory irq_handler
368 driver operation. It will get passed directly to
369 <function>request_irq</function> and thus has the same prototype as all
370 IRQ handlers. It will get called with a pointer to the DRM device as the
374 Finally the function calls the optional
375 <methodname>irq_postinstall</methodname> driver operation. The operation
376 usually enables interrupts (excluding the vblank interrupt, which is
377 enabled separately), but drivers may choose to enable/disable interrupts
381 <function>drm_irq_uninstall</function> is similarly used to uninstall an
382 IRQ handler. It starts by waking up all processes waiting on a vblank
383 interrupt to make sure they don't hang, and then calls the optional
384 <methodname>irq_uninstall</methodname> driver operation. The operation
385 must disable all hardware interrupts. Finally the function frees the IRQ
386 by calling <function>free_irq</function>.
390 <title>Manual IRQ Registration</title>
392 Drivers that require multiple interrupt handlers can't use the managed
393 IRQ registration functions. In that case IRQs must be registered and
394 unregistered manually (usually with the <function>request_irq</function>
395 and <function>free_irq</function> functions, or their devm_* equivalent).
398 When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ
399 driver feature flag, and must not provide the
400 <methodname>irq_handler</methodname> driver operation. They must set the
401 <structname>drm_device</structname> <structfield>irq_enabled</structfield>
402 field to 1 upon registration of the IRQs, and clear it to 0 after
403 unregistering the IRQs.
408 <title>Memory Manager Initialization</title>
410 Every DRM driver requires a memory manager which must be initialized at
411 load time. DRM currently contains two memory managers, the Translation
412 Table Manager (TTM) and the Graphics Execution Manager (GEM).
413 This document describes the use of the GEM memory manager only. See
414 <xref linkend="drm-memory-management"/> for details.
418 <title>Miscellaneous Device Configuration</title>
420 Another task that may be necessary for PCI devices during configuration
421 is mapping the video BIOS. On many devices, the VBIOS describes device
422 configuration, LCD panel timings (if any), and contains flags indicating
423 device state. Mapping the BIOS can be done using the pci_map_rom() call,
424 a convenience function that takes care of mapping the actual ROM,
425 whether it has been shadowed into memory (typically at address 0xc0000)
426 or exists on the PCI device in the ROM BAR. Note that after the ROM has
427 been mapped and any necessary information has been extracted, it should
428 be unmapped; on many devices, the ROM address decoder is shared with
429 other BARs, so leaving it mapped could cause undesired behaviour like
430 hangs or memory corruption.
431 <!--!Fdrivers/pci/rom.c pci_map_rom-->
437 <!-- Internals: memory management -->
439 <sect1 id="drm-memory-management">
440 <title>Memory management</title>
442 Modern Linux systems require large amount of graphics memory to store
443 frame buffers, textures, vertices and other graphics-related data. Given
444 the very dynamic nature of many of that data, managing graphics memory
445 efficiently is thus crucial for the graphics stack and plays a central
446 role in the DRM infrastructure.
449 The DRM core includes two memory managers, namely Translation Table Maps
450 (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory
451 manager to be developed and tried to be a one-size-fits-them all
452 solution. It provides a single userspace API to accommodate the need of
453 all hardware, supporting both Unified Memory Architecture (UMA) devices
454 and devices with dedicated video RAM (i.e. most discrete video cards).
455 This resulted in a large, complex piece of code that turned out to be
456 hard to use for driver development.
459 GEM started as an Intel-sponsored project in reaction to TTM's
460 complexity. Its design philosophy is completely different: instead of
461 providing a solution to every graphics memory-related problems, GEM
462 identified common code between drivers and created a support library to
463 share it. GEM has simpler initialization and execution requirements than
464 TTM, but has no video RAM management capabilities and is thus limited to
468 <title>The Translation Table Manager (TTM)</title>
470 TTM design background and information belongs here.
473 <title>TTM initialization</title>
474 <warning><para>This section is outdated.</para></warning>
476 Drivers wishing to support TTM must fill out a drm_bo_driver
477 structure. The structure contains several fields with function
478 pointers for initializing the TTM, allocating and freeing memory,
479 waiting for command completion and fence synchronization, and memory
480 migration. See the radeon_ttm.c file for an example of usage.
483 The ttm_global_reference structure is made up of several fields:
486 struct ttm_global_reference {
487 enum ttm_global_types global_type;
490 int (*init) (struct ttm_global_reference *);
491 void (*release) (struct ttm_global_reference *);
495 There should be one global reference structure for your memory
496 manager as a whole, and there will be others for each object
497 created by the memory manager at runtime. Your global TTM should
498 have a type of TTM_GLOBAL_TTM_MEM. The size field for the global
499 object should be sizeof(struct ttm_mem_global), and the init and
500 release hooks should point at your driver-specific init and
501 release routines, which probably eventually call
502 ttm_mem_global_init and ttm_mem_global_release, respectively.
505 Once your global TTM accounting structure is set up and initialized
506 by calling ttm_global_item_ref() on it,
507 you need to create a buffer object TTM to
508 provide a pool for buffer object allocation by clients and the
509 kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO,
510 and its size should be sizeof(struct ttm_bo_global). Again,
511 driver-specific init and release functions may be provided,
512 likely eventually calling ttm_bo_global_init() and
513 ttm_bo_global_release(), respectively. Also, like the previous
514 object, ttm_global_item_ref() is used to create an initial reference
515 count for the TTM, which will call your initialization function.
520 <title>The Graphics Execution Manager (GEM)</title>
522 The GEM design approach has resulted in a memory manager that doesn't
523 provide full coverage of all (or even all common) use cases in its
524 userspace or kernel API. GEM exposes a set of standard memory-related
525 operations to userspace and a set of helper functions to drivers, and let
526 drivers implement hardware-specific operations with their own private API.
529 The GEM userspace API is described in the
530 <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics
531 Execution Manager</citetitle></ulink> article on LWN. While slightly
532 outdated, the document provides a good overview of the GEM API principles.
533 Buffer allocation and read and write operations, described as part of the
534 common GEM API, are currently implemented using driver-specific ioctls.
537 GEM is data-agnostic. It manages abstract buffer objects without knowing
538 what individual buffers contain. APIs that require knowledge of buffer
539 contents or purpose, such as buffer allocation or synchronization
540 primitives, are thus outside of the scope of GEM and must be implemented
541 using driver-specific ioctls.
544 On a fundamental level, GEM involves several operations:
546 <listitem>Memory allocation and freeing</listitem>
547 <listitem>Command execution</listitem>
548 <listitem>Aperture management at command execution time</listitem>
550 Buffer object allocation is relatively straightforward and largely
551 provided by Linux's shmem layer, which provides memory to back each
555 Device-specific operations, such as command execution, pinning, buffer
556 read & write, mapping, and domain ownership transfers are left to
557 driver-specific ioctls.
560 <title>GEM Initialization</title>
562 Drivers that use GEM must set the DRIVER_GEM bit in the struct
563 <structname>drm_driver</structname>
564 <structfield>driver_features</structfield> field. The DRM core will
565 then automatically initialize the GEM core before calling the
566 <methodname>load</methodname> operation. Behind the scene, this will
567 create a DRM Memory Manager object which provides an address space
568 pool for object allocation.
571 In a KMS configuration, drivers need to allocate and initialize a
572 command ring buffer following core GEM initialization if required by
573 the hardware. UMA devices usually have what is called a "stolen"
574 memory region, which provides space for the initial framebuffer and
575 large, contiguous memory regions required by the device. This space is
576 typically not managed by GEM, and must be initialized separately into
577 its own DRM MM object.
581 <title>GEM Objects Creation</title>
583 GEM splits creation of GEM objects and allocation of the memory that
584 backs them in two distinct operations.
587 GEM objects are represented by an instance of struct
588 <structname>drm_gem_object</structname>. Drivers usually need to extend
589 GEM objects with private information and thus create a driver-specific
590 GEM object structure type that embeds an instance of struct
591 <structname>drm_gem_object</structname>.
594 To create a GEM object, a driver allocates memory for an instance of its
595 specific GEM object type and initializes the embedded struct
596 <structname>drm_gem_object</structname> with a call to
597 <function>drm_gem_object_init</function>. The function takes a pointer to
598 the DRM device, a pointer to the GEM object and the buffer object size
602 GEM uses shmem to allocate anonymous pageable memory.
603 <function>drm_gem_object_init</function> will create an shmfs file of
604 the requested size and store it into the struct
605 <structname>drm_gem_object</structname> <structfield>filp</structfield>
606 field. The memory is used as either main storage for the object when the
607 graphics hardware uses system memory directly or as a backing store
611 Drivers are responsible for the actual physical pages allocation by
612 calling <function>shmem_read_mapping_page_gfp</function> for each page.
613 Note that they can decide to allocate pages when initializing the GEM
614 object, or to delay allocation until the memory is needed (for instance
615 when a page fault occurs as a result of a userspace memory access or
616 when the driver needs to start a DMA transfer involving the memory).
619 Anonymous pageable memory allocation is not always desired, for instance
620 when the hardware requires physically contiguous system memory as is
621 often the case in embedded devices. Drivers can create GEM objects with
622 no shmfs backing (called private GEM objects) by initializing them with
623 a call to <function>drm_gem_private_object_init</function> instead of
624 <function>drm_gem_object_init</function>. Storage for private GEM
625 objects must be managed by drivers.
628 Drivers that do not need to extend GEM objects with private information
629 can call the <function>drm_gem_object_alloc</function> function to
630 allocate and initialize a struct <structname>drm_gem_object</structname>
631 instance. The GEM core will call the optional driver
632 <methodname>gem_init_object</methodname> operation after initializing
633 the GEM object with <function>drm_gem_object_init</function>.
634 <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis>
637 No alloc-and-init function exists for private GEM objects.
641 <title>GEM Objects Lifetime</title>
643 All GEM objects are reference-counted by the GEM core. References can be
644 acquired and release by <function>calling drm_gem_object_reference</function>
645 and <function>drm_gem_object_unreference</function> respectively. The
646 caller must hold the <structname>drm_device</structname>
647 <structfield>struct_mutex</structfield> lock. As a convenience, GEM
648 provides the <function>drm_gem_object_reference_unlocked</function> and
649 <function>drm_gem_object_unreference_unlocked</function> functions that
650 can be called without holding the lock.
653 When the last reference to a GEM object is released the GEM core calls
654 the <structname>drm_driver</structname>
655 <methodname>gem_free_object</methodname> operation. That operation is
656 mandatory for GEM-enabled drivers and must free the GEM object and all
657 associated resources.
660 <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis>
661 Drivers are responsible for freeing all GEM object resources, including
662 the resources created by the GEM core. If an mmap offset has been
663 created for the object (in which case
664 <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield>
665 is not NULL) it must be freed by a call to
666 <function>drm_gem_free_mmap_offset</function>. The shmfs backing store
667 must be released by calling <function>drm_gem_object_release</function>
668 (that function can safely be called if no shmfs backing store has been
673 <title>GEM Objects Naming</title>
675 Communication between userspace and the kernel refers to GEM objects
676 using local handles, global names or, more recently, file descriptors.
677 All of those are 32-bit integer values; the usual Linux kernel limits
678 apply to the file descriptors.
681 GEM handles are local to a DRM file. Applications get a handle to a GEM
682 object through a driver-specific ioctl, and can use that handle to refer
683 to the GEM object in other standard or driver-specific ioctls. Closing a
684 DRM file handle frees all its GEM handles and dereferences the
685 associated GEM objects.
688 To create a handle for a GEM object drivers call
689 <function>drm_gem_handle_create</function>. The function takes a pointer
690 to the DRM file and the GEM object and returns a locally unique handle.
691 When the handle is no longer needed drivers delete it with a call to
692 <function>drm_gem_handle_delete</function>. Finally the GEM object
693 associated with a handle can be retrieved by a call to
694 <function>drm_gem_object_lookup</function>.
697 Handles don't take ownership of GEM objects, they only take a reference
698 to the object that will be dropped when the handle is destroyed. To
699 avoid leaking GEM objects, drivers must make sure they drop the
700 reference(s) they own (such as the initial reference taken at object
701 creation time) as appropriate, without any special consideration for the
702 handle. For example, in the particular case of combined GEM object and
703 handle creation in the implementation of the
704 <methodname>dumb_create</methodname> operation, drivers must drop the
705 initial reference to the GEM object before returning the handle.
708 GEM names are similar in purpose to handles but are not local to DRM
709 files. They can be passed between processes to reference a GEM object
710 globally. Names can't be used directly to refer to objects in the DRM
711 API, applications must convert handles to names and names to handles
712 using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls
713 respectively. The conversion is handled by the DRM core without any
714 driver-specific support.
717 GEM also supports buffer sharing with dma-buf file descriptors through
718 PRIME. GEM-based drivers must use the provided helpers functions to
719 implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />.
720 Since sharing file descriptors is inherently more secure than the
721 easily guessable and global GEM names it is the preferred buffer
722 sharing mechanism. Sharing buffers through GEM names is only supported
723 for legacy userspace. Furthermore PRIME also allows cross-device
724 buffer sharing since it is based on dma-bufs.
727 <sect3 id="drm-gem-objects-mapping">
728 <title>GEM Objects Mapping</title>
730 Because mapping operations are fairly heavyweight GEM favours
731 read/write-like access to buffers, implemented through driver-specific
732 ioctls, over mapping buffers to userspace. However, when random access
733 to the buffer is needed (to perform software rendering for instance),
734 direct access to the object can be more efficient.
737 The mmap system call can't be used directly to map GEM objects, as they
738 don't have their own file handle. Two alternative methods currently
739 co-exist to map GEM objects to userspace. The first method uses a
740 driver-specific ioctl to perform the mapping operation, calling
741 <function>do_mmap</function> under the hood. This is often considered
742 dubious, seems to be discouraged for new GEM-enabled drivers, and will
743 thus not be described here.
746 The second method uses the mmap system call on the DRM file handle.
747 <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd,
748 off_t offset);</synopsis>
749 DRM identifies the GEM object to be mapped by a fake offset passed
750 through the mmap offset argument. Prior to being mapped, a GEM object
751 must thus be associated with a fake offset. To do so, drivers must call
752 <function>drm_gem_create_mmap_offset</function> on the object. The
753 function allocates a fake offset range from a pool and stores the
754 offset divided by PAGE_SIZE in
755 <literal>obj->map_list.hash.key</literal>. Care must be taken not to
756 call <function>drm_gem_create_mmap_offset</function> if a fake offset
757 has already been allocated for the object. This can be tested by
758 <literal>obj->map_list.map</literal> being non-NULL.
