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" []> 4 5<book id="drmDevelopersGuide"> 6 <bookinfo> 7 <title>Linux DRM Developer's Guide</title> 8 9 <authorgroup> 10 <author> 11 <firstname>Jesse</firstname> 12 <surname>Barnes</surname> 13 <contrib>Initial version</contrib> 14 <affiliation> 15 <orgname>Intel Corporation</orgname> 16 <address> 17 <email>jesse.barnes@intel.com</email> 18 </address> 19 </affiliation> 20 </author> 21 <author> 22 <firstname>Laurent</firstname> 23 <surname>Pinchart</surname> 24 <contrib>Driver internals</contrib> 25 <affiliation> 26 <orgname>Ideas on board SPRL</orgname> 27 <address> 28 <email>laurent.pinchart@ideasonboard.com</email> 29 </address> 30 </affiliation> 31 </author> 32 <author> 33 <firstname>Daniel</firstname> 34 <surname>Vetter</surname> 35 <contrib>Contributions all over the place</contrib> 36 <affiliation> 37 <orgname>Intel Corporation</orgname> 38 <address> 39 <email>daniel.vetter@ffwll.ch</email> 40 </address> 41 </affiliation> 42 </author> 43 </authorgroup> 44 45 <copyright> 46 <year>2008-2009</year> 47 <year>2013-2014</year> 48 <holder>Intel Corporation</holder> 49 </copyright> 50 <copyright> 51 <year>2012</year> 52 <holder>Laurent Pinchart</holder> 53 </copyright> 54 55 <legalnotice> 56 <para> 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. 60 </para> 61 </legalnotice> 62 63 <revhistory> 64 <!-- Put document revisions here, newest first. --> 65 <revision> 66 <revnumber>1.0</revnumber> 67 <date>2012-07-13</date> 68 <authorinitials>LP</authorinitials> 69 <revremark>Added extensive documentation about driver internals. 70 </revremark> 71 </revision> 72 </revhistory> 73 </bookinfo> 74 75<toc></toc> 76 77<part id="drmCore"> 78 <title>DRM Core</title> 79 <partintro> 80 <para> 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. 84 </para> 85 </partintro> 86 87 <chapter id="drmIntroduction"> 88 <title>Introduction</title> 89 <para> 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. 96 </para> 97 <para> 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. 102 </para> 103 <para> 104 [Insert diagram of typical DRM stack here] 105 </para> 106 </chapter> 107 108 <!-- Internals --> 109 110 <chapter id="drmInternals"> 111 <title>DRM Internals</title> 112 <para> 113 This chapter documents DRM internals relevant to driver authors 114 and developers working to add support for the latest features to 115 existing drivers. 116 </para> 117 <para> 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. 123 </para> 124 <para> 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 131 services. 132 </para> 133 134 <!-- Internals: driver init --> 135 136 <sect1> 137 <title>Driver Initialization</title> 138 <para> 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. 143 </para> 144 <para> 145 Newer drivers that no longer require a <structname>drm_bus</structname> 146 structure can alternatively use the low-level device initialization and 147 registration functions such as <function>drm_dev_alloc()</function> and 148 <function>drm_dev_register()</function> directly. 149 </para> 150 <para> 151 The <structname>drm_driver</structname> structure contains static 152 information that describes the driver and features it supports, and 153 pointers to methods that the DRM core will call to implement the DRM API. 154 We will first go through the <structname>drm_driver</structname> static 155 information fields, and will then describe individual operations in 156 details as they get used in later sections. 157 </para> 158 <sect2> 159 <title>Driver Information</title> 160 <sect3> 161 <title>Driver Features</title> 162 <para> 163 Drivers inform the DRM core about their requirements and supported 164 features by setting appropriate flags in the 165 <structfield>driver_features</structfield> field. Since those flags 166 influence the DRM core behaviour since registration time, most of them 167 must be set to registering the <structname>drm_driver</structname> 168 instance. 169 </para> 170 <synopsis>u32 driver_features;</synopsis> 171 <variablelist> 172 <title>Driver Feature Flags</title> 173 <varlistentry> 174 <term>DRIVER_USE_AGP</term> 175 <listitem><para> 176 Driver uses AGP interface, the DRM core will manage AGP resources. 177 </para></listitem> 178 </varlistentry> 179 <varlistentry> 180 <term>DRIVER_REQUIRE_AGP</term> 181 <listitem><para> 182 Driver needs AGP interface to function. AGP initialization failure 183 will become a fatal error. 184 </para></listitem> 185 </varlistentry> 186 <varlistentry> 187 <term>DRIVER_PCI_DMA</term> 188 <listitem><para> 189 Driver is capable of PCI DMA, mapping of PCI DMA buffers to 190 userspace will be enabled. Deprecated. 191 </para></listitem> 192 </varlistentry> 193 <varlistentry> 194 <term>DRIVER_SG</term> 195 <listitem><para> 196 Driver can perform scatter/gather DMA, allocation and mapping of 197 scatter/gather buffers will be enabled. Deprecated. 198 </para></listitem> 199 </varlistentry> 200 <varlistentry> 201 <term>DRIVER_HAVE_DMA</term> 202 <listitem><para> 203 Driver supports DMA, the userspace DMA API will be supported. 204 Deprecated. 205 </para></listitem> 206 </varlistentry> 207 <varlistentry> 208 <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term> 209 <listitem><para> 210 DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler 211 managed by the DRM Core. The core will support simple IRQ handler 212 installation when the flag is set. The installation process is 213 described in <xref linkend="drm-irq-registration"/>.</para> 214 <para>DRIVER_IRQ_SHARED indicates whether the device & handler 215 support shared IRQs (note that this is required of PCI drivers). 216 </para></listitem> 217 </varlistentry> 218 <varlistentry> 219 <term>DRIVER_GEM</term> 220 <listitem><para> 221 Driver use the GEM memory manager. 222 </para></listitem> 223 </varlistentry> 224 <varlistentry> 225 <term>DRIVER_MODESET</term> 226 <listitem><para> 227 Driver supports mode setting interfaces (KMS). 228 </para></listitem> 229 </varlistentry> 230 <varlistentry> 231 <term>DRIVER_PRIME</term> 232 <listitem><para> 233 Driver implements DRM PRIME buffer sharing. 234 </para></listitem> 235 </varlistentry> 236 <varlistentry> 237 <term>DRIVER_RENDER</term> 238 <listitem><para> 239 Driver supports dedicated render nodes. 240 </para></listitem> 241 </varlistentry> 242 </variablelist> 243 </sect3> 244 <sect3> 245 <title>Major, Minor and Patchlevel</title> 246 <synopsis>int major; 247int minor; 248int patchlevel;</synopsis> 249 <para> 250 The DRM core identifies driver versions by a major, minor and patch 251 level triplet. The information is printed to the kernel log at 252 initialization time and passed to userspace through the 253 DRM_IOCTL_VERSION ioctl. 254 </para> 255 <para> 256 The major and minor numbers are also used to verify the requested driver 257 API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes 258 between minor versions, applications can call DRM_IOCTL_SET_VERSION to 259 select a specific version of the API. If the requested major isn't equal 260 to the driver major, or the requested minor is larger than the driver 261 minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise 262 the driver's set_version() method will be called with the requested 263 version. 264 </para> 265 </sect3> 266 <sect3> 267 <title>Name, Description and Date</title> 268 <synopsis>char *name; 269char *desc; 270char *date;</synopsis> 271 <para> 272 The driver name is printed to the kernel log at initialization time, 273 used for IRQ registration and passed to userspace through 274 DRM_IOCTL_VERSION. 275 </para> 276 <para> 277 The driver description is a purely informative string passed to 278 userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by 279 the kernel. 280 </para> 281 <para> 282 The driver date, formatted as YYYYMMDD, is meant to identify the date of 283 the latest modification to the driver. However, as most drivers fail to 284 update it, its value is mostly useless. The DRM core prints it to the 285 kernel log at initialization time and passes it to userspace through the 286 DRM_IOCTL_VERSION ioctl. 287 </para> 288 </sect3> 289 </sect2> 290 <sect2> 291 <title>Device Registration</title> 292 <para> 293 A number of functions are provided to help with device registration. 294 The functions deal with PCI and platform devices, respectively. 295 </para> 296!Edrivers/gpu/drm/drm_pci.c 297!Edrivers/gpu/drm/drm_platform.c 298 <para> 299 New drivers that no longer rely on the services provided by the 300 <structname>drm_bus</structname> structure can call the low-level 301 device registration functions directly. The 302 <function>drm_dev_alloc()</function> function can be used to allocate 303 and initialize a new <structname>drm_device</structname> structure. 304 Drivers will typically want to perform some additional setup on this 305 structure, such as allocating driver-specific data and storing a 306 pointer to it in the DRM device's <structfield>dev_private</structfield> 307 field. Drivers should also set the device's unique name using the 308 <function>drm_dev_set_unique()</function> function. After it has been 309 set up a device can be registered with the DRM subsystem by calling 310 <function>drm_dev_register()</function>. This will cause the device to 311 be exposed to userspace and will call the driver's 312 <structfield>.load()</structfield> implementation. When a device is 313 removed, the DRM device can safely be unregistered and freed by calling 314 <function>drm_dev_unregister()</function> followed by a call to 315 <function>drm_dev_unref()</function>. 316 </para> 317!Edrivers/gpu/drm/drm_drv.c 318 </sect2> 319 <sect2> 320 <title>Driver Load</title> 321 <para> 322 The <methodname>load</methodname> method is the driver and device 323 initialization entry point. The method is responsible for allocating and 324 initializing driver private data, performing resource allocation and 325 mapping (e.g. acquiring 326 clocks, mapping registers or allocating command buffers), initializing 327 the memory manager (<xref linkend="drm-memory-management"/>), installing 328 the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up 329 vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode 330 setting (<xref linkend="drm-mode-setting"/>) and initial output 331 configuration (<xref linkend="drm-kms-init"/>). 332 </para> 333 <note><para> 334 If compatibility is a concern (e.g. with drivers converted over from 335 User Mode Setting to Kernel Mode Setting), care must be taken to prevent 336 device initialization and control that is incompatible with currently 337 active userspace drivers. For instance, if user level mode setting 338 drivers are in use, it would be problematic to perform output discovery 339 & configuration at load time. Likewise, if user-level drivers 340 unaware of memory management are in use, memory management and command 341 buffer setup may need to be omitted. These requirements are 342 driver-specific, and care needs to be taken to keep both old and new 343 applications and libraries working. 344 </para></note> 345 <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis> 346 <para> 347 The method takes two arguments, a pointer to the newly created 348 <structname>drm_device</structname> and flags. The flags are used to 349 pass the <structfield>driver_data</structfield> field of the device id 350 corresponding to the device passed to <function>drm_*_init()</function>. 351 Only PCI devices currently use this, USB and platform DRM drivers have 352 their <methodname>load</methodname> method called with flags to 0. 353 </para> 354 <sect3> 355 <title>Driver Private Data</title> 356 <para> 357 The driver private hangs off the main 358 <structname>drm_device</structname> structure and can be used for 359 tracking various device-specific bits of information, like register 360 offsets, command buffer status, register state for suspend/resume, etc. 361 At load time, a driver may simply allocate one and set 362 <structname>drm_device</structname>.<structfield>dev_priv</structfield> 363 appropriately; it should be freed and 364 <structname>drm_device</structname>.<structfield>dev_priv</structfield> 365 set to NULL when the driver is unloaded. 366 </para> 367 </sect3> 368 <sect3 id="drm-irq-registration"> 369 <title>IRQ Registration</title> 370 <para> 371 The DRM core tries to facilitate IRQ handler registration and 372 unregistration by providing <function>drm_irq_install</function> and 373 <function>drm_irq_uninstall</function> functions. Those functions only 374 support a single interrupt per device, devices that use more than one 375 IRQs need to be handled manually. 376 </para> 377 <sect4> 378 <title>Managed IRQ Registration</title> 379 <para> 380 <function>drm_irq_install</function> starts by calling the 381 <methodname>irq_preinstall</methodname> driver operation. The operation 382 is optional and must make sure that the interrupt will not get fired by 383 clearing all pending interrupt flags or disabling the interrupt. 384 </para> 385 <para> 386 The passed-in IRQ will then be requested by a call to 387 <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver 388 feature flag is set, a shared (IRQF_SHARED) IRQ handler will be 389 requested. 390 </para> 391 <para> 392 The IRQ handler function must be provided as the mandatory irq_handler 393 driver operation. It will get passed directly to 394 <function>request_irq</function> and thus has the same prototype as all 395 IRQ handlers. It will get called with a pointer to the DRM device as the 396 second argument. 397 </para> 398 <para> 399 Finally the function calls the optional 400 <methodname>irq_postinstall</methodname> driver operation. The operation 401 usually enables interrupts (excluding the vblank interrupt, which is 402 enabled separately), but drivers may choose to enable/disable interrupts 403 at a different time. 404 </para> 405 <para> 406 <function>drm_irq_uninstall</function> is similarly used to uninstall an 407 IRQ handler. It starts by waking up all processes waiting on a vblank 408 interrupt to make sure they don't hang, and then calls the optional 409 <methodname>irq_uninstall</methodname> driver operation. The operation 410 must disable all hardware interrupts. Finally the function frees the IRQ 411 by calling <function>free_irq</function>. 412 </para> 413 </sect4> 414 <sect4> 415 <title>Manual IRQ Registration</title> 416 <para> 417 Drivers that require multiple interrupt handlers can't use the managed 418 IRQ registration functions. In that case IRQs must be registered and 419 unregistered manually (usually with the <function>request_irq</function> 420 and <function>free_irq</function> functions, or their devm_* equivalent). 421 </para> 422 <para> 423 When manually registering IRQs, drivers must not set the DRIVER_HAVE_IRQ 424 driver feature flag, and must not provide the 425 <methodname>irq_handler</methodname> driver operation. They must set the 426 <structname>drm_device</structname> <structfield>irq_enabled</structfield> 427 field to 1 upon registration of the IRQs, and clear it to 0 after 428 unregistering the IRQs. 429 </para> 430 </sect4> 431 </sect3> 432 <sect3> 433 <title>Memory Manager Initialization</title> 434 <para> 435 Every DRM driver requires a memory manager which must be initialized at 436 load time. DRM currently contains two memory managers, the Translation 437 Table Manager (TTM) and the Graphics Execution Manager (GEM). 438 This document describes the use of the GEM memory manager only. See 439 <xref linkend="drm-memory-management"/> for details. 440 </para> 441 </sect3> 442 <sect3> 443 <title>Miscellaneous Device Configuration</title> 444 <para> 445 Another task that may be necessary for PCI devices during configuration 446 is mapping the video BIOS. On many devices, the VBIOS describes device 447 configuration, LCD panel timings (if any), and contains flags indicating 448 device state. Mapping the BIOS can be done using the pci_map_rom() call, 449 a convenience function that takes care of mapping the actual ROM, 450 whether it has been shadowed into memory (typically at address 0xc0000) 451 or exists on the PCI device in the ROM BAR. Note that after the ROM has 452 been mapped and any necessary information has been extracted, it should 453 be unmapped; on many devices, the ROM address decoder is shared with 454 other BARs, so leaving it mapped could cause undesired behaviour like 455 hangs or memory corruption. 456 <!--!Fdrivers/pci/rom.c pci_map_rom--> 457 </para> 458 </sect3> 459 </sect2> 460 </sect1> 461 462 <!-- Internals: memory management --> 463 464 <sect1 id="drm-memory-management"> 465 <title>Memory management</title> 466 <para> 467 Modern Linux systems require large amount of graphics memory to store 468 frame buffers, textures, vertices and other graphics-related data. Given 469 the very dynamic nature of many of that data, managing graphics memory 470 efficiently is thus crucial for the graphics stack and plays a central 471 role in the DRM infrastructure. 472 </para> 473 <para> 474 The DRM core includes two memory managers, namely Translation Table Maps 475 (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory 476 manager to be developed and tried to be a one-size-fits-them all 477 solution. It provides a single userspace API to accommodate the need of 478 all hardware, supporting both Unified Memory Architecture (UMA) devices 479 and devices with dedicated video RAM (i.e. most discrete video cards). 480 This resulted in a large, complex piece of code that turned out to be 481 hard to use for driver development. 482 </para> 483 <para> 484 GEM started as an Intel-sponsored project in reaction to TTM's 485 complexity. Its design philosophy is completely different: instead of 486 providing a solution to every graphics memory-related problems, GEM 487 identified common code between drivers and created a support library to 488 share it. GEM has simpler initialization and execution requirements than 489 TTM, but has no video RAM management capabilities and is thus limited to 490 UMA devices. 491 </para> 492 <sect2> 493 <title>The Translation Table Manager (TTM)</title> 494 <para> 495 TTM design background and information belongs here. 496 </para> 497 <sect3> 498 <title>TTM initialization</title> 499 <warning><para>This section is outdated.</para></warning> 500 <para> 501 Drivers wishing to support TTM must fill out a drm_bo_driver 502 structure. The structure contains several fields with function 503 pointers for initializing the TTM, allocating and freeing memory, 504 waiting for command completion and fence synchronization, and memory 505 migration. See the radeon_ttm.c file for an example of usage. 