Blame view
Documentation/DocBook/drm.tmpl
115 KB
2d2ef8227 drm: add initial ... |
1 2 3 4 5 6 7 |
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> <book id="drmDevelopersGuide"> <bookinfo> <title>Linux DRM Developer's Guide</title> |
9cad9c95d Documentation: Do... |
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 |
<authorgroup> <author> <firstname>Jesse</firstname> <surname>Barnes</surname> <contrib>Initial version</contrib> <affiliation> <orgname>Intel Corporation</orgname> <address> <email>jesse.barnes@intel.com</email> </address> </affiliation> </author> <author> <firstname>Laurent</firstname> <surname>Pinchart</surname> <contrib>Driver internals</contrib> <affiliation> <orgname>Ideas on board SPRL</orgname> <address> <email>laurent.pinchart@ideasonboard.com</email> </address> </affiliation> </author> </authorgroup> |
2d2ef8227 drm: add initial ... |
32 33 |
<copyright> <year>2008-2009</year> |
9cad9c95d Documentation: Do... |
34 35 36 |
<year>2012</year> <holder>Intel Corporation</holder> <holder>Laurent Pinchart</holder> |
2d2ef8227 drm: add initial ... |
37 38 39 40 41 42 43 44 45 |
</copyright> <legalnotice> <para> The contents of this file may be used under the terms of the GNU General Public License version 2 (the "GPL") as distributed in the kernel source COPYING file. </para> </legalnotice> |
9cad9c95d Documentation: Do... |
46 47 48 49 50 51 52 53 54 55 56 |
<revhistory> <!-- Put document revisions here, newest first. --> <revision> <revnumber>1.0</revnumber> <date>2012-07-13</date> <authorinitials>LP</authorinitials> <revremark>Added extensive documentation about driver internals. </revremark> </revision> </revhistory> |
2d2ef8227 drm: add initial ... |
57 58 59 60 61 62 63 64 65 66 67 68 |
</bookinfo> <toc></toc> <!-- Introduction --> <chapter id="drmIntroduction"> <title>Introduction</title> <para> The Linux DRM layer contains code intended to support the needs of complex graphics devices, usually containing programmable pipelines well suited to 3D graphics acceleration. Graphics |
f11aca045 DocBook/drm: can ... |
69 |
drivers in the kernel may make use of DRM functions to make |
2d2ef8227 drm: add initial ... |
70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 |
tasks like memory management, interrupt handling and DMA easier, and provide a uniform interface to applications. </para> <para> A note on versions: this guide covers features found in the DRM tree, including the TTM memory manager, output configuration and mode setting, and the new vblank internals, in addition to all the regular features found in current kernels. </para> <para> [Insert diagram of typical DRM stack here] </para> </chapter> <!-- Internals --> <chapter id="drmInternals"> <title>DRM Internals</title> <para> This chapter documents DRM internals relevant to driver authors and developers working to add support for the latest features to existing drivers. </para> <para> |
a78f6787a DocBook/drm: Erad... |
94 |
First, we go over some typical driver initialization |
2d2ef8227 drm: add initial ... |
95 96 |
requirements, like setting up command buffers, creating an initial output configuration, and initializing core services. |
a78f6787a DocBook/drm: Erad... |
97 |
Subsequent sections cover core internals in more detail, |
2d2ef8227 drm: add initial ... |
98 99 100 101 102 103 104 105 106 107 108 |
providing implementation notes and examples. </para> <para> The DRM layer provides several services to graphics drivers, many of them driven by the application interfaces it provides through libdrm, the library that wraps most of the DRM ioctls. These include vblank event handling, memory management, output management, framebuffer management, command submission & fencing, suspend/resume support, and DMA services. </para> |
2d2ef8227 drm: add initial ... |
109 110 111 112 |
<!-- Internals: driver init --> <sect1> |
9cad9c95d Documentation: Do... |
113 114 115 116 117 118 |
<title>Driver Initialization</title> <para> At the core of every DRM driver is a <structname>drm_driver</structname> structure. Drivers typically statically initialize a drm_driver structure, and then pass it to one of the <function>drm_*_init()</function> functions to register it with the DRM subsystem. |
2d2ef8227 drm: add initial ... |
119 |
</para> |
9cad9c95d Documentation: Do... |
120 121 122 123 124 125 126 |
<para> The <structname>drm_driver</structname> structure contains static information that describes the driver and features it supports, and pointers to methods that the DRM core will call to implement the DRM API. We will first go through the <structname>drm_driver</structname> static information fields, and will then describe individual operations in details as they get used in later sections. |
2d2ef8227 drm: add initial ... |
127 |
</para> |
2d2ef8227 drm: add initial ... |
128 |
<sect2> |
9cad9c95d Documentation: Do... |
129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 |
<title>Driver Information</title> <sect3> <title>Driver Features</title> <para> Drivers inform the DRM core about their requirements and supported features by setting appropriate flags in the <structfield>driver_features</structfield> field. Since those flags influence the DRM core behaviour since registration time, most of them must be set to registering the <structname>drm_driver</structname> instance. </para> <synopsis>u32 driver_features;</synopsis> <variablelist> <title>Driver Feature Flags</title> <varlistentry> <term>DRIVER_USE_AGP</term> <listitem><para> Driver uses AGP interface, the DRM core will manage AGP resources. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_REQUIRE_AGP</term> <listitem><para> Driver needs AGP interface to function. AGP initialization failure will become a fatal error. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_USE_MTRR</term> <listitem><para> Driver uses MTRR interface for mapping memory, the DRM core will manage MTRR resources. Deprecated. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_PCI_DMA</term> <listitem><para> Driver is capable of PCI DMA, mapping of PCI DMA buffers to userspace will be enabled. Deprecated. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_SG</term> <listitem><para> Driver can perform scatter/gather DMA, allocation and mapping of scatter/gather buffers will be enabled. Deprecated. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_HAVE_DMA</term> <listitem><para> Driver supports DMA, the userspace DMA API will be supported. Deprecated. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term> <listitem><para> DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler. The DRM core will automatically register an interrupt handler when the flag is set. DRIVER_IRQ_SHARED indicates whether the device & handler support shared IRQs (note that this is required of PCI drivers). </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_IRQ_VBL</term> <listitem><para>Unused. Deprecated.</para></listitem> </varlistentry> <varlistentry> <term>DRIVER_DMA_QUEUE</term> <listitem><para> Should be set if the driver queues DMA requests and completes them asynchronously. Deprecated. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_FB_DMA</term> <listitem><para> Driver supports DMA to/from the framebuffer, mapping of frambuffer DMA buffers to userspace will be supported. Deprecated. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_IRQ_VBL2</term> <listitem><para>Unused. Deprecated.