761 Once allocated, the fake offset value
762 (<literal>obj->map_list.hash.key << PAGE_SHIFT</literal>)
763 must be passed to the application in a driver-specific way and can then
764 be used as the mmap offset argument.
767 The GEM core provides a helper method <function>drm_gem_mmap</function>
768 to handle object mapping. The method can be set directly as the mmap
769 file operation handler. It will look up the GEM object based on the
770 offset value and set the VMA operations to the
771 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
772 field. Note that <function>drm_gem_mmap</function> doesn't map memory to
773 userspace, but relies on the driver-provided fault handler to map pages
777 To use <function>drm_gem_mmap</function>, drivers must fill the struct
778 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield>
779 field with a pointer to VM operations.
782 <synopsis>struct vm_operations_struct *gem_vm_ops
784 struct vm_operations_struct {
785 void (*open)(struct vm_area_struct * area);
786 void (*close)(struct vm_area_struct * area);
787 int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
791 The <methodname>open</methodname> and <methodname>close</methodname>
792 operations must update the GEM object reference count. Drivers can use
793 the <function>drm_gem_vm_open</function> and
794 <function>drm_gem_vm_close</function> helper functions directly as open
798 The fault operation handler is responsible for mapping individual pages
799 to userspace when a page fault occurs. Depending on the memory
800 allocation scheme, drivers can allocate pages at fault time, or can
801 decide to allocate memory for the GEM object at the time the object is
805 Drivers that want to map the GEM object upfront instead of handling page
806 faults can implement their own mmap file operation handler.
810 <title>Memory Coherency</title>
812 When mapped to the device or used in a command buffer, backing pages
813 for an object are flushed to memory and marked write combined so as to
814 be coherent with the GPU. Likewise, if the CPU accesses an object
815 after the GPU has finished rendering to the object, then the object
816 must be made coherent with the CPU's view of memory, usually involving
817 GPU cache flushing of various kinds. This core CPU<->GPU
818 coherency management is provided by a device-specific ioctl, which
819 evaluates an object's current domain and performs any necessary
820 flushing or synchronization to put the object into the desired
821 coherency domain (note that the object may be busy, i.e. an active
822 render target; in that case, setting the domain blocks the client and
823 waits for rendering to complete before performing any necessary
824 flushing operations).
828 <title>Command Execution</title>
830 Perhaps the most important GEM function for GPU devices is providing a
831 command execution interface to clients. Client programs construct
832 command buffers containing references to previously allocated memory
833 objects, and then submit them to GEM. At that point, GEM takes care to
834 bind all the objects into the GTT, execute the buffer, and provide
835 necessary synchronization between clients accessing the same buffers.
836 This often involves evicting some objects from the GTT and re-binding
837 others (a fairly expensive operation), and providing relocation
838 support which hides fixed GTT offsets from clients. Clients must take
839 care not to submit command buffers that reference more objects than
840 can fit in the GTT; otherwise, GEM will reject them and no rendering
841 will occur. Similarly, if several objects in the buffer require fence
842 registers to be allocated for correct rendering (e.g. 2D blits on
843 pre-965 chips), care must be taken not to require more fence registers
844 than are available to the client. Such resource management should be
845 abstracted from the client in libdrm.
849 <title>GEM Function Reference</title>
850 !Edrivers/gpu/drm/drm_gem.c
854 <title>VMA Offset Manager</title>
855 !Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager
856 !Edrivers/gpu/drm/drm_vma_manager.c
857 !Iinclude/drm/drm_vma_manager.h
859 <sect2 id="drm-prime-support">
860 <title>PRIME Buffer Sharing</title>
862 PRIME is the cross device buffer sharing framework in drm, originally
863 created for the OPTIMUS range of multi-gpu platforms. To userspace
864 PRIME buffers are dma-buf based file descriptors.
867 <title>Overview and Driver Interface</title>
869 Similar to GEM global names, PRIME file descriptors are
870 also used to share buffer objects across processes. They offer
871 additional security: as file descriptors must be explicitly sent over
872 UNIX domain sockets to be shared between applications, they can't be
873 guessed like the globally unique GEM names.
876 Drivers that support the PRIME
877 API must set the DRIVER_PRIME bit in the struct
878 <structname>drm_driver</structname>
879 <structfield>driver_features</structfield> field, and implement the
880 <methodname>prime_handle_to_fd</methodname> and
881 <methodname>prime_fd_to_handle</methodname> operations.
884 <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev,
885 struct drm_file *file_priv, uint32_t handle,
886 uint32_t flags, int *prime_fd);
887 int (*prime_fd_to_handle)(struct drm_device *dev,
888 struct drm_file *file_priv, int prime_fd,
889 uint32_t *handle);</synopsis>
890 Those two operations convert a handle to a PRIME file descriptor and
891 vice versa. Drivers must use the kernel dma-buf buffer sharing framework
892 to manage the PRIME file descriptors. Similar to the mode setting
893 API PRIME is agnostic to the underlying buffer object manager, as
894 long as handles are 32bit unsigned integers.
897 While non-GEM drivers must implement the operations themselves, GEM
898 drivers must use the <function>drm_gem_prime_handle_to_fd</function>
899 and <function>drm_gem_prime_fd_to_handle</function> helper functions.
900 Those helpers rely on the driver
901 <methodname>gem_prime_export</methodname> and
902 <methodname>gem_prime_import</methodname> operations to create a dma-buf
903 instance from a GEM object (dma-buf exporter role) and to create a GEM
904 object from a dma-buf instance (dma-buf importer role).
907 <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev,
908 struct drm_gem_object *obj,
910 struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev,
911 struct dma_buf *dma_buf);</synopsis>
912 These two operations are mandatory for GEM drivers that support
917 <title>PRIME Helper Functions</title>
918 !Pdrivers/gpu/drm/drm_prime.c PRIME Helpers
922 <title>PRIME Function References</title>
923 !Edrivers/gpu/drm/drm_prime.c
926 <title>DRM MM Range Allocator</title>
928 <title>Overview</title>
929 !Pdrivers/gpu/drm/drm_mm.c Overview
932 <title>LRU Scan/Eviction Support</title>
933 !Pdrivers/gpu/drm/drm_mm.c lru scan roaster
937 <title>DRM MM Range Allocator Function References</title>
938 !Edrivers/gpu/drm/drm_mm.c
939 !Iinclude/drm/drm_mm.h
943 <!-- Internals: mode setting -->
945 <sect1 id="drm-mode-setting">
946 <title>Mode Setting</title>
948 Drivers must initialize the mode setting core by calling
949 <function>drm_mode_config_init</function> on the DRM device. The function
950 initializes the <structname>drm_device</structname>
951 <structfield>mode_config</structfield> field and never fails. Once done,
952 mode configuration must be setup by initializing the following fields.
956 <synopsis>int min_width, min_height;
957 int max_width, max_height;</synopsis>
959 Minimum and maximum width and height of the frame buffers in pixel
964 <synopsis>struct drm_mode_config_funcs *funcs;</synopsis>
965 <para>Mode setting functions.</para>
969 <title>Display Modes Function Reference</title>
970 !Iinclude/drm/drm_modes.h
971 !Edrivers/gpu/drm/drm_modes.c
974 <title>Frame Buffer Creation</title>
975 <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev,
976 struct drm_file *file_priv,
977 struct drm_mode_fb_cmd2 *mode_cmd);</synopsis>
979 Frame buffers are abstract memory objects that provide a source of
980 pixels to scanout to a CRTC. Applications explicitly request the
981 creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and
982 receive an opaque handle that can be passed to the KMS CRTC control,
983 plane configuration and page flip functions.
986 Frame buffers rely on the underneath memory manager for low-level memory
987 operations. When creating a frame buffer applications pass a memory
988 handle (or a list of memory handles for multi-planar formats) through
989 the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using
990 GEM as their userspace buffer management interface this would be a GEM
991 handle. Drivers are however free to use their own backing storage object
992 handles, e.g. vmwgfx directly exposes special TTM handles to userspace
993 and so expects TTM handles in the create ioctl and not GEM handles.
996 Drivers must first validate the requested frame buffer parameters passed
997 through the mode_cmd argument. In particular this is where invalid
998 sizes, pixel formats or pitches can be caught.
1001 If the parameters are deemed valid, drivers then create, initialize and
1002 return an instance of struct <structname>drm_framebuffer</structname>.
1003 If desired the instance can be embedded in a larger driver-specific
1004 structure. Drivers must fill its <structfield>width</structfield>,
1005 <structfield>height</structfield>, <structfield>pitches</structfield>,
1006 <structfield>offsets</structfield>, <structfield>depth</structfield>,
1007 <structfield>bits_per_pixel</structfield> and
1008 <structfield>pixel_format</structfield> fields from the values passed
1009 through the <parameter>drm_mode_fb_cmd2</parameter> argument. They
1010 should call the <function>drm_helper_mode_fill_fb_struct</function>
1011 helper function to do so.
1015 The initialization of the new framebuffer instance is finalized with a
1016 call to <function>drm_framebuffer_init</function> which takes a pointer
1017 to DRM frame buffer operations (struct
1018 <structname>drm_framebuffer_funcs</structname>). Note that this function
1019 publishes the framebuffer and so from this point on it can be accessed
1020 concurrently from other threads. Hence it must be the last step in the
1021 driver's framebuffer initialization sequence. Frame buffer operations
1025 <synopsis>int (*create_handle)(struct drm_framebuffer *fb,
1026 struct drm_file *file_priv, unsigned int *handle);</synopsis>
1028 Create a handle to the frame buffer underlying memory object. If
1029 the frame buffer uses a multi-plane format, the handle will
1030 reference the memory object associated with the first plane.
1033 Drivers call <function>drm_gem_handle_create</function> to create
1038 <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis>
1040 Destroy the frame buffer object and frees all associated
1041 resources. Drivers must call
1042 <function>drm_framebuffer_cleanup</function> to free resources
1043 allocated by the DRM core for the frame buffer object, and must
1044 make sure to unreference all memory objects associated with the
1045 frame buffer. Handles created by the
1046 <methodname>create_handle</methodname> operation are released by
1051 <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer,
1052 struct drm_file *file_priv, unsigned flags, unsigned color,
1053 struct drm_clip_rect *clips, unsigned num_clips);</synopsis>
1055 This optional operation notifies the driver that a region of the
1056 frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB
1063 The lifetime of a drm framebuffer is controlled with a reference count,
1064 drivers can grab additional references with
1065 <function>drm_framebuffer_reference</function>and drop them
1066 again with <function>drm_framebuffer_unreference</function>. For
1067 driver-private framebuffers for which the last reference is never
1068 dropped (e.g. for the fbdev framebuffer when the struct
1069 <structname>drm_framebuffer</structname> is embedded into the fbdev
1070 helper struct) drivers can manually clean up a framebuffer at module
1072 <function>drm_framebuffer_unregister_private</function>.
1076 <title>Dumb Buffer Objects</title>
1078 The KMS API doesn't standardize backing storage object creation and
1079 leaves it to driver-specific ioctls. Furthermore actually creating a
1080 buffer object even for GEM-based drivers is done through a
1081 driver-specific ioctl - GEM only has a common userspace interface for
1082 sharing and destroying objects. While not an issue for full-fledged
1083 graphics stacks that include device-specific userspace components (in
1084 libdrm for instance), this limit makes DRM-based early boot graphics
1085 unnecessarily complex.
1088 Dumb objects partly alleviate the problem by providing a standard
1089 API to create dumb buffers suitable for scanout, which can then be used
1090 to create KMS frame buffers.
1093 To support dumb objects drivers must implement the
1094 <methodname>dumb_create</methodname>,
1095 <methodname>dumb_destroy</methodname> and
1096 <methodname>dumb_map_offset</methodname> operations.
1100 <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev,
1101 struct drm_mode_create_dumb *args);</synopsis>
1103 The <methodname>dumb_create</methodname> operation creates a driver
1104 object (GEM or TTM handle) suitable for scanout based on the
1105 width, height and depth from the struct
1106 <structname>drm_mode_create_dumb</structname> argument. It fills the
1107 argument's <structfield>handle</structfield>,
1108 <structfield>pitch</structfield> and <structfield>size</structfield>
1109 fields with a handle for the newly created object and its line
1110 pitch and size in bytes.
1114 <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev,
1115 uint32_t handle);</synopsis>
1117 The <methodname>dumb_destroy</methodname> operation destroys a dumb
1118 object created by <methodname>dumb_create</methodname>.
1122 <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev,
1123 uint32_t handle, uint64_t *offset);</synopsis>
1125 The <methodname>dumb_map_offset</methodname> operation associates an
1126 mmap fake offset with the object given by the handle and returns
1127 it. Drivers must use the
1128 <function>drm_gem_create_mmap_offset</function> function to
1129 associate the fake offset as described in
1130 <xref linkend="drm-gem-objects-mapping"/>.
1135 Note that dumb objects may not be used for gpu acceleration, as has been
1136 attempted on some ARM embedded platforms. Such drivers really must have
1137 a hardware-specific ioctl to allocate suitable buffer objects.
1141 <title>Output Polling</title>
1142 <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis>
1144 This operation notifies the driver that the status of one or more
1145 connectors has changed. Drivers that use the fb helper can just call the
1146 <function>drm_fb_helper_hotplug_event</function> function to handle this
1151 <title>Locking</title>
1153 Beside some lookup structures with their own locking (which is hidden
1154 behind the interface functions) most of the modeset state is protected
1155 by the <code>dev-<mode_config.lock</code> mutex and additionally
1156 per-crtc locks to allow cursor updates, pageflips and similar operations
1157 to occur concurrently with background tasks like output detection.
1158 Operations which cross domains like a full modeset always grab all
1159 locks. Drivers there need to protect resources shared between crtcs with
1160 additional locking. They also need to be careful to always grab the
1161 relevant crtc locks if a modset functions touches crtc state, e.g. for
1162 load detection (which does only grab the <code>mode_config.lock</code>
1163 to allow concurrent screen updates on live crtcs).
1168 <!-- Internals: kms initialization and cleanup -->
1170 <sect1 id="drm-kms-init">
1171 <title>KMS Initialization and Cleanup</title>
1173 A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders
1174 and connectors. KMS drivers must thus create and initialize all those
1175 objects at load time after initializing mode setting.