506 </para> 507 <para> 508 The ttm_global_reference structure is made up of several fields: 509 </para> 510 <programlisting> 511 struct ttm_global_reference { 512 enum ttm_global_types global_type; 513 size_t size; 514 void *object; 515 int (*init) (struct ttm_global_reference *); 516 void (*release) (struct ttm_global_reference *); 517 }; 518 </programlisting> 519 <para> 520 There should be one global reference structure for your memory 521 manager as a whole, and there will be others for each object 522 created by the memory manager at runtime. Your global TTM should 523 have a type of TTM_GLOBAL_TTM_MEM. The size field for the global 524 object should be sizeof(struct ttm_mem_global), and the init and 525 release hooks should point at your driver-specific init and 526 release routines, which probably eventually call 527 ttm_mem_global_init and ttm_mem_global_release, respectively. 528 </para> 529 <para> 530 Once your global TTM accounting structure is set up and initialized 531 by calling ttm_global_item_ref() on it, 532 you need to create a buffer object TTM to 533 provide a pool for buffer object allocation by clients and the 534 kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO, 535 and its size should be sizeof(struct ttm_bo_global). Again, 536 driver-specific init and release functions may be provided, 537 likely eventually calling ttm_bo_global_init() and 538 ttm_bo_global_release(), respectively. Also, like the previous 539 object, ttm_global_item_ref() is used to create an initial reference 540 count for the TTM, which will call your initialization function. 541 </para> 542 </sect3> 543 </sect2> 544 <sect2 id="drm-gem"> 545 <title>The Graphics Execution Manager (GEM)</title> 546 <para> 547 The GEM design approach has resulted in a memory manager that doesn't 548 provide full coverage of all (or even all common) use cases in its 549 userspace or kernel API. GEM exposes a set of standard memory-related 550 operations to userspace and a set of helper functions to drivers, and let 551 drivers implement hardware-specific operations with their own private API. 552 </para> 553 <para> 554 The GEM userspace API is described in the 555 <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics 556 Execution Manager</citetitle></ulink> article on LWN. While slightly 557 outdated, the document provides a good overview of the GEM API principles. 558 Buffer allocation and read and write operations, described as part of the 559 common GEM API, are currently implemented using driver-specific ioctls. 560 </para> 561 <para> 562 GEM is data-agnostic. It manages abstract buffer objects without knowing 563 what individual buffers contain. APIs that require knowledge of buffer 564 contents or purpose, such as buffer allocation or synchronization 565 primitives, are thus outside of the scope of GEM and must be implemented 566 using driver-specific ioctls. 567 </para> 568 <para> 569 On a fundamental level, GEM involves several operations: 570 <itemizedlist> 571 <listitem>Memory allocation and freeing</listitem> 572 <listitem>Command execution</listitem> 573 <listitem>Aperture management at command execution time</listitem> 574 </itemizedlist> 575 Buffer object allocation is relatively straightforward and largely 576 provided by Linux's shmem layer, which provides memory to back each 577 object. 578 </para> 579 <para> 580 Device-specific operations, such as command execution, pinning, buffer 581 read & write, mapping, and domain ownership transfers are left to 582 driver-specific ioctls. 583 </para> 584 <sect3> 585 <title>GEM Initialization</title> 586 <para> 587 Drivers that use GEM must set the DRIVER_GEM bit in the struct 588 <structname>drm_driver</structname> 589 <structfield>driver_features</structfield> field. The DRM core will 590 then automatically initialize the GEM core before calling the 591 <methodname>load</methodname> operation. Behind the scene, this will 592 create a DRM Memory Manager object which provides an address space 593 pool for object allocation. 594 </para> 595 <para> 596 In a KMS configuration, drivers need to allocate and initialize a 597 command ring buffer following core GEM initialization if required by 598 the hardware. UMA devices usually have what is called a "stolen" 599 memory region, which provides space for the initial framebuffer and 600 large, contiguous memory regions required by the device. This space is 601 typically not managed by GEM, and must be initialized separately into 602 its own DRM MM object. 603 </para> 604 </sect3> 605 <sect3> 606 <title>GEM Objects Creation</title> 607 <para> 608 GEM splits creation of GEM objects and allocation of the memory that 609 backs them in two distinct operations. 610 </para> 611 <para> 612 GEM objects are represented by an instance of struct 613 <structname>drm_gem_object</structname>. Drivers usually need to extend 614 GEM objects with private information and thus create a driver-specific 615 GEM object structure type that embeds an instance of struct 616 <structname>drm_gem_object</structname>. 617 </para> 618 <para> 619 To create a GEM object, a driver allocates memory for an instance of its 620 specific GEM object type and initializes the embedded struct 621 <structname>drm_gem_object</structname> with a call to 622 <function>drm_gem_object_init</function>. The function takes a pointer to 623 the DRM device, a pointer to the GEM object and the buffer object size 624 in bytes. 625 </para> 626 <para> 627 GEM uses shmem to allocate anonymous pageable memory. 628 <function>drm_gem_object_init</function> will create an shmfs file of 629 the requested size and store it into the struct 630 <structname>drm_gem_object</structname> <structfield>filp</structfield> 631 field. The memory is used as either main storage for the object when the 632 graphics hardware uses system memory directly or as a backing store 633 otherwise. 634 </para> 635 <para> 636 Drivers are responsible for the actual physical pages allocation by 637 calling <function>shmem_read_mapping_page_gfp</function> for each page. 638 Note that they can decide to allocate pages when initializing the GEM 639 object, or to delay allocation until the memory is needed (for instance 640 when a page fault occurs as a result of a userspace memory access or 641 when the driver needs to start a DMA transfer involving the memory). 642 </para> 643 <para> 644 Anonymous pageable memory allocation is not always desired, for instance 645 when the hardware requires physically contiguous system memory as is 646 often the case in embedded devices. Drivers can create GEM objects with 647 no shmfs backing (called private GEM objects) by initializing them with 648 a call to <function>drm_gem_private_object_init</function> instead of 649 <function>drm_gem_object_init</function>. Storage for private GEM 650 objects must be managed by drivers. 651 </para> 652 <para> 653 Drivers that do not need to extend GEM objects with private information 654 can call the <function>drm_gem_object_alloc</function> function to 655 allocate and initialize a struct <structname>drm_gem_object</structname> 656 instance. The GEM core will call the optional driver 657 <methodname>gem_init_object</methodname> operation after initializing 658 the GEM object with <function>drm_gem_object_init</function>. 659 <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis> 660 </para> 661 <para> 662 No alloc-and-init function exists for private GEM objects. 663 </para> 664 </sect3> 665 <sect3> 666 <title>GEM Objects Lifetime</title> 667 <para> 668 All GEM objects are reference-counted by the GEM core. References can be 669 acquired and release by <function>calling drm_gem_object_reference</function> 670 and <function>drm_gem_object_unreference</function> respectively. The 671 caller must hold the <structname>drm_device</structname> 672 <structfield>struct_mutex</structfield> lock. As a convenience, GEM 673 provides the <function>drm_gem_object_reference_unlocked</function> and 674 <function>drm_gem_object_unreference_unlocked</function> functions that 675 can be called without holding the lock. 676 </para> 677 <para> 678 When the last reference to a GEM object is released the GEM core calls 679 the <structname>drm_driver</structname> 680 <methodname>gem_free_object</methodname> operation. That operation is 681 mandatory for GEM-enabled drivers and must free the GEM object and all 682 associated resources. 683 </para> 684 <para> 685 <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis> 686 Drivers are responsible for freeing all GEM object resources, including 687 the resources created by the GEM core. If an mmap offset has been 688 created for the object (in which case 689 <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield> 690 is not NULL) it must be freed by a call to 691 <function>drm_gem_free_mmap_offset</function>. The shmfs backing store 692 must be released by calling <function>drm_gem_object_release</function> 693 (that function can safely be called if no shmfs backing store has been 694 created). 695 </para> 696 </sect3> 697 <sect3> 698 <title>GEM Objects Naming</title> 699 <para> 700 Communication between userspace and the kernel refers to GEM objects 701 using local handles, global names or, more recently, file descriptors. 702 All of those are 32-bit integer values; the usual Linux kernel limits 703 apply to the file descriptors. 704 </para> 705 <para> 706 GEM handles are local to a DRM file. Applications get a handle to a GEM 707 object through a driver-specific ioctl, and can use that handle to refer 708 to the GEM object in other standard or driver-specific ioctls. Closing a 709 DRM file handle frees all its GEM handles and dereferences the 710 associated GEM objects. 711 </para> 712 <para> 713 To create a handle for a GEM object drivers call 714 <function>drm_gem_handle_create</function>. The function takes a pointer 715 to the DRM file and the GEM object and returns a locally unique handle. 716 When the handle is no longer needed drivers delete it with a call to 717 <function>drm_gem_handle_delete</function>. Finally the GEM object 718 associated with a handle can be retrieved by a call to 719 <function>drm_gem_object_lookup</function>. 720 </para> 721 <para> 722 Handles don't take ownership of GEM objects, they only take a reference 723 to the object that will be dropped when the handle is destroyed. To 724 avoid leaking GEM objects, drivers must make sure they drop the 725 reference(s) they own (such as the initial reference taken at object 726 creation time) as appropriate, without any special consideration for the 727 handle. For example, in the particular case of combined GEM object and 728 handle creation in the implementation of the 729 <methodname>dumb_create</methodname> operation, drivers must drop the 730 initial reference to the GEM object before returning the handle. 731 </para> 732 <para> 733 GEM names are similar in purpose to handles but are not local to DRM 734 files. They can be passed between processes to reference a GEM object 735 globally. Names can't be used directly to refer to objects in the DRM 736 API, applications must convert handles to names and names to handles 737 using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls 738 respectively. The conversion is handled by the DRM core without any 739 driver-specific support. 740 </para> 741 <para> 742 GEM also supports buffer sharing with dma-buf file descriptors through 743 PRIME. GEM-based drivers must use the provided helpers functions to 744 implement the exporting and importing correctly. See <xref linkend="drm-prime-support" />. 745 Since sharing file descriptors is inherently more secure than the 746 easily guessable and global GEM names it is the preferred buffer 747 sharing mechanism. Sharing buffers through GEM names is only supported 748 for legacy userspace. Furthermore PRIME also allows cross-device 749 buffer sharing since it is based on dma-bufs. 750 </para> 751 </sect3> 752 <sect3 id="drm-gem-objects-mapping"> 753 <title>GEM Objects Mapping</title> 754 <para> 755 Because mapping operations are fairly heavyweight GEM favours 756 read/write-like access to buffers, implemented through driver-specific 757 ioctls, over mapping buffers to userspace. However, when random access 758 to the buffer is needed (to perform software rendering for instance), 759 direct access to the object can be more efficient. 760 </para> 761 <para> 762 The mmap system call can't be used directly to map GEM objects, as they 763 don't have their own file handle. Two alternative methods currently 764 co-exist to map GEM objects to userspace. The first method uses a 765 driver-specific ioctl to perform the mapping operation, calling 766 <function>do_mmap</function> under the hood. This is often considered 767 dubious, seems to be discouraged for new GEM-enabled drivers, and will 768 thus not be described here. 769 </para> 770 <para> 771 The second method uses the mmap system call on the DRM file handle. 772 <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd, 773 off_t offset);</synopsis> 774 DRM identifies the GEM object to be mapped by a fake offset passed 775 through the mmap offset argument. Prior to being mapped, a GEM object 776 must thus be associated with a fake offset. To do so, drivers must call 777 <function>drm_gem_create_mmap_offset</function> on the object. The 778 function allocates a fake offset range from a pool and stores the 779 offset divided by PAGE_SIZE in 780 <literal>obj->map_list.hash.key</literal>. Care must be taken not to 781 call <function>drm_gem_create_mmap_offset</function> if a fake offset 782 has already been allocated for the object. This can be tested by 783 <literal>obj->map_list.map</literal> being non-NULL. 784 </para> 785 <para> 786 Once allocated, the fake offset value 787 (<literal>obj->map_list.hash.key << PAGE_SHIFT</literal>) 788 must be passed to the application in a driver-specific way and can then 789 be used as the mmap offset argument. 790 </para> 791 <para> 792 The GEM core provides a helper method <function>drm_gem_mmap</function> 793 to handle object mapping. The method can be set directly as the mmap 794 file operation handler. It will look up the GEM object based on the 795 offset value and set the VMA operations to the 796 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield> 797 field. Note that <function>drm_gem_mmap</function> doesn't map memory to 798 userspace, but relies on the driver-provided fault handler to map pages 799 individually. 800 </para> 801 <para> 802 To use <function>drm_gem_mmap</function>, drivers must fill the struct 803 <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield> 804 field with a pointer to VM operations. 805 </para> 806 <para> 807 <synopsis>struct vm_operations_struct *gem_vm_ops 808 809 struct vm_operations_struct { 810 void (*open)(struct vm_area_struct * area); 811 void (*close)(struct vm_area_struct * area); 812 int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf); 813 };</synopsis> 814 </para> 815 <para> 816 The <methodname>open</methodname> and <methodname>close</methodname> 817 operations must update the GEM object reference count. Drivers can use 818 the <function>drm_gem_vm_open</function> and 819 <function>drm_gem_vm_close</function> helper functions directly as open 820 and close handlers. 821 </para> 822 <para> 823 The fault operation handler is responsible for mapping individual pages 824 to userspace when a page fault occurs. Depending on the memory 825 allocation scheme, drivers can allocate pages at fault time, or can 826 decide to allocate memory for the GEM object at the time the object is 827 created. 828 </para> 829 <para> 830 Drivers that want to map the GEM object upfront instead of handling page 831 faults can implement their own mmap file operation handler. 832 </para> 833 </sect3> 834 <sect3> 835 <title>Memory Coherency</title> 836 <para> 837 When mapped to the device or used in a command buffer, backing pages 838 for an object are flushed to memory and marked write combined so as to 839 be coherent with the GPU. Likewise, if the CPU accesses an object 840 after the GPU has finished rendering to the object, then the object 841 must be made coherent with the CPU's view of memory, usually involving 842 GPU cache flushing of various kinds. This core CPU<->GPU 843 coherency management is provided by a device-specific ioctl, which 844 evaluates an object's current domain and performs any necessary 845 flushing or synchronization to put the object into the desired 846 coherency domain (note that the object may be busy, i.e. an active 847 render target; in that case, setting the domain blocks the client and 848 waits for rendering to complete before performing any necessary 849 flushing operations). 850 </para> 851 </sect3> 852 <sect3> 853 <title>Command Execution</title> 854 <para> 855 Perhaps the most important GEM function for GPU devices is providing a 856 command execution interface to clients. Client programs construct 857 command buffers containing references to previously allocated memory 858 objects, and then submit them to GEM. At that point, GEM takes care to 859 bind all the objects into the GTT, execute the buffer, and provide 860 necessary synchronization between clients accessing the same buffers. 861 This often involves evicting some objects from the GTT and re-binding 862 others (a fairly expensive operation), and providing relocation 863 support which hides fixed GTT offsets from clients. Clients must take 864 care not to submit command buffers that reference more objects than 865 can fit in the GTT; otherwise, GEM will reject them and no rendering 866 will occur. Similarly, if several objects in the buffer require fence 867 registers to be allocated for correct rendering (e.g. 2D blits on 868 pre-965 chips), care must be taken not to require more fence registers 869 than are available to the client. Such resource management should be 870 abstracted from the client in libdrm. 871 </para> 872 </sect3> 873 <sect3> 874 <title>GEM Function Reference</title> 875!Edrivers/gpu/drm/drm_gem.c 876 </sect3> 877 </sect2> 878 <sect2> 879 <title>VMA Offset Manager</title> 880!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager 881!Edrivers/gpu/drm/drm_vma_manager.c 882!Iinclude/drm/drm_vma_manager.h 883 </sect2> 884 <sect2 id="drm-prime-support"> 885 <title>PRIME Buffer Sharing</title> 886 <para> 887 PRIME is the cross device buffer sharing framework in drm, originally 888 created for the OPTIMUS range of multi-gpu platforms. To userspace 889 PRIME buffers are dma-buf based file descriptors. 890 </para> 891 <sect3> 892 <title>Overview and Driver Interface</title> 893 <para> 894 Similar to GEM global names, PRIME file descriptors are 895 also used to share buffer objects across processes. They offer 896 additional security: as file descriptors must be explicitly sent over 897 UNIX domain sockets to be shared between applications, they can't be 898 guessed like the globally unique GEM names. 899 </para> 900 <para> 901 Drivers that support the PRIME 902 API must set the DRIVER_PRIME bit in the struct 903 <structname>drm_driver</structname> 904 <structfield>driver_features</structfield> field, and implement the 905 <methodname>prime_handle_to_fd</methodname> and 906 <methodname>prime_fd_to_handle</methodname> operations. 