</para></listitem> </varlistentry> <varlistentry> <term>DRIVER_GEM</term> <listitem><para> Driver use the GEM memory manager. </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_MODESET</term> <listitem><para> Driver supports mode setting interfaces (KMS). </para></listitem> </varlistentry> <varlistentry> <term>DRIVER_PRIME</term> <listitem><para> Driver implements DRM PRIME buffer sharing. </para></listitem> </varlistentry> </variablelist> </sect3> <sect3> <title>Major, Minor and Patchlevel</title> <synopsis>int major; int minor; int patchlevel;</synopsis> <para> The DRM core identifies driver versions by a major, minor and patch level triplet. The information is printed to the kernel log at initialization time and passed to userspace through the DRM_IOCTL_VERSION ioctl. </para> <para> The major and minor numbers are also used to verify the requested driver API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes between minor versions, applications can call DRM_IOCTL_SET_VERSION to select a specific version of the API. If the requested major isn't equal to the driver major, or the requested minor is larger than the driver minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise the driver's set_version() method will be called with the requested version. </para> </sect3> <sect3> <title>Name, Description and Date</title> <synopsis>char *name; char *desc; char *date;</synopsis> <para> The driver name is printed to the kernel log at initialization time, used for IRQ registration and passed to userspace through DRM_IOCTL_VERSION. </para> <para> The driver description is a purely informative string passed to userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by the kernel. </para> <para> The driver date, formatted as YYYYMMDD, is meant to identify the date of the latest modification to the driver. However, as most drivers fail to update it, its value is mostly useless. The DRM core prints it to the kernel log at initialization time and passes it to userspace through the DRM_IOCTL_VERSION ioctl. </para> </sect3> </sect2> <sect2> <title>Driver Load</title> |
2d2ef8227 drm: add initial ... |
284 |
<para> |
9cad9c95d Documentation: Do... |
285 286 287 288 289 290 291 292 293 294 |
The <methodname>load</methodname> method is the driver and device initialization entry point. The method is responsible for allocating and initializing driver private data, specifying supported performance counters, performing resource allocation and mapping (e.g. acquiring clocks, mapping registers or allocating command buffers), initializing the memory manager (<xref linkend="drm-memory-management"/>), installing the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode setting (<xref linkend="drm-mode-setting"/>) and initial output configuration (<xref linkend="drm-kms-init"/>). |
2d2ef8227 drm: add initial ... |
295 |
</para> |
9cad9c95d Documentation: Do... |
296 297 298 299 300 301 302 303 304 305 306 307 308 |
<note><para> If compatibility is a concern (e.g. with drivers converted over from User Mode Setting to Kernel Mode Setting), care must be taken to prevent device initialization and control that is incompatible with currently active userspace drivers. For instance, if user level mode setting drivers are in use, it would be problematic to perform output discovery & configuration at load time. Likewise, if user-level drivers unaware of memory management are in use, memory management and command buffer setup may need to be omitted. These requirements are driver-specific, and care needs to be taken to keep both old and new applications and libraries working. </para></note> <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis> |
2d2ef8227 drm: add initial ... |
309 |
<para> |
9cad9c95d Documentation: Do... |
310 311 312 313 314 315 |
The method takes two arguments, a pointer to the newly created <structname>drm_device</structname> and flags. The flags are used to pass the <structfield>driver_data</structfield> field of the device id corresponding to the device passed to <function>drm_*_init()</function>. Only PCI devices currently use this, USB and platform DRM drivers have their <methodname>load</methodname> method called with flags to 0. |
2d2ef8227 drm: add initial ... |
316 |
</para> |
9cad9c95d Documentation: Do... |
317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 |
<sect3> <title>Driver Private & Performance Counters</title> <para> The driver private hangs off the main <structname>drm_device</structname> structure and can be used for tracking various device-specific bits of information, like register offsets, command buffer status, register state for suspend/resume, etc. At load time, a driver may simply allocate one and set <structname>drm_device</structname>.<structfield>dev_priv</structfield> appropriately; it should be freed and <structname>drm_device</structname>.<structfield>dev_priv</structfield> set to NULL when the driver is unloaded. </para> <para> DRM supports several counters which were used for rough performance characterization. This stat counter system is deprecated and should not be used. If performance monitoring is desired, the developer should investigate and potentially enhance the kernel perf and tracing infrastructure to export GPU related performance information for consumption by performance monitoring tools and applications. </para> </sect3> <sect3 id="drm-irq-registration"> <title>IRQ Registration</title> <para> The DRM core tries to facilitate IRQ handler registration and unregistration by providing <function>drm_irq_install</function> and <function>drm_irq_uninstall</function> functions. Those functions only support a single interrupt per device. </para> <!--!Fdrivers/char/drm/drm_irq.c drm_irq_install--> <para> Both functions get the device IRQ by calling <function>drm_dev_to_irq</function>. This inline function will call a bus-specific operation to retrieve the IRQ number. For platform devices, <function>platform_get_irq</function>(..., 0) is used to retrieve the IRQ number. </para> <para> <function>drm_irq_install</function> starts by calling the <methodname>irq_preinstall</methodname> driver operation. The operation is optional and must make sure that the interrupt will not get fired by clearing all pending interrupt flags or disabling the interrupt. </para> <para> The IRQ will then be requested by a call to <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver feature flag is set, a shared (IRQF_SHARED) IRQ handler will be requested. </para> <para> The IRQ handler function must be provided as the mandatory irq_handler driver operation. It will get passed directly to <function>request_irq</function> and thus has the same prototype as all IRQ handlers. It will get called with a pointer to the DRM device as the second argument. </para> <para> Finally the function calls the optional <methodname>irq_postinstall</methodname> driver operation. The operation usually enables interrupts (excluding the vblank interrupt, which is enabled separately), but drivers may choose to enable/disable interrupts at a different time. </para> <para> <function>drm_irq_uninstall</function> is similarly used to uninstall an IRQ handler. It starts by waking up all processes waiting on a vblank interrupt to make sure they don't hang, and then calls the optional <methodname>irq_uninstall</methodname> driver operation. The operation must disable all hardware interrupts. Finally the function frees the IRQ by calling <function>free_irq</function>. </para> </sect3> <sect3> <title>Memory