1178 <title>CRTCs (struct <structname>drm_crtc</structname>)</title>
1180 A CRTC is an abstraction representing a part of the chip that contains a
1181 pointer to a scanout buffer. Therefore, the number of CRTCs available
1182 determines how many independent scanout buffers can be active at any
1183 given time. The CRTC structure contains several fields to support this:
1184 a pointer to some video memory (abstracted as a frame buffer object), a
1185 display mode, and an (x, y) offset into the video memory to support
1186 panning or configurations where one piece of video memory spans multiple
1190 <title>CRTC Initialization</title>
1192 A KMS device must create and register at least one struct
1193 <structname>drm_crtc</structname> instance. The instance is allocated
1194 and zeroed by the driver, possibly as part of a larger structure, and
1195 registered with a call to <function>drm_crtc_init</function> with a
1196 pointer to CRTC functions.
1199 <sect3 id="drm-kms-crtcops">
1200 <title>CRTC Operations</title>
1202 <title>Set Configuration</title>
1203 <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis>
1205 Apply a new CRTC configuration to the device. The configuration
1206 specifies a CRTC, a frame buffer to scan out from, a (x,y) position in
1207 the frame buffer, a display mode and an array of connectors to drive
1208 with the CRTC if possible.
1211 If the frame buffer specified in the configuration is NULL, the driver
1212 must detach all encoders connected to the CRTC and all connectors
1213 attached to those encoders and disable them.
1216 This operation is called with the mode config lock held.
1219 Note that the drm core has no notion of restoring the mode setting
1220 state after resume, since all resume handling is in the full
1221 responsibility of the driver. The common mode setting helper library
1222 though provides a helper which can be used for this:
1223 <function>drm_helper_resume_force_mode</function>.
1227 <title>Page Flipping</title>
1228 <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb,
1229 struct drm_pending_vblank_event *event);</synopsis>
1231 Schedule a page flip to the given frame buffer for the CRTC. This
1232 operation is called with the mode config mutex held.
1235 Page flipping is a synchronization mechanism that replaces the frame
1236 buffer being scanned out by the CRTC with a new frame buffer during
1237 vertical blanking, avoiding tearing. When an application requests a page
1238 flip the DRM core verifies that the new frame buffer is large enough to
1239 be scanned out by the CRTC in the currently configured mode and then
1240 calls the CRTC <methodname>page_flip</methodname> operation with a
1241 pointer to the new frame buffer.
1244 The <methodname>page_flip</methodname> operation schedules a page flip.
1245 Once any pending rendering targeting the new frame buffer has
1246 completed, the CRTC will be reprogrammed to display that frame buffer
1247 after the next vertical refresh. The operation must return immediately
1248 without waiting for rendering or page flip to complete and must block
1249 any new rendering to the frame buffer until the page flip completes.
1252 If a page flip can be successfully scheduled the driver must set the
1253 <code>drm_crtc-<fb</code> field to the new framebuffer pointed to
1254 by <code>fb</code>. This is important so that the reference counting
1255 on framebuffers stays balanced.
1258 If a page flip is already pending, the
1259 <methodname>page_flip</methodname> operation must return
1260 -<errorname>EBUSY</errorname>.
1263 To synchronize page flip to vertical blanking the driver will likely
1264 need to enable vertical blanking interrupts. It should call
1265 <function>drm_vblank_get</function> for that purpose, and call
1266 <function>drm_vblank_put</function> after the page flip completes.
1269 If the application has requested to be notified when page flip completes
1270 the <methodname>page_flip</methodname> operation will be called with a
1271 non-NULL <parameter>event</parameter> argument pointing to a
1272 <structname>drm_pending_vblank_event</structname> instance. Upon page
1273 flip completion the driver must call <methodname>drm_send_vblank_event</methodname>
1274 to fill in the event and send to wake up any waiting processes.
1275 This can be performed with
1276 <programlisting><![CDATA[
1277 spin_lock_irqsave(&dev->event_lock, flags);
1279 drm_send_vblank_event(dev, pipe, event);
1280 spin_unlock_irqrestore(&dev->event_lock, flags);
1281 ]]></programlisting>
1284 FIXME: Could drivers that don't need to wait for rendering to complete
1285 just add the event to <literal>dev->vblank_event_list</literal> and
1286 let the DRM core handle everything, as for "normal" vertical blanking
1290 While waiting for the page flip to complete, the
1291 <literal>event->base.link</literal> list head can be used freely by
1292 the driver to store the pending event in a driver-specific list.
1295 If the file handle is closed before the event is signaled, drivers must
1296 take care to destroy the event in their
1297 <methodname>preclose</methodname> operation (and, if needed, call
1298 <function>drm_vblank_put</function>).
1302 <title>Miscellaneous</title>
1305 <synopsis>void (*set_property)(struct drm_crtc *crtc,
1306 struct drm_property *property, uint64_t value);</synopsis>
1308 Set the value of the given CRTC property to
1309 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1310 for more information about properties.
1314 <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
1315 uint32_t start, uint32_t size);</synopsis>
1317 Apply a gamma table to the device. The operation is optional.
1321 <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis>
1323 Destroy the CRTC when not needed anymore. See
1324 <xref linkend="drm-kms-init"/>.
1332 <title>Planes (struct <structname>drm_plane</structname>)</title>
1334 A plane represents an image source that can be blended with or overlayed
1335 on top of a CRTC during the scanout process. Planes are associated with
1336 a frame buffer to crop a portion of the image memory (source) and
1337 optionally scale it to a destination size. The result is then blended
1338 with or overlayed on top of a CRTC.
1341 The DRM core recognizes three types of planes:
1344 DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. Primary
1345 planes are the planes operated upon by by CRTC modesetting and flipping
1346 operations described in <xref linkend="drm-kms-crtcops"/>.
1349 DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. Cursor
1350 planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and
1351 DRM_IOCTL_MODE_CURSOR2 ioctls.
1354 DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes.
1355 Some drivers refer to these types of planes as "sprites" internally.
1358 For compatibility with legacy userspace, only overlay planes are made
1359 available to userspace by default. Userspace clients may set the
1360 DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that
1361 they wish to receive a universal plane list containing all plane types.
1364 <title>Plane Initialization</title>
1366 To create a plane, a KMS drivers allocates and
1367 zeroes an instances of struct <structname>drm_plane</structname>
1368 (possibly as part of a larger structure) and registers it with a call
1369 to <function>drm_universal_plane_init</function>. The function takes a bitmask
1370 of the CRTCs that can be associated with the plane, a pointer to the
1371 plane functions, a list of format supported formats, and the type of
1372 plane (primary, cursor, or overlay) being initialized.
1375 Cursor and overlay planes are optional. All drivers should provide
1376 one primary plane per CRTC (although this requirement may change in
1377 the future); drivers that do not wish to provide special handling for
1378 primary planes may make use of the helper functions described in
1379 <xref linkend="drm-kms-planehelpers"/> to create and register a
1380 primary plane with standard capabilities.
1384 <title>Plane Operations</title>
1387 <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc,
1388 struct drm_framebuffer *fb, int crtc_x, int crtc_y,
1389 unsigned int crtc_w, unsigned int crtc_h,
1390 uint32_t src_x, uint32_t src_y,
1391 uint32_t src_w, uint32_t src_h);</synopsis>
1393 Enable and configure the plane to use the given CRTC and frame buffer.
1396 The source rectangle in frame buffer memory coordinates is given by
1397 the <parameter>src_x</parameter>, <parameter>src_y</parameter>,
1398 <parameter>src_w</parameter> and <parameter>src_h</parameter>
1399 parameters (as 16.16 fixed point values). Devices that don't support
1400 subpixel plane coordinates can ignore the fractional part.
1403 The destination rectangle in CRTC coordinates is given by the
1404 <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>,
1405 <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter>
1406 parameters (as integer values). Devices scale the source rectangle to
1407 the destination rectangle. If scaling is not supported, and the source
1408 rectangle size doesn't match the destination rectangle size, the
1409 driver must return a -<errorname>EINVAL</errorname> error.
1413 <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis>
1415 Disable the plane. The DRM core calls this method in response to a
1416 DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0.
1417 Disabled planes must not be processed by the CRTC.
1421 <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis>
1423 Destroy the plane when not needed anymore. See
1424 <xref linkend="drm-kms-init"/>.
1431 <title>Encoders (struct <structname>drm_encoder</structname>)</title>
1433 An encoder takes pixel data from a CRTC and converts it to a format
1434 suitable for any attached connectors. On some devices, it may be
1435 possible to have a CRTC send data to more than one encoder. In that
1436 case, both encoders would receive data from the same scanout buffer,
1437 resulting in a "cloned" display configuration across the connectors
1438 attached to each encoder.
1441 <title>Encoder Initialization</title>
1443 As for CRTCs, a KMS driver must create, initialize and register at
1444 least one struct <structname>drm_encoder</structname> instance. The
1445 instance is allocated and zeroed by the driver, possibly as part of a
1449 Drivers must initialize the struct <structname>drm_encoder</structname>
1450 <structfield>possible_crtcs</structfield> and
1451 <structfield>possible_clones</structfield> fields before registering the
1452 encoder. Both fields are bitmasks of respectively the CRTCs that the
1453 encoder can be connected to, and sibling encoders candidate for cloning.
1456 After being initialized, the encoder must be registered with a call to
1457 <function>drm_encoder_init</function>. The function takes a pointer to
1458 the encoder functions and an encoder type. Supported types are
1461 DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A
1464 DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort
1467 DRM_MODE_ENCODER_LVDS for display panels
1470 DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component,
1474 DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
1479 Encoders must be attached to a CRTC to be used. DRM drivers leave
1480 encoders unattached at initialization time. Applications (or the fbdev
1481 compatibility layer when implemented) are responsible for attaching the
1482 encoders they want to use to a CRTC.
1486 <title>Encoder Operations</title>
1489 <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis>
1491 Called to destroy the encoder when not needed anymore. See
1492 <xref linkend="drm-kms-init"/>.
1496 <synopsis>void (*set_property)(struct drm_plane *plane,
1497 struct drm_property *property, uint64_t value);</synopsis>
1499 Set the value of the given plane property to
1500 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1501 for more information about properties.
1508 <title>Connectors (struct <structname>drm_connector</structname>)</title>
1510 A connector is the final destination for pixel data on a device, and
1511 usually connects directly to an external display device like a monitor
1512 or laptop panel. A connector can only be attached to one encoder at a
1513 time. The connector is also the structure where information about the
1514 attached display is kept, so it contains fields for display data, EDID
1515 data, DPMS & connection status, and information about modes
1516 supported on the attached displays.
1519 <title>Connector Initialization</title>
1521 Finally a KMS driver must create, initialize, register and attach at
1522 least one struct <structname>drm_connector</structname> instance. The
1523 instance is created as other KMS objects and initialized by setting the
1528 <term><structfield>interlace_allowed</structfield></term>
1530 Whether the connector can handle interlaced modes.
1534 <term><structfield>doublescan_allowed</structfield></term>
1536 Whether the connector can handle doublescan.
1540 <term><structfield>display_info
1541 </structfield></term>
1543 Display information is filled from EDID information when a display
1544 is detected. For non hot-pluggable displays such as flat panels in
1545 embedded systems, the driver should initialize the
1546 <structfield>display_info</structfield>.<structfield>width_mm</structfield>
1548 <structfield>display_info</structfield>.<structfield>height_mm</structfield>
1549 fields with the physical size of the display.
1553 <term id="drm-kms-connector-polled"><structfield>polled</structfield></term>
1555 Connector polling mode, a combination of
1558 <term>DRM_CONNECTOR_POLL_HPD</term>
1560 The connector generates hotplug events and doesn't need to be
1561 periodically polled. The CONNECT and DISCONNECT flags must not
1562 be set together with the HPD flag.
1566 <term>DRM_CONNECTOR_POLL_CONNECT</term>
1568 Periodically poll the connector for connection.
1572 <term>DRM_CONNECTOR_POLL_DISCONNECT</term>
1574 Periodically poll the connector for disconnection.
1578 Set to 0 for connectors that don't support connection status
1584 The connector is then registered with a call to
1585 <function>drm_connector_init</function> with a pointer to the connector
1586 functions and a connector type, and exposed through sysfs with a call to
1587 <function>drm_sysfs_connector_add</function>.
1590 Supported connector types are
1592 <listitem>DRM_MODE_CONNECTOR_VGA</listitem>
1593 <listitem>DRM_MODE_CONNECTOR_DVII</listitem>
1594 <listitem>DRM_MODE_CONNECTOR_DVID</listitem>
1595 <listitem>DRM_MODE_CONNECTOR_DVIA</listitem>
1596 <listitem>DRM_MODE_CONNECTOR_Composite</listitem>
1597 <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem>
1598 <listitem>DRM_MODE_CONNECTOR_LVDS</listitem>
1599 <listitem>DRM_MODE_CONNECTOR_Component</listitem>
1600 <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem>
1601 <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem>
1602 <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem>
1603 <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem>
1604 <listitem>DRM_MODE_CONNECTOR_TV</listitem>
1605 <listitem>DRM_MODE_CONNECTOR_eDP</listitem>
1606 <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem>
1610 Connectors must be attached to an encoder to be used. For devices that
1611 map connectors to encoders 1:1, the connector should be attached at
1612 initialization time with a call to
1613 <function>drm_mode_connector_attach_encoder</function>. The driver must
1614 also set the <structname>drm_connector</structname>
1615 <structfield>encoder</structfield> field to point to the attached
1619 Finally, drivers must initialize the connectors state change detection
1620 with a call to <function>drm_kms_helper_poll_init</function>. If at
1621 least one connector is pollable but can't generate hotplug interrupts
1622 (indicated by the DRM_CONNECTOR_POLL_CONNECT and
1623 DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will
1624 automatically be queued to periodically poll for changes. Connectors
1625 that can generate hotplug interrupts must be marked with the
1626 DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must
1627 call <function>drm_helper_hpd_irq_event</function>. The function will
1628 queue a delayed work to check the state of all connectors, but no
1629 periodic polling will be done.
1633 <title>Connector Operations</title>
1635 Unless otherwise state, all operations are mandatory.
1639 <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis>
1641 The DPMS operation sets the power state of a connector. The mode
1644 <listitem><para>DRM_MODE_DPMS_ON</para></listitem>
1645 <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem>
1646 <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem>
1647 <listitem><para>DRM_MODE_DPMS_OFF</para></listitem>
1651 In all but DPMS_ON mode the encoder to which the connector is attached
1652 should put the display in low-power mode by driving its signals
1653 appropriately. If more than one connector is attached to the encoder
1654 care should be taken not to change the power state of other displays as
1655 a side effect. Low-power mode should be propagated to the encoders and
1656 CRTCs when all related connectors are put in low-power mode.
1660 <title>Modes</title>
1661 <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width,
1662 uint32_t max_height);</synopsis>
1664 Fill the mode list with all supported modes for the connector. If the
1665 <parameter>max_width</parameter> and <parameter>max_height</parameter>
1666 arguments are non-zero, the implementation must ignore all modes wider
1667 than <parameter>max_width</parameter> or higher than
1668 <parameter>max_height</parameter>.