907 </para> 908 <para> 909 <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev, 910 struct drm_file *file_priv, uint32_t handle, 911 uint32_t flags, int *prime_fd); 912int (*prime_fd_to_handle)(struct drm_device *dev, 913 struct drm_file *file_priv, int prime_fd, 914 uint32_t *handle);</synopsis> 915 Those two operations convert a handle to a PRIME file descriptor and 916 vice versa. Drivers must use the kernel dma-buf buffer sharing framework 917 to manage the PRIME file descriptors. Similar to the mode setting 918 API PRIME is agnostic to the underlying buffer object manager, as 919 long as handles are 32bit unsigned integers. 920 </para> 921 <para> 922 While non-GEM drivers must implement the operations themselves, GEM 923 drivers must use the <function>drm_gem_prime_handle_to_fd</function> 924 and <function>drm_gem_prime_fd_to_handle</function> helper functions. 925 Those helpers rely on the driver 926 <methodname>gem_prime_export</methodname> and 927 <methodname>gem_prime_import</methodname> operations to create a dma-buf 928 instance from a GEM object (dma-buf exporter role) and to create a GEM 929 object from a dma-buf instance (dma-buf importer role). 930 </para> 931 <para> 932 <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev, 933 struct drm_gem_object *obj, 934 int flags); 935struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev, 936 struct dma_buf *dma_buf);</synopsis> 937 These two operations are mandatory for GEM drivers that support 938 PRIME. 939 </para> 940 </sect3> 941 <sect3> 942 <title>PRIME Helper Functions</title> 943!Pdrivers/gpu/drm/drm_prime.c PRIME Helpers 944 </sect3> 945 </sect2> 946 <sect2> 947 <title>PRIME Function References</title> 948!Edrivers/gpu/drm/drm_prime.c 949 </sect2> 950 <sect2> 951 <title>DRM MM Range Allocator</title> 952 <sect3> 953 <title>Overview</title> 954!Pdrivers/gpu/drm/drm_mm.c Overview 955 </sect3> 956 <sect3> 957 <title>LRU Scan/Eviction Support</title> 958!Pdrivers/gpu/drm/drm_mm.c lru scan roaster 959 </sect3> 960 </sect2> 961 <sect2> 962 <title>DRM MM Range Allocator Function References</title> 963!Edrivers/gpu/drm/drm_mm.c 964!Iinclude/drm/drm_mm.h 965 </sect2> 966 </sect1> 967 968 <!-- Internals: mode setting --> 969 970 <sect1 id="drm-mode-setting"> 971 <title>Mode Setting</title> 972 <para> 973 Drivers must initialize the mode setting core by calling 974 <function>drm_mode_config_init</function> on the DRM device. The function 975 initializes the <structname>drm_device</structname> 976 <structfield>mode_config</structfield> field and never fails. Once done, 977 mode configuration must be setup by initializing the following fields. 978 </para> 979 <itemizedlist> 980 <listitem> 981 <synopsis>int min_width, min_height; 982int max_width, max_height;</synopsis> 983 <para> 984 Minimum and maximum width and height of the frame buffers in pixel 985 units. 986 </para> 987 </listitem> 988 <listitem> 989 <synopsis>struct drm_mode_config_funcs *funcs;</synopsis> 990 <para>Mode setting functions.</para> 991 </listitem> 992 </itemizedlist> 993 <sect2> 994 <title>Display Modes Function Reference</title> 995!Iinclude/drm/drm_modes.h 996!Edrivers/gpu/drm/drm_modes.c 997 </sect2> 998 <sect2> 999 <title>Frame Buffer Creation</title> 1000 <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev, 1001 struct drm_file *file_priv, 1002 struct drm_mode_fb_cmd2 *mode_cmd);</synopsis> 1003 <para> 1004 Frame buffers are abstract memory objects that provide a source of 1005 pixels to scanout to a CRTC. Applications explicitly request the 1006 creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and 1007 receive an opaque handle that can be passed to the KMS CRTC control, 1008 plane configuration and page flip functions. 1009 </para> 1010 <para> 1011 Frame buffers rely on the underneath memory manager for low-level memory 1012 operations. When creating a frame buffer applications pass a memory 1013 handle (or a list of memory handles for multi-planar formats) through 1014 the <parameter>drm_mode_fb_cmd2</parameter> argument. For drivers using 1015 GEM as their userspace buffer management interface this would be a GEM 1016 handle. Drivers are however free to use their own backing storage object 1017 handles, e.g. vmwgfx directly exposes special TTM handles to userspace 1018 and so expects TTM handles in the create ioctl and not GEM handles. 1019 </para> 1020 <para> 1021 Drivers must first validate the requested frame buffer parameters passed 1022 through the mode_cmd argument. In particular this is where invalid 1023 sizes, pixel formats or pitches can be caught. 1024 </para> 1025 <para> 1026 If the parameters are deemed valid, drivers then create, initialize and 1027 return an instance of struct <structname>drm_framebuffer</structname>. 1028 If desired the instance can be embedded in a larger driver-specific 1029 structure. Drivers must fill its <structfield>width</structfield>, 1030 <structfield>height</structfield>, <structfield>pitches</structfield>, 1031 <structfield>offsets</structfield>, <structfield>depth</structfield>, 1032 <structfield>bits_per_pixel</structfield> and 1033 <structfield>pixel_format</structfield> fields from the values passed 1034 through the <parameter>drm_mode_fb_cmd2</parameter> argument. They 1035 should call the <function>drm_helper_mode_fill_fb_struct</function> 1036 helper function to do so. 1037 </para> 1038 1039 <para> 1040 The initialization of the new framebuffer instance is finalized with a 1041 call to <function>drm_framebuffer_init</function> which takes a pointer 1042 to DRM frame buffer operations (struct 1043 <structname>drm_framebuffer_funcs</structname>). Note that this function 1044 publishes the framebuffer and so from this point on it can be accessed 1045 concurrently from other threads. Hence it must be the last step in the 1046 driver's framebuffer initialization sequence. Frame buffer operations 1047 are 1048 <itemizedlist> 1049 <listitem> 1050 <synopsis>int (*create_handle)(struct drm_framebuffer *fb, 1051 struct drm_file *file_priv, unsigned int *handle);</synopsis> 1052 <para> 1053 Create a handle to the frame buffer underlying memory object. If 1054 the frame buffer uses a multi-plane format, the handle will 1055 reference the memory object associated with the first plane. 1056 </para> 1057 <para> 1058 Drivers call <function>drm_gem_handle_create</function> to create 1059 the handle. 1060 </para> 1061 </listitem> 1062 <listitem> 1063 <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis> 1064 <para> 1065 Destroy the frame buffer object and frees all associated 1066 resources. Drivers must call 1067 <function>drm_framebuffer_cleanup</function> to free resources 1068 allocated by the DRM core for the frame buffer object, and must 1069 make sure to unreference all memory objects associated with the 1070 frame buffer. Handles created by the 1071 <methodname>create_handle</methodname> operation are released by 1072 the DRM core. 1073 </para> 1074 </listitem> 1075 <listitem> 1076 <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer, 1077 struct drm_file *file_priv, unsigned flags, unsigned color, 1078 struct drm_clip_rect *clips, unsigned num_clips);</synopsis> 1079 <para> 1080 This optional operation notifies the driver that a region of the 1081 frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB 1082 ioctl call. 1083 </para> 1084 </listitem> 1085 </itemizedlist> 1086 </para> 1087 <para> 1088 The lifetime of a drm framebuffer is controlled with a reference count, 1089 drivers can grab additional references with 1090 <function>drm_framebuffer_reference</function>and drop them 1091 again with <function>drm_framebuffer_unreference</function>. For 1092 driver-private framebuffers for which the last reference is never 1093 dropped (e.g. for the fbdev framebuffer when the struct 1094 <structname>drm_framebuffer</structname> is embedded into the fbdev 1095 helper struct) drivers can manually clean up a framebuffer at module 1096 unload time with 1097 <function>drm_framebuffer_unregister_private</function>. 1098 </para> 1099 </sect2> 1100 <sect2> 1101 <title>Dumb Buffer Objects</title> 1102 <para> 1103 The KMS API doesn't standardize backing storage object creation and 1104 leaves it to driver-specific ioctls. Furthermore actually creating a 1105 buffer object even for GEM-based drivers is done through a 1106 driver-specific ioctl - GEM only has a common userspace interface for 1107 sharing and destroying objects. While not an issue for full-fledged 1108 graphics stacks that include device-specific userspace components (in 1109 libdrm for instance), this limit makes DRM-based early boot graphics 1110 unnecessarily complex. 1111 </para> 1112 <para> 1113 Dumb objects partly alleviate the problem by providing a standard 1114 API to create dumb buffers suitable for scanout, which can then be used 1115 to create KMS frame buffers. 1116 </para> 1117 <para> 1118 To support dumb objects drivers must implement the 1119 <methodname>dumb_create</methodname>, 1120 <methodname>dumb_destroy</methodname> and 1121 <methodname>dumb_map_offset</methodname> operations. 1122 </para> 1123 <itemizedlist> 1124 <listitem> 1125 <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, 1126 struct drm_mode_create_dumb *args);</synopsis> 1127 <para> 1128 The <methodname>dumb_create</methodname> operation creates a driver 1129 object (GEM or TTM handle) suitable for scanout based on the 1130 width, height and depth from the struct 1131 <structname>drm_mode_create_dumb</structname> argument. It fills the 1132 argument's <structfield>handle</structfield>, 1133 <structfield>pitch</structfield> and <structfield>size</structfield> 1134 fields with a handle for the newly created object and its line 1135 pitch and size in bytes. 1136 </para> 1137 </listitem> 1138 <listitem> 1139 <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, 1140 uint32_t handle);</synopsis> 1141 <para> 1142 The <methodname>dumb_destroy</methodname> operation destroys a dumb 1143 object created by <methodname>dumb_create</methodname>. 1144 </para> 1145 </listitem> 1146 <listitem> 1147 <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, 1148 uint32_t handle, uint64_t *offset);</synopsis> 1149 <para> 1150 The <methodname>dumb_map_offset</methodname> operation associates an 1151 mmap fake offset with the object given by the handle and returns 1152 it. Drivers must use the 1153 <function>drm_gem_create_mmap_offset</function> function to 1154 associate the fake offset as described in 1155 <xref linkend="drm-gem-objects-mapping"/>. 1156 </para> 1157 </listitem> 1158 </itemizedlist> 1159 <para> 1160 Note that dumb objects may not be used for gpu acceleration, as has been 1161 attempted on some ARM embedded platforms. Such drivers really must have 1162 a hardware-specific ioctl to allocate suitable buffer objects. 1163 </para> 1164 </sect2> 1165 <sect2> 1166 <title>Output Polling</title> 1167 <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis> 1168 <para> 1169 This operation notifies the driver that the status of one or more 1170 connectors has changed. Drivers that use the fb helper can just call the 1171 <function>drm_fb_helper_hotplug_event</function> function to handle this 1172 operation. 1173 </para> 1174 </sect2> 1175 <sect2> 1176 <title>Locking</title> 1177 <para> 1178 Beside some lookup structures with their own locking (which is hidden 1179 behind the interface functions) most of the modeset state is protected 1180 by the <code>dev-<mode_config.lock</code> mutex and additionally 1181 per-crtc locks to allow cursor updates, pageflips and similar operations 1182 to occur concurrently with background tasks like output detection. 1183 Operations which cross domains like a full modeset always grab all 1184 locks. Drivers there need to protect resources shared between crtcs with 1185 additional locking. They also need to be careful to always grab the 1186 relevant crtc locks if a modset functions touches crtc state, e.g. for 1187 load detection (which does only grab the <code>mode_config.lock</code> 1188 to allow concurrent screen updates on live crtcs). 1189 </para> 1190 </sect2> 1191 </sect1> 1192 1193 <!-- Internals: kms initialization and cleanup --> 1194 1195 <sect1 id="drm-kms-init"> 1196 <title>KMS Initialization and Cleanup</title> 1197 <para> 1198 A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders 1199 and connectors. KMS drivers must thus create and initialize all those 1200 objects at load time after initializing mode setting. 1201 </para> 1202 <sect2> 1203 <title>CRTCs (struct <structname>drm_crtc</structname>)</title> 1204 <para> 1205 A CRTC is an abstraction representing a part of the chip that contains a 1206 pointer to a scanout buffer. Therefore, the number of CRTCs available 1207 determines how many independent scanout buffers can be active at any 1208 given time. The CRTC structure contains several fields to support this: 1209 a pointer to some video memory (abstracted as a frame buffer object), a 1210 display mode, and an (x, y) offset into the video memory to support 1211 panning or configurations where one piece of video memory spans multiple 1212 CRTCs. 1213 </para> 1214 <sect3> 1215 <title>CRTC Initialization</title> 1216 <para> 1217 A KMS device must create and register at least one struct 1218 <structname>drm_crtc</structname> instance. The instance is allocated 1219 and zeroed by the driver, possibly as part of a larger structure, and 1220 registered with a call to <function>drm_crtc_init</function> with a 1221 pointer to CRTC functions. 1222 </para> 1223 </sect3> 1224 <sect3 id="drm-kms-crtcops"> 1225 <title>CRTC Operations</title> 1226 <sect4> 1227 <title>Set Configuration</title> 1228 <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis> 1229 <para> 1230 Apply a new CRTC configuration to the device. The configuration 1231 specifies a CRTC, a frame buffer to scan out from, a (x,y) position in 1232 the frame buffer, a display mode and an array of connectors to drive 1233 with the CRTC if possible. 1234 </para> 1235 <para> 1236 If the frame buffer specified in the configuration is NULL, the driver 1237 must detach all encoders connected to the CRTC and all connectors 1238 attached to those encoders and disable them. 1239 </para> 1240 <para> 1241 This operation is called with the mode config lock held. 1242 </para> 1243 <note><para> 1244 Note that the drm core has no notion of restoring the mode setting 1245 state after resume, since all resume handling is in the full 1246 responsibility of the driver. The common mode setting helper library 1247 though provides a helper which can be used for this: 1248 <function>drm_helper_resume_force_mode</function>. 1249 </para></note> 1250 </sect4> 1251 <sect4> 1252 <title>Page Flipping</title> 1253 <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb, 1254 struct drm_pending_vblank_event *event);</synopsis> 1255 <para> 1256 Schedule a page flip to the given frame buffer for the CRTC. This 1257 operation is called with the mode config mutex held. 1258 </para> 1259 <para> 1260 Page flipping is a synchronization mechanism that replaces the frame 1261 buffer being scanned out by the CRTC with a new frame buffer during 1262 vertical blanking, avoiding tearing. When an application requests a page 1263 flip the DRM core verifies that the new frame buffer is large enough to 1264 be scanned out by the CRTC in the currently configured mode and then 1265 calls the CRTC <methodname>page_flip</methodname> operation with a 1266 pointer to the new frame buffer. 1267 </para> 1268 <para> 1269 The <methodname>page_flip</methodname> operation schedules a page flip. 1270 Once any pending rendering targeting the new frame buffer has 1271 completed, the CRTC will be reprogrammed to display that frame buffer 1272 after the next vertical refresh. The operation must return immediately 1273 without waiting for rendering or page flip to complete and must block 1274 any new rendering to the frame buffer until the page flip completes. 1275 </para> 1276 <para> 1277 If a page flip can be successfully scheduled the driver must set the 1278 <code>drm_crtc-<fb</code> field to the new framebuffer pointed to 1279 by <code>fb</code>. This is important so that the reference counting 1280 on framebuffers stays balanced. 1281 </para> 1282 <para> 1283 If a page flip is already pending, the 1284 <methodname>page_flip</methodname> operation must return 1285 -<errorname>EBUSY</errorname>. 1286 </para> 1287 <para> 1288 To synchronize page flip to vertical blanking the driver will likely 1289 need to enable vertical blanking interrupts. It should call 1290 <function>drm_vblank_get</function> for that purpose, and call 1291 <function>drm_vblank_put</function> after the page flip completes. 1292 </para> 1293 <para> 1294 If the application has requested to be notified when page flip completes 1295 the <methodname>page_flip</methodname> operation will be called with a 1296 non-NULL <parameter>event</parameter> argument pointing to a 1297 <structname>drm_pending_vblank_event</structname> instance. Upon page 1298 flip completion the driver must call <methodname>drm_send_vblank_event</methodname> 1299 to fill in the event and send to wake up any waiting processes. 1300 This can be performed with 1301 <programlisting><![CDATA[ 1302 spin_lock_irqsave(&dev->event_lock, flags); 1303 ... 1304 drm_send_vblank_event(dev, pipe, event); 1305 spin_unlock_irqrestore(&dev->event_lock, flags); 1306 ]]></programlisting> 1307 </para> 1308 <note><para> 1309 FIXME: Could drivers that don't need to wait for rendering to complete 1310 just add the event to <literal>dev->vblank_event_list</literal> and 1311 let the DRM core handle everything, as for "normal" vertical blanking 1312 events? 1313 </para></note> 1314 <para> 1315 While waiting for the page flip to complete, the 1316 <literal>event->base.link</literal> list head can be used freely by 1317 the driver to store the pending event in a driver-specific list. 1318 </para> 1319 <para> 1320 If the file handle is closed before the event is signaled, drivers must 1321 take care to destroy the event in their 1322 <methodname>preclose</methodname> operation (and, if needed, call 1323 <function>drm_vblank_put</function>). 1324 </para> 1325 </sect4> 1326 <sect4> 1327 <title>Miscellaneous</title> 1328 <itemizedlist> 1329 <listitem> 1330 <synopsis>void (*set_property)(struct drm_crtc *crtc, 1331 struct drm_property *property, uint64_t value);</synopsis> 1332 <para> 1333 Set the value of the given CRTC property to 1334 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/> 1335 for more information about properties. 1336 </para> 1337 </listitem> 1338 <listitem> 1339 <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b, 1340 uint32_t start, uint32_t size);</synopsis> 1341 <para> 1342 Apply a gamma table to the device. The operation is optional. 1343 </para> 1344 </listitem> 1345 <listitem> 1346 <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis> 1347 <para> 1348 Destroy the CRTC when not needed anymore. See 1349 <xref linkend="drm-kms-init"/>. 