Manager Initialization</title> <para> Every DRM driver requires a memory manager which must be initialized at load time. DRM currently contains two memory managers, the Translation Table Manager (TTM) and the Graphics Execution Manager (GEM). This document describes the use of the GEM memory manager only. See <xref linkend="drm-memory-management"/> for details. </para> </sect3> <sect3> <title>Miscellaneous Device Configuration</title> <para> Another task that may be necessary for PCI devices during configuration is mapping the video BIOS. On many devices, the VBIOS describes device configuration, LCD panel timings (if any), and contains flags indicating device state. Mapping the BIOS can be done using the pci_map_rom() call, a convenience function that takes care of mapping the actual ROM, whether it has been shadowed into memory (typically at address 0xc0000) or exists on the PCI device in the ROM BAR. Note that after the ROM has been mapped and any necessary information has been extracted, it should be unmapped; on many devices, the ROM address decoder is shared with other BARs, so leaving it mapped could cause undesired behaviour like hangs or memory corruption. <!--!Fdrivers/pci/rom.c pci_map_rom--> </para> </sect3> |
2d2ef8227 drm: add initial ... |
417 |
</sect2> |
9cad9c95d Documentation: Do... |
418 |
</sect1> |
2d2ef8227 drm: add initial ... |
419 |
|
9cad9c95d Documentation: Do... |
420 |
<!-- Internals: memory management --> |
2d2ef8227 drm: add initial ... |
421 |
|
9cad9c95d Documentation: Do... |
422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 |
<sect1 id="drm-memory-management"> <title>Memory management</title> <para> Modern Linux systems require large amount of graphics memory to store frame buffers, textures, vertices and other graphics-related data. Given the very dynamic nature of many of that data, managing graphics memory efficiently is thus crucial for the graphics stack and plays a central role in the DRM infrastructure. </para> <para> The DRM core includes two memory managers, namely Translation Table Maps (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory manager to be developed and tried to be a one-size-fits-them all solution. It provides a single userspace API to accomodate the need of all hardware, supporting both Unified Memory Architecture (UMA) devices and devices with dedicated video RAM (i.e. most discrete video cards). This resulted in a large, complex piece of code that turned out to be hard to use for driver development. </para> <para> GEM started as an Intel-sponsored project in reaction to TTM's complexity. Its design philosophy is completely different: instead of providing a solution to every graphics memory-related problems, GEM identified common code between drivers and created a support library to share it. GEM has simpler initialization and execution requirements than TTM, but has no video RAM management capabitilies and is thus limited to UMA devices. </para> |
2d2ef8227 drm: add initial ... |
450 |
<sect2> |
9cad9c95d Documentation: Do... |
451 |
<title>The Translation Table Manager (TTM)</title> |
2d2ef8227 drm: add initial ... |
452 |
<para> |
9cad9c95d Documentation: Do... |
453 |
TTM design background and information belongs here. |
2d2ef8227 drm: add initial ... |
454 455 456 |
</para> <sect3> <title>TTM initialization</title> |
9cad9c95d Documentation: Do... |
457 458 459 460 461 462 463 |
<warning><para>This section is outdated.</para></warning> <para> Drivers wishing to support TTM must fill out a drm_bo_driver structure. The structure contains several fields with function pointers for initializing the TTM, allocating and freeing memory, waiting for command completion and fence synchronization, and memory migration. See the radeon_ttm.c file for an example of usage. |
2d2ef8227 drm: add initial ... |
464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 |
</para> <para> The ttm_global_reference structure is made up of several fields: </para> <programlisting> struct ttm_global_reference { enum ttm_global_types global_type; size_t size; void *object; int (*init) (struct ttm_global_reference *); void (*release) (struct ttm_global_reference *); }; </programlisting> <para> There should be one global reference structure for your memory manager as a whole, and there will be others for each object created by the memory manager at runtime. Your global TTM should have a type of TTM_GLOBAL_TTM_MEM. The size field for the global object should be sizeof(struct ttm_mem_global), and the init and |
a5294e01f DocBook/drm: `(de... |
483 |
release hooks should point at your driver-specific init and |
a78f6787a DocBook/drm: Erad... |
484 |
release routines, which probably eventually call |
005d7f4a0 DocBook/drm: Inse... |
485 |
ttm_mem_global_init and ttm_mem_global_release, respectively. |
2d2ef8227 drm: add initial ... |
486 487 488 |
</para> <para> Once your global TTM accounting structure is set up and initialized |
ae63d793a DocBook/drm: Inse... |
489 |
by calling ttm_global_item_ref() on it, |
1c86de221 DocBook/drm: Remo... |
490 |
you need to create a buffer object TTM to |
2d2ef8227 drm: add initial ... |
491 492 493 |
provide a pool for buffer object allocation by clients and the kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO, and its size should be sizeof(struct ttm_bo_global). Again, |
a5294e01f DocBook/drm: `(de... |
494 |
driver-specific init and release functions may be provided, |
ae63d793a DocBook/drm: Inse... |
495 496 497 |
likely eventually calling ttm_bo_global_init() and ttm_bo_global_release(), respectively. Also, like the previous object, ttm_global_item_ref() is used to create an initial reference |
ce04cc089 drm: fix typos in... |
498 |
count for the TTM, which will call your initialization function. |
2d2ef8227 drm: add initial ... |
499 500 |
</para> </sect3> |
9cad9c95d Documentation: Do... |
501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 |
</sect2> <sect2 id="drm-gem"> <title>The Graphics Execution Manager (GEM)</title> <para> The GEM design approach has resulted in a memory manager that doesn't provide full coverage of all (or even all common) use cases in its userspace or kernel API. GEM exposes a set of standard memory-related operations to userspace and a set of helper functions to drivers, and let drivers implement hardware-specific operations with their own private API. </para> <para> The GEM userspace API is described in the <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics Execution Manager</citetitle></ulink> article on LWN. While slightly outdated, the document provides a good overview of the GEM API principles. Buffer allocation and read and write operations, described as part of the common GEM API, are currently implemented using driver-specific ioctls. </para> <para> GEM is data-agnostic. It manages abstract buffer objects without knowing what individual buffers contain. APIs that require knowledge of buffer contents or purpose, such as buffer allocation or synchronization primitives, are thus outside of the scope of GEM and must be implemented using driver-specific ioctls. </para> <para> On a fundamental level, GEM involves several operations: <itemizedlist> <listitem>Memory allocation and freeing</listitem> <listitem>Command execution</listitem> <listitem>Aperture management at command execution time</listitem> </itemizedlist> Buffer object allocation is relatively straightforward and largely