1671 The connector must also fill in this operation its
1672 <structfield>display_info</structfield>
1673 <structfield>width_mm</structfield> and
1674 <structfield>height_mm</structfield> fields with the connected display
1675 physical size in millimeters. The fields should be set to 0 if the value
1676 isn't known or is not applicable (for instance for projector devices).
1680 <title>Connection Status</title>
1682 The connection status is updated through polling or hotplug events when
1683 supported (see <xref linkend="drm-kms-connector-polled"/>). The status
1684 value is reported to userspace through ioctls and must not be used
1685 inside the driver, as it only gets initialized by a call to
1686 <function>drm_mode_getconnector</function> from userspace.
1688 <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector,
1689 bool force);</synopsis>
1691 Check to see if anything is attached to the connector. The
1692 <parameter>force</parameter> parameter is set to false whilst polling or
1693 to true when checking the connector due to user request.
1694 <parameter>force</parameter> can be used by the driver to avoid
1695 expensive, destructive operations during automated probing.
1698 Return connector_status_connected if something is connected to the
1699 connector, connector_status_disconnected if nothing is connected and
1700 connector_status_unknown if the connection state isn't known.
1703 Drivers should only return connector_status_connected if the connection
1704 status has really been probed as connected. Connectors that can't detect
1705 the connection status, or failed connection status probes, should return
1706 connector_status_unknown.
1710 <title>Miscellaneous</title>
1713 <synopsis>void (*set_property)(struct drm_connector *connector,
1714 struct drm_property *property, uint64_t value);</synopsis>
1716 Set the value of the given connector property to
1717 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
1718 for more information about properties.
1722 <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
1724 Destroy the connector when not needed anymore. See
1725 <xref linkend="drm-kms-init"/>.
1733 <title>Cleanup</title>
1735 The DRM core manages its objects' lifetime. When an object is not needed
1736 anymore the core calls its destroy function, which must clean up and
1737 free every resource allocated for the object. Every
1738 <function>drm_*_init</function> call must be matched with a
1739 corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs
1740 (<function>drm_crtc_cleanup</function>), planes
1741 (<function>drm_plane_cleanup</function>), encoders
1742 (<function>drm_encoder_cleanup</function>) and connectors
1743 (<function>drm_connector_cleanup</function>). Furthermore, connectors
1744 that have been added to sysfs must be removed by a call to
1745 <function>drm_sysfs_connector_remove</function> before calling
1746 <function>drm_connector_cleanup</function>.
1749 Connectors state change detection must be cleanup up with a call to
1750 <function>drm_kms_helper_poll_fini</function>.
1754 <title>Output discovery and initialization example</title>
1755 <programlisting><![CDATA[
1756 void intel_crt_init(struct drm_device *dev)
1758 struct drm_connector *connector;
1759 struct intel_output *intel_output;
1761 intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL);
1765 connector = &intel_output->base;
1766 drm_connector_init(dev, &intel_output->base,
1767 &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA);
1769 drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs,
1770 DRM_MODE_ENCODER_DAC);
1772 drm_mode_connector_attach_encoder(&intel_output->base,
1773 &intel_output->enc);
1775 /* Set up the DDC bus. */
1776 intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A");
1777 if (!intel_output->ddc_bus) {
1778 dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration "
1783 intel_output->type = INTEL_OUTPUT_ANALOG;
1784 connector->interlace_allowed = 0;
1785 connector->doublescan_allowed = 0;
1787 drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs);
1788 drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs);
1790 drm_sysfs_connector_add(connector);
1791 }]]></programlisting>
1793 In the example above (taken from the i915 driver), a CRTC, connector and
1794 encoder combination is created. A device-specific i2c bus is also
1795 created for fetching EDID data and performing monitor detection. Once
1796 the process is complete, the new connector is registered with sysfs to
1797 make its properties available to applications.
1801 <title>KMS API Functions</title>
1802 !Edrivers/gpu/drm/drm_crtc.c
1805 <title>KMS Locking</title>
1806 !Pdrivers/gpu/drm/drm_modeset_lock.c kms locking
1807 !Iinclude/drm/drm_modeset_lock.h
1808 !Edrivers/gpu/drm/drm_modeset_lock.c
1812 <!-- Internals: kms helper functions -->
1815 <title>Mode Setting Helper Functions</title>
1817 The plane, CRTC, encoder and connector functions provided by the drivers
1818 implement the DRM API. They're called by the DRM core and ioctl handlers
1819 to handle device state changes and configuration request. As implementing
1820 those functions often requires logic not specific to drivers, mid-layer
1821 helper functions are available to avoid duplicating boilerplate code.
1824 The DRM core contains one mid-layer implementation. The mid-layer provides
1825 implementations of several plane, CRTC, encoder and connector functions
1826 (called from the top of the mid-layer) that pre-process requests and call
1827 lower-level functions provided by the driver (at the bottom of the
1828 mid-layer). For instance, the
1829 <function>drm_crtc_helper_set_config</function> function can be used to
1830 fill the struct <structname>drm_crtc_funcs</structname>
1831 <structfield>set_config</structfield> field. When called, it will split
1832 the <methodname>set_config</methodname> operation in smaller, simpler
1833 operations and call the driver to handle them.
1836 To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>,
1837 <function>drm_encoder_helper_add</function> and
1838 <function>drm_connector_helper_add</function> functions to install their
1839 mid-layer bottom operations handlers, and fill the
1840 <structname>drm_crtc_funcs</structname>,
1841 <structname>drm_encoder_funcs</structname> and
1842 <structname>drm_connector_funcs</structname> structures with pointers to
1843 the mid-layer top API functions. Installing the mid-layer bottom operation
1844 handlers is best done right after registering the corresponding KMS object.
1847 The mid-layer is not split between CRTC, encoder and connector operations.
1848 To use it, a driver must provide bottom functions for all of the three KMS
1852 <title>Helper Functions</title>
1855 <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis>
1857 The <function>drm_crtc_helper_set_config</function> helper function
1858 is a CRTC <methodname>set_config</methodname> implementation. It
1859 first tries to locate the best encoder for each connector by calling
1860 the connector <methodname>best_encoder</methodname> helper
1864 After locating the appropriate encoders, the helper function will
1865 call the <methodname>mode_fixup</methodname> encoder and CRTC helper
1866 operations to adjust the requested mode, or reject it completely in
1867 which case an error will be returned to the application. If the new
1868 configuration after mode adjustment is identical to the current
1869 configuration the helper function will return without performing any
1873 If the adjusted mode is identical to the current mode but changes to
1874 the frame buffer need to be applied, the
1875 <function>drm_crtc_helper_set_config</function> function will call
1876 the CRTC <methodname>mode_set_base</methodname> helper operation. If
1877 the adjusted mode differs from the current mode, or if the
1878 <methodname>mode_set_base</methodname> helper operation is not
1879 provided, the helper function performs a full mode set sequence by
1880 calling the <methodname>prepare</methodname>,
1881 <methodname>mode_set</methodname> and
1882 <methodname>commit</methodname> CRTC and encoder helper operations,
1887 <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis>
1889 The <function>drm_helper_connector_dpms</function> helper function
1890 is a connector <methodname>dpms</methodname> implementation that
1891 tracks power state of connectors. To use the function, drivers must
1892 provide <methodname>dpms</methodname> helper operations for CRTCs
1893 and encoders to apply the DPMS state to the device.
1896 The mid-layer doesn't track the power state of CRTCs and encoders.
1897 The <methodname>dpms</methodname> helper operations can thus be
1898 called with a mode identical to the currently active mode.
1902 <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
1903 uint32_t maxX, uint32_t maxY);</synopsis>
1905 The <function>drm_helper_probe_single_connector_modes</function> helper
1906 function is a connector <methodname>fill_modes</methodname>
1907 implementation that updates the connection status for the connector
1908 and then retrieves a list of modes by calling the connector
1909 <methodname>get_modes</methodname> helper operation.
1912 The function filters out modes larger than
1913 <parameter>max_width</parameter> and <parameter>max_height</parameter>
1914 if specified. It then calls the optional connector
1915 <methodname>mode_valid</methodname> helper operation for each mode in
1916 the probed list to check whether the mode is valid for the connector.
1922 <title>CRTC Helper Operations</title>
1924 <listitem id="drm-helper-crtc-mode-fixup">
1925 <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc,
1926 const struct drm_display_mode *mode,
1927 struct drm_display_mode *adjusted_mode);</synopsis>
1929 Let CRTCs adjust the requested mode or reject it completely. This
1930 operation returns true if the mode is accepted (possibly after being
1931 adjusted) or false if it is rejected.
1934 The <methodname>mode_fixup</methodname> operation should reject the
1935 mode if it can't reasonably use it. The definition of "reasonable"
1936 is currently fuzzy in this context. One possible behaviour would be
1937 to set the adjusted mode to the panel timings when a fixed-mode
1938 panel is used with hardware capable of scaling. Another behaviour
1939 would be to accept any input mode and adjust it to the closest mode
1940 supported by the hardware (FIXME: This needs to be clarified).
1944 <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y,
1945 struct drm_framebuffer *old_fb)</synopsis>
1947 Move the CRTC on the current frame buffer (stored in
1948 <literal>crtc->fb</literal>) to position (x,y). Any of the frame
1949 buffer, x position or y position may have been modified.
1952 This helper operation is optional. If not provided, the
1953 <function>drm_crtc_helper_set_config</function> function will fall
1954 back to the <methodname>mode_set</methodname> helper operation.
1957 FIXME: Why are x and y passed as arguments, as they can be accessed
1958 through <literal>crtc->x</literal> and
1959 <literal>crtc->y</literal>?
1963 <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis>
1965 Prepare the CRTC for mode setting. This operation is called after
1966 validating the requested mode. Drivers use it to perform
1967 device-specific operations required before setting the new mode.
1971 <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode,
1972 struct drm_display_mode *adjusted_mode, int x, int y,
1973 struct drm_framebuffer *old_fb);</synopsis>
1975 Set a new mode, position and frame buffer. Depending on the device
1976 requirements, the mode can be stored internally by the driver and
1977 applied in the <methodname>commit</methodname> operation, or
1978 programmed to the hardware immediately.
1981 The <methodname>mode_set</methodname> operation returns 0 on success
1982 or a negative error code if an error occurs.
1986 <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis>
1988 Commit a mode. This operation is called after setting the new mode.
1989 Upon return the device must use the new mode and be fully
1996 <title>Encoder Helper Operations</title>
1999 <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder,
2000 const struct drm_display_mode *mode,
2001 struct drm_display_mode *adjusted_mode);</synopsis>
2003 Let encoders adjust the requested mode or reject it completely. This
2004 operation returns true if the mode is accepted (possibly after being
2005 adjusted) or false if it is rejected. See the
2006 <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper
2007 operation</link> for an explanation of the allowed adjustments.
2011 <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis>
2013 Prepare the encoder for mode setting. This operation is called after
2014 validating the requested mode. Drivers use it to perform
2015 device-specific operations required before setting the new mode.
2019 <synopsis>void (*mode_set)(struct drm_encoder *encoder,
2020 struct drm_display_mode *mode,
2021 struct drm_display_mode *adjusted_mode);</synopsis>
2023 Set a new mode. Depending on the device requirements, the mode can
2024 be stored internally by the driver and applied in the
2025 <methodname>commit</methodname> operation, or programmed to the
2026 hardware immediately.
2030 <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis>
2032 Commit a mode. This operation is called after setting the new mode.
2033 Upon return the device must use the new mode and be fully
2040 <title>Connector Helper Operations</title>
2043 <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis>
2045 Return a pointer to the best encoder for the connecter. Device that
2046 map connectors to encoders 1:1 simply return the pointer to the
2047 associated encoder. This operation is mandatory.
2051 <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis>
2053 Fill the connector's <structfield>probed_modes</structfield> list
2054 by parsing EDID data with <function>drm_add_edid_modes</function> or
2055 calling <function>drm_mode_probed_add</function> directly for every
2056 supported mode and return the number of modes it has detected. This
2057 operation is mandatory.
2060 When adding modes manually the driver creates each mode with a call to
2061 <function>drm_mode_create</function> and must fill the following fields.
2064 <synopsis>__u32 type;</synopsis>
2066 Mode type bitmask, a combination of
2069 <term>DRM_MODE_TYPE_BUILTIN</term>
2070 <listitem><para>not used?</para></listitem>
2073 <term>DRM_MODE_TYPE_CLOCK_C</term>
2074 <listitem><para>not used?</para></listitem>
2077 <term>DRM_MODE_TYPE_CRTC_C</term>
2078 <listitem><para>not used?</para></listitem>
2082 DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector
2085 <para>not used?</para>
2089 <term>DRM_MODE_TYPE_DEFAULT</term>
2090 <listitem><para>not used?</para></listitem>
2093 <term>DRM_MODE_TYPE_USERDEF</term>
2094 <listitem><para>not used?</para></listitem>
2097 <term>DRM_MODE_TYPE_DRIVER</term>
2100 The mode has been created by the driver (as opposed to
2101 to user-created modes).
2106 Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they
2107 create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred
2112 <synopsis>__u32 clock;</synopsis>
2113 <para>Pixel clock frequency in kHz unit</para>
2116 <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal;
2117 __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis>
2118 <para>Horizontal and vertical timing information</para>
2120 Active Front Sync Back
2122 <-----------------------><----------------><-------------><-------------->
2124 //////////////////////|
2125 ////////////////////// |
2126 ////////////////////// |.................. ................
2129 <----- [hv]display ----->
2130 <------------- [hv]sync_start ------------>
2131 <--------------------- [hv]sync_end --------------------->
2132 <-------------------------------- [hv]total ----------------------------->
2136 <synopsis>__u16 hskew;
2137 __u16 vscan;</synopsis>
2138 <para>Unknown</para>
2141 <synopsis>__u32 flags;</synopsis>
2143 Mode flags, a combination of
2146 <term>DRM_MODE_FLAG_PHSYNC</term>
2148 Horizontal sync is active high
2152 <term>DRM_MODE_FLAG_NHSYNC</term>
2154 Horizontal sync is active low
2158 <term>DRM_MODE_FLAG_PVSYNC</term>
2160 Vertical sync is active high
2164 <term>DRM_MODE_FLAG_NVSYNC</term>
2166 Vertical sync is active low
2170 <term>DRM_MODE_FLAG_INTERLACE</term>
2176 <term>DRM_MODE_FLAG_DBLSCAN</term>
2178 Mode uses doublescan
2182 <term>DRM_MODE_FLAG_CSYNC</term>
2184 Mode uses composite sync
2188 <term>DRM_MODE_FLAG_PCSYNC</term>
2190 Composite sync is active high
2194 <term>DRM_MODE_FLAG_NCSYNC</term>
2196 Composite sync is active low
2200 <term>DRM_MODE_FLAG_HSKEW</term>
2202 hskew provided (not used?)