1350 </para> 1351 </listitem> 1352 </itemizedlist> 1353 </sect4> 1354 </sect3> 1355 </sect2> 1356 <sect2> 1357 <title>Planes (struct <structname>drm_plane</structname>)</title> 1358 <para> 1359 A plane represents an image source that can be blended with or overlayed 1360 on top of a CRTC during the scanout process. Planes are associated with 1361 a frame buffer to crop a portion of the image memory (source) and 1362 optionally scale it to a destination size. The result is then blended 1363 with or overlayed on top of a CRTC. 1364 </para> 1365 <para> 1366 The DRM core recognizes three types of planes: 1367 <itemizedlist> 1368 <listitem> 1369 DRM_PLANE_TYPE_PRIMARY represents a "main" plane for a CRTC. Primary 1370 planes are the planes operated upon by by CRTC modesetting and flipping 1371 operations described in <xref linkend="drm-kms-crtcops"/>. 1372 </listitem> 1373 <listitem> 1374 DRM_PLANE_TYPE_CURSOR represents a "cursor" plane for a CRTC. Cursor 1375 planes are the planes operated upon by the DRM_IOCTL_MODE_CURSOR and 1376 DRM_IOCTL_MODE_CURSOR2 ioctls. 1377 </listitem> 1378 <listitem> 1379 DRM_PLANE_TYPE_OVERLAY represents all non-primary, non-cursor planes. 1380 Some drivers refer to these types of planes as "sprites" internally. 1381 </listitem> 1382 </itemizedlist> 1383 For compatibility with legacy userspace, only overlay planes are made 1384 available to userspace by default. Userspace clients may set the 1385 DRM_CLIENT_CAP_UNIVERSAL_PLANES client capability bit to indicate that 1386 they wish to receive a universal plane list containing all plane types. 1387 </para> 1388 <sect3> 1389 <title>Plane Initialization</title> 1390 <para> 1391 To create a plane, a KMS drivers allocates and 1392 zeroes an instances of struct <structname>drm_plane</structname> 1393 (possibly as part of a larger structure) and registers it with a call 1394 to <function>drm_universal_plane_init</function>. The function takes a bitmask 1395 of the CRTCs that can be associated with the plane, a pointer to the 1396 plane functions, a list of format supported formats, and the type of 1397 plane (primary, cursor, or overlay) being initialized. 1398 </para> 1399 <para> 1400 Cursor and overlay planes are optional. All drivers should provide 1401 one primary plane per CRTC (although this requirement may change in 1402 the future); drivers that do not wish to provide special handling for 1403 primary planes may make use of the helper functions described in 1404 <xref linkend="drm-kms-planehelpers"/> to create and register a 1405 primary plane with standard capabilities. 1406 </para> 1407 </sect3> 1408 <sect3> 1409 <title>Plane Operations</title> 1410 <itemizedlist> 1411 <listitem> 1412 <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc, 1413 struct drm_framebuffer *fb, int crtc_x, int crtc_y, 1414 unsigned int crtc_w, unsigned int crtc_h, 1415 uint32_t src_x, uint32_t src_y, 1416 uint32_t src_w, uint32_t src_h);</synopsis> 1417 <para> 1418 Enable and configure the plane to use the given CRTC and frame buffer. 1419 </para> 1420 <para> 1421 The source rectangle in frame buffer memory coordinates is given by 1422 the <parameter>src_x</parameter>, <parameter>src_y</parameter>, 1423 <parameter>src_w</parameter> and <parameter>src_h</parameter> 1424 parameters (as 16.16 fixed point values). Devices that don't support 1425 subpixel plane coordinates can ignore the fractional part. 1426 </para> 1427 <para> 1428 The destination rectangle in CRTC coordinates is given by the 1429 <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>, 1430 <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter> 1431 parameters (as integer values). Devices scale the source rectangle to 1432 the destination rectangle. If scaling is not supported, and the source 1433 rectangle size doesn't match the destination rectangle size, the 1434 driver must return a -<errorname>EINVAL</errorname> error. 1435 </para> 1436 </listitem> 1437 <listitem> 1438 <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis> 1439 <para> 1440 Disable the plane. The DRM core calls this method in response to a 1441 DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0. 1442 Disabled planes must not be processed by the CRTC. 1443 </para> 1444 </listitem> 1445 <listitem> 1446 <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis> 1447 <para> 1448 Destroy the plane when not needed anymore. See 1449 <xref linkend="drm-kms-init"/>. 1450 </para> 1451 </listitem> 1452 </itemizedlist> 1453 </sect3> 1454 </sect2> 1455 <sect2> 1456 <title>Encoders (struct <structname>drm_encoder</structname>)</title> 1457 <para> 1458 An encoder takes pixel data from a CRTC and converts it to a format 1459 suitable for any attached connectors. On some devices, it may be 1460 possible to have a CRTC send data to more than one encoder. In that 1461 case, both encoders would receive data from the same scanout buffer, 1462 resulting in a "cloned" display configuration across the connectors 1463 attached to each encoder. 1464 </para> 1465 <sect3> 1466 <title>Encoder Initialization</title> 1467 <para> 1468 As for CRTCs, a KMS driver must create, initialize and register at 1469 least one struct <structname>drm_encoder</structname> instance. The 1470 instance is allocated and zeroed by the driver, possibly as part of a 1471 larger structure. 1472 </para> 1473 <para> 1474 Drivers must initialize the struct <structname>drm_encoder</structname> 1475 <structfield>possible_crtcs</structfield> and 1476 <structfield>possible_clones</structfield> fields before registering the 1477 encoder. Both fields are bitmasks of respectively the CRTCs that the 1478 encoder can be connected to, and sibling encoders candidate for cloning. 1479 </para> 1480 <para> 1481 After being initialized, the encoder must be registered with a call to 1482 <function>drm_encoder_init</function>. The function takes a pointer to 1483 the encoder functions and an encoder type. Supported types are 1484 <itemizedlist> 1485 <listitem> 1486 DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A 1487 </listitem> 1488 <listitem> 1489 DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort 1490 </listitem> 1491 <listitem> 1492 DRM_MODE_ENCODER_LVDS for display panels 1493 </listitem> 1494 <listitem> 1495 DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component, 1496 SCART) 1497 </listitem> 1498 <listitem> 1499 DRM_MODE_ENCODER_VIRTUAL for virtual machine displays 1500 </listitem> 1501 </itemizedlist> 1502 </para> 1503 <para> 1504 Encoders must be attached to a CRTC to be used. DRM drivers leave 1505 encoders unattached at initialization time. Applications (or the fbdev 1506 compatibility layer when implemented) are responsible for attaching the 1507 encoders they want to use to a CRTC. 1508 </para> 1509 </sect3> 1510 <sect3> 1511 <title>Encoder Operations</title> 1512 <itemizedlist> 1513 <listitem> 1514 <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis> 1515 <para> 1516 Called to destroy the encoder when not needed anymore. See 1517 <xref linkend="drm-kms-init"/>. 1518 </para> 1519 </listitem> 1520 <listitem> 1521 <synopsis>void (*set_property)(struct drm_plane *plane, 1522 struct drm_property *property, uint64_t value);</synopsis> 1523 <para> 1524 Set the value of the given plane property to 1525 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/> 1526 for more information about properties. 1527 </para> 1528 </listitem> 1529 </itemizedlist> 1530 </sect3> 1531 </sect2> 1532 <sect2> 1533 <title>Connectors (struct <structname>drm_connector</structname>)</title> 1534 <para> 1535 A connector is the final destination for pixel data on a device, and 1536 usually connects directly to an external display device like a monitor 1537 or laptop panel. A connector can only be attached to one encoder at a 1538 time. The connector is also the structure where information about the 1539 attached display is kept, so it contains fields for display data, EDID 1540 data, DPMS & connection status, and information about modes 1541 supported on the attached displays. 1542 </para> 1543 <sect3> 1544 <title>Connector Initialization</title> 1545 <para> 1546 Finally a KMS driver must create, initialize, register and attach at 1547 least one struct <structname>drm_connector</structname> instance. The 1548 instance is created as other KMS objects and initialized by setting the 1549 following fields. 1550 </para> 1551 <variablelist> 1552 <varlistentry> 1553 <term><structfield>interlace_allowed</structfield></term> 1554 <listitem><para> 1555 Whether the connector can handle interlaced modes. 1556 </para></listitem> 1557 </varlistentry> 1558 <varlistentry> 1559 <term><structfield>doublescan_allowed</structfield></term> 1560 <listitem><para> 1561 Whether the connector can handle doublescan. 1562 </para></listitem> 1563 </varlistentry> 1564 <varlistentry> 1565 <term><structfield>display_info 1566 </structfield></term> 1567 <listitem><para> 1568 Display information is filled from EDID information when a display 1569 is detected. For non hot-pluggable displays such as flat panels in 1570 embedded systems, the driver should initialize the 1571 <structfield>display_info</structfield>.<structfield>width_mm</structfield> 1572 and 1573 <structfield>display_info</structfield>.<structfield>height_mm</structfield> 1574 fields with the physical size of the display. 1575 </para></listitem> 1576 </varlistentry> 1577 <varlistentry> 1578 <term id="drm-kms-connector-polled"><structfield>polled</structfield></term> 1579 <listitem><para> 1580 Connector polling mode, a combination of 1581 <variablelist> 1582 <varlistentry> 1583 <term>DRM_CONNECTOR_POLL_HPD</term> 1584 <listitem><para> 1585 The connector generates hotplug events and doesn't need to be 1586 periodically polled. The CONNECT and DISCONNECT flags must not 1587 be set together with the HPD flag. 1588 </para></listitem> 1589 </varlistentry> 1590 <varlistentry> 1591 <term>DRM_CONNECTOR_POLL_CONNECT</term> 1592 <listitem><para> 1593 Periodically poll the connector for connection. 1594 </para></listitem> 1595 </varlistentry> 1596 <varlistentry> 1597 <term>DRM_CONNECTOR_POLL_DISCONNECT</term> 1598 <listitem><para> 1599 Periodically poll the connector for disconnection. 1600 </para></listitem> 1601 </varlistentry> 1602 </variablelist> 1603 Set to 0 for connectors that don't support connection status 1604 discovery. 1605 </para></listitem> 1606 </varlistentry> 1607 </variablelist> 1608 <para> 1609 The connector is then registered with a call to 1610 <function>drm_connector_init</function> with a pointer to the connector 1611 functions and a connector type, and exposed through sysfs with a call to 1612 <function>drm_connector_register</function>. 1613 </para> 1614 <para> 1615 Supported connector types are 1616 <itemizedlist> 1617 <listitem>DRM_MODE_CONNECTOR_VGA</listitem> 1618 <listitem>DRM_MODE_CONNECTOR_DVII</listitem> 1619 <listitem>DRM_MODE_CONNECTOR_DVID</listitem> 1620 <listitem>DRM_MODE_CONNECTOR_DVIA</listitem> 1621 <listitem>DRM_MODE_CONNECTOR_Composite</listitem> 1622 <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem> 1623 <listitem>DRM_MODE_CONNECTOR_LVDS</listitem> 1624 <listitem>DRM_MODE_CONNECTOR_Component</listitem> 1625 <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem> 1626 <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem> 1627 <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem> 1628 <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem> 1629 <listitem>DRM_MODE_CONNECTOR_TV</listitem> 1630 <listitem>DRM_MODE_CONNECTOR_eDP</listitem> 1631 <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem> 1632 </itemizedlist> 1633 </para> 1634 <para> 1635 Connectors must be attached to an encoder to be used. For devices that 1636 map connectors to encoders 1:1, the connector should be attached at 1637 initialization time with a call to 1638 <function>drm_mode_connector_attach_encoder</function>. The driver must 1639 also set the <structname>drm_connector</structname> 1640 <structfield>encoder</structfield> field to point to the attached 1641 encoder. 1642 </para> 1643 <para> 1644 Finally, drivers must initialize the connectors state change detection 1645 with a call to <function>drm_kms_helper_poll_init</function>. If at 1646 least one connector is pollable but can't generate hotplug interrupts 1647 (indicated by the DRM_CONNECTOR_POLL_CONNECT and 1648 DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will 1649 automatically be queued to periodically poll for changes. Connectors 1650 that can generate hotplug interrupts must be marked with the 1651 DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must 1652 call <function>drm_helper_hpd_irq_event</function>. The function will 1653 queue a delayed work to check the state of all connectors, but no 1654 periodic polling will be done. 1655 </para> 1656 </sect3> 1657 <sect3> 1658 <title>Connector Operations</title> 1659 <note><para> 1660 Unless otherwise state, all operations are mandatory. 1661 </para></note> 1662 <sect4> 1663 <title>DPMS</title> 1664 <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis> 1665 <para> 1666 The DPMS operation sets the power state of a connector. The mode 1667 argument is one of 1668 <itemizedlist> 1669 <listitem><para>DRM_MODE_DPMS_ON</para></listitem> 1670 <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem> 1671 <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem> 1672 <listitem><para>DRM_MODE_DPMS_OFF</para></listitem> 1673 </itemizedlist> 1674 </para> 1675 <para> 1676 In all but DPMS_ON mode the encoder to which the connector is attached 1677 should put the display in low-power mode by driving its signals 1678 appropriately. If more than one connector is attached to the encoder 1679 care should be taken not to change the power state of other displays as 1680 a side effect. Low-power mode should be propagated to the encoders and 1681 CRTCs when all related connectors are put in low-power mode. 1682 </para> 1683 </sect4> 1684 <sect4> 1685 <title>Modes</title> 1686 <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width, 1687 uint32_t max_height);</synopsis> 1688 <para> 1689 Fill the mode list with all supported modes for the connector. If the 1690 <parameter>max_width</parameter> and <parameter>max_height</parameter> 1691 arguments are non-zero, the implementation must ignore all modes wider 1692 than <parameter>max_width</parameter> or higher than 1693 <parameter>max_height</parameter>. 1694 </para> 1695 <para> 1696 The connector must also fill in this operation its 1697 <structfield>display_info</structfield> 1698 <structfield>width_mm</structfield> and 1699 <structfield>height_mm</structfield> fields with the connected display 1700 physical size in millimeters. The fields should be set to 0 if the value 1701 isn't known or is not applicable (for instance for projector devices). 1702 </para> 1703 </sect4> 1704 <sect4> 1705 <title>Connection Status</title> 1706 <para> 1707 The connection status is updated through polling or hotplug events when 1708 supported (see <xref linkend="drm-kms-connector-polled"/>). The status 1709 value is reported to userspace through ioctls and must not be used 1710 inside the driver, as it only gets initialized by a call to 1711 <function>drm_mode_getconnector</function> from userspace. 1712 </para> 1713 <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector, 1714 bool force);</synopsis> 1715 <para> 1716 Check to see if anything is attached to the connector. The 1717 <parameter>force</parameter> parameter is set to false whilst polling or 1718 to true when checking the connector due to user request. 1719 <parameter>force</parameter> can be used by the driver to avoid 1720 expensive, destructive operations during automated probing. 1721 </para> 1722 <para> 1723 Return connector_status_connected if something is connected to the 1724 connector, connector_status_disconnected if nothing is connected and 1725 connector_status_unknown if the connection state isn't known. 1726 </para> 1727 <para> 1728 Drivers should only return connector_status_connected if the connection 1729 status has really been probed as connected. Connectors that can't detect 1730 the connection status, or failed connection status probes, should return 1731 connector_status_unknown. 1732 </para> 1733 </sect4> 1734 <sect4> 1735 <title>Miscellaneous</title> 1736 <itemizedlist> 1737 <listitem> 1738 <synopsis>void (*set_property)(struct drm_connector *connector, 1739 struct drm_property *property, uint64_t value);</synopsis> 1740 <para> 1741 Set the value of the given connector property to 1742 <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/> 1743 for more information about properties. 1744 </para> 1745 </listitem> 1746 <listitem> 1747 <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis> 1748 <para> 1749 Destroy the connector when not needed anymore. See 1750 <xref linkend="drm-kms-init"/>. 1751 </para> 1752 </listitem> 1753 </itemizedlist> 1754 </sect4> 1755 </sect3> 1756 </sect2> 1757 <sect2> 1758 <title>Cleanup</title> 1759 <para> 1760 The DRM core manages its objects' lifetime. When an object is not needed 1761 anymore the core calls its destroy function, which must clean up and 1762 free every resource allocated for the object. Every 1763 <function>drm_*_init</function> call must be matched with a 1764 corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs 1765 (<function>drm_crtc_cleanup</function>), planes 1766 (<function>drm_plane_cleanup</function>), encoders 1767 (<function>drm_encoder_cleanup</function>) and connectors 1768 (<function>drm_connector_cleanup</function>). Furthermore, connectors 1769 that have been added to sysfs must be removed by a call to 1770 <function>drm_connector_unregister</function> before calling 1771 <function>drm_connector_cleanup</function>. 1772 </para> 1773 <para> 1774 Connectors state change detection must be cleanup up with a call to 1775 <function>drm_kms_helper_poll_fini</function>. 1776 </para> 1777 </sect2> 1778 <sect2> 1779 <title>Output discovery and initialization example</title> 1780 <programlisting><![CDATA[ 1781void intel_crt_init(struct drm_device *dev) 1782{ 1783 struct drm_connector *connector; 1784 struct intel_output *intel_output; 1785 1786 intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL); 1787 if (!intel_output) 1788 return; 1789 1790 connector = &intel_output->base; 1791 drm_connector_init(dev, &intel_output->base, 1792 &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA); 1793 1794 drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs, 1795 DRM_MODE_ENCODER_DAC); 1796 1797 drm_mode_connector_attach_encoder(&intel_output->base, 1798 &intel_output->enc); 1799 1800 /* Set up the DDC bus. */ 1801 intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A"); 1802 if (!intel_output->ddc_bus) { 1803 dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration " 1804 "failed.\n"); 1805 return; 1806 } 1807 1808 intel_output->type = INTEL_OUTPUT_ANALOG; 1809 connector->interlace_allowed = 0; 1810 connector->doublescan_allowed = 0; 1811 1812 drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs); 1813 drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); 1814 1815 drm_connector_register(connector); 1816}]]></programlisting> 1817 <para> 1818 In the example above (taken from the i915 driver), a CRTC, connector and 1819 encoder combination is created. A device-specific i2c bus is also 1820 created for fetching EDID data and performing monitor detection. Once 1821 the process is complete, the new connector is registered with sysfs to 1822 make its properties available to applications. 