provided by Linux's shmem layer, which provides memory to back each object. </para> <para> Device-specific operations, such as command execution, pinning, buffer read & write, mapping, and domain ownership transfers are left to driver-specific ioctls. </para> <sect3> <title>GEM Initialization</title> <para> Drivers that use GEM must set the DRIVER_GEM bit in the struct <structname>drm_driver</structname> <structfield>driver_features</structfield> field. The DRM core will then automatically initialize the GEM core before calling the <methodname>load</methodname> operation. Behind the scene, this will create a DRM Memory Manager object which provides an address space pool for object allocation. </para> <para> In a KMS configuration, drivers need to allocate and initialize a command ring buffer following core GEM initialization if required by the hardware. UMA devices usually have what is called a "stolen" memory region, which provides space for the initial framebuffer and large, contiguous memory regions required by the device. This space is typically not managed by GEM, and must be initialized separately into its own DRM MM object. </para> </sect3> |
2d2ef8227 drm: add initial ... |
563 |
<sect3> |
9cad9c95d Documentation: Do... |
564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 |
<title>GEM Objects Creation</title> <para> GEM splits creation of GEM objects and allocation of the memory that backs them in two distinct operations. </para> <para> GEM objects are represented by an instance of struct <structname>drm_gem_object</structname>. Drivers usually need to extend GEM objects with private information and thus create a driver-specific GEM object structure type that embeds an instance of struct <structname>drm_gem_object</structname>. </para> <para> To create a GEM object, a driver allocates memory for an instance of its specific GEM object type and initializes the embedded struct <structname>drm_gem_object</structname> with a call to <function>drm_gem_object_init</function>. The function takes a pointer to the DRM device, a pointer to the GEM object and the buffer object size in bytes. </para> <para> GEM uses shmem to allocate anonymous pageable memory. <function>drm_gem_object_init</function> will create an shmfs file of the requested size and store it into the struct <structname>drm_gem_object</structname> <structfield>filp</structfield> field. The memory is used as either main storage for the object when the graphics hardware uses system memory directly or as a backing store otherwise. </para> <para> Drivers are responsible for the actual physical pages allocation by calling <function>shmem_read_mapping_page_gfp</function> for each page. Note that they can decide to allocate pages when initializing the GEM object, or to delay allocation until the memory is needed (for instance when a page fault occurs as a result of a userspace memory access or when the driver needs to start a DMA transfer involving the memory). </para> <para> Anonymous pageable memory allocation is not always desired, for instance when the hardware requires physically contiguous system memory as is often the case in embedded devices. Drivers can create GEM objects with no shmfs backing (called private GEM objects) by initializing them with a call to <function>drm_gem_private_object_init</function> instead of <function>drm_gem_object_init</function>. Storage for private GEM objects must be managed by drivers. </para> <para> Drivers that do not need to extend GEM objects with private information can call the <function>drm_gem_object_alloc</function> function to allocate and initialize a struct <structname>drm_gem_object</structname> instance. The GEM core will call the optional driver <methodname>gem_init_object</methodname> operation after initializing the GEM object with <function>drm_gem_object_init</function>. <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis> </para> <para> No alloc-and-init function exists for private GEM objects. </para> </sect3> <sect3> <title>GEM Objects Lifetime</title> <para> All GEM objects are reference-counted by the GEM core. References can be acquired and release by <function>calling drm_gem_object_reference</function> and <function>drm_gem_object_unreference</function> respectively. The caller must hold the <structname>drm_device</structname> <structfield>struct_mutex</structfield> lock. As a convenience, GEM provides the <function>drm_gem_object_reference_unlocked</function> and <function>drm_gem_object_unreference_unlocked</function> functions that can be called without holding the lock. </para> <para> When the last reference to a GEM object is released the GEM core calls the <structname>drm_driver</structname> <methodname>gem_free_object</methodname> operation. That operation is mandatory for GEM-enabled drivers and must free the GEM object and all associated resources. </para> <para> <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis> Drivers are responsible for freeing all GEM object resources, including the resources created by the GEM core. If an mmap offset has been created for the object (in which case <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield> is not NULL) it must be freed by a call to <function>drm_gem_free_mmap_offset</function>. The shmfs backing store must be released by calling <function>drm_gem_object_release</function> (that function can safely be called if no shmfs backing store has been created). </para> </sect3> <sect3> <title>GEM Objects Naming</title> <para> Communication between userspace and the kernel refers to GEM objects using local handles, global names or, more recently, file descriptors. All of those are 32-bit integer values; the usual Linux kernel limits apply to the file descriptors. </para> <para> GEM handles are local to a DRM file. Applications get a handle to a GEM object through a driver-specific ioctl, and can use that handle to refer to the GEM object in other standard or driver-specific ioctls. Closing a DRM file handle frees all its GEM handles and dereferences the associated GEM objects. </para> <para> To create a handle for a GEM object drivers call <function>drm_gem_handle_create</function>. The function takes a pointer to the DRM file and the GEM object and returns a locally unique handle. When the handle is no longer needed drivers delete it with a call to <function>drm_gem_handle_delete</function>. Finally the GEM object associated with a handle can be retrieved by a call to <function>drm_gem_object_lookup</function>. </para> <para> Handles don't take ownership of GEM objects, they only take a reference to the object that will be dropped when the handle is destroyed. To avoid leaking GEM objects, drivers must make sure they drop the reference(s) they own (such as the initial reference taken at object creation time) as appropriate, without any special consideration for the handle. For example, in the particular case of combined GEM object and handle creation in the implementation of the <methodname>dumb_create</methodname> operation, drivers must drop the initial reference to the GEM object before returning the handle. </para> <para> GEM names are similar in purpose to handles but are not local to DRM files. They can be passed between processes to reference a GEM object globally. Names can't be used directly to refer to objects in the DRM API, applications must convert handles to names and names to handles using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls respectively. The conversion is handled by the DRM core without any driver-specific support. </para> <para> Similar to global names, GEM file descriptors are also used to share GEM objects across processes. They offer additional security: as file descriptors must be explictly sent over UNIX domain sockets to be shared between applications, they can't be guessed like the globally unique GEM names. </para> <para> Drivers that support GEM file descriptors, also known as the DRM PRIME API, must set the DRIVER_PRIME bit in the struct <structname>drm_driver</structname> <structfield>driver_features</structfield> field, and implement the <methodname>prime_handle_to_fd</methodname> and <methodname>prime_fd_to_handle</methodname> operations. </para> <para> <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev, struct drm_file *file_priv, uint32_t handle, uint32_t flags, int *prime_fd); int (*prime_fd_to_handle)(struct drm_device *dev, struct drm_file *file_priv, int prime_fd, uint32_t *handle);</synopsis> Those two operations convert a handle to a PRIME file descriptor and vice versa. Drivers must use the kernel dma-buf buffer sharing framework to manage the PRIME file descriptors. </para> <para> While non-GEM drivers must implement the operations themselves, GEM drivers must use the <function>drm_gem_prime_handle_to_fd</function> and <function>drm_gem_prime_fd_to_handle</function> helper functions. Those helpers rely on the driver <methodname>gem_prime_export</methodname> and <methodname>gem_prime_import</methodname> operations to create a dma-buf instance from a GEM object (dma-buf exporter role) and to create a GEM object from a dma-buf instance (dma-buf importer role). </para> <para> <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev, struct drm_gem_object *obj, int flags); struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev, struct dma_buf *dma_buf);</synopsis> These two operations are mandatory for GEM drivers that support DRM PRIME. </para> |
89177644a drm: add prime he... |
744 745 746 747 |
<sect4> <title>DRM PRIME Helper Functions Reference</title> !Pdrivers/gpu/drm/drm_prime.c PRIME Helpers </sect4> |
9cad9c95d Documentation: Do... |
748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 |
</sect3> <sect3 id="drm-gem-objects-mapping"> <title>GEM Objects Mapping</title> <para> Because mapping operations are fairly heavyweight GEM favours read/write-like access to buffers, implemented through driver-specific ioctls, over mapping buffers to userspace. However, when random access to the buffer is needed (to perform software rendering for instance), direct access to the object can be more efficient. </para> <para> The mmap system call can't be used directly to map GEM objects, as they don't have their own file handle. Two alternative methods currently co-exist to map GEM objects to userspace. The first method uses a driver-specific ioctl to perform the mapping operation, calling <function>do_mmap</function> under the hood. This is often considered dubious, seems to be discouraged for new GEM-enabled drivers, and will thus not be described here. </para> <para> The second method uses the mmap system call on the DRM file handle. <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);</synopsis> DRM identifies the GEM object to be mapped by a fake offset passed through the mmap offset argument. Prior to being mapped, a GEM object must thus be associated with a fake offset. To do so, drivers must call <function>drm_gem_create_mmap_offset</function> on the object. The function allocates a fake offset range from a pool and stores the offset divided by PAGE_SIZE in <literal>obj->map_list.hash.key</literal>. Care must be taken not to call <function>drm_gem_create_mmap_offset</function> if a fake offset has already been allocated for the object. This can be tested by <literal>obj->map_list.map</literal> being non-NULL. </para> <para> Once allocated, the fake offset value (<literal>obj->map_list.hash.key << PAGE_SHIFT</literal>) must be passed to the application in a driver-specific way and can then be used as the mmap offset argument. </para> <para> The GEM core provides a helper method <function>drm_gem_mmap</function> to handle object mapping. The method can be set directly as the mmap file operation handler. It will look up the GEM object based on the offset value and set the VMA operations to the <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield> field. Note that <function>drm_gem_mmap</function> doesn't map memory to userspace, but relies on the driver-provided fault handler to map pages individually. </para> <para> To use <function>drm_gem_mmap</function>, drivers must fill the struct <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield> field with a pointer to VM operations. </para> <para> <synopsis>struct vm_operations_struct *gem_vm_ops struct vm_operations_struct { void (*open)(struct vm_area_struct * area); void (*close)(struct vm_area_struct * area); int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf); };</synopsis> </para> <para> The <methodname>open</methodname> and <methodname>close</methodname> operations must update the GEM object reference count. Drivers can use the <function>drm_gem_vm_open</function> and <function>drm_gem_vm_close</function> helper functions directly as open and close handlers. </para> <para> The fault operation handler is responsible for mapping individual pages to userspace when a page fault occurs. Depending on the memory allocation scheme, drivers can allocate pages at fault time, or can decide to allocate memory for the GEM object at the time the object is created. </para> <para> Drivers that want to map the GEM object upfront instead of handling page faults can implement their own mmap file operation handler. </para> </sect3> <sect3> <title>Dumb GEM Objects</title> <para> The GEM API doesn't standardize GEM objects creation and leaves it to driver-specific ioctls. While not an issue for full-fledged graphics stacks that include device-specific userspace components (in libdrm for instance), this limit makes DRM-based early boot graphics unnecessarily complex. </para> <para> Dumb GEM objects partly alleviate the problem by providing a standard API to create dumb buffers suitable for scanout, which can then be used to create KMS frame buffers. </para> <para> To support dumb GEM objects drivers must implement the <methodname>dumb_create</methodname>, <methodname>dumb_destroy</methodname> and <methodname>dumb_map_offset</methodname> operations. </para> <itemizedlist> <listitem> <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, struct drm_mode_create_dumb *args);</synopsis> <para> The <methodname>dumb_create</methodname> operation creates a GEM object suitable for scanout based on the width, height and depth from the struct <structname>drm_mode_create_dumb</structname> argument. It fills the argument's <structfield>handle</structfield>, <structfield>pitch</structfield> and <structfield>size</structfield> fields with a handle for the newly created GEM object and its line pitch and size in bytes. </para> </listitem> <listitem> <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, uint32_t handle);</synopsis> <para> The <methodname>dumb_destroy</methodname> operation destroys a dumb GEM object created by <methodname>dumb_create</methodname>. </para> </listitem> <listitem> <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, uint32_t handle, uint64_t *offset);</synopsis> <para> The <methodname>dumb_map_offset</methodname> operation associates an mmap fake offset with the GEM object given by the handle and returns it. Drivers must use the <function>drm_gem_create_mmap_offset</function> function to associate the fake offset as described in <xref linkend="drm-gem-objects-mapping"/>. </para> </listitem> </itemizedlist> </sect3> <sect3> <title>Memory Coherency</title> <para> When mapped to the device or used in a command buffer, backing pages for an object are flushed to memory and marked write combined so as to be coherent with the GPU. Likewise, if the CPU accesses an object after the GPU has finished rendering to the object, then the object must be made coherent with the CPU's view of memory, usually involving GPU cache flushing of various kinds. This core CPU<->GPU coherency management is provided by a device-specific ioctl, which evaluates an object's current domain and performs any necessary flushing or synchronization to put the object into the desired coherency domain (note that the object may be busy, i.e. an active render target; in that case, setting the domain blocks the client and waits for rendering to complete before performing any necessary flushing operations). </para> </sect3> <sect3> <title>Command Execution</title> <para> Perhaps the most important GEM function for GPU devices is providing a command execution interface to clients. Client programs construct command buffers containing references to previously allocated memory objects, and then submit them to GEM. At that point, GEM takes care to bind all the objects into the GTT, execute the buffer, and provide necessary synchronization between clients accessing the same buffers. This often involves evicting some objects from the GTT and re-binding others (a fairly expensive operation), and providing relocation support which hides fixed GTT offsets from clients. Clients must take care not to submit command buffers that reference more objects than can fit in the GTT; otherwise, GEM will reject them and no rendering will occur. Similarly, if several objects in the buffer require fence registers to be allocated for correct rendering (e.g. 2D blits on pre-965 chips), care must be taken not to require more fence registers than are available to the client. Such resource management should be abstracted from the client in libdrm. </para> |
2d2ef8227 drm: add initial ... |
925 926 |
</sect3> </sect2> |
9cad9c95d Documentation: Do... |
927 928 929 |
</sect1> <!-- Internals: mode setting --> |
2d2ef8227 drm: add initial ... |
930 |
|
9cad9c95d Documentation: Do... |
931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 |
<sect1 id="drm-mode-setting"> <title>Mode Setting</title> <para> Drivers must initialize the mode setting core by calling <function>drm_mode_config_init</function> on the DRM device. The function initializes the <structname>drm_device</structname> <structfield>mode_config</structfield> field and never fails. Once done, mode configuration must be setup by initializing the following fields. </para> <itemizedlist> <listitem> <synopsis>int min_width, min_height; int max_width, max_height;</synopsis> <para> Minimum and maximum width and height of the frame buffers in pixel units. </para> </listitem> <listitem> <synopsis>struct drm_mode_config_funcs *funcs;</synopsis> <para>Mode setting functions.</para> </listitem> </itemizedlist> |
2d2ef8227 drm: add initial ... |
954 |
<sect2> |
9cad9c95d Documentation: Do... |
955 956 957 958 |
<title>Frame Buffer Creation</title> <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev, struct drm_file *file_priv, struct drm_mode_fb_cmd2 *mode_cmd);</synopsis> |
2d2ef8227 drm: add initial ... |
959 |
<para> |
9cad9c95d Documentation: Do... |
960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 |
Frame buffers are abstract memory objects that provide a source of pixels to scanout to a CRTC. Applications explicitly request the creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and receive an opaque handle that can be passed to the KMS CRTC control, plane configuration and page flip functions. </para> <para> Frame buffers rely on the underneath memory manager for low-level memory operations. When creating a frame buffer applications pass a memory handle (or a list of memory handles for multi-planar formats) through the <parameter>drm_mode_fb_cmd2</parameter> argument. This document assumes that the driver uses GEM, those handles thus reference GEM objects. </para> <para> Drivers must first validate the requested frame buffer parameters passed through the mode_cmd argument. In particular this is where invalid sizes, pixel formats or pitches can be caught. </para> <para> If the parameters are deemed valid, drivers then create, initialize and return an instance of struct <structname>drm_framebuffer</structname>. If desired the instance can be embedded in a larger driver-specific |
5d7a95153 drm/doc: updates ... |
983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 |
structure. Drivers must fill its <structfield>width</structfield>, <structfield>height</structfield>, <structfield>pitches</structfield>, <structfield>offsets</structfield>, <structfield>depth</structfield>, <structfield>bits_per_pixel</structfield> and <structfield>pixel_format</structfield> fields from the values passed through the <parameter>drm_mode_fb_cmd2</parameter> argument. They should call the <function>drm_helper_mode_fill_fb_struct</function> helper function to do so. </para> <para> The initailization of the new framebuffer instance is finalized with a call to <function>drm_framebuffer_init</function> which takes a pointer to DRM frame buffer operations (struct <structname>drm_framebuffer_funcs</structname>). Note that this function publishes the framebuffer and so from this point on it can be accessed concurrently from other threads. Hence it must be the last step in the driver's framebuffer initialization sequence. Frame buffer operations are |
9cad9c95d Documentation: Do... |
1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 |
<itemizedlist> <listitem> <synopsis>int (*create_handle)(struct drm_framebuffer *fb, struct drm_file *file_priv, unsigned int *handle);</synopsis> <para> Create a handle to the frame buffer underlying memory object. If the frame buffer uses a multi-plane format, the handle will reference the memory object associated with the first plane. </para> <para> Drivers call <function>drm_gem_handle_create</function> to create the handle. </para> </listitem> <listitem> <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis> <para> Destroy the frame buffer object and frees all associated resources. Drivers must call <function>drm_framebuffer_cleanup</function> to free resources allocated by the DRM core for the frame buffer object, and must make sure to unreference all memory objects associated with the frame buffer. Handles created by the <methodname>create_handle</methodname> operation are released by the DRM core. </para> </listitem> <listitem> <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer, struct drm_file *file_priv, unsigned flags, unsigned color, struct drm_clip_rect *clips, unsigned num_clips);</synopsis> <para> This optional operation notifies the driver that a region of the frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB ioctl call. </para> </listitem> </itemizedlist> </para> <para> |
5d7a95153 drm/doc: updates ... |
1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 |