2206 <term>DRM_MODE_FLAG_BCAST</term>
2212 <term>DRM_MODE_FLAG_PIXMUX</term>
2218 <term>DRM_MODE_FLAG_DBLCLK</term>
2224 <term>DRM_MODE_FLAG_CLKDIV2</term>
2232 Note that modes marked with the INTERLACE or DBLSCAN flags will be
2234 <function>drm_helper_probe_single_connector_modes</function> if
2235 the connector's <structfield>interlace_allowed</structfield> or
2236 <structfield>doublescan_allowed</structfield> field is set to 0.
2240 <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis>
2242 Mode name. The driver must call
2243 <function>drm_mode_set_name</function> to fill the mode name from
2244 <structfield>hdisplay</structfield>,
2245 <structfield>vdisplay</structfield> and interlace flag after
2246 filling the corresponding fields.
2252 The <structfield>vrefresh</structfield> value is computed by
2253 <function>drm_helper_probe_single_connector_modes</function>.
2256 When parsing EDID data, <function>drm_add_edid_modes</function> fill the
2257 connector <structfield>display_info</structfield>
2258 <structfield>width_mm</structfield> and
2259 <structfield>height_mm</structfield> fields. When creating modes
2260 manually the <methodname>get_modes</methodname> helper operation must
2261 set the <structfield>display_info</structfield>
2262 <structfield>width_mm</structfield> and
2263 <structfield>height_mm</structfield> fields if they haven't been set
2264 already (for instance at initialization time when a fixed-size panel is
2265 attached to the connector). The mode <structfield>width_mm</structfield>
2266 and <structfield>height_mm</structfield> fields are only used internally
2267 during EDID parsing and should not be set when creating modes manually.
2271 <synopsis>int (*mode_valid)(struct drm_connector *connector,
2272 struct drm_display_mode *mode);</synopsis>
2274 Verify whether a mode is valid for the connector. Return MODE_OK for
2275 supported modes and one of the enum drm_mode_status values (MODE_*)
2276 for unsupported modes. This operation is optional.
2279 As the mode rejection reason is currently not used beside for
2280 immediately removing the unsupported mode, an implementation can
2281 return MODE_BAD regardless of the exact reason why the mode is not
2285 Note that the <methodname>mode_valid</methodname> helper operation is
2286 only called for modes detected by the device, and
2287 <emphasis>not</emphasis> for modes set by the user through the CRTC
2288 <methodname>set_config</methodname> operation.
2294 <title>Modeset Helper Functions Reference</title>
2295 !Edrivers/gpu/drm/drm_crtc_helper.c
2298 <title>Output Probing Helper Functions Reference</title>
2299 !Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview
2300 !Edrivers/gpu/drm/drm_probe_helper.c
2303 <title>fbdev Helper Functions Reference</title>
2304 !Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers
2305 !Edrivers/gpu/drm/drm_fb_helper.c
2306 !Iinclude/drm/drm_fb_helper.h
2309 <title>Display Port Helper Functions Reference</title>
2310 !Pdrivers/gpu/drm/drm_dp_helper.c dp helpers
2311 !Iinclude/drm/drm_dp_helper.h
2312 !Edrivers/gpu/drm/drm_dp_helper.c
2315 <title>EDID Helper Functions Reference</title>
2316 !Edrivers/gpu/drm/drm_edid.c
2319 <title>Rectangle Utilities Reference</title>
2320 !Pinclude/drm/drm_rect.h rect utils
2321 !Iinclude/drm/drm_rect.h
2322 !Edrivers/gpu/drm/drm_rect.c
2325 <title>Flip-work Helper Reference</title>
2326 !Pinclude/drm/drm_flip_work.h flip utils
2327 !Iinclude/drm/drm_flip_work.h
2328 !Edrivers/gpu/drm/drm_flip_work.c
2331 <title>HDMI Infoframes Helper Reference</title>
2333 Strictly speaking this is not a DRM helper library but generally useable
2334 by any driver interfacing with HDMI outputs like v4l or alsa drivers.
2335 But it nicely fits into the overall topic of mode setting helper
2336 libraries and hence is also included here.
2338 !Iinclude/linux/hdmi.h
2339 !Edrivers/video/hdmi.c
2342 <title id="drm-kms-planehelpers">Plane Helper Reference</title>
2343 !Edrivers/gpu/drm/drm_plane_helper.c Plane Helpers
2347 <!-- Internals: kms properties -->
2349 <sect1 id="drm-kms-properties">
2350 <title>KMS Properties</title>
2352 Drivers may need to expose additional parameters to applications than
2353 those described in the previous sections. KMS supports attaching
2354 properties to CRTCs, connectors and planes and offers a userspace API to
2355 list, get and set the property values.
2358 Properties are identified by a name that uniquely defines the property
2359 purpose, and store an associated value. For all property types except blob
2360 properties the value is a 64-bit unsigned integer.
2363 KMS differentiates between properties and property instances. Drivers
2364 first create properties and then create and associate individual instances
2365 of those properties to objects. A property can be instantiated multiple
2366 times and associated with different objects. Values are stored in property
2367 instances, and all other property information are stored in the property
2368 and shared between all instances of the property.
2371 Every property is created with a type that influences how the KMS core
2372 handles the property. Supported property types are
2375 <term>DRM_MODE_PROP_RANGE</term>
2376 <listitem><para>Range properties report their minimum and maximum
2377 admissible values. The KMS core verifies that values set by
2378 application fit in that range.</para></listitem>
2381 <term>DRM_MODE_PROP_ENUM</term>
2382 <listitem><para>Enumerated properties take a numerical value that
2383 ranges from 0 to the number of enumerated values defined by the
2384 property minus one, and associate a free-formed string name to each
2385 value. Applications can retrieve the list of defined value-name pairs
2386 and use the numerical value to get and set property instance values.
2390 <term>DRM_MODE_PROP_BITMASK</term>
2391 <listitem><para>Bitmask properties are enumeration properties that
2392 additionally restrict all enumerated values to the 0..63 range.
2393 Bitmask property instance values combine one or more of the
2394 enumerated bits defined by the property.</para></listitem>
2397 <term>DRM_MODE_PROP_BLOB</term>
2398 <listitem><para>Blob properties store a binary blob without any format
2399 restriction. The binary blobs are created as KMS standalone objects,
2400 and blob property instance values store the ID of their associated
2402 <para>Blob properties are only used for the connector EDID property
2403 and cannot be created by drivers.</para></listitem>
2408 To create a property drivers call one of the following functions depending
2409 on the property type. All property creation functions take property flags
2410 and name, as well as type-specific arguments.
2413 <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
2415 uint64_t min, uint64_t max);</synopsis>
2416 <para>Create a range property with the given minimum and maximum
2420 <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags,
2422 const struct drm_prop_enum_list *props,
2423 int num_values);</synopsis>
2424 <para>Create an enumerated property. The <parameter>props</parameter>
2425 argument points to an array of <parameter>num_values</parameter>
2426 value-name pairs.</para>
2429 <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev,
2430 int flags, const char *name,
2431 const struct drm_prop_enum_list *props,
2432 int num_values);</synopsis>
2433 <para>Create a bitmask property. The <parameter>props</parameter>
2434 argument points to an array of <parameter>num_values</parameter>
2435 value-name pairs.</para>
2440 Properties can additionally be created as immutable, in which case they
2441 will be read-only for applications but can be modified by the driver. To
2442 create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE
2443 flag at property creation time.
2446 When no array of value-name pairs is readily available at property
2447 creation time for enumerated or range properties, drivers can create
2448 the property using the <function>drm_property_create</function> function
2449 and manually add enumeration value-name pairs by calling the
2450 <function>drm_property_add_enum</function> function. Care must be taken to
2451 properly specify the property type through the <parameter>flags</parameter>
2455 After creating properties drivers can attach property instances to CRTC,
2456 connector and plane objects by calling the
2457 <function>drm_object_attach_property</function>. The function takes a
2458 pointer to the target object, a pointer to the previously created property
2459 and an initial instance value.
2462 <title>Existing KMS Properties</title>
2464 The following table gives description of drm properties exposed by various
2467 <table border="1" cellpadding="0" cellspacing="0">
2469 <tr style="font-weight: bold;">
2470 <td valign="top" >Owner Module/Drivers</td>
2471 <td valign="top" >Group</td>
2472 <td valign="top" >Property Name</td>
2473 <td valign="top" >Type</td>
2474 <td valign="top" >Property Values</td>
2475 <td valign="top" >Object attached</td>
2476 <td valign="top" >Description/Restrictions</td>
2479 <td rowspan="19" valign="top" >DRM</td>
2480 <td rowspan="2" valign="top" >Generic</td>
2481 <td valign="top" >“EDID”</td>
2482 <td valign="top" >BLOB | IMMUTABLE</td>
2483 <td valign="top" >0</td>
2484 <td valign="top" >Connector</td>
2485 <td valign="top" >Contains id of edid blob ptr object.</td>
2488 <td valign="top" >“DPMS”</td>
2489 <td valign="top" >ENUM</td>
2490 <td valign="top" >{ “On”, “Standby”, “Suspend”, “Off” }</td>
2491 <td valign="top" >Connector</td>
2492 <td valign="top" >Contains DPMS operation mode value.</td>
2495 <td rowspan="2" valign="top" >DVI-I</td>
2496 <td valign="top" >“subconnector”</td>
2497 <td valign="top" >ENUM</td>
2498 <td valign="top" >{ “Unknown”, “DVI-D”, “DVI-A” }</td>
2499 <td valign="top" >Connector</td>
2500 <td valign="top" >TBD</td>
2503 <td valign="top" >“select subconnector”</td>
2504 <td valign="top" >ENUM</td>
2505 <td valign="top" >{ “Automatic”, “DVI-D”, “DVI-A” }</td>
2506 <td valign="top" >Connector</td>
2507 <td valign="top" >TBD</td>
2510 <td rowspan="13" valign="top" >TV</td>
2511 <td valign="top" >“subconnector”</td>
2512 <td valign="top" >ENUM</td>
2513 <td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td>
2514 <td valign="top" >Connector</td>
2515 <td valign="top" >TBD</td>
2518 <td valign="top" >“select subconnector”</td>
2519 <td valign="top" >ENUM</td>
2520 <td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td>
2521 <td valign="top" >Connector</td>
2522 <td valign="top" >TBD</td>
2525 <td valign="top" >“mode”</td>
2526 <td valign="top" >ENUM</td>
2527 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2528 <td valign="top" >Connector</td>
2529 <td valign="top" >TBD</td>
2532 <td valign="top" >“left margin”</td>
2533 <td valign="top" >RANGE</td>
2534 <td valign="top" >Min=0, Max=100</td>
2535 <td valign="top" >Connector</td>
2536 <td valign="top" >TBD</td>
2539 <td valign="top" >“right margin”</td>
2540 <td valign="top" >RANGE</td>
2541 <td valign="top" >Min=0, Max=100</td>
2542 <td valign="top" >Connector</td>
2543 <td valign="top" >TBD</td>
2546 <td valign="top" >“top margin”</td>
2547 <td valign="top" >RANGE</td>
2548 <td valign="top" >Min=0, Max=100</td>
2549 <td valign="top" >Connector</td>
2550 <td valign="top" >TBD</td>
2553 <td valign="top" >“bottom margin”</td>
2554 <td valign="top" >RANGE</td>
2555 <td valign="top" >Min=0, Max=100</td>
2556 <td valign="top" >Connector</td>
2557 <td valign="top" >TBD</td>
2560 <td valign="top" >“brightness”</td>
2561 <td valign="top" >RANGE</td>
2562 <td valign="top" >Min=0, Max=100</td>
2563 <td valign="top" >Connector</td>
2564 <td valign="top" >TBD</td>
2567 <td valign="top" >“contrast”</td>
2568 <td valign="top" >RANGE</td>
2569 <td valign="top" >Min=0, Max=100</td>
2570 <td valign="top" >Connector</td>
2571 <td valign="top" >TBD</td>
2574 <td valign="top" >“flicker reduction”</td>
2575 <td valign="top" >RANGE</td>
2576 <td valign="top" >Min=0, Max=100</td>
2577 <td valign="top" >Connector</td>
2578 <td valign="top" >TBD</td>
2581 <td valign="top" >“overscan”</td>
2582 <td valign="top" >RANGE</td>
2583 <td valign="top" >Min=0, Max=100</td>
2584 <td valign="top" >Connector</td>
2585 <td valign="top" >TBD</td>
2588 <td valign="top" >“saturation”</td>
2589 <td valign="top" >RANGE</td>
2590 <td valign="top" >Min=0, Max=100</td>
2591 <td valign="top" >Connector</td>
2592 <td valign="top" >TBD</td>
2595 <td valign="top" >“hue”</td>
2596 <td valign="top" >RANGE</td>
2597 <td valign="top" >Min=0, Max=100</td>
2598 <td valign="top" >Connector</td>
2599 <td valign="top" >TBD</td>
2602 <td rowspan="2" valign="top" >Optional</td>