1823 </para> 1824 </sect2> 1825 <sect2> 1826 <title>KMS API Functions</title> 1827!Edrivers/gpu/drm/drm_crtc.c 1828 </sect2> 1829 <sect2> 1830 <title>KMS Locking</title> 1831!Pdrivers/gpu/drm/drm_modeset_lock.c kms locking 1832!Iinclude/drm/drm_modeset_lock.h 1833!Edrivers/gpu/drm/drm_modeset_lock.c 1834 </sect2> 1835 </sect1> 1836 1837 <!-- Internals: kms helper functions --> 1838 1839 <sect1> 1840 <title>Mode Setting Helper Functions</title> 1841 <para> 1842 The plane, CRTC, encoder and connector functions provided by the drivers 1843 implement the DRM API. They're called by the DRM core and ioctl handlers 1844 to handle device state changes and configuration request. As implementing 1845 those functions often requires logic not specific to drivers, mid-layer 1846 helper functions are available to avoid duplicating boilerplate code. 1847 </para> 1848 <para> 1849 The DRM core contains one mid-layer implementation. The mid-layer provides 1850 implementations of several plane, CRTC, encoder and connector functions 1851 (called from the top of the mid-layer) that pre-process requests and call 1852 lower-level functions provided by the driver (at the bottom of the 1853 mid-layer). For instance, the 1854 <function>drm_crtc_helper_set_config</function> function can be used to 1855 fill the struct <structname>drm_crtc_funcs</structname> 1856 <structfield>set_config</structfield> field. When called, it will split 1857 the <methodname>set_config</methodname> operation in smaller, simpler 1858 operations and call the driver to handle them. 1859 </para> 1860 <para> 1861 To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>, 1862 <function>drm_encoder_helper_add</function> and 1863 <function>drm_connector_helper_add</function> functions to install their 1864 mid-layer bottom operations handlers, and fill the 1865 <structname>drm_crtc_funcs</structname>, 1866 <structname>drm_encoder_funcs</structname> and 1867 <structname>drm_connector_funcs</structname> structures with pointers to 1868 the mid-layer top API functions. Installing the mid-layer bottom operation 1869 handlers is best done right after registering the corresponding KMS object. 1870 </para> 1871 <para> 1872 The mid-layer is not split between CRTC, encoder and connector operations. 1873 To use it, a driver must provide bottom functions for all of the three KMS 1874 entities. 1875 </para> 1876 <sect2> 1877 <title>Helper Functions</title> 1878 <itemizedlist> 1879 <listitem> 1880 <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis> 1881 <para> 1882 The <function>drm_crtc_helper_set_config</function> helper function 1883 is a CRTC <methodname>set_config</methodname> implementation. It 1884 first tries to locate the best encoder for each connector by calling 1885 the connector <methodname>best_encoder</methodname> helper 1886 operation. 1887 </para> 1888 <para> 1889 After locating the appropriate encoders, the helper function will 1890 call the <methodname>mode_fixup</methodname> encoder and CRTC helper 1891 operations to adjust the requested mode, or reject it completely in 1892 which case an error will be returned to the application. If the new 1893 configuration after mode adjustment is identical to the current 1894 configuration the helper function will return without performing any 1895 other operation. 1896 </para> 1897 <para> 1898 If the adjusted mode is identical to the current mode but changes to 1899 the frame buffer need to be applied, the 1900 <function>drm_crtc_helper_set_config</function> function will call 1901 the CRTC <methodname>mode_set_base</methodname> helper operation. If 1902 the adjusted mode differs from the current mode, or if the 1903 <methodname>mode_set_base</methodname> helper operation is not 1904 provided, the helper function performs a full mode set sequence by 1905 calling the <methodname>prepare</methodname>, 1906 <methodname>mode_set</methodname> and 1907 <methodname>commit</methodname> CRTC and encoder helper operations, 1908 in that order. 1909 </para> 1910 </listitem> 1911 <listitem> 1912 <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis> 1913 <para> 1914 The <function>drm_helper_connector_dpms</function> helper function 1915 is a connector <methodname>dpms</methodname> implementation that 1916 tracks power state of connectors. To use the function, drivers must 1917 provide <methodname>dpms</methodname> helper operations for CRTCs 1918 and encoders to apply the DPMS state to the device. 1919 </para> 1920 <para> 1921 The mid-layer doesn't track the power state of CRTCs and encoders. 1922 The <methodname>dpms</methodname> helper operations can thus be 1923 called with a mode identical to the currently active mode. 1924 </para> 1925 </listitem> 1926 <listitem> 1927 <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector, 1928 uint32_t maxX, uint32_t maxY);</synopsis> 1929 <para> 1930 The <function>drm_helper_probe_single_connector_modes</function> helper 1931 function is a connector <methodname>fill_modes</methodname> 1932 implementation that updates the connection status for the connector 1933 and then retrieves a list of modes by calling the connector 1934 <methodname>get_modes</methodname> helper operation. 1935 </para> 1936 <para> 1937 The function filters out modes larger than 1938 <parameter>max_width</parameter> and <parameter>max_height</parameter> 1939 if specified. It then calls the optional connector 1940 <methodname>mode_valid</methodname> helper operation for each mode in 1941 the probed list to check whether the mode is valid for the connector. 1942 </para> 1943 </listitem> 1944 </itemizedlist> 1945 </sect2> 1946 <sect2> 1947 <title>CRTC Helper Operations</title> 1948 <itemizedlist> 1949 <listitem id="drm-helper-crtc-mode-fixup"> 1950 <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc, 1951 const struct drm_display_mode *mode, 1952 struct drm_display_mode *adjusted_mode);</synopsis> 1953 <para> 1954 Let CRTCs adjust the requested mode or reject it completely. This 1955 operation returns true if the mode is accepted (possibly after being 1956 adjusted) or false if it is rejected. 1957 </para> 1958 <para> 1959 The <methodname>mode_fixup</methodname> operation should reject the 1960 mode if it can't reasonably use it. The definition of "reasonable" 1961 is currently fuzzy in this context. One possible behaviour would be 1962 to set the adjusted mode to the panel timings when a fixed-mode 1963 panel is used with hardware capable of scaling. Another behaviour 1964 would be to accept any input mode and adjust it to the closest mode 1965 supported by the hardware (FIXME: This needs to be clarified). 1966 </para> 1967 </listitem> 1968 <listitem> 1969 <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y, 1970 struct drm_framebuffer *old_fb)</synopsis> 1971 <para> 1972 Move the CRTC on the current frame buffer (stored in 1973 <literal>crtc->fb</literal>) to position (x,y). Any of the frame 1974 buffer, x position or y position may have been modified. 1975 </para> 1976 <para> 1977 This helper operation is optional. If not provided, the 1978 <function>drm_crtc_helper_set_config</function> function will fall 1979 back to the <methodname>mode_set</methodname> helper operation. 1980 </para> 1981 <note><para> 1982 FIXME: Why are x and y passed as arguments, as they can be accessed 1983 through <literal>crtc->x</literal> and 1984 <literal>crtc->y</literal>? 1985 </para></note> 1986 </listitem> 1987 <listitem> 1988 <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis> 1989 <para> 1990 Prepare the CRTC for mode setting. This operation is called after 1991 validating the requested mode. Drivers use it to perform 1992 device-specific operations required before setting the new mode. 1993 </para> 1994 </listitem> 1995 <listitem> 1996 <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode, 1997 struct drm_display_mode *adjusted_mode, int x, int y, 1998 struct drm_framebuffer *old_fb);</synopsis> 1999 <para> 2000 Set a new mode, position and frame buffer. Depending on the device 2001 requirements, the mode can be stored internally by the driver and 2002 applied in the <methodname>commit</methodname> operation, or 2003 programmed to the hardware immediately. 2004 </para> 2005 <para> 2006 The <methodname>mode_set</methodname> operation returns 0 on success 2007 or a negative error code if an error occurs. 2008 </para> 2009 </listitem> 2010 <listitem> 2011 <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis> 2012 <para> 2013 Commit a mode. This operation is called after setting the new mode. 2014 Upon return the device must use the new mode and be fully 2015 operational. 2016 </para> 2017 </listitem> 2018 </itemizedlist> 2019 </sect2> 2020 <sect2> 2021 <title>Encoder Helper Operations</title> 2022 <itemizedlist> 2023 <listitem> 2024 <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder, 2025 const struct drm_display_mode *mode, 2026 struct drm_display_mode *adjusted_mode);</synopsis> 2027 <para> 2028 Let encoders adjust the requested mode or reject it completely. This 2029 operation returns true if the mode is accepted (possibly after being 2030 adjusted) or false if it is rejected. See the 2031 <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper 2032 operation</link> for an explanation of the allowed adjustments. 2033 </para> 2034 </listitem> 2035 <listitem> 2036 <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis> 2037 <para> 2038 Prepare the encoder for mode setting. This operation is called after 2039 validating the requested mode. Drivers use it to perform 2040 device-specific operations required before setting the new mode. 2041 </para> 2042 </listitem> 2043 <listitem> 2044 <synopsis>void (*mode_set)(struct drm_encoder *encoder, 2045 struct drm_display_mode *mode, 2046 struct drm_display_mode *adjusted_mode);</synopsis> 2047 <para> 2048 Set a new mode. Depending on the device requirements, the mode can 2049 be stored internally by the driver and applied in the 2050 <methodname>commit</methodname> operation, or programmed to the 2051 hardware immediately. 2052 </para> 2053 </listitem> 2054 <listitem> 2055 <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis> 2056 <para> 2057 Commit a mode. This operation is called after setting the new mode. 2058 Upon return the device must use the new mode and be fully 2059 operational. 2060 </para> 2061 </listitem> 2062 </itemizedlist> 2063 </sect2> 2064 <sect2> 2065 <title>Connector Helper Operations</title> 2066 <itemizedlist> 2067 <listitem> 2068 <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis> 2069 <para> 2070 Return a pointer to the best encoder for the connecter. Device that 2071 map connectors to encoders 1:1 simply return the pointer to the 2072 associated encoder. This operation is mandatory. 2073 </para> 2074 </listitem> 2075 <listitem> 2076 <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis> 2077 <para> 2078 Fill the connector's <structfield>probed_modes</structfield> list 2079 by parsing EDID data with <function>drm_add_edid_modes</function> or 2080 calling <function>drm_mode_probed_add</function> directly for every 2081 supported mode and return the number of modes it has detected. This 2082 operation is mandatory. 2083 </para> 2084 <para> 2085 When adding modes manually the driver creates each mode with a call to 2086 <function>drm_mode_create</function> and must fill the following fields. 2087 <itemizedlist> 2088 <listitem> 2089 <synopsis>__u32 type;</synopsis> 2090 <para> 2091 Mode type bitmask, a combination of 2092 <variablelist> 2093 <varlistentry> 2094 <term>DRM_MODE_TYPE_BUILTIN</term> 2095 <listitem><para>not used?</para></listitem> 2096 </varlistentry> 2097 <varlistentry> 2098 <term>DRM_MODE_TYPE_CLOCK_C</term> 2099 <listitem><para>not used?</para></listitem> 2100 </varlistentry> 2101 <varlistentry> 2102 <term>DRM_MODE_TYPE_CRTC_C</term> 2103 <listitem><para>not used?</para></listitem> 2104 </varlistentry> 2105 <varlistentry> 2106 <term> 2107 DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector 2108 </term> 2109 <listitem> 2110 <para>not used?</para> 2111 </listitem> 2112 </varlistentry> 2113 <varlistentry> 2114 <term>DRM_MODE_TYPE_DEFAULT</term> 2115 <listitem><para>not used?</para></listitem> 2116 </varlistentry> 2117 <varlistentry> 2118 <term>DRM_MODE_TYPE_USERDEF</term> 2119 <listitem><para>not used?</para></listitem> 2120 </varlistentry> 2121 <varlistentry> 2122 <term>DRM_MODE_TYPE_DRIVER</term> 2123 <listitem> 2124 <para> 2125 The mode has been created by the driver (as opposed to 2126 to user-created modes). 2127 </para> 2128 </listitem> 2129 </varlistentry> 2130 </variablelist> 2131 Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they 2132 create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred 2133 mode. 2134 </para> 2135 </listitem> 2136 <listitem> 2137 <synopsis>__u32 clock;</synopsis> 2138 <para>Pixel clock frequency in kHz unit</para> 2139 </listitem> 2140 <listitem> 2141 <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal; 2142 __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis> 2143 <para>Horizontal and vertical timing information</para> 2144 <screen><![CDATA[ 2145 Active Front Sync Back 2146 Region Porch Porch 2147 <-----------------------><----------------><-------------><--------------> 2148 2149 //////////////////////| 2150 ////////////////////// | 2151 ////////////////////// |.................. ................ 2152 _______________ 2153 2154 <----- [hv]display -----> 2155 <------------- [hv]sync_start ------------> 2156 <--------------------- [hv]sync_end ---------------------> 2157 <-------------------------------- [hv]total -----------------------------> 2158]]></screen> 2159 </listitem> 2160 <listitem> 2161 <synopsis>__u16 hskew; 2162 __u16 vscan;</synopsis> 2163 <para>Unknown</para> 2164 </listitem> 2165 <listitem> 2166 <synopsis>__u32 flags;</synopsis> 2167 <para> 2168 Mode flags, a combination of 2169 <variablelist> 2170 <varlistentry> 2171 <term>DRM_MODE_FLAG_PHSYNC</term> 2172 <listitem><para> 2173 Horizontal sync is active high 2174 </para></listitem> 2175 </varlistentry> 2176 <varlistentry> 2177 <term>DRM_MODE_FLAG_NHSYNC</term> 2178 <listitem><para> 2179 Horizontal sync is active low 2180 </para></listitem> 2181 </varlistentry> 2182 <varlistentry> 2183 <term>DRM_MODE_FLAG_PVSYNC</term> 2184 <listitem><para> 2185 Vertical sync is active high 2186 </para></listitem> 2187 </varlistentry> 2188 <varlistentry> 2189 <term>DRM_MODE_FLAG_NVSYNC</term> 2190 <listitem><para> 2191 Vertical sync is active low 2192 </para></listitem> 2193 </varlistentry> 2194 <varlistentry> 2195 <term>DRM_MODE_FLAG_INTERLACE</term> 2196 <listitem><para> 2197 Mode is interlaced 2198 </para></listitem> 2199 </varlistentry> 2200 <varlistentry> 2201 <term>DRM_MODE_FLAG_DBLSCAN</term> 2202 <listitem><para> 2203 Mode uses doublescan 2204 </para></listitem> 2205 </varlistentry> 2206 <varlistentry> 2207 <term>DRM_MODE_FLAG_CSYNC</term> 2208 <listitem><para> 2209 Mode uses composite sync 2210 </para></listitem> 2211 </varlistentry> 2212 <varlistentry> 2213 <term>DRM_MODE_FLAG_PCSYNC</term> 2214 <listitem><para> 2215 Composite sync is active high 2216 </para></listitem> 2217 </varlistentry> 2218 <varlistentry> 2219 <term>DRM_MODE_FLAG_NCSYNC</term> 2220 <listitem><para> 2221 Composite sync is active low 2222 </para></listitem> 2223 </varlistentry> 2224 <varlistentry> 2225 <term>DRM_MODE_FLAG_HSKEW</term> 2226 <listitem><para> 2227 hskew provided (not used?) 2228 </para></listitem> 2229 </varlistentry> 2230 <varlistentry> 2231 <term>DRM_MODE_FLAG_BCAST</term> 2232 <listitem><para> 2233 not used? 2234 </para></listitem> 2235 </varlistentry> 2236 <varlistentry> 2237 <term>DRM_MODE_FLAG_PIXMUX</term> 2238 <listitem><para> 2239 not used? 2240 </para></listitem> 2241 </varlistentry> 2242 <varlistentry> 2243 <term>DRM_MODE_FLAG_DBLCLK</term> 2244 <listitem><para> 2245 not used? 2246 </para></listitem> 2247 </varlistentry> 2248 <varlistentry> 2249 <term>DRM_MODE_FLAG_CLKDIV2</term> 2250 <listitem><para> 2251 ? 2252 </para></listitem> 2253 </varlistentry> 2254 </variablelist> 2255 </para> 2256 <para> 2257 Note that modes marked with the INTERLACE or DBLSCAN flags will be 2258 filtered out by 2259 <function>drm_helper_probe_single_connector_modes</function> if 2260 the connector's <structfield>interlace_allowed</structfield> or 2261 <structfield>doublescan_allowed</structfield> field is set to 0. 2262 </para> 2263 </listitem> 2264 <listitem> 2265 <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis> 2266 <para> 2267 Mode name. The driver must call 2268 <function>drm_mode_set_name</function> to fill the mode name from 2269 <structfield>hdisplay</structfield>, 2270 <structfield>vdisplay</structfield> and interlace flag after 2271 filling the corresponding fields. 2272 </para> 2273 </listitem> 2274 </itemizedlist> 2275 </para> 2276 <para> 2277 The <structfield>vrefresh</structfield> value is computed by 2278 <function>drm_helper_probe_single_connector_modes</function>. 2279 </para> 2280 <para> 2281 When parsing EDID data, <function>drm_add_edid_modes</function> fill the 2282 connector <structfield>display_info</structfield> 2283 <structfield>width_mm</structfield> and 2284 <structfield>height_mm</structfield> fields. When creating modes 2285 manually the <methodname>get_modes</methodname> helper operation must 2286 set the <structfield>display_info</structfield> 2287 <structfield>width_mm</structfield> and 2288 <structfield>height_mm</structfield> fields if they haven't been set 2289 already (for instance at initialization time when a fixed-size panel is 2290 attached to the connector). The mode <structfield>width_mm</structfield> 2291 and <structfield>height_mm</structfield> fields are only used internally 2292 during EDID parsing and should not be set when creating modes manually. 2293 </para> 2294 </listitem> 2295 <listitem> 2296 <synopsis>int (*mode_valid)(struct drm_connector *connector, 2297 struct drm_display_mode *mode);</synopsis> 2298 <para> 2299 Verify whether a mode is valid for the connector. Return MODE_OK for 2300 supported modes and one of the enum drm_mode_status values (MODE_*) 2301 for unsupported modes. This operation is optional. 2302 </para> 2303 <para> 2304 As the mode rejection reason is currently not used beside for 2305 immediately removing the unsupported mode, an implementation can 2306 return MODE_BAD regardless of the exact reason why the mode is not 2307 valid. 2308 </para> 2309 <note><para> 2310 Note that the <methodname>mode_valid</methodname> helper operation is 2311 only called for modes detected by the device, and 2312 <emphasis>not</emphasis> for modes set by the user through the CRTC 2313 <methodname>set_config</methodname> operation. 