The lifetime of a drm framebuffer is controlled with a reference count, drivers can grab additional references with <function>drm_framebuffer_reference</function> </para> and drop them again with <function>drm_framebuffer_unreference</function>. For driver-private framebuffers for which the last reference is never dropped (e.g. for the fbdev framebuffer when the struct <structname>drm_framebuffer</structname> is embedded into the fbdev helper struct) drivers can manually clean up a framebuffer at module unload time with <function>drm_framebuffer_unregister_private</function>. |
9cad9c95d Documentation: Do... |
1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 |
</sect2> <sect2> <title>Output Polling</title> <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis> <para> This operation notifies the driver that the status of one or more connectors has changed. Drivers that use the fb helper can just call the <function>drm_fb_helper_hotplug_event</function> function to handle this operation. </para> </sect2> |
5d7a95153 drm/doc: updates ... |
1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 |
<sect2> <title>Locking</title> <para> Beside some lookup structures with their own locking (which is hidden behind the interface functions) most of the modeset state is protected by the <code>dev-<mode_config.lock</code> mutex and additionally per-crtc locks to allow cursor updates, pageflips and similar operations to occur concurrently with background tasks like output detection. Operations which cross domains like a full modeset always grab all locks. Drivers there need to protect resources shared between crtcs with additional locking. They also need to be careful to always grab the relevant crtc locks if a modset functions touches crtc state, e.g. for load detection (which does only grab the <code>mode_config.lock</code> to allow concurrent screen updates on live crtcs). </para> </sect2> |
9cad9c95d Documentation: Do... |
1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 |
</sect1> <!-- Internals: kms initialization and cleanup --> <sect1 id="drm-kms-init"> <title>KMS Initialization and Cleanup</title> <para> A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders and connectors. KMS drivers must thus create and initialize all those objects at load time after initializing mode setting. </para> <sect2> <title>CRTCs (struct <structname>drm_crtc</structname>)</title> <para> A CRTC is an abstraction representing a part of the chip that contains a pointer to a scanout buffer. Therefore, the number of CRTCs available determines how many independent scanout buffers can be active at any given time. The CRTC structure contains several fields to support this: a pointer to some video memory (abstracted as a frame buffer object), a display mode, and an (x, y) offset into the video memory to support panning or configurations where one piece of video memory spans multiple CRTCs. |
2d2ef8227 drm: add initial ... |
1101 1102 |
</para> <sect3> |
9cad9c95d Documentation: Do... |
1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 |
<title>CRTC Initialization</title> <para> A KMS device must create and register at least one struct <structname>drm_crtc</structname> instance. The instance is allocated and zeroed by the driver, possibly as part of a larger structure, and registered with a call to <function>drm_crtc_init</function> with a pointer to CRTC functions. </para> </sect3> <sect3> <title>CRTC Operations</title> <sect4> <title>Set Configuration</title> <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis> <para> Apply a new CRTC configuration to the device. The configuration specifies a CRTC, a frame buffer to scan out from, a (x,y) position in the frame buffer, a display mode and an array of connectors to drive with the CRTC if possible. </para> <para> If the frame buffer specified in the configuration is NULL, the driver must detach all encoders connected to the CRTC and all connectors attached to those encoders and disable them. </para> <para> This operation is called with the mode config lock held. </para> <note><para> FIXME: How should set_config interact with DPMS? If the CRTC is suspended, should it be resumed? </para></note> </sect4> <sect4> <title>Page Flipping</title> <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb, struct drm_pending_vblank_event *event);</synopsis> <para> Schedule a page flip to the given frame buffer for the CRTC. This operation is called with the mode config mutex held. </para> <para> Page flipping is a synchronization mechanism that replaces the frame buffer being scanned out by the CRTC with a new frame buffer during vertical blanking, avoiding tearing. When an application requests a page flip the DRM core verifies that the new frame buffer is large enough to be scanned out by the CRTC in the currently configured mode and then calls the CRTC <methodname>page_flip</methodname> operation with a pointer to the new frame buffer. </para> <para> The <methodname>page_flip</methodname> operation schedules a page flip. Once any pending rendering targetting the new frame buffer has completed, the CRTC will be reprogrammed to display that frame buffer after the next vertical refresh. The operation must return immediately without waiting for rendering or page flip to complete and must block any new rendering to the frame buffer until the page flip completes. </para> <para> |
8cf1e9811 drm: Add consiste... |
1162 1163 1164 1165 1166 1167 |
If a page flip can be successfully scheduled the driver must set the <code>drm_crtc-<fb</code> field to the new framebuffer pointed to by <code>fb</code>. This is important so that the reference counting on framebuffers stays balanced. </para> <para> |
9cad9c95d Documentation: Do... |
1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 |
If a page flip is already pending, the <methodname>page_flip</methodname> operation must return -<errorname>EBUSY</errorname>. </para> <para> To synchronize page flip to vertical blanking the driver will likely need to enable vertical blanking interrupts. It should call <function>drm_vblank_get</function> for that purpose, and call <function>drm_vblank_put</function> after the page flip completes. </para> <para> If the application has requested to be notified when page flip completes the <methodname>page_flip</methodname> operation will be called with a non-NULL <parameter>event</parameter> argument pointing to a <structname>drm_pending_vblank_event</structname> instance. Upon page |
c6eefa175 drm: add drm_send... |
1183 1184 1185 |
flip completion the driver must call <methodname>drm_send_vblank_event</methodname> to fill in the event and send to wake up any waiting processes. This can be performed with |
9cad9c95d Documentation: Do... |
1186 |
<programlisting><![CDATA[ |
9cad9c95d Documentation: Do... |
1187 |
spin_lock_irqsave(&dev->event_lock, flags); |
c6eefa175 drm: add drm_send... |
1188 1189 |
... drm_send_vblank_event(dev, pipe, event); |
9cad9c95d Documentation: Do... |
1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 |