2603 <td valign="top" >“scaling mode”</td>
2604 <td valign="top" >ENUM</td>
2605 <td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td>
2606 <td valign="top" >Connector</td>
2607 <td valign="top" >TBD</td>
2610 <td valign="top" >“dirty”</td>
2611 <td valign="top" >ENUM | IMMUTABLE</td>
2612 <td valign="top" >{ "Off", "On", "Annotate" }</td>
2613 <td valign="top" >Connector</td>
2614 <td valign="top" >TBD</td>
2617 <td rowspan="21" valign="top" >i915</td>
2618 <td rowspan="3" valign="top" >Generic</td>
2619 <td valign="top" >"Broadcast RGB"</td>
2620 <td valign="top" >ENUM</td>
2621 <td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td>
2622 <td valign="top" >Connector</td>
2623 <td valign="top" >TBD</td>
2626 <td valign="top" >“audio”</td>
2627 <td valign="top" >ENUM</td>
2628 <td valign="top" >{ "force-dvi", "off", "auto", "on" }</td>
2629 <td valign="top" >Connector</td>
2630 <td valign="top" >TBD</td>
2633 <td valign="top" >Standard name as in DRM</td>
2634 <td valign="top" >Standard type as in DRM</td>
2635 <td valign="top" >Standard value as in DRM</td>
2636 <td valign="top" >Standard Object as in DRM</td>
2637 <td valign="top" >TBD</td>
2640 <td rowspan="17" valign="top" >SDVO-TV</td>
2641 <td valign="top" >“mode”</td>
2642 <td valign="top" >ENUM</td>
2643 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2644 <td valign="top" >Connector</td>
2645 <td valign="top" >TBD</td>
2648 <td valign="top" >"left_margin"</td>
2649 <td valign="top" >RANGE</td>
2650 <td valign="top" >Min=0, Max= SDVO dependent</td>
2651 <td valign="top" >Connector</td>
2652 <td valign="top" >TBD</td>
2655 <td valign="top" >"right_margin"</td>
2656 <td valign="top" >RANGE</td>
2657 <td valign="top" >Min=0, Max= SDVO dependent</td>
2658 <td valign="top" >Connector</td>
2659 <td valign="top" >TBD</td>
2662 <td valign="top" >"top_margin"</td>
2663 <td valign="top" >RANGE</td>
2664 <td valign="top" >Min=0, Max= SDVO dependent</td>
2665 <td valign="top" >Connector</td>
2666 <td valign="top" >TBD</td>
2669 <td valign="top" >"bottom_margin"</td>
2670 <td valign="top" >RANGE</td>
2671 <td valign="top" >Min=0, Max= SDVO dependent</td>
2672 <td valign="top" >Connector</td>
2673 <td valign="top" >TBD</td>
2676 <td valign="top" >“hpos”</td>
2677 <td valign="top" >RANGE</td>
2678 <td valign="top" >Min=0, Max= SDVO dependent</td>
2679 <td valign="top" >Connector</td>
2680 <td valign="top" >TBD</td>
2683 <td valign="top" >“vpos”</td>
2684 <td valign="top" >RANGE</td>
2685 <td valign="top" >Min=0, Max= SDVO dependent</td>
2686 <td valign="top" >Connector</td>
2687 <td valign="top" >TBD</td>
2690 <td valign="top" >“contrast”</td>
2691 <td valign="top" >RANGE</td>
2692 <td valign="top" >Min=0, Max= SDVO dependent</td>
2693 <td valign="top" >Connector</td>
2694 <td valign="top" >TBD</td>
2697 <td valign="top" >“saturation”</td>
2698 <td valign="top" >RANGE</td>
2699 <td valign="top" >Min=0, Max= SDVO dependent</td>
2700 <td valign="top" >Connector</td>
2701 <td valign="top" >TBD</td>
2704 <td valign="top" >“hue”</td>
2705 <td valign="top" >RANGE</td>
2706 <td valign="top" >Min=0, Max= SDVO dependent</td>
2707 <td valign="top" >Connector</td>
2708 <td valign="top" >TBD</td>
2711 <td valign="top" >“sharpness”</td>
2712 <td valign="top" >RANGE</td>
2713 <td valign="top" >Min=0, Max= SDVO dependent</td>
2714 <td valign="top" >Connector</td>
2715 <td valign="top" >TBD</td>
2718 <td valign="top" >“flicker_filter”</td>
2719 <td valign="top" >RANGE</td>
2720 <td valign="top" >Min=0, Max= SDVO dependent</td>
2721 <td valign="top" >Connector</td>
2722 <td valign="top" >TBD</td>
2725 <td valign="top" >“flicker_filter_adaptive”</td>
2726 <td valign="top" >RANGE</td>
2727 <td valign="top" >Min=0, Max= SDVO dependent</td>
2728 <td valign="top" >Connector</td>
2729 <td valign="top" >TBD</td>
2732 <td valign="top" >“flicker_filter_2d”</td>
2733 <td valign="top" >RANGE</td>
2734 <td valign="top" >Min=0, Max= SDVO dependent</td>
2735 <td valign="top" >Connector</td>
2736 <td valign="top" >TBD</td>
2739 <td valign="top" >“tv_chroma_filter”</td>
2740 <td valign="top" >RANGE</td>
2741 <td valign="top" >Min=0, Max= SDVO dependent</td>
2742 <td valign="top" >Connector</td>
2743 <td valign="top" >TBD</td>
2746 <td valign="top" >“tv_luma_filter”</td>
2747 <td valign="top" >RANGE</td>
2748 <td valign="top" >Min=0, Max= SDVO dependent</td>
2749 <td valign="top" >Connector</td>
2750 <td valign="top" >TBD</td>
2753 <td valign="top" >“dot_crawl”</td>
2754 <td valign="top" >RANGE</td>
2755 <td valign="top" >Min=0, Max=1</td>
2756 <td valign="top" >Connector</td>
2757 <td valign="top" >TBD</td>
2760 <td valign="top" >SDVO-TV/LVDS</td>
2761 <td valign="top" >“brightness”</td>
2762 <td valign="top" >RANGE</td>
2763 <td valign="top" >Min=0, Max= SDVO dependent</td>
2764 <td valign="top" >Connector</td>
2765 <td valign="top" >TBD</td>
2768 <td rowspan="3" valign="top" >CDV gma-500</td>
2769 <td rowspan="3" valign="top" >Generic</td>
2770 <td valign="top" >"Broadcast RGB"</td>
2771 <td valign="top" >ENUM</td>
2772 <td valign="top" >{ “Full”, “Limited 16:235” }</td>
2773 <td valign="top" >Connector</td>
2774 <td valign="top" >TBD</td>
2777 <td valign="top" >"Broadcast RGB"</td>
2778 <td valign="top" >ENUM</td>
2779 <td valign="top" >{ “off”, “auto”, “on” }</td>
2780 <td valign="top" >Connector</td>
2781 <td valign="top" >TBD</td>
2784 <td valign="top" >Standard name as in DRM</td>
2785 <td valign="top" >Standard type as in DRM</td>
2786 <td valign="top" >Standard value as in DRM</td>
2787 <td valign="top" >Standard Object as in DRM</td>
2788 <td valign="top" >TBD</td>
2791 <td rowspan="20" valign="top" >Poulsbo</td>
2792 <td rowspan="2" valign="top" >Generic</td>
2793 <td valign="top" >“backlight”</td>
2794 <td valign="top" >RANGE</td>
2795 <td valign="top" >Min=0, Max=100</td>
2796 <td valign="top" >Connector</td>
2797 <td valign="top" >TBD</td>
2800 <td valign="top" >Standard name as in DRM</td>
2801 <td valign="top" >Standard type as in DRM</td>
2802 <td valign="top" >Standard value as in DRM</td>
2803 <td valign="top" >Standard Object as in DRM</td>
2804 <td valign="top" >TBD</td>
2807 <td rowspan="17" valign="top" >SDVO-TV</td>
2808 <td valign="top" >“mode”</td>
2809 <td valign="top" >ENUM</td>
2810 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td>
2811 <td valign="top" >Connector</td>
2812 <td valign="top" >TBD</td>
2815 <td valign="top" >"left_margin"</td>
2816 <td valign="top" >RANGE</td>
2817 <td valign="top" >Min=0, Max= SDVO dependent</td>
2818 <td valign="top" >Connector</td>
2819 <td valign="top" >TBD</td>
2822 <td valign="top" >"right_margin"</td>
2823 <td valign="top" >RANGE</td>
2824 <td valign="top" >Min=0, Max= SDVO dependent</td>
2825 <td valign="top" >Connector</td>
2826 <td valign="top" >TBD</td>
2829 <td valign="top" >"top_margin"</td>
2830 <td valign="top" >RANGE</td>
2831 <td valign="top" >Min=0, Max= SDVO dependent</td>
2832 <td valign="top" >Connector</td>
2833 <td valign="top" >TBD</td>
2836 <td valign="top" >"bottom_margin"</td>
2837 <td valign="top" >RANGE</td>
2838 <td valign="top" >Min=0, Max= SDVO dependent</td>
2839 <td valign="top" >Connector</td>
2840 <td valign="top" >TBD</td>
2843 <td valign="top" >“hpos”</td>
2844 <td valign="top" >RANGE</td>
2845 <td valign="top" >Min=0, Max= SDVO dependent</td>
2846 <td valign="top" >Connector</td>
2847 <td valign="top" >TBD</td>
2850 <td valign="top" >“vpos”</td>
2851 <td valign="top" >RANGE</td>
2852 <td valign="top" >Min=0, Max= SDVO dependent</td>
2853 <td valign="top" >Connector</td>
2854 <td valign="top" >TBD</td>
2857 <td valign="top" >“contrast”</td>
2858 <td valign="top" >RANGE</td>
2859 <td valign="top" >Min=0, Max= SDVO dependent</td>
2860 <td valign="top" >Connector</td>
2861 <td valign="top" >TBD</td>
2864 <td valign="top" >“saturation”</td>
2865 <td valign="top" >RANGE</td>
2866 <td valign="top" >Min=0, Max= SDVO dependent</td>
2867 <td valign="top" >Connector</td>
2868 <td valign="top" >TBD</td>
2871 <td valign="top" >“hue”</td>
2872 <td valign="top" >RANGE</td>
2873 <td valign="top" >Min=0, Max= SDVO dependent</td>
2874 <td valign="top" >Connector</td>
2875 <td valign="top" >TBD</td>
2878 <td valign="top" >“sharpness”</td>
2879 <td valign="top" >RANGE</td>
2880 <td valign="top" >Min=0, Max= SDVO dependent</td>
2881 <td valign="top" >Connector</td>
2882 <td valign="top" >TBD</td>
2885 <td valign="top" >“flicker_filter”</td>
2886 <td valign="top" >RANGE</td>
2887 <td valign="top" >Min=0, Max= SDVO dependent</td>
2888 <td valign="top" >Connector</td>
2889 <td valign="top" >TBD</td>
2892 <td valign="top" >“flicker_filter_adaptive”</td>
2893 <td valign="top" >RANGE</td>
2894 <td valign="top" >Min=0, Max= SDVO dependent</td>
2895 <td valign="top" >Connector</td>
2896 <td valign="top" >TBD</td>
2899 <td valign="top" >“flicker_filter_2d”</td>
2900 <td valign="top" >RANGE</td>
2901 <td valign="top" >Min=0, Max= SDVO dependent</td>
2902 <td valign="top" >Connector</td>
2903 <td valign="top" >TBD</td>
2906 <td valign="top" >“tv_chroma_filter”</td>
2907 <td valign="top" >RANGE</td>
2908 <td valign="top" >Min=0, Max= SDVO dependent</td>
2909 <td valign="top" >Connector</td>
2910 <td valign="top" >TBD</td>
2913 <td valign="top" >“tv_luma_filter”</td>
2914 <td valign="top" >RANGE</td>
2915 <td valign="top" >Min=0, Max= SDVO dependent</td>
2916 <td valign="top" >Connector</td>
2917 <td valign="top" >TBD</td>
2920 <td valign="top" >“dot_crawl”</td>
2921 <td valign="top" >RANGE</td>
2922 <td valign="top" >Min=0, Max=1</td>
2923 <td valign="top" >Connector</td>
2924 <td valign="top" >TBD</td>
2927 <td valign="top" >SDVO-TV/LVDS</td>
2928 <td valign="top" >“brightness”</td>
2929 <td valign="top" >RANGE</td>
2930 <td valign="top" >Min=0, Max= SDVO dependent</td>
2931 <td valign="top" >Connector</td>
2932 <td valign="top" >TBD</td>
2935 <td rowspan="11" valign="top" >armada</td>
2936 <td rowspan="2" valign="top" >CRTC</td>
2937 <td valign="top" >"CSC_YUV"</td>
2938 <td valign="top" >ENUM</td>
2939 <td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td>
2940 <td valign="top" >CRTC</td>
2941 <td valign="top" >TBD</td>
2944 <td valign="top" >"CSC_RGB"</td>
2945 <td valign="top" >ENUM</td>
2946 <td valign="top" >{ "Auto", "Computer system", "Studio" }</td>
2947 <td valign="top" >CRTC</td>
2948 <td valign="top" >TBD</td>
2951 <td rowspan="9" valign="top" >Overlay</td>
2952 <td valign="top" >"colorkey"</td>
2953 <td valign="top" >RANGE</td>
2954 <td valign="top" >Min=0, Max=0xffffff</td>
2955 <td valign="top" >Plane</td>
2956 <td valign="top" >TBD</td>
2959 <td valign="top" >"colorkey_min"</td>
2960 <td valign="top" >RANGE</td>
2961 <td valign="top" >Min=0, Max=0xffffff</td>
2962 <td valign="top" >Plane</td>
2963 <td valign="top" >TBD</td>
2966 <td valign="top" >"colorkey_max"</td>
2967 <td valign="top" >RANGE</td>
2968 <td valign="top" >Min=0, Max=0xffffff</td>
2969 <td valign="top" >Plane</td>
2970 <td valign="top" >TBD</td>
2973 <td valign="top" >"colorkey_val"</td>
2974 <td valign="top" >RANGE</td>
2975 <td valign="top" >Min=0, Max=0xffffff</td>
2976 <td valign="top" >Plane</td>
2977 <td valign="top" >TBD</td>
2980 <td valign="top" >"colorkey_alpha"</td>
2981 <td valign="top" >RANGE</td>
2982 <td valign="top" >Min=0, Max=0xffffff</td>
2983 <td valign="top" >Plane</td>
2984 <td valign="top" >TBD</td>
2987 <td valign="top" >"colorkey_mode"</td>
2988 <td valign="top" >ENUM</td>
2989 <td valign="top" >{ "disabled", "Y component", "U component"
2990 , "V component", "RGB", “R component", "G component", "B component" }</td>
2991 <td valign="top" >Plane</td>
2992 <td valign="top" >TBD</td>
2995 <td valign="top" >"brightness"</td>
2996 <td valign="top" >RANGE</td>
2997 <td valign="top" >Min=0, Max=256 + 255</td>
2998 <td valign="top" >Plane</td>
2999 <td valign="top" >TBD</td>
3002 <td valign="top" >"contrast"</td>
3003 <td valign="top" >RANGE</td>
3004 <td valign="top" >Min=0, Max=0x7fff</td>
3005 <td valign="top" >Plane</td>
3006 <td valign="top" >TBD</td>
3009 <td valign="top" >"saturation"</td>
3010 <td valign="top" >RANGE</td>
3011 <td valign="top" >Min=0, Max=0x7fff</td>
3012 <td valign="top" >Plane</td>
3013 <td valign="top" >TBD</td>
3016 <td rowspan="2" valign="top" >exynos</td>
3017 <td valign="top" >CRTC</td>
3018 <td valign="top" >“mode”</td>
3019 <td valign="top" >ENUM</td>
3020 <td valign="top" >{ "normal", "blank" }</td>
3021 <td valign="top" >CRTC</td>
3022 <td valign="top" >TBD</td>
3025 <td valign="top" >Overlay</td>
3026 <td valign="top" >“zpos”</td>
3027 <td valign="top" >RANGE</td>
3028 <td valign="top" >Min=0, Max=MAX_PLANE-1</td>
3029 <td valign="top" >Plane</td>
3030 <td valign="top" >TBD</td>
3033 <td rowspan="3" valign="top" >i2c/ch7006_drv</td>
3034 <td valign="top" >Generic</td>