2314 </para></note> 2315 </listitem> 2316 </itemizedlist> 2317 </sect2> 2318 <sect2> 2319 <title>Modeset Helper Functions Reference</title> 2320!Edrivers/gpu/drm/drm_crtc_helper.c 2321 </sect2> 2322 <sect2> 2323 <title>Output Probing Helper Functions Reference</title> 2324!Pdrivers/gpu/drm/drm_probe_helper.c output probing helper overview 2325!Edrivers/gpu/drm/drm_probe_helper.c 2326 </sect2> 2327 <sect2> 2328 <title>fbdev Helper Functions Reference</title> 2329!Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers 2330!Edrivers/gpu/drm/drm_fb_helper.c 2331!Iinclude/drm/drm_fb_helper.h 2332 </sect2> 2333 <sect2> 2334 <title>Display Port Helper Functions Reference</title> 2335!Pdrivers/gpu/drm/drm_dp_helper.c dp helpers 2336!Iinclude/drm/drm_dp_helper.h 2337!Edrivers/gpu/drm/drm_dp_helper.c 2338 </sect2> 2339 <sect2> 2340 <title>Display Port MST Helper Functions Reference</title> 2341!Pdrivers/gpu/drm/drm_dp_mst_topology.c dp mst helper 2342!Iinclude/drm/drm_dp_mst_helper.h 2343!Edrivers/gpu/drm/drm_dp_mst_topology.c 2344 </sect2> 2345 <sect2> 2346 <title>EDID Helper Functions Reference</title> 2347!Edrivers/gpu/drm/drm_edid.c 2348 </sect2> 2349 <sect2> 2350 <title>Rectangle Utilities Reference</title> 2351!Pinclude/drm/drm_rect.h rect utils 2352!Iinclude/drm/drm_rect.h 2353!Edrivers/gpu/drm/drm_rect.c 2354 </sect2> 2355 <sect2> 2356 <title>Flip-work Helper Reference</title> 2357!Pinclude/drm/drm_flip_work.h flip utils 2358!Iinclude/drm/drm_flip_work.h 2359!Edrivers/gpu/drm/drm_flip_work.c 2360 </sect2> 2361 <sect2> 2362 <title>HDMI Infoframes Helper Reference</title> 2363 <para> 2364 Strictly speaking this is not a DRM helper library but generally useable 2365 by any driver interfacing with HDMI outputs like v4l or alsa drivers. 2366 But it nicely fits into the overall topic of mode setting helper 2367 libraries and hence is also included here. 2368 </para> 2369!Iinclude/linux/hdmi.h 2370!Edrivers/video/hdmi.c 2371 </sect2> 2372 <sect2> 2373 <title id="drm-kms-planehelpers">Plane Helper Reference</title> 2374!Edrivers/gpu/drm/drm_plane_helper.c Plane Helpers 2375 </sect2> 2376 </sect1> 2377 2378 <!-- Internals: kms properties --> 2379 2380 <sect1 id="drm-kms-properties"> 2381 <title>KMS Properties</title> 2382 <para> 2383 Drivers may need to expose additional parameters to applications than 2384 those described in the previous sections. KMS supports attaching 2385 properties to CRTCs, connectors and planes and offers a userspace API to 2386 list, get and set the property values. 2387 </para> 2388 <para> 2389 Properties are identified by a name that uniquely defines the property 2390 purpose, and store an associated value. For all property types except blob 2391 properties the value is a 64-bit unsigned integer. 2392 </para> 2393 <para> 2394 KMS differentiates between properties and property instances. Drivers 2395 first create properties and then create and associate individual instances 2396 of those properties to objects. A property can be instantiated multiple 2397 times and associated with different objects. Values are stored in property 2398 instances, and all other property information are stored in the property 2399 and shared between all instances of the property. 2400 </para> 2401 <para> 2402 Every property is created with a type that influences how the KMS core 2403 handles the property. Supported property types are 2404 <variablelist> 2405 <varlistentry> 2406 <term>DRM_MODE_PROP_RANGE</term> 2407 <listitem><para>Range properties report their minimum and maximum 2408 admissible values. The KMS core verifies that values set by 2409 application fit in that range.</para></listitem> 2410 </varlistentry> 2411 <varlistentry> 2412 <term>DRM_MODE_PROP_ENUM</term> 2413 <listitem><para>Enumerated properties take a numerical value that 2414 ranges from 0 to the number of enumerated values defined by the 2415 property minus one, and associate a free-formed string name to each 2416 value. Applications can retrieve the list of defined value-name pairs 2417 and use the numerical value to get and set property instance values. 2418 </para></listitem> 2419 </varlistentry> 2420 <varlistentry> 2421 <term>DRM_MODE_PROP_BITMASK</term> 2422 <listitem><para>Bitmask properties are enumeration properties that 2423 additionally restrict all enumerated values to the 0..63 range. 2424 Bitmask property instance values combine one or more of the 2425 enumerated bits defined by the property.</para></listitem> 2426 </varlistentry> 2427 <varlistentry> 2428 <term>DRM_MODE_PROP_BLOB</term> 2429 <listitem><para>Blob properties store a binary blob without any format 2430 restriction. The binary blobs are created as KMS standalone objects, 2431 and blob property instance values store the ID of their associated 2432 blob object.</para> 2433 <para>Blob properties are only used for the connector EDID property 2434 and cannot be created by drivers.</para></listitem> 2435 </varlistentry> 2436 </variablelist> 2437 </para> 2438 <para> 2439 To create a property drivers call one of the following functions depending 2440 on the property type. All property creation functions take property flags 2441 and name, as well as type-specific arguments. 2442 <itemizedlist> 2443 <listitem> 2444 <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags, 2445 const char *name, 2446 uint64_t min, uint64_t max);</synopsis> 2447 <para>Create a range property with the given minimum and maximum 2448 values.</para> 2449 </listitem> 2450 <listitem> 2451 <synopsis>struct drm_property *drm_property_create_enum(struct drm_device *dev, int flags, 2452 const char *name, 2453 const struct drm_prop_enum_list *props, 2454 int num_values);</synopsis> 2455 <para>Create an enumerated property. The <parameter>props</parameter> 2456 argument points to an array of <parameter>num_values</parameter> 2457 value-name pairs.</para> 2458 </listitem> 2459 <listitem> 2460 <synopsis>struct drm_property *drm_property_create_bitmask(struct drm_device *dev, 2461 int flags, const char *name, 2462 const struct drm_prop_enum_list *props, 2463 int num_values);</synopsis> 2464 <para>Create a bitmask property. The <parameter>props</parameter> 2465 argument points to an array of <parameter>num_values</parameter> 2466 value-name pairs.</para> 2467 </listitem> 2468 </itemizedlist> 2469 </para> 2470 <para> 2471 Properties can additionally be created as immutable, in which case they 2472 will be read-only for applications but can be modified by the driver. To 2473 create an immutable property drivers must set the DRM_MODE_PROP_IMMUTABLE 2474 flag at property creation time. 2475 </para> 2476 <para> 2477 When no array of value-name pairs is readily available at property 2478 creation time for enumerated or range properties, drivers can create 2479 the property using the <function>drm_property_create</function> function 2480 and manually add enumeration value-name pairs by calling the 2481 <function>drm_property_add_enum</function> function. Care must be taken to 2482 properly specify the property type through the <parameter>flags</parameter> 2483 argument. 2484 </para> 2485 <para> 2486 After creating properties drivers can attach property instances to CRTC, 2487 connector and plane objects by calling the 2488 <function>drm_object_attach_property</function>. The function takes a 2489 pointer to the target object, a pointer to the previously created property 2490 and an initial instance value. 2491 </para> 2492 <sect2> 2493 <title>Existing KMS Properties</title> 2494 <para> 2495 The following table gives description of drm properties exposed by various 2496 modules/drivers. 2497 </para> 2498 <table border="1" cellpadding="0" cellspacing="0"> 2499 <tbody> 2500 <tr style="font-weight: bold;"> 2501 <td valign="top" >Owner Module/Drivers</td> 2502 <td valign="top" >Group</td> 2503 <td valign="top" >Property Name</td> 2504 <td valign="top" >Type</td> 2505 <td valign="top" >Property Values</td> 2506 <td valign="top" >Object attached</td> 2507 <td valign="top" >Description/Restrictions</td> 2508 </tr> 2509 <tr> 2510 <td rowspan="21" valign="top" >DRM</td> 2511 <td rowspan="2" valign="top" >Generic</td> 2512 <td valign="top" >“EDID”</td> 2513 <td valign="top" >BLOB | IMMUTABLE</td> 2514 <td valign="top" >0</td> 2515 <td valign="top" >Connector</td> 2516 <td valign="top" >Contains id of edid blob ptr object.</td> 2517 </tr> 2518 <tr> 2519 <td valign="top" >“DPMS”</td> 2520 <td valign="top" >ENUM</td> 2521 <td valign="top" >{ “On”, “Standby”, “Suspend”, “Off” }</td> 2522 <td valign="top" >Connector</td> 2523 <td valign="top" >Contains DPMS operation mode value.</td> 2524 </tr> 2525 <tr> 2526 <td rowspan="1" valign="top" >Plane</td> 2527 <td valign="top" >“type”</td> 2528 <td valign="top" >ENUM | IMMUTABLE</td> 2529 <td valign="top" >{ "Overlay", "Primary", "Cursor" }</td> 2530 <td valign="top" >Plane</td> 2531 <td valign="top" >Plane type</td> 2532 </tr> 2533 <tr> 2534 <td rowspan="2" valign="top" >DVI-I</td> 2535 <td valign="top" >“subconnector”</td> 2536 <td valign="top" >ENUM</td> 2537 <td valign="top" >{ “Unknown”, “DVI-D”, “DVI-A” }</td> 2538 <td valign="top" >Connector</td> 2539 <td valign="top" >TBD</td> 2540 </tr> 2541 <tr> 2542 <td valign="top" >“select subconnector”</td> 2543 <td valign="top" >ENUM</td> 2544 <td valign="top" >{ “Automatic”, “DVI-D”, “DVI-A” }</td> 2545 <td valign="top" >Connector</td> 2546 <td valign="top" >TBD</td> 2547 </tr> 2548 <tr> 2549 <td rowspan="13" valign="top" >TV</td> 2550 <td valign="top" >“subconnector”</td> 2551 <td valign="top" >ENUM</td> 2552 <td valign="top" >{ "Unknown", "Composite", "SVIDEO", "Component", "SCART" }</td> 2553 <td valign="top" >Connector</td> 2554 <td valign="top" >TBD</td> 2555 </tr> 2556 <tr> 2557 <td valign="top" >“select subconnector”</td> 2558 <td valign="top" >ENUM</td> 2559 <td valign="top" >{ "Automatic", "Composite", "SVIDEO", "Component", "SCART" }</td> 2560 <td valign="top" >Connector</td> 2561 <td valign="top" >TBD</td> 2562 </tr> 2563 <tr> 2564 <td valign="top" >“mode”</td> 2565 <td valign="top" >ENUM</td> 2566 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td> 2567 <td valign="top" >Connector</td> 2568 <td valign="top" >TBD</td> 2569 </tr> 2570 <tr> 2571 <td valign="top" >“left margin”</td> 2572 <td valign="top" >RANGE</td> 2573 <td valign="top" >Min=0, Max=100</td> 2574 <td valign="top" >Connector</td> 2575 <td valign="top" >TBD</td> 2576 </tr> 2577 <tr> 2578 <td valign="top" >“right margin”</td> 2579 <td valign="top" >RANGE</td> 2580 <td valign="top" >Min=0, Max=100</td> 2581 <td valign="top" >Connector</td> 2582 <td valign="top" >TBD</td> 2583 </tr> 2584 <tr> 2585 <td valign="top" >“top margin”</td> 2586 <td valign="top" >RANGE</td> 2587 <td valign="top" >Min=0, Max=100</td> 2588 <td valign="top" >Connector</td> 2589 <td valign="top" >TBD</td> 2590 </tr> 2591 <tr> 2592 <td valign="top" >“bottom margin”</td> 2593 <td valign="top" >RANGE</td> 2594 <td valign="top" >Min=0, Max=100</td> 2595 <td valign="top" >Connector</td> 2596 <td valign="top" >TBD</td> 2597 </tr> 2598 <tr> 2599 <td valign="top" >“brightness”</td> 2600 <td valign="top" >RANGE</td> 2601 <td valign="top" >Min=0, Max=100</td> 2602 <td valign="top" >Connector</td> 2603 <td valign="top" >TBD</td> 2604 </tr> 2605 <tr> 2606 <td valign="top" >“contrast”</td> 2607 <td valign="top" >RANGE</td> 2608 <td valign="top" >Min=0, Max=100</td> 2609 <td valign="top" >Connector</td> 2610 <td valign="top" >TBD</td> 2611 </tr> 2612 <tr> 2613 <td valign="top" >“flicker reduction”</td> 2614 <td valign="top" >RANGE</td> 2615 <td valign="top" >Min=0, Max=100</td> 2616 <td valign="top" >Connector</td> 2617 <td valign="top" >TBD</td> 2618 </tr> 2619 <tr> 2620 <td valign="top" >“overscan”</td> 2621 <td valign="top" >RANGE</td> 2622 <td valign="top" >Min=0, Max=100</td> 2623 <td valign="top" >Connector</td> 2624 <td valign="top" >TBD</td> 2625 </tr> 2626 <tr> 2627 <td valign="top" >“saturation”</td> 2628 <td valign="top" >RANGE</td> 2629 <td valign="top" >Min=0, Max=100</td> 2630 <td valign="top" >Connector</td> 2631 <td valign="top" >TBD</td> 2632 </tr> 2633 <tr> 2634 <td valign="top" >“hue”</td> 2635 <td valign="top" >RANGE</td> 2636 <td valign="top" >Min=0, Max=100</td> 2637 <td valign="top" >Connector</td> 2638 <td valign="top" >TBD</td> 2639 </tr> 2640 <tr> 2641 <td rowspan="3" valign="top" >Optional</td> 2642 <td valign="top" >“scaling mode”</td> 2643 <td valign="top" >ENUM</td> 2644 <td valign="top" >{ "None", "Full", "Center", "Full aspect" }</td> 2645 <td valign="top" >Connector</td> 2646 <td valign="top" >TBD</td> 2647 </tr> 2648 <tr> 2649 <td valign="top" >"aspect ratio"</td> 2650 <td valign="top" >ENUM</td> 2651 <td valign="top" >{ "None", "4:3", "16:9" }</td> 2652 <td valign="top" >Connector</td> 2653 <td valign="top" >DRM property to set aspect ratio from user space app. 2654 This enum is made generic to allow addition of custom aspect 2655 ratios.</td> 2656 </tr> 2657 <tr> 2658 <td valign="top" >“dirty”</td> 2659 <td valign="top" >ENUM | IMMUTABLE</td> 2660 <td valign="top" >{ "Off", "On", "Annotate" }</td> 2661 <td valign="top" >Connector</td> 2662 <td valign="top" >TBD</td> 2663 </tr> 2664 <tr> 2665 <td rowspan="21" valign="top" >i915</td> 2666 <td rowspan="2" valign="top" >Generic</td> 2667 <td valign="top" >"Broadcast RGB"</td> 2668 <td valign="top" >ENUM</td> 2669 <td valign="top" >{ "Automatic", "Full", "Limited 16:235" }</td> 2670 <td valign="top" >Connector</td> 2671 <td valign="top" >TBD</td> 2672 </tr> 2673 <tr> 2674 <td valign="top" >“audio”</td> 2675 <td valign="top" >ENUM</td> 2676 <td valign="top" >{ "force-dvi", "off", "auto", "on" }</td> 2677 <td valign="top" >Connector</td> 2678 <td valign="top" >TBD</td> 2679 </tr> 2680 <tr> 2681 <td rowspan="1" valign="top" >Plane</td> 2682 <td valign="top" >“rotation”</td> 2683 <td valign="top" >BITMASK</td> 2684 <td valign="top" >{ 0, "rotate-0" }, { 2, "rotate-180" }</td> 2685 <td valign="top" >Plane</td> 2686 <td valign="top" >TBD</td> 2687 </tr> 2688 <tr> 2689 <td rowspan="17" valign="top" >SDVO-TV</td> 2690 <td valign="top" >“mode”</td> 2691 <td valign="top" >ENUM</td> 2692 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td> 2693 <td valign="top" >Connector</td> 2694 <td valign="top" >TBD</td> 2695 </tr> 2696 <tr> 2697 <td valign="top" >"left_margin"</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> 2702 </tr> 2703 <tr> 2704 <td valign="top" >"right_margin"</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> 2709 </tr> 2710 <tr> 2711 <td valign="top" >"top_margin"</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> 2716 </tr> 2717 <tr> 2718 <td valign="top" >"bottom_margin"</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> 2723 </tr> 2724 <tr> 2725 <td valign="top" >“hpos”</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> 2730 </tr> 2731 <tr> 2732 <td valign="top" >“vpos”</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> 2737 </tr> 2738 <tr> 2739 <td valign="top" >“contrast”</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> 2744 </tr> 2745 <tr> 2746 <td valign="top" >“saturation”</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> 2751 </tr> 2752 <tr> 2753 <td valign="top" >“hue”</td> 2754 <td valign="top" >RANGE</td> 2755 <td valign="top" >Min=0, Max= SDVO dependent</td> 2756 <td valign="top" >Connector</td> 2757 <td valign="top" >TBD</td> 2758 </tr> 2759 <tr> 2760 <td valign="top" >“sharpness”</td> 2761 <td valign="top" >RANGE</td> 2762 <td valign="top" >Min=0, Max= SDVO dependent</td> 2763 <td valign="top" >Connector</td> 2764 <td valign="top" >TBD</td> 2765 </tr> 2766 <tr> 2767 <td valign="top" >“flicker_filter”</td> 2768 <td valign="top" >RANGE</td> 2769 <td valign="top" >Min=0, Max= SDVO dependent</td> 2770 <td valign="top" >Connector</td> 2771 <td valign="top" >TBD</td> 2772 </tr> 2773 <tr> 2774 <td valign="top" >“flicker_filter_adaptive”</td> 2775 <td valign="top" >RANGE</td> 2776 <td valign="top" >Min=0, Max= SDVO dependent</td> 2777 <td valign="top" >Connector</td> 2778 <td valign="top" >TBD</td> 2779 </tr> 2780 <tr> 2781 <td valign="top" >“flicker_filter_2d”</td> 2782 <td valign="top" >RANGE</td> 2783 <td valign="top" >Min=0, Max= SDVO dependent</td> 2784 <td valign="top" >Connector</td> 2785 <td valign="top" >TBD</td> 2786 </tr> 2787 <tr> 2788 <td valign="top" >“tv_chroma_filter”</td> 2789 <td valign="top" >RANGE</td> 2790 <td valign="top" >Min=0, Max= SDVO dependent</td> 2791 <td valign="top" >Connector</td> 2792 <td valign="top" >TBD</td> 2793 </tr> 2794 <tr> 2795 <td valign="top" >“tv_luma_filter”</td> 2796 <td valign="top" >RANGE</td> 2797 <td valign="top" >Min=0, Max= SDVO dependent</td> 2798 <td valign="top" >Connector</td> 2799 <td valign="top" >TBD</td> 2800 </tr> 2801 <tr> 2802 <td valign="top" >“dot_crawl”</td> 2803 <td valign="top" >RANGE</td> 2804 <td valign="top" >Min=0, Max=1</td> 2805 <td valign="top" >Connector</td> 2806 <td valign="top" >TBD</td> 2807 </tr> 2808 <tr> 2809 <td valign="top" >SDVO-TV/LVDS</td> 2810 <td valign="top" >“brightness”</td> 2811 <td valign="top" >RANGE</td> 2812 <td valign="top" >Min=0, Max= SDVO dependent</td> 2813 <td valign="top" >Connector</td> 2814 <td valign="top" >TBD</td> 2815 </tr> 2816 <tr> 2817 <td rowspan="2" valign="top" >CDV gma-500</td> 2818 <td rowspan="2" valign="top" >Generic</td> 2819 <td valign="top" >"Broadcast RGB"</td> 2820 <td valign="top" >ENUM</td> 2821 <td valign="top" >{ “Full”, “Limited 16:235” }</td> 2822 <td valign="top" >Connector</td> 2823 <td valign="top" >TBD</td> 2824 </tr> 2825 <tr> 2826 <td valign="top" >"Broadcast RGB"</td> 2827 <td valign="top" >ENUM</td> 2828 <td valign="top" >{ “off”, “auto”, “on” }</td> 2829 <td valign="top" >Connector</td> 2830 <td valign="top" >TBD</td> 2831 </tr> 2832 <tr> 2833 <td rowspan="19" valign="top" >Poulsbo</td> 2834 <td rowspan="1" valign="top" >Generic</td> 2835 <td valign="top" >“backlight”</td> 2836 <td valign="top" >RANGE</td> 2837 <td valign="top" >Min=0, Max=100</td> 2838 <td valign="top" >Connector</td> 2839 <td valign="top" >TBD</td> 2840 </tr> 2841 <tr> 2842 <td rowspan="17" valign="top" >SDVO-TV</td> 2843 <td valign="top" >“mode”</td> 2844 <td valign="top" >ENUM</td> 2845 <td valign="top" >{ "NTSC_M", "NTSC_J", "NTSC_443", "PAL_B" } etc.