spin_unlock_irqrestore(&dev->event_lock, flags); ]]></programlisting> </para> <note><para> FIXME: Could drivers that don't need to wait for rendering to complete just add the event to <literal>dev->vblank_event_list</literal> and let the DRM core handle everything, as for "normal" vertical blanking events? </para></note> <para> While waiting for the page flip to complete, the <literal>event->base.link</literal> list head can be used freely by the driver to store the pending event in a driver-specific list. </para> <para> If the file handle is closed before the event is signaled, drivers must take care to destroy the event in their <methodname>preclose</methodname> operation (and, if needed, call <function>drm_vblank_put</function>). </para> </sect4> <sect4> <title>Miscellaneous</title> <itemizedlist> <listitem> <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b, uint32_t start, uint32_t size);</synopsis> <para> Apply a gamma table to the device. The operation is optional. </para> </listitem> <listitem> <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis> <para> Destroy the CRTC when not needed anymore. See <xref linkend="drm-kms-init"/>. </para> </listitem> </itemizedlist> </sect4> </sect3> </sect2> <sect2> <title>Planes (struct <structname>drm_plane</structname>)</title> <para> A plane represents an image source that can be blended with or overlayed on top of a CRTC during the scanout process. Planes are associated with a frame buffer to crop a portion of the image memory (source) and optionally scale it to a destination size. The result is then blended with or overlayed on top of a CRTC. </para> <sect3> <title>Plane Initialization</title> <para> Planes are optional. To create a plane, a KMS drivers allocates and zeroes an instances of struct <structname>drm_plane</structname> (possibly as part of a larger structure) and registers it with a call to <function>drm_plane_init</function>. The function takes a bitmask of the CRTCs that can be associated with the plane, a pointer to the plane functions and a list of format supported formats. </para> </sect3> <sect3> <title>Plane Operations</title> <itemizedlist> <listitem> <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc, struct drm_framebuffer *fb, int crtc_x, int crtc_y, unsigned int crtc_w, unsigned int crtc_h, uint32_t src_x, uint32_t src_y, uint32_t src_w, uint32_t src_h);</synopsis> <para> Enable and configure the plane to use the given CRTC and frame buffer. </para> <para> The source rectangle in frame buffer memory coordinates is given by the <parameter>src_x</parameter>, <parameter>src_y</parameter>, <parameter>src_w</parameter> and <parameter>src_h</parameter> parameters (as 16.16 fixed point values). Devices that don't support subpixel plane coordinates can ignore the fractional part. </para> <para> The destination rectangle in CRTC coordinates is given by the <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>, <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter> parameters (as integer values). Devices scale the source rectangle to the destination rectangle. If scaling is not supported, and the source rectangle size doesn't match the destination rectangle size, the driver must return a -<errorname>EINVAL</errorname> error. </para> </listitem> <listitem> <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis> <para> Disable the plane. The DRM core calls this method in response to a DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0. Disabled planes must not be processed by the CRTC. </para> </listitem> <listitem> <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis> <para> Destroy the plane when not needed anymore. See <xref linkend="drm-kms-init"/>. </para> </listitem> </itemizedlist> </sect3> </sect2> <sect2> <title>Encoders (struct <structname>drm_encoder</structname>)</title> <para> An encoder takes pixel data from a CRTC and converts it to a format suitable for any attached connectors. On some devices, it may be possible to have a CRTC send data to more than one encoder. In that case, both encoders would receive data from the same scanout buffer, resulting in a "cloned" display configuration across the connectors attached to each encoder. </para> <sect3> <title>Encoder Initialization</title> <para> As for CRTCs, a KMS driver must create, initialize and register at least one struct <structname>drm_encoder</structname> instance. The instance is allocated and zeroed by the driver, possibly as part of a larger structure. </para> <para> Drivers must initialize the struct <structname>drm_encoder</structname> <structfield>possible_crtcs</structfield> and <structfield>possible_clones</structfield> fields before registering the encoder. Both fields are bitmasks of respectively the CRTCs that the encoder can be connected to, and sibling encoders candidate for cloning. </para> <para> After being initialized, the encoder must be registered with a call to <function>drm_encoder_init</function>. The function takes a pointer to the encoder functions and an encoder type. Supported types are <itemizedlist> <listitem> DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A </listitem> <listitem> DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort </listitem> <listitem> DRM_MODE_ENCODER_LVDS for display panels </listitem> <listitem> DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component, SCART) </listitem> <listitem> DRM_MODE_ENCODER_VIRTUAL for virtual machine displays </listitem> </itemizedlist> </para> <para> Encoders must be attached to a CRTC to be used. DRM drivers leave encoders unattached at initialization time. Applications (or the fbdev compatibility layer when implemented) are responsible for attaching the encoders they want to use to a CRTC. </para> </sect3> <sect3> <title>Encoder Operations</title> <itemizedlist> <listitem> <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis> <para> Called to destroy the encoder when not needed anymore. See <xref linkend="drm-kms-init"/>. </para> </listitem> </itemizedlist> </sect3> </sect2> <sect2> <title>Connectors (struct <structname>drm_connector</structname>)</title> <para> A connector is the final destination for pixel data on a device, and usually connects directly to an external display device like a monitor or laptop panel. A connector can only be attached to one encoder at a time. The connector is also the structure where information about the attached display is kept, so it contains fields for display data, EDID data, DPMS & connection status, and information about modes supported on the attached displays. </para> <sect3> <title>Connector Initialization</title> <para> Finally a KMS driver must create, initialize, register and attach at least one struct <structname>drm_connector</structname> instance. The instance is created as other KMS objects and initialized by setting the following fields. </para> <variablelist> <varlistentry> <term><structfield>interlace_allowed</structfield></term> <listitem><para> Whether the connector can handle interlaced modes. </para></listitem> </varlistentry> <varlistentry> <term><structfield>doublescan_allowed</structfield></term> <listitem><para> Whether the connector can handle doublescan. </para></listitem> </varlistentry> <varlistentry> <term><structfield>display_info </structfield></term> <listitem><para> Display information is filled from EDID information when a display is detected. For non hot-pluggable displays such as flat panels in embedded systems, the driver should initialize the <structfield>display_info</structfield>.<structfield>width_mm</structfield> and <structfield>display_info</structfield>.<structfield>height_mm</structfield> fields with the physical size of the display. </para></listitem> </varlistentry> <varlistentry> <term id="drm-kms-connector-polled"><structfield>polled</structfield></term> <listitem><para> Connector polling