3035 <td valign="top" >“scale”</td>
3036 <td valign="top" >RANGE</td>
3037 <td valign="top" >Min=0, Max=2</td>
3038 <td valign="top" >Connector</td>
3039 <td valign="top" >TBD</td>
3042 <td rowspan="2" valign="top" >TV</td>
3043 <td valign="top" >Standard names as in DRM</td>
3044 <td valign="top" >Standard types as in DRM</td>
3045 <td valign="top" >Standard Values as in DRM</td>
3046 <td valign="top" >Standard object as in DRM</td>
3047 <td valign="top" >TBD</td>
3050 <td valign="top" >“mode”</td>
3051 <td valign="top" >ENUM</td>
3052 <td valign="top" >{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc"
3053 , "PAL-60", "NTSC-M", "NTSC-J" }</td>
3054 <td valign="top" >Connector</td>
3055 <td valign="top" >TBD</td>
3058 <td rowspan="16" valign="top" >noveau</td>
3059 <td rowspan="6" valign="top" >NV10 Overlay</td>
3060 <td valign="top" >"colorkey"</td>
3061 <td valign="top" >RANGE</td>
3062 <td valign="top" >Min=0, Max=0x01ffffff</td>
3063 <td valign="top" >Plane</td>
3064 <td valign="top" >TBD</td>
3067 <td valign="top" >“contrast”</td>
3068 <td valign="top" >RANGE</td>
3069 <td valign="top" >Min=0, Max=8192-1</td>
3070 <td valign="top" >Plane</td>
3071 <td valign="top" >TBD</td>
3074 <td valign="top" >“brightness”</td>
3075 <td valign="top" >RANGE</td>
3076 <td valign="top" >Min=0, Max=1024</td>
3077 <td valign="top" >Plane</td>
3078 <td valign="top" >TBD</td>
3081 <td valign="top" >“hue”</td>
3082 <td valign="top" >RANGE</td>
3083 <td valign="top" >Min=0, Max=359</td>
3084 <td valign="top" >Plane</td>
3085 <td valign="top" >TBD</td>
3088 <td valign="top" >“saturation”</td>
3089 <td valign="top" >RANGE</td>
3090 <td valign="top" >Min=0, Max=8192-1</td>
3091 <td valign="top" >Plane</td>
3092 <td valign="top" >TBD</td>
3095 <td valign="top" >“iturbt_709”</td>
3096 <td valign="top" >RANGE</td>
3097 <td valign="top" >Min=0, Max=1</td>
3098 <td valign="top" >Plane</td>
3099 <td valign="top" >TBD</td>
3102 <td rowspan="2" valign="top" >Nv04 Overlay</td>
3103 <td valign="top" >“colorkey”</td>
3104 <td valign="top" >RANGE</td>
3105 <td valign="top" >Min=0, Max=0x01ffffff</td>
3106 <td valign="top" >Plane</td>
3107 <td valign="top" >TBD</td>
3110 <td valign="top" >“brightness”</td>
3111 <td valign="top" >RANGE</td>
3112 <td valign="top" >Min=0, Max=1024</td>
3113 <td valign="top" >Plane</td>
3114 <td valign="top" >TBD</td>
3117 <td rowspan="7" valign="top" >Display</td>
3118 <td valign="top" >“dithering mode”</td>
3119 <td valign="top" >ENUM</td>
3120 <td valign="top" >{ "auto", "off", "on" }</td>
3121 <td valign="top" >Connector</td>
3122 <td valign="top" >TBD</td>
3125 <td valign="top" >“dithering depth”</td>
3126 <td valign="top" >ENUM</td>
3127 <td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td>
3128 <td valign="top" >Connector</td>
3129 <td valign="top" >TBD</td>
3132 <td valign="top" >“underscan”</td>
3133 <td valign="top" >ENUM</td>
3134 <td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td>
3135 <td valign="top" >Connector</td>
3136 <td valign="top" >TBD</td>
3139 <td valign="top" >“underscan hborder”</td>
3140 <td valign="top" >RANGE</td>
3141 <td valign="top" >Min=0, Max=128</td>
3142 <td valign="top" >Connector</td>
3143 <td valign="top" >TBD</td>
3146 <td valign="top" >“underscan vborder”</td>
3147 <td valign="top" >RANGE</td>
3148 <td valign="top" >Min=0, Max=128</td>
3149 <td valign="top" >Connector</td>
3150 <td valign="top" >TBD</td>
3153 <td valign="top" >“vibrant hue”</td>
3154 <td valign="top" >RANGE</td>
3155 <td valign="top" >Min=0, Max=180</td>
3156 <td valign="top" >Connector</td>
3157 <td valign="top" >TBD</td>
3160 <td valign="top" >“color vibrance”</td>
3161 <td valign="top" >RANGE</td>
3162 <td valign="top" >Min=0, Max=200</td>
3163 <td valign="top" >Connector</td>
3164 <td valign="top" >TBD</td>
3167 <td valign="top" >Generic</td>
3168 <td valign="top" >Standard name as in DRM</td>
3169 <td valign="top" >Standard type as in DRM</td>
3170 <td valign="top" >Standard value as in DRM</td>
3171 <td valign="top" >Standard Object as in DRM</td>
3172 <td valign="top" >TBD</td>
3175 <td rowspan="2" valign="top" >omap</td>
3176 <td rowspan="2" valign="top" >Generic</td>
3177 <td valign="top" >“rotation”</td>
3178 <td valign="top" >BITMASK</td>
3179 <td valign="top" >{ 0, "rotate-0" },
3181 { 2, "rotate-180" },
3182 { 3, "rotate-270" },
3184 { 5, "reflect-y" }</td>
3185 <td valign="top" >CRTC, Plane</td>
3186 <td valign="top" >TBD</td>
3189 <td valign="top" >“zorder”</td>
3190 <td valign="top" >RANGE</td>
3191 <td valign="top" >Min=0, Max=3</td>
3192 <td valign="top" >CRTC, Plane</td>
3193 <td valign="top" >TBD</td>
3196 <td valign="top" >qxl</td>
3197 <td valign="top" >Generic</td>
3198 <td valign="top" >“hotplug_mode_update"</td>
3199 <td valign="top" >RANGE</td>
3200 <td valign="top" >Min=0, Max=1</td>
3201 <td valign="top" >Connector</td>
3202 <td valign="top" >TBD</td>
3205 <td rowspan="10" valign="top" >radeon</td>
3206 <td valign="top" >DVI-I</td>
3207 <td valign="top" >“coherent”</td>
3208 <td valign="top" >RANGE</td>
3209 <td valign="top" >Min=0, Max=1</td>
3210 <td valign="top" >Connector</td>
3211 <td valign="top" >TBD</td>
3214 <td valign="top" >DAC enable load detect</td>
3215 <td valign="top" >“load detection”</td>
3216 <td valign="top" >RANGE</td>
3217 <td valign="top" >Min=0, Max=1</td>
3218 <td valign="top" >Connector</td>
3219 <td valign="top" >TBD</td>
3222 <td valign="top" >TV Standard</td>
3223 <td valign="top" >"tv standard"</td>
3224 <td valign="top" >ENUM</td>
3225 <td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j"
3226 , "scart-pal", "pal-cn", "secam" }</td>
3227 <td valign="top" >Connector</td>
3228 <td valign="top" >TBD</td>
3231 <td valign="top" >legacy TMDS PLL detect</td>
3232 <td valign="top" >"tmds_pll"</td>
3233 <td valign="top" >ENUM</td>
3234 <td valign="top" >{ "driver", "bios" }</td>
3235 <td valign="top" >-</td>
3236 <td valign="top" >TBD</td>
3239 <td rowspan="3" valign="top" >Underscan</td>
3240 <td valign="top" >"underscan"</td>
3241 <td valign="top" >ENUM</td>
3242 <td valign="top" >{ "off", "on", "auto" }</td>
3243 <td valign="top" >Connector</td>
3244 <td valign="top" >TBD</td>
3247 <td valign="top" >"underscan hborder"</td>
3248 <td valign="top" >RANGE</td>
3249 <td valign="top" >Min=0, Max=128</td>
3250 <td valign="top" >Connector</td>
3251 <td valign="top" >TBD</td>
3254 <td valign="top" >"underscan vborder"</td>
3255 <td valign="top" >RANGE</td>
3256 <td valign="top" >Min=0, Max=128</td>
3257 <td valign="top" >Connector</td>
3258 <td valign="top" >TBD</td>
3261 <td valign="top" >Audio</td>
3262 <td valign="top" >“audio”</td>
3263 <td valign="top" >ENUM</td>
3264 <td valign="top" >{ "off", "on", "auto" }</td>
3265 <td valign="top" >Connector</td>
3266 <td valign="top" >TBD</td>
3269 <td valign="top" >FMT Dithering</td>
3270 <td valign="top" >“dither”</td>
3271 <td valign="top" >ENUM</td>
3272 <td valign="top" >{ "off", "on" }</td>
3273 <td valign="top" >Connector</td>
3274 <td valign="top" >TBD</td>
3277 <td valign="top" >Generic</td>
3278 <td valign="top" >Standard name as in DRM</td>
3279 <td valign="top" >Standard type as in DRM</td>
3280 <td valign="top" >Standard value as in DRM</td>
3281 <td valign="top" >Standard Object as in DRM</td>
3282 <td valign="top" >TBD</td>
3285 <td rowspan="3" valign="top" >rcar-du</td>
3286 <td rowspan="3" valign="top" >Generic</td>
3287 <td valign="top" >"alpha"</td>
3288 <td valign="top" >RANGE</td>
3289 <td valign="top" >Min=0, Max=255</td>
3290 <td valign="top" >Plane</td>
3291 <td valign="top" >TBD</td>
3294 <td valign="top" >"colorkey"</td>
3295 <td valign="top" >RANGE</td>
3296 <td valign="top" >Min=0, Max=0x01ffffff</td>
3297 <td valign="top" >Plane</td>
3298 <td valign="top" >TBD</td>
3301 <td valign="top" >"zpos"</td>
3302 <td valign="top" >RANGE</td>
3303 <td valign="top" >Min=1, Max=7</td>
3304 <td valign="top" >Plane</td>
3305 <td valign="top" >TBD</td>
3312 <!-- Internals: vertical blanking -->
3314 <sect1 id="drm-vertical-blank">
3315 <title>Vertical Blanking</title>
3317 Vertical blanking plays a major role in graphics rendering. To achieve
3318 tear-free display, users must synchronize page flips and/or rendering to
3319 vertical blanking. The DRM API offers ioctls to perform page flips
3320 synchronized to vertical blanking and wait for vertical blanking.
3323 The DRM core handles most of the vertical blanking management logic, which
3324 involves filtering out spurious interrupts, keeping race-free blanking
3325 counters, coping with counter wrap-around and resets and keeping use
3326 counts. It relies on the driver to generate vertical blanking interrupts
3327 and optionally provide a hardware vertical blanking counter. Drivers must
3328 implement the following operations.
3332 <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc);
3333 void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis>
3335 Enable or disable vertical blanking interrupts for the given CRTC.
3339 <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis>
3341 Retrieve the value of the vertical blanking counter for the given
3342 CRTC. If the hardware maintains a vertical blanking counter its value
3343 should be returned. Otherwise drivers can use the
3344 <function>drm_vblank_count</function> helper function to handle this
3350 Drivers must initialize the vertical blanking handling core with a call to
3351 <function>drm_vblank_init</function> in their
3352 <methodname>load</methodname> operation. The function will set the struct
3353 <structname>drm_device</structname>
3354 <structfield>vblank_disable_allowed</structfield> field to 0. This will
3355 keep vertical blanking interrupts enabled permanently until the first mode
3356 set operation, where <structfield>vblank_disable_allowed</structfield> is
3357 set to 1. The reason behind this is not clear. Drivers can set the field
3358 to 1 after <function>calling drm_vblank_init</function> to make vertical
3359 blanking interrupts dynamically managed from the beginning.
3362 Vertical blanking interrupts can be enabled by the DRM core or by drivers
3363 themselves (for instance to handle page flipping operations). The DRM core
3364 maintains a vertical blanking use count to ensure that the interrupts are
3365 not disabled while a user still needs them. To increment the use count,
3366 drivers call <function>drm_vblank_get</function>. Upon return vertical
3367 blanking interrupts are guaranteed to be enabled.
3370 To decrement the use count drivers call
3371 <function>drm_vblank_put</function>. Only when the use count drops to zero
3372 will the DRM core disable the vertical blanking interrupts after a delay
3373 by scheduling a timer. The delay is accessible through the vblankoffdelay
3374 module parameter or the <varname>drm_vblank_offdelay</varname> global
3375 variable and expressed in milliseconds. Its default value is 5000 ms.
3378 When a vertical blanking interrupt occurs drivers only need to call the
3379 <function>drm_handle_vblank</function> function to account for the
3383 Resources allocated by <function>drm_vblank_init</function> must be freed
3384 with a call to <function>drm_vblank_cleanup</function> in the driver
3385 <methodname>unload</methodname> operation handler.
3388 <title>Vertical Blanking and Interrupt Handling Functions Reference</title>
3389 !Edrivers/gpu/drm/drm_irq.c
3393 <!-- Internals: open/close, file operations and ioctls -->
3396 <title>Open/Close, File Operations and IOCTLs</title>
3398 <title>Open and Close</title>
3399 <synopsis>int (*firstopen) (struct drm_device *);
3400 void (*lastclose) (struct drm_device *);
3401 int (*open) (struct drm_device *, struct drm_file *);
3402 void (*preclose) (struct drm_device *, struct drm_file *);
3403 void (*postclose) (struct drm_device *, struct drm_file *);</synopsis>
3404 <abstract>Open and close handlers. None of those methods are mandatory.
3407 The <methodname>firstopen</methodname> method is called by the DRM core
3408 for legacy UMS (User Mode Setting) drivers only when an application
3409 opens a device that has no other opened file handle. UMS drivers can
3410 implement it to acquire device resources. KMS drivers can't use the
3411 method and must acquire resources in the <methodname>load</methodname>
3415 Similarly the <methodname>lastclose</methodname> method is called when
3416 the last application holding a file handle opened on the device closes
3417 it, for both UMS and KMS drivers. Additionally, the method is also
3418 called at module unload time or, for hot-pluggable devices, when the
3419 device is unplugged. The <methodname>firstopen</methodname> and
3420 <methodname>lastclose</methodname> calls can thus be unbalanced.