</td> 2846 <td valign="top" >Connector</td> 2847 <td valign="top" >TBD</td> 2848 </tr> 2849 <tr> 2850 <td valign="top" >"left_margin"</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> 2855 </tr> 2856 <tr> 2857 <td valign="top" >"right_margin"</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> 2862 </tr> 2863 <tr> 2864 <td valign="top" >"top_margin"</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> 2869 </tr> 2870 <tr> 2871 <td valign="top" >"bottom_margin"</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> 2876 </tr> 2877 <tr> 2878 <td valign="top" >“hpos”</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> 2883 </tr> 2884 <tr> 2885 <td valign="top" >“vpos”</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> 2890 </tr> 2891 <tr> 2892 <td valign="top" >“contrast”</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> 2897 </tr> 2898 <tr> 2899 <td valign="top" >“saturation”</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> 2904 </tr> 2905 <tr> 2906 <td valign="top" >“hue”</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> 2911 </tr> 2912 <tr> 2913 <td valign="top" >“sharpness”</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> 2918 </tr> 2919 <tr> 2920 <td valign="top" >“flicker_filter”</td> 2921 <td valign="top" >RANGE</td> 2922 <td valign="top" >Min=0, Max= SDVO dependent</td> 2923 <td valign="top" >Connector</td> 2924 <td valign="top" >TBD</td> 2925 </tr> 2926 <tr> 2927 <td valign="top" >“flicker_filter_adaptive”</td> 2928 <td valign="top" >RANGE</td> 2929 <td valign="top" >Min=0, Max= SDVO dependent</td> 2930 <td valign="top" >Connector</td> 2931 <td valign="top" >TBD</td> 2932 </tr> 2933 <tr> 2934 <td valign="top" >“flicker_filter_2d”</td> 2935 <td valign="top" >RANGE</td> 2936 <td valign="top" >Min=0, Max= SDVO dependent</td> 2937 <td valign="top" >Connector</td> 2938 <td valign="top" >TBD</td> 2939 </tr> 2940 <tr> 2941 <td valign="top" >“tv_chroma_filter”</td> 2942 <td valign="top" >RANGE</td> 2943 <td valign="top" >Min=0, Max= SDVO dependent</td> 2944 <td valign="top" >Connector</td> 2945 <td valign="top" >TBD</td> 2946 </tr> 2947 <tr> 2948 <td valign="top" >“tv_luma_filter”</td> 2949 <td valign="top" >RANGE</td> 2950 <td valign="top" >Min=0, Max= SDVO dependent</td> 2951 <td valign="top" >Connector</td> 2952 <td valign="top" >TBD</td> 2953 </tr> 2954 <tr> 2955 <td valign="top" >“dot_crawl”</td> 2956 <td valign="top" >RANGE</td> 2957 <td valign="top" >Min=0, Max=1</td> 2958 <td valign="top" >Connector</td> 2959 <td valign="top" >TBD</td> 2960 </tr> 2961 <tr> 2962 <td valign="top" >SDVO-TV/LVDS</td> 2963 <td valign="top" >“brightness”</td> 2964 <td valign="top" >RANGE</td> 2965 <td valign="top" >Min=0, Max= SDVO dependent</td> 2966 <td valign="top" >Connector</td> 2967 <td valign="top" >TBD</td> 2968 </tr> 2969 <tr> 2970 <td rowspan="11" valign="top" >armada</td> 2971 <td rowspan="2" valign="top" >CRTC</td> 2972 <td valign="top" >"CSC_YUV"</td> 2973 <td valign="top" >ENUM</td> 2974 <td valign="top" >{ "Auto" , "CCIR601", "CCIR709" }</td> 2975 <td valign="top" >CRTC</td> 2976 <td valign="top" >TBD</td> 2977 </tr> 2978 <tr> 2979 <td valign="top" >"CSC_RGB"</td> 2980 <td valign="top" >ENUM</td> 2981 <td valign="top" >{ "Auto", "Computer system", "Studio" }</td> 2982 <td valign="top" >CRTC</td> 2983 <td valign="top" >TBD</td> 2984 </tr> 2985 <tr> 2986 <td rowspan="9" valign="top" >Overlay</td> 2987 <td valign="top" >"colorkey"</td> 2988 <td valign="top" >RANGE</td> 2989 <td valign="top" >Min=0, Max=0xffffff</td> 2990 <td valign="top" >Plane</td> 2991 <td valign="top" >TBD</td> 2992 </tr> 2993 <tr> 2994 <td valign="top" >"colorkey_min"</td> 2995 <td valign="top" >RANGE</td> 2996 <td valign="top" >Min=0, Max=0xffffff</td> 2997 <td valign="top" >Plane</td> 2998 <td valign="top" >TBD</td> 2999 </tr> 3000 <tr> 3001 <td valign="top" >"colorkey_max"</td> 3002 <td valign="top" >RANGE</td> 3003 <td valign="top" >Min=0, Max=0xffffff</td> 3004 <td valign="top" >Plane</td> 3005 <td valign="top" >TBD</td> 3006 </tr> 3007 <tr> 3008 <td valign="top" >"colorkey_val"</td> 3009 <td valign="top" >RANGE</td> 3010 <td valign="top" >Min=0, Max=0xffffff</td> 3011 <td valign="top" >Plane</td> 3012 <td valign="top" >TBD</td> 3013 </tr> 3014 <tr> 3015 <td valign="top" >"colorkey_alpha"</td> 3016 <td valign="top" >RANGE</td> 3017 <td valign="top" >Min=0, Max=0xffffff</td> 3018 <td valign="top" >Plane</td> 3019 <td valign="top" >TBD</td> 3020 </tr> 3021 <tr> 3022 <td valign="top" >"colorkey_mode"</td> 3023 <td valign="top" >ENUM</td> 3024 <td valign="top" >{ "disabled", "Y component", "U component" 3025 , "V component", "RGB", “R component", "G component", "B component" }</td> 3026 <td valign="top" >Plane</td> 3027 <td valign="top" >TBD</td> 3028 </tr> 3029 <tr> 3030 <td valign="top" >"brightness"</td> 3031 <td valign="top" >RANGE</td> 3032 <td valign="top" >Min=0, Max=256 + 255</td> 3033 <td valign="top" >Plane</td> 3034 <td valign="top" >TBD</td> 3035 </tr> 3036 <tr> 3037 <td valign="top" >"contrast"</td> 3038 <td valign="top" >RANGE</td> 3039 <td valign="top" >Min=0, Max=0x7fff</td> 3040 <td valign="top" >Plane</td> 3041 <td valign="top" >TBD</td> 3042 </tr> 3043 <tr> 3044 <td valign="top" >"saturation"</td> 3045 <td valign="top" >RANGE</td> 3046 <td valign="top" >Min=0, Max=0x7fff</td> 3047 <td valign="top" >Plane</td> 3048 <td valign="top" >TBD</td> 3049 </tr> 3050 <tr> 3051 <td rowspan="2" valign="top" >exynos</td> 3052 <td valign="top" >CRTC</td> 3053 <td valign="top" >“mode”</td> 3054 <td valign="top" >ENUM</td> 3055 <td valign="top" >{ "normal", "blank" }</td> 3056 <td valign="top" >CRTC</td> 3057 <td valign="top" >TBD</td> 3058 </tr> 3059 <tr> 3060 <td valign="top" >Overlay</td> 3061 <td valign="top" >“zpos”</td> 3062 <td valign="top" >RANGE</td> 3063 <td valign="top" >Min=0, Max=MAX_PLANE-1</td> 3064 <td valign="top" >Plane</td> 3065 <td valign="top" >TBD</td> 3066 </tr> 3067 <tr> 3068 <td rowspan="2" valign="top" >i2c/ch7006_drv</td> 3069 <td valign="top" >Generic</td> 3070 <td valign="top" >“scale”</td> 3071 <td valign="top" >RANGE</td> 3072 <td valign="top" >Min=0, Max=2</td> 3073 <td valign="top" >Connector</td> 3074 <td valign="top" >TBD</td> 3075 </tr> 3076 <tr> 3077 <td rowspan="1" valign="top" >TV</td> 3078 <td valign="top" >“mode”</td> 3079 <td valign="top" >ENUM</td> 3080 <td valign="top" >{ "PAL", "PAL-M","PAL-N"}, ”PAL-Nc" 3081 , "PAL-60", "NTSC-M", "NTSC-J" }</td> 3082 <td valign="top" >Connector</td> 3083 <td valign="top" >TBD</td> 3084 </tr> 3085 <tr> 3086 <td rowspan="15" valign="top" >nouveau</td> 3087 <td rowspan="6" valign="top" >NV10 Overlay</td> 3088 <td valign="top" >"colorkey"</td> 3089 <td valign="top" >RANGE</td> 3090 <td valign="top" >Min=0, Max=0x01ffffff</td> 3091 <td valign="top" >Plane</td> 3092 <td valign="top" >TBD</td> 3093 </tr> 3094 <tr> 3095 <td valign="top" >“contrast”</td> 3096 <td valign="top" >RANGE</td> 3097 <td valign="top" >Min=0, Max=8192-1</td> 3098 <td valign="top" >Plane</td> 3099 <td valign="top" >TBD</td> 3100 </tr> 3101 <tr> 3102 <td valign="top" >“brightness”</td> 3103 <td valign="top" >RANGE</td> 3104 <td valign="top" >Min=0, Max=1024</td> 3105 <td valign="top" >Plane</td> 3106 <td valign="top" >TBD</td> 3107 </tr> 3108 <tr> 3109 <td valign="top" >“hue”</td> 3110 <td valign="top" >RANGE</td> 3111 <td valign="top" >Min=0, Max=359</td> 3112 <td valign="top" >Plane</td> 3113 <td valign="top" >TBD</td> 3114 </tr> 3115 <tr> 3116 <td valign="top" >“saturation”</td> 3117 <td valign="top" >RANGE</td> 3118 <td valign="top" >Min=0, Max=8192-1</td> 3119 <td valign="top" >Plane</td> 3120 <td valign="top" >TBD</td> 3121 </tr> 3122 <tr> 3123 <td valign="top" >“iturbt_709”</td> 3124 <td valign="top" >RANGE</td> 3125 <td valign="top" >Min=0, Max=1</td> 3126 <td valign="top" >Plane</td> 3127 <td valign="top" >TBD</td> 3128 </tr> 3129 <tr> 3130 <td rowspan="2" valign="top" >Nv04 Overlay</td> 3131 <td valign="top" >“colorkey”</td> 3132 <td valign="top" >RANGE</td> 3133 <td valign="top" >Min=0, Max=0x01ffffff</td> 3134 <td valign="top" >Plane</td> 3135 <td valign="top" >TBD</td> 3136 </tr> 3137 <tr> 3138 <td valign="top" >“brightness”</td> 3139 <td valign="top" >RANGE</td> 3140 <td valign="top" >Min=0, Max=1024</td> 3141 <td valign="top" >Plane</td> 3142 <td valign="top" >TBD</td> 3143 </tr> 3144 <tr> 3145 <td rowspan="7" valign="top" >Display</td> 3146 <td valign="top" >“dithering mode”</td> 3147 <td valign="top" >ENUM</td> 3148 <td valign="top" >{ "auto", "off", "on" }</td> 3149 <td valign="top" >Connector</td> 3150 <td valign="top" >TBD</td> 3151 </tr> 3152 <tr> 3153 <td valign="top" >“dithering depth”</td> 3154 <td valign="top" >ENUM</td> 3155 <td valign="top" >{ "auto", "off", "on", "static 2x2", "dynamic 2x2", "temporal" }</td> 3156 <td valign="top" >Connector</td> 3157 <td valign="top" >TBD</td> 3158 </tr> 3159 <tr> 3160 <td valign="top" >“underscan”</td> 3161 <td valign="top" >ENUM</td> 3162 <td valign="top" >{ "auto", "6 bpc", "8 bpc" }</td> 3163 <td valign="top" >Connector</td> 3164 <td valign="top" >TBD</td> 3165 </tr> 3166 <tr> 3167 <td valign="top" >“underscan hborder”</td> 3168 <td valign="top" >RANGE</td> 3169 <td valign="top" >Min=0, Max=128</td> 3170 <td valign="top" >Connector</td> 3171 <td valign="top" >TBD</td> 3172 </tr> 3173 <tr> 3174 <td valign="top" >“underscan vborder”</td> 3175 <td valign="top" >RANGE</td> 3176 <td valign="top" >Min=0, Max=128</td> 3177 <td valign="top" >Connector</td> 3178 <td valign="top" >TBD</td> 3179 </tr> 3180 <tr> 3181 <td valign="top" >“vibrant hue”</td> 3182 <td valign="top" >RANGE</td> 3183 <td valign="top" >Min=0, Max=180</td> 3184 <td valign="top" >Connector</td> 3185 <td valign="top" >TBD</td> 3186 </tr> 3187 <tr> 3188 <td valign="top" >“color vibrance”</td> 3189 <td valign="top" >RANGE</td> 3190 <td valign="top" >Min=0, Max=200</td> 3191 <td valign="top" >Connector</td> 3192 <td valign="top" >TBD</td> 3193 </tr> 3194 <tr> 3195 <td rowspan="2" valign="top" >omap</td> 3196 <td rowspan="2" valign="top" >Generic</td> 3197 <td valign="top" >“rotation”</td> 3198 <td valign="top" >BITMASK</td> 3199 <td valign="top" >{ 0, "rotate-0" }, 3200 { 1, "rotate-90" }, 3201 { 2, "rotate-180" }, 3202 { 3, "rotate-270" }, 3203 { 4, "reflect-x" }, 3204 { 5, "reflect-y" }</td> 3205 <td valign="top" >CRTC, Plane</td> 3206 <td valign="top" >TBD</td> 3207 </tr> 3208 <tr> 3209 <td valign="top" >“zorder”</td> 3210 <td valign="top" >RANGE</td> 3211 <td valign="top" >Min=0, Max=3</td> 3212 <td valign="top" >CRTC, Plane</td> 3213 <td valign="top" >TBD</td> 3214 </tr> 3215 <tr> 3216 <td valign="top" >qxl</td> 3217 <td valign="top" >Generic</td> 3218 <td valign="top" >“hotplug_mode_update"</td> 3219 <td valign="top" >RANGE</td> 3220 <td valign="top" >Min=0, Max=1</td> 3221 <td valign="top" >Connector</td> 3222 <td valign="top" >TBD</td> 3223 </tr> 3224 <tr> 3225 <td rowspan="9" valign="top" >radeon</td> 3226 <td valign="top" >DVI-I</td> 3227 <td valign="top" >“coherent”</td> 3228 <td valign="top" >RANGE</td> 3229 <td valign="top" >Min=0, Max=1</td> 3230 <td valign="top" >Connector</td> 3231 <td valign="top" >TBD</td> 3232 </tr> 3233 <tr> 3234 <td valign="top" >DAC enable load detect</td> 3235 <td valign="top" >“load detection”</td> 3236 <td valign="top" >RANGE</td> 3237 <td valign="top" >Min=0, Max=1</td> 3238 <td valign="top" >Connector</td> 3239 <td valign="top" >TBD</td> 3240 </tr> 3241 <tr> 3242 <td valign="top" >TV Standard</td> 3243 <td valign="top" >"tv standard"</td> 3244 <td valign="top" >ENUM</td> 3245 <td valign="top" >{ "ntsc", "pal", "pal-m", "pal-60", "ntsc-j" 3246 , "scart-pal", "pal-cn", "secam" }</td> 3247 <td valign="top" >Connector</td> 3248 <td valign="top" >TBD</td> 3249 </tr> 3250 <tr> 3251 <td valign="top" >legacy TMDS PLL detect</td> 3252 <td valign="top" >"tmds_pll"</td> 3253 <td valign="top" >ENUM</td> 3254 <td valign="top" >{ "driver", "bios" }</td> 3255 <td valign="top" >-</td> 3256 <td valign="top" >TBD</td> 3257 </tr> 3258 <tr> 3259 <td rowspan="3" valign="top" >Underscan</td> 3260 <td valign="top" >"underscan"</td> 3261 <td valign="top" >ENUM</td> 3262 <td valign="top" >{ "off", "on", "auto" }</td> 3263 <td valign="top" >Connector</td> 3264 <td valign="top" >TBD</td> 3265 </tr> 3266 <tr> 3267 <td valign="top" >"underscan hborder"</td> 3268 <td valign="top" >RANGE</td> 3269 <td valign="top" >Min=0, Max=128</td> 3270 <td valign="top" >Connector</td> 3271 <td valign="top" >TBD</td> 3272 </tr> 3273 <tr> 3274 <td valign="top" >"underscan vborder"</td> 3275 <td valign="top" >RANGE</td> 3276 <td valign="top" >Min=0, Max=128</td> 3277 <td valign="top" >Connector</td> 3278 <td valign="top" >TBD</td> 3279 </tr> 3280 <tr> 3281 <td valign="top" >Audio</td> 3282 <td valign="top" >“audio”</td> 3283 <td valign="top" >ENUM</td> 3284 <td valign="top" >{ "off", "on", "auto" }</td> 3285 <td valign="top" >Connector</td> 3286 <td valign="top" >TBD</td> 3287 </tr> 3288 <tr> 3289 <td valign="top" >FMT Dithering</td> 3290 <td valign="top" >“dither”</td> 3291 <td valign="top" >ENUM</td> 3292 <td valign="top" >{ "off", "on" }</td> 3293 <td valign="top" >Connector</td> 3294 <td valign="top" >TBD</td> 3295 </tr> 3296 <tr> 3297 <td rowspan="3" valign="top" >rcar-du</td> 3298 <td rowspan="3" valign="top" >Generic</td> 3299 <td valign="top" >"alpha"</td> 3300 <td valign="top" >RANGE</td> 3301 <td valign="top" >Min=0, Max=255</td> 3302 <td valign="top" >Plane</td> 3303 <td valign="top" >TBD</td> 3304 </tr> 3305 <tr> 3306 <td valign="top" >"colorkey"</td> 3307 <td valign="top" >RANGE</td> 3308 <td valign="top" >Min=0, Max=0x01ffffff</td> 3309 <td valign="top" >Plane</td> 3310 <td valign="top" >TBD</td> 3311 </tr> 3312 <tr> 3313 <td valign="top" >"zpos"</td> 3314 <td valign="top" >RANGE</td> 3315 <td valign="top" >Min=1, Max=7</td> 3316 <td valign="top" >Plane</td> 3317 <td valign="top" >TBD</td> 3318 </tr> 3319 </tbody> 3320 </table> 3321 </sect2> 3322 </sect1> 3323 3324 <!-- Internals: vertical blanking --> 3325 3326 <sect1 id="drm-vertical-blank"> 3327 <title>Vertical Blanking</title> 3328 <para> 3329 Vertical blanking plays a major role in graphics rendering. To achieve 3330 tear-free display, users must synchronize page flips and/or rendering to 3331 vertical blanking. The DRM API offers ioctls to perform page flips 3332 synchronized to vertical blanking and wait for vertical blanking. 3333 </para> 3334 <para> 3335 The DRM core handles most of the vertical blanking management logic, which 3336 involves filtering out spurious interrupts, keeping race-free blanking 3337 counters, coping with counter wrap-around and resets and keeping use 3338 counts. It relies on the driver to generate vertical blanking interrupts 3339 and optionally provide a hardware vertical blanking counter. Drivers must 3340 implement the following operations. 3341 </para> 3342 <itemizedlist> 3343 <listitem> 3344 <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc); 3345void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis> 3346 <para> 3347 Enable or disable vertical blanking interrupts for the given CRTC. 3348 </para> 3349 </listitem> 3350 <listitem> 3351 <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis> 3352 <para> 3353 Retrieve the value of the vertical blanking counter for the given 3354 CRTC. If the hardware maintains a vertical blanking counter its value 3355 should be returned. Otherwise drivers can use the 3356 <function>drm_vblank_count</function> helper function to handle this 3357 operation. 3358 </para> 3359 </listitem> 3360 </itemizedlist> 3361 <para> 3362 Drivers must initialize the vertical blanking handling core with a call to 3363 <function>drm_vblank_init</function> in their 3364 <methodname>load</methodname> operation. The function will set the struct 3365 <structname>drm_device</structname> 3366 <structfield>vblank_disable_allowed</structfield> field to 0. This will 3367 keep vertical blanking interrupts enabled permanently until the first mode 3368 set operation, where <structfield>vblank_disable_allowed</structfield> is 3369 set to 1. The reason behind this is not clear. Drivers can set the field 3370 to 1 after <function>calling drm_vblank_init</function> to make vertical 3371 blanking interrupts dynamically managed from the beginning. 3372 </para> 3373 <para> 3374 Vertical blanking interrupts can be enabled by the DRM core or by drivers 3375 themselves (for instance to handle page flipping operations). The DRM core 3376 maintains a vertical blanking use count to ensure that the interrupts are 3377 not disabled while a user still needs them. To increment the use count, 3378 drivers call <function>drm_vblank_get</function>. Upon return vertical 3379 blanking interrupts are guaranteed to be enabled. 3380 </para> 3381 <para> 3382 To decrement the use count drivers call 3383 <function>drm_vblank_put</function>. Only when the use count drops to zero 3384 will the DRM core disable the vertical blanking interrupts after a delay 3385 by scheduling a timer. The delay is accessible through the vblankoffdelay 3386 module parameter or the <varname>drm_vblank_offdelay</varname> global 3387 variable and expressed in milliseconds. Its default value is 5000 ms. 3388 Zero means never disable, and a negative value means disable immediately. 3389 Drivers may override the behaviour by setting the 3390 <structname>drm_device</structname> 3391 <structfield>vblank_disable_immediate</structfield> flag, which when set 3392 causes vblank interrupts to be disabled immediately regardless of the 3393 drm_vblank_offdelay value. The flag should only be set if there's a 3394 properly working hardware vblank counter present. 3395 </para> 3396 <para> 3397 When a vertical blanking interrupt occurs drivers only need to call the 3398 <function>drm_handle_vblank</function> function to account for the 3399 interrupt. 3400 </para> 3401 <para> 3402 Resources allocated by <function>drm_vblank_init</function> must be freed 3403 with a call to <function>drm_vblank_cleanup</function> in the driver 3404 <methodname>unload</methodname> operation handler. 3405 </para> 3406 <sect2> 3407 <title>Vertical Blanking and Interrupt Handling Functions Reference</title> 3408!Edrivers/gpu/drm/drm_irq.c 3409!Finclude/drm/drmP.h drm_crtc_vblank_waitqueue 3410 </sect2> 3411 </sect1> 3412 3413 <!-- Internals: open/close, file operations and ioctls --> 3414 3415 <sect1> 3416 <title>Open/Close, File Operations and IOCTLs</title> 3417 <sect2> 3418 <title>Open and Close</title> 3419 <synopsis>int (*firstopen) (struct drm_device *); 3420void (*lastclose) (struct drm_device *); 3421int (*open) (struct drm_device *, struct drm_file *); 3422void (*preclose) (struct drm_device *, struct drm_file *); 3423void (*postclose) (struct drm_device *, struct drm_file *);</synopsis> 3424 <abstract>Open and close handlers. None of those methods are mandatory. 3425 </abstract> 3426 <para> 3427 The <methodname>firstopen</methodname> method is called by the DRM core 3428 for legacy UMS (User Mode Setting) drivers only when an application 3429 opens a device that has no other opened file handle. UMS drivers can 3430 implement it to acquire device resources. KMS drivers can't use the 3431 method and must acquire resources in the <methodname>load</methodname> 3432 method instead. 3433 </para> 3434 <para> 3435 Similarly the <methodname>lastclose</methodname> method is called when 3436 the last application holding a file handle opened on the device closes 3437 it, for both UMS and KMS drivers. Additionally, the method is also 3438 called at module unload time or, for hot-pluggable devices, when the 3439 device is unplugged. The <methodname>firstopen</methodname> and 3440 <methodname>lastclose</methodname> calls can thus be unbalanced. 3441 </para> 3442 <para> 3443 The <methodname>open</methodname> method is called every time the device 3444 is opened by an application. Drivers can allocate per-file private data 3445 in this method and store them in the struct 3446 <structname>drm_file</structname> <structfield>driver_priv</structfield> 3447 field. Note that the <methodname>open</methodname> method is called 3448 before <methodname>firstopen</methodname>. 3449 </para> 3450 <para> 3451 The close operation is split into <methodname>preclose</methodname> and 3452 <methodname>postclose</methodname> methods. Drivers must stop and 3453 cleanup all per-file operations in the <methodname>preclose</methodname> 3454 method. For instance pending vertical blanking and page flip events must 3455 be cancelled. No per-file operation is allowed on the file handle after 3456 returning from the <methodname>preclose</methodname> method. 3457 </para> 3458 <para> 3459 Finally the <methodname>postclose</methodname> method is called as the 3460 last step of the close operation, right before calling the 3461 <methodname>lastclose</methodname> method if no other open file handle 3462 exists for the device. Drivers that have allocated per-file private data 3463 in the <methodname>open</methodname> method should free it here. 3464 </para> 3465 <para> 3466 The <methodname>lastclose</methodname> method should restore CRTC and 3467 plane properties to default value, so that a subsequent open of the 3468 device will not inherit state from the previous user. It can also be 3469 used to execute delayed power switching state changes, e.g. in 3470 conjunction with the vga-switcheroo infrastructure. Beyond that KMS 3471 drivers should not do any further cleanup. Only legacy UMS drivers might 3472 need to clean up device state so that the vga console or an independent 3473 fbdev driver could take over. 3474 </para> 3475 </sect2> 3476 <sect2> 3477 <title>File Operations</title> 3478 <synopsis>const struct file_operations *fops</synopsis> 3479 <abstract>File operations for the DRM device node.</abstract> 3480 <para> 3481 Drivers must define the file operations structure that forms the DRM 3482 userspace API entry point, even though most of those operations are 3483 implemented in the DRM core. The <methodname>open</methodname>, 3484 <methodname>release</methodname> and <methodname>ioctl</methodname> 3485 operations are handled by 3486 <programlisting> 3487 .owner = THIS_MODULE, 3488 .open = drm_open, 3489 .release = drm_release, 3490 .unlocked_ioctl = drm_ioctl, 3491 #ifdef CONFIG_COMPAT 3492 .compat_ioctl = drm_compat_ioctl, 3493 #endif 3494 </programlisting> 3495 </para> 3496 <para> 3497 Drivers that implement private ioctls that requires 32/64bit 3498 compatibility support must provide their own 3499 <methodname>compat_ioctl</methodname> handler that processes private 3500 ioctls and calls <function>drm_compat_ioctl</function> for core ioctls. 3501 </para> 3502 <para> 3503 The <methodname>read</methodname> and <methodname>poll</methodname> 3504 operations provide support for reading DRM events and polling them. They 3505 are implemented by 3506 <programlisting> 3507 .poll = drm_poll, 3508 .read = drm_read, 3509 .llseek = no_llseek, 3510 </programlisting> 3511 </para> 3512 <para> 3513 The memory mapping implementation varies depending on how the driver 3514 manages memory. Pre-GEM drivers will use <function>drm_mmap</function>, 3515 while GEM-aware drivers will use <function>drm_gem_mmap</function>. See 3516 <xref linkend="drm-gem"/>. 3517 <programlisting> 3518 .mmap = drm_gem_mmap, 3519 </programlisting> 3520 </para> 3521 <para> 3522 No other file operation is supported by the DRM API. 3523 </para> 3524 </sect2> 3525 <sect2> 3526 <title>IOCTLs</title> 3527 <synopsis>struct drm_ioctl_desc *ioctls; 3528int num_ioctls;</synopsis> 3529 <abstract>Driver-specific ioctls descriptors table.</abstract> 3530 <para> 3531 Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls 3532 descriptors table is indexed by the ioctl number offset from the base 3533 value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the 3534 table entries. 3535 </para> 3536 <para> 3537 <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting> 3538 <para> 3539 <parameter>ioctl</parameter> is the ioctl name. Drivers must define 3540 the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number 3541 offset from DRM_COMMAND_BASE and the ioctl number respectively. The 3542 first macro is private to the device while the second must be exposed 3543 to userspace in a public header. 3544 </para> 3545 <para> 3546 <parameter>func</parameter> is a pointer to the ioctl handler function 3547 compatible with the <type>drm_ioctl_t</type> type. 3548 <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data, 3549 struct drm_file *file_priv);</programlisting> 3550 </para> 3551 <para> 3552 <parameter>flags</parameter> is a bitmask combination of the following 3553 values. It restricts how the ioctl is allowed to be called. 3554 <itemizedlist> 3555 <listitem><para> 3556 DRM_AUTH - Only authenticated callers allowed 3557 </para></listitem> 3558 <listitem><para> 3559 DRM_MASTER - The ioctl can only be called on the master file 3560 handle 3561 </para></listitem> 3562 <listitem><para> 3563 DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed 3564 </para></listitem> 3565 <listitem><para> 3566 DRM_CONTROL_ALLOW - The ioctl can only be called on a control 3567 device 3568 </para></listitem> 3569 <listitem><para> 3570 DRM_UNLOCKED - The ioctl handler will be called without locking 3571 the DRM global mutex 3572 </para></listitem> 3573 </itemizedlist> 3574 </para> 3575 </para> 3576 </sect2> 3577 </sect1> 3578 <sect1> 3579 <title>Legacy Support Code</title> 3580 <para> 3581 The section very briefly covers some of the old legacy support code which 3582 is only used by old DRM drivers which have done a so-called shadow-attach 3583 to the underlying device instead of registering as a real driver. This 3584 also includes some of the old generic buffer management and command 3585 submission code. Do not use any of this in new and modern drivers. 3586 </para> 3587 3588 <sect2> 3589 <title>Legacy Suspend/Resume</title> 3590 <para> 3591 The DRM core provides some suspend/resume code, but drivers wanting full 3592 suspend/resume support should provide save() and restore() functions. 3593 These are called at suspend, hibernate, or resume time, and should perform 3594 any state save or restore required by your device across suspend or 3595 hibernate states. 3596 </para> 3597 <synopsis>int (*suspend) (struct drm_device *, pm_message_t state); 3598 int (*resume) (struct drm_device *);</synopsis> 3599 <para> 3600 Those are legacy suspend and resume methods which 3601 <emphasis>only</emphasis> work with the legacy shadow-attach driver 3602 registration functions. New driver should use the power management 3603 interface provided by their bus type (usually through 3604 the struct <structname>device_driver</structname> dev_pm_ops) and set 3605 these methods to NULL. 3606 </para> 3607 </sect2> 3608 3609 <sect2> 3610 <title>Legacy DMA Services</title> 3611 <para> 3612 This should cover how DMA mapping etc. is supported by the core. 3613 These functions are deprecated and should not be used. 3614 </para> 3615 </sect2> 3616 </sect1> 3617 </chapter> 3618 3619<!-- TODO 3620 3621- Add a glossary 3622- Document the struct_mutex catch-all lock 3623- Document connector properties 3624 3625- Why is the load method optional? 3626- What are drivers supposed to set the initial display state to, and how? 3627 Connector's DPMS states are not initialized and are thus equal to 3628 DRM_MODE_DPMS_ON. The fbcon compatibility layer calls 3629 drm_helper_disable_unused_functions(), which disables unused encoders and 3630 CRTCs, but doesn't touch the connectors' DPMS state, and 3631 drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers 3632 that don't implement (or just don't use) fbcon compatibility need to call 3633 those functions themselves? 3634- KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset() 3635 around mode setting. Should this be done in the DRM core? 3636- vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset() 3637 call and never set back to 0. It seems to be safe to permanently set it to 1 3638 in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as 3639 well. This should be investigated. 3640- crtc and connector .save and .restore operations are only used internally in 3641 drivers, should they be removed from the core? 3642- encoder mid-layer .save and .restore operations are only used internally in 3643 drivers, should they be removed from the core? 3644- encoder mid-layer .detect operation is only used internally in drivers, 3645 should it be removed from the core? 3646--> 3647 3648 <!-- External interfaces --> 3649 3650 <chapter id="drmExternals"> 3651 <title>Userland interfaces</title> 3652 <para> 3653 The DRM core exports several interfaces to applications, 3654 generally intended to be used through corresponding libdrm 3655 wrapper functions. In addition, drivers export device-specific 3656 interfaces for use by userspace drivers & device-aware 3657 applications through ioctls and sysfs files. 3658 </para> 3659 <para> 3660 External interfaces include: memory mapping, context management, 3661 DMA operations, AGP management, vblank control, fence 3662 management, memory management, and output management. 3663 </para> 3664 <para> 3665 Cover generic ioctls and sysfs layout here. We only need high-level 3666 info, since man pages should cover the rest. 3667 </para> 3668 3669 <!-- External: render nodes --> 3670 3671 <sect1> 3672 <title>Render nodes</title> 3673 <para> 3674 DRM core provides multiple character-devices for user-space to use. 3675 Depending on which device is opened, user-space can perform a different 3676 set of operations (mainly ioctls). The primary node is always created 3677 and called card<num>. Additionally, a currently 3678 unused control node, called controlD<num> is also 3679 created. The primary node provides all legacy operations and 3680 historically was the only interface used by userspace. With KMS, the 3681 control node was introduced. However, the planned KMS control interface 3682 has never been written and so the control node stays unused to date. 3683 </para> 3684 <para> 3685 With the increased use of offscreen renderers and GPGPU applications, 3686 clients no longer require running compositors or graphics servers to 3687 make use of a GPU. But the DRM API required unprivileged clients to 3688 authenticate to a DRM-Master prior to getting GPU access. To avoid this 3689 step and to grant clients GPU access without authenticating, render 3690 nodes were introduced. Render nodes solely serve render clients, that 3691 is, no modesetting or privileged ioctls can be issued on render nodes. 3692 Only non-global rendering commands are allowed. If a driver supports 3693 render nodes, it must advertise it via the DRIVER_RENDER 3694 DRM driver capability. If not supported, the primary node must be used 3695 for render clients together with the legacy drmAuth authentication 3696 procedure. 3697 </para> 3698 <para> 3699 If a driver advertises render node support, DRM core will create a 3700 separate render node called renderD<num>. There will 3701 be one render node per device. No ioctls except PRIME-related ioctls 3702 will be allowed on this node. Especially GEM_OPEN will be 3703 explicitly prohibited. Render nodes are designed to avoid the 3704 buffer-leaks, which occur if clients guess the flink names or mmap 3705 offsets on the legacy interface. Additionally to this basic interface, 3706 drivers must mark their driver-dependent render-only ioctls as 3707 DRM_RENDER_ALLOW so render clients can use them. Driver 3708 authors must be careful not to allow any privileged ioctls on render 3709 nodes. 3710 </para> 3711 <para> 3712 With render nodes, user-space can now control access to the render node 3713 via basic file-system access-modes. A running graphics server which 3714 authenticates clients on the privileged primary/legacy node is no longer 3715 required. Instead, a client can open the render node and is immediately 3716 granted GPU access. Communication between clients (or servers) is done 3717 via PRIME. FLINK from render node to legacy node is not supported. New 3718 clients must not use the insecure FLINK interface. 3719 </para> 3720 <para> 3721 Besides dropping all modeset/global ioctls, render nodes also drop the 3722 DRM-Master concept. There is no reason to associate render clients with 3723 a DRM-Master as they are independent of any graphics server. Besides, 3724 they must work without any running master, anyway. 3725 Drivers must be able to run without a master object if they support 3726 render nodes. If, on the other hand, a driver requires shared state 3727 between clients which is visible to user-space and accessible beyond 3728 open-file boundaries, they cannot support render nodes. 3729 </para> 3730 </sect1> 3731 3732 <!-- External: vblank handling --> 3733 3734 <sect1> 3735 <title>VBlank event handling</title> 3736 <para> 3737 The DRM core exposes two vertical blank related ioctls: 3738 <variablelist> 3739 <varlistentry> 3740 <term>DRM_IOCTL_WAIT_VBLANK</term> 3741 <listitem> 3742 <para> 3743 This takes a struct drm_wait_vblank structure as its argument, 3744 and it is used to block or request a signal when a specified 3745 vblank event occurs. 3746 </para> 3747 </listitem> 3748 </varlistentry> 3749 <varlistentry> 3750 <term>DRM_IOCTL_MODESET_CTL</term> 3751 <listitem> 3752 <para> 3753 This was only used for user-mode-settind drivers around 3754 modesetting changes to allow the kernel to update the vblank 3755 interrupt after mode setting, since on many devices the vertical 3756 blank counter is reset to 0 at some point during modeset. Modern 3757 drivers should not call this any more since with kernel mode 3758 setting it is a no-op. 3759 </para> 3760 </listitem> 3761 </varlistentry> 3762 </variablelist> 3763 </para> 3764 </sect1> 3765 3766 </chapter> 3767</part> 3768<part id="drmDrivers"> 3769 <title>DRM Drivers</title> 3770 3771 <partintro> 3772 <para> 3773 This second part of the DRM Developer's Guide documents driver code, 3774 implementation details and also all the driver-specific userspace 3775 interfaces. Especially since all hardware-acceleration interfaces to 3776 userspace are driver specific for efficiency and other reasons these 3777 interfaces can be rather substantial. Hence every driver has its own 3778 chapter. 3779 </para> 3780 </partintro> 3781 3782 <chapter id="drmI915"> 3783 <title>drm/i915 Intel GFX Driver</title> 3784 <para> 3785 The drm/i915 driver supports all (with the exception of some very early 3786 models) integrated GFX chipsets with both Intel display and rendering 3787 blocks. This excludes a set of SoC platforms with an SGX rendering unit, 3788 those have basic support through the gma500 drm driver. 3789 </para> 3790 <sect1> 3791 <title>Display Hardware Handling</title> 3792 <para> 3793 This section covers everything related to the display hardware including 3794 the mode setting infrastructure, plane, sprite and cursor handling and 3795 display, output probing and related topics. 3796 </para> 3797 <sect2> 3798 <title>Mode Setting Infrastructure</title> 3799 <para> 3800 The i915 driver is thus far the only DRM driver which doesn't use the 3801 common DRM helper code to implement mode setting sequences. Thus it 3802 has its own tailor-made infrastructure for executing a display 3803 configuration change. 3804 </para> 3805 </sect2> 3806 <sect2> 3807 <title>Plane Configuration</title> 3808 <para> 3809 This section covers plane configuration and composition with the 3810 primary plane, sprites, cursors and overlays. This includes the 3811 infrastructure to do atomic vsync'ed updates of all this state and 3812 also tightly coupled topics like watermark setup and computation, 3813 framebuffer compression and panel self refresh. 3814 </para> 3815 </sect2> 3816 <sect2> 3817 <title>Output Probing</title> 3818 <para> 3819 This section covers output probing and related infrastructure like the 3820 hotplug interrupt storm detection and mitigation code. Note that the 3821 i915 driver still uses most of the common DRM helper code for output 3822 probing, so those sections fully apply. 3823 </para> 3824 </sect2> 3825 <sect2> 3826 <title>DPIO</title> 3827!Pdrivers/gpu/drm/i915/i915_reg.h DPIO 3828 <table id="dpiox2"> 3829 <title>Dual channel PHY (VLV/CHV)</title> 3830 <tgroup cols="8"> 3831 <colspec colname="c0" /> 3832 <colspec colname="c1" /> 3833 <colspec colname="c2" /> 3834 <colspec colname="c3" /> 3835 <colspec colname="c4" /> 3836 <colspec colname="c5" /> 3837 <colspec colname="c6" /> 3838 <colspec colname="c7" /> 3839 <spanspec spanname="ch0" namest="c0" nameend="c3" /> 3840 <spanspec spanname="ch1" namest="c4" nameend="c7" /> 3841 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" /> 3842 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" /> 3843 <spanspec spanname="ch1pcs01" namest="c4" nameend="c5" /> 3844 <spanspec spanname="ch1pcs23" namest="c6" nameend="c7" /> 3845 <thead> 3846 <row> 3847 <entry spanname="ch0">CH0</entry> 3848 <entry spanname="ch1">CH1</entry> 3849 </row> 3850 </thead> 3851 <tbody valign="top" align="center"> 3852 <row> 3853 <entry spanname="ch0">CMN/PLL/REF</entry> 3854 <entry spanname="ch1">CMN/PLL/REF</entry> 3855 </row> 3856 <row> 3857 <entry spanname="ch0pcs01">PCS01</entry> 3858 <entry spanname="ch0pcs23">PCS23</entry> 3859 <entry spanname="ch1pcs01">PCS01</entry> 3860 <entry spanname="ch1pcs23">PCS23</entry> 3861 </row> 3862 <row> 3863 <entry>TX0</entry> 3864 <entry>TX1</entry> 3865 <entry>TX2</entry> 3866 <entry>TX3</entry> 3867 <entry>TX0</entry> 3868 <entry>TX1</entry> 3869 <entry>TX2</entry> 3870 <entry>TX3</entry> 3871 </row> 3872 <row> 3873 <entry spanname="ch0">DDI0</entry> 3874 <entry spanname="ch1">DDI1</entry> 3875 </row> 3876 </tbody> 3877 </tgroup> 3878 </table> 3879 <table id="dpiox1"> 3880 <title>Single channel PHY (CHV)</title> 3881 <tgroup cols="4"> 3882 <colspec colname="c0" /> 3883 <colspec colname="c1" /> 3884 <colspec colname="c2" /> 3885 <colspec colname="c3" /> 3886 <spanspec spanname="ch0" namest="c0" nameend="c3" /> 3887 <spanspec spanname="ch0pcs01" namest="c0" nameend="c1" /> 3888 <spanspec spanname="ch0pcs23" namest="c2" nameend="c3" /> 3889 <thead> 3890 <row> 3891 <entry spanname="ch0">CH0</entry> 3892 </row> 3893 </thead> 3894 <tbody valign="top" align="center"> 3895 <row> 3896 <entry spanname="ch0">CMN/PLL/REF</entry> 3897 </row> 3898 <row> 3899 <entry spanname="ch0pcs01">PCS01</entry> 3900 <entry spanname="ch0pcs23">PCS23</entry> 3901 </row> 3902 <row> 3903 <entry>TX0</entry> 3904 <entry>TX1</entry> 3905 <entry>TX2</entry> 3906 <entry>TX3</entry> 3907 </row> 3908 <row> 3909 <entry spanname="ch0">DDI2</entry> 3910 </row> 3911 </tbody> 3912 </tgroup> 3913 </table> 3914 </sect2> 3915 </sect1> 3916 3917 <sect1> 3918 <title>Memory Management and Command Submission</title> 3919 <para> 3920 This sections covers all things related to the GEM implementation in the 3921 i915 driver. 3922 </para> 3923 <sect2> 3924 <title>Batchbuffer Parsing</title> 3925!Pdrivers/gpu/drm/i915/i915_cmd_parser.c batch buffer command parser 3926!Idrivers/gpu/drm/i915/i915_cmd_parser.c 3927 </sect2> 3928 <sect2> 3929 <title>Logical Rings, Logical Ring Contexts and Execlists</title> 3930!Pdrivers/gpu/drm/i915/intel_lrc.c Logical Rings, Logical Ring Contexts and Execlists 3931!Idrivers/gpu/drm/i915/intel_lrc.c 3932 </sect2> 3933 </sect1> 3934 </chapter> 3935</part> 3936</book> 3937