3423 The <methodname>open</methodname> method is called every time the device
3424 is opened by an application. Drivers can allocate per-file private data
3425 in this method and store them in the struct
3426 <structname>drm_file</structname> <structfield>driver_priv</structfield>
3427 field. Note that the <methodname>open</methodname> method is called
3428 before <methodname>firstopen</methodname>.
3431 The close operation is split into <methodname>preclose</methodname> and
3432 <methodname>postclose</methodname> methods. Drivers must stop and
3433 cleanup all per-file operations in the <methodname>preclose</methodname>
3434 method. For instance pending vertical blanking and page flip events must
3435 be cancelled. No per-file operation is allowed on the file handle after
3436 returning from the <methodname>preclose</methodname> method.
3439 Finally the <methodname>postclose</methodname> method is called as the
3440 last step of the close operation, right before calling the
3441 <methodname>lastclose</methodname> method if no other open file handle
3442 exists for the device. Drivers that have allocated per-file private data
3443 in the <methodname>open</methodname> method should free it here.
3446 The <methodname>lastclose</methodname> method should restore CRTC and
3447 plane properties to default value, so that a subsequent open of the
3448 device will not inherit state from the previous user. It can also be
3449 used to execute delayed power switching state changes, e.g. in
3450 conjunction with the vga-switcheroo infrastructure. Beyond that KMS
3451 drivers should not do any further cleanup. Only legacy UMS drivers might
3452 need to clean up device state so that the vga console or an independent
3453 fbdev driver could take over.
3457 <title>File Operations</title>
3458 <synopsis>const struct file_operations *fops</synopsis>
3459 <abstract>File operations for the DRM device node.</abstract>
3461 Drivers must define the file operations structure that forms the DRM
3462 userspace API entry point, even though most of those operations are
3463 implemented in the DRM core. The <methodname>open</methodname>,
3464 <methodname>release</methodname> and <methodname>ioctl</methodname>
3465 operations are handled by
3467 .owner = THIS_MODULE,
3469 .release = drm_release,
3470 .unlocked_ioctl = drm_ioctl,
3471 #ifdef CONFIG_COMPAT
3472 .compat_ioctl = drm_compat_ioctl,
3477 Drivers that implement private ioctls that requires 32/64bit
3478 compatibility support must provide their own
3479 <methodname>compat_ioctl</methodname> handler that processes private
3480 ioctls and calls <function>drm_compat_ioctl</function> for core ioctls.
3483 The <methodname>read</methodname> and <methodname>poll</methodname>
3484 operations provide support for reading DRM events and polling them. They
3489 .llseek = no_llseek,
3493 The memory mapping implementation varies depending on how the driver
3494 manages memory. Pre-GEM drivers will use <function>drm_mmap</function>,
3495 while GEM-aware drivers will use <function>drm_gem_mmap</function>. See
3496 <xref linkend="drm-gem"/>.
3498 .mmap = drm_gem_mmap,
3502 No other file operation is supported by the DRM API.
3506 <title>IOCTLs</title>
3507 <synopsis>struct drm_ioctl_desc *ioctls;
3508 int num_ioctls;</synopsis>
3509 <abstract>Driver-specific ioctls descriptors table.</abstract>
3511 Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls
3512 descriptors table is indexed by the ioctl number offset from the base
3513 value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the
3517 <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting>
3519 <parameter>ioctl</parameter> is the ioctl name. Drivers must define
3520 the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number
3521 offset from DRM_COMMAND_BASE and the ioctl number respectively. The
3522 first macro is private to the device while the second must be exposed
3523 to userspace in a public header.
3526 <parameter>func</parameter> is a pointer to the ioctl handler function
3527 compatible with the <type>drm_ioctl_t</type> type.
3528 <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data,
3529 struct drm_file *file_priv);</programlisting>
3532 <parameter>flags</parameter> is a bitmask combination of the following
3533 values. It restricts how the ioctl is allowed to be called.
3536 DRM_AUTH - Only authenticated callers allowed
3539 DRM_MASTER - The ioctl can only be called on the master file
3543 DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed
3546 DRM_CONTROL_ALLOW - The ioctl can only be called on a control
3550 DRM_UNLOCKED - The ioctl handler will be called without locking
3551 the DRM global mutex
3559 <title>Legacy Support Code</title>
3561 The section very briefly covers some of the old legacy support code which
3562 is only used by old DRM drivers which have done a so-called shadow-attach
3563 to the underlying device instead of registering as a real driver. This
3564 also includes some of the old generic buffer management and command
3565 submission code. Do not use any of this in new and modern drivers.
3569 <title>Legacy Suspend/Resume</title>
3571 The DRM core provides some suspend/resume code, but drivers wanting full
3572 suspend/resume support should provide save() and restore() functions.
3573 These are called at suspend, hibernate, or resume time, and should perform
3574 any state save or restore required by your device across suspend or
3577 <synopsis>int (*suspend) (struct drm_device *, pm_message_t state);
3578 int (*resume) (struct drm_device *);</synopsis>
3580 Those are legacy suspend and resume methods which
3581 <emphasis>only</emphasis> work with the legacy shadow-attach driver
3582 registration functions. New driver should use the power management
3583 interface provided by their bus type (usually through
3584 the struct <structname>device_driver</structname> dev_pm_ops) and set
3585 these methods to NULL.
3590 <title>Legacy DMA Services</title>
3592 This should cover how DMA mapping etc. is supported by the core.
3593 These functions are deprecated and should not be used.
3602 - Document the struct_mutex catch-all lock
3603 - Document connector properties
3605 - Why is the load method optional?
3606 - What are drivers supposed to set the initial display state to, and how?
3607 Connector's DPMS states are not initialized and are thus equal to
3608 DRM_MODE_DPMS_ON. The fbcon compatibility layer calls
3609 drm_helper_disable_unused_functions(), which disables unused encoders and
3610 CRTCs, but doesn't touch the connectors' DPMS state, and
3611 drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers
3612 that don't implement (or just don't use) fbcon compatibility need to call
3613 those functions themselves?
3614 - KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset()
3615 around mode setting. Should this be done in the DRM core?
3616 - vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset()
3617 call and never set back to 0. It seems to be safe to permanently set it to 1
3618 in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as
3619 well. This should be investigated.
3620 - crtc and connector .save and .restore operations are only used internally in
3621 drivers, should they be removed from the core?
3622 - encoder mid-layer .save and .restore operations are only used internally in
3623 drivers, should they be removed from the core?
3624 - encoder mid-layer .detect operation is only used internally in drivers,
3625 should it be removed from the core?
3628 <!-- External interfaces -->
3630 <chapter id="drmExternals">
3631 <title>Userland interfaces</title>
3633 The DRM core exports several interfaces to applications,
3634 generally intended to be used through corresponding libdrm
3635 wrapper functions. In addition, drivers export device-specific
3636 interfaces for use by userspace drivers & device-aware
3637 applications through ioctls and sysfs files.
3640 External interfaces include: memory mapping, context management,
3641 DMA operations, AGP management, vblank control, fence
3642 management, memory management, and output management.
3645 Cover generic ioctls and sysfs layout here. We only need high-level
3646 info, since man pages should cover the rest.
3649 <!-- External: render nodes -->
3652 <title>Render nodes</title>
3654 DRM core provides multiple character-devices for user-space to use.
3655 Depending on which device is opened, user-space can perform a different
3656 set of operations (mainly ioctls). The primary node is always created
3657 and called card<num>. Additionally, a currently
3658 unused control node, called controlD<num> is also
3659 created. The primary node provides all legacy operations and
3660 historically was the only interface used by userspace. With KMS, the
3661 control node was introduced. However, the planned KMS control interface
3662 has never been written and so the control node stays unused to date.
3665 With the increased use of offscreen renderers and GPGPU applications,
3666 clients no longer require running compositors or graphics servers to
3667 make use of a GPU. But the DRM API required unprivileged clients to
3668 authenticate to a DRM-Master prior to getting GPU access. To avoid this
3669 step and to grant clients GPU access without authenticating, render
3670 nodes were introduced. Render nodes solely serve render clients, that
3671 is, no modesetting or privileged ioctls can be issued on render nodes.
3672 Only non-global rendering commands are allowed. If a driver supports
3673 render nodes, it must advertise it via the DRIVER_RENDER
3674 DRM driver capability. If not supported, the primary node must be used
3675 for render clients together with the legacy drmAuth authentication
3679 If a driver advertises render node support, DRM core will create a
3680 separate render node called renderD<num>. There will
3681 be one render node per device. No ioctls except PRIME-related ioctls
3682 will be allowed on this node. Especially GEM_OPEN will be
3683 explicitly prohibited. Render nodes are designed to avoid the
3684 buffer-leaks, which occur if clients guess the flink names or mmap
3685 offsets on the legacy interface. Additionally to this basic interface,
3686 drivers must mark their driver-dependent render-only ioctls as
3687 DRM_RENDER_ALLOW so render clients can use them. Driver
3688 authors must be careful not to allow any privileged ioctls on render
3692 With render nodes, user-space can now control access to the render node
3693 via basic file-system access-modes. A running graphics server which
3694 authenticates clients on the privileged primary/legacy node is no longer
3695 required. Instead, a client can open the render node and is immediately
3696 granted GPU access. Communication between clients (or servers) is done
3697 via PRIME. FLINK from render node to legacy node is not supported. New
3698 clients must not use the insecure FLINK interface.
3701 Besides dropping all modeset/global ioctls, render nodes also drop the
3702 DRM-Master concept. There is no reason to associate render clients with
3703 a DRM-Master as they are independent of any graphics server. Besides,
3704 they must work without any running master, anyway.
3705 Drivers must be able to run without a master object if they support
3706 render nodes. If, on the other hand, a driver requires shared state
3707 between clients which is visible to user-space and accessible beyond
3708 open-file boundaries, they cannot support render nodes.
3712 <!-- External: vblank handling -->
3715 <title>VBlank event handling</title>
3717 The DRM core exposes two vertical blank related ioctls:
3720 <term>DRM_IOCTL_WAIT_VBLANK</term>
3723 This takes a struct drm_wait_vblank structure as its argument,
3724 and it is used to block or request a signal when a specified
3725 vblank event occurs.
3730 <term>DRM_IOCTL_MODESET_CTL</term>
3733 This was only used for user-mode-settind drivers around
3734 modesetting changes to allow the kernel to update the vblank
3735 interrupt after mode setting, since on many devices the vertical
3736 blank counter is reset to 0 at some point during modeset. Modern
3737 drivers should not call this any more since with kernel mode
3738 setting it is a no-op.
3748 <part id="drmDrivers">
3749 <title>DRM Drivers</title>
3753 This second part of the DRM Developer's Guide documents driver code,
3754 implementation details and also all the driver-specific userspace
3755 interfaces. Especially since all hardware-acceleration interfaces to
3756 userspace are driver specific for efficiency and other reasons these
3757 interfaces can be rather substantial. Hence every driver has its own
3762 <chapter id="drmI915">
3763 <title>drm/i915 Intel GFX Driver</title>
3765 The drm/i915 driver supports all (with the exception of some very early
3766 models) integrated GFX chipsets with both Intel display and rendering
3767 blocks. This excludes a set of SoC platforms with an SGX rendering unit,
3768 those have basic support through the gma500 drm driver.
3771 <title>Display Hardware Handling</title>
3773 This section covers everything related to the display hardware including
3774 the mode setting infrastructure, plane, sprite and cursor handling and
3775 display, output probing and related topics.
3778 <title>Mode Setting Infrastructure</title>
3780 The i915 driver is thus far the only DRM driver which doesn't use the
3781 common DRM helper code to implement mode setting sequences. Thus it
3782 has its own tailor-made infrastructure for executing a display
3783 configuration change.
3787 <title>Plane Configuration</title>
3789 This section covers plane configuration and composition with the
3790 primary plane, sprites, cursors and overlays. This includes the
3791 infrastructure to do atomic vsync'ed updates of all this state and
3792 also tightly coupled topics like watermark setup and computation,
3793 framebuffer compression and panel self refresh.
3797 <title>Output Probing</title>
3799 This section covers output probing and related infrastructure like the
3800 hotplug interrupt storm detection and mitigation code. Note that the
3801 i915 driver still uses most of the common DRM helper code for output
3802 probing, so those sections fully apply.
3807 !Pdrivers/gpu/drm/i915/i915_reg.h DPIO
3809 <title>Dual channel PHY (VLV/CHV)</title>
3811 <colspec colname="c0" />
3812 <colspec colname="c1" />
3813 <colspec colname="c2" />
3814 <colspec colname="c3" />
3815 <colspec colname="c4" />
3816 <colspec colname="c5" />
3817 <colspec colname="c6" />
3818 <colspec colname="c7" />
3819 <spanspec spanname="ch0" namest="c0" nameend="c3" />
3820 <spanspec spanname="ch1" namest="c4" nameend="c7" />
3821 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
3822 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
3823 <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" />
3824 <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" />
3827 <entry spanname="ch0">CH0</entry>
3828 <entry spanname="ch1">CH1</entry>
3831 <tbody valign="top" align="center">
3833 <entry spanname="ch0">CMN/PLL/REF</entry>
3834 <entry spanname="ch1">CMN/PLL/REF</entry>
3837 <entry spanname="ch0pcs01">PCS01</entry>
3838 <entry spanname="ch0pcs23">PCS23</entry>
3839 <entry spanname="ch1pcs01">PCS01</entry>
3840 <entry spanname="ch1pcs23">PCS23</entry>
3853 <entry spanname="ch0">DDI0</entry>
3854 <entry spanname="ch1">DDI1</entry>
3860 <title>Single channel PHY (CHV)</title>
3862 <colspec colname="c0" />
3863 <colspec colname="c1" />
3864 <colspec colname="c2" />
3865 <colspec colname="c3" />
3866 <spanspec spanname="ch0" namest="c0" nameend="c3" />
3867 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" />
3868 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" />
3871 <entry spanname="ch0">CH0</entry>
3874 <tbody valign="top" align="center">
3876 <entry spanname="ch0">CMN/PLL/REF</entry>
3879 <entry spanname="ch0pcs01">PCS01</entry>
3880 <entry spanname="ch0pcs23">PCS23</entry>
3889 <entry spanname="ch0">DDI2</entry>
3898 <title>Memory Management and Command Submission</title>
3900 This sections covers all things related to the GEM implementation in the
3904 <title>Batchbuffer Parsing</title>
3905 !Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser
3906 !Idrivers/gpu/drm/i915/i915_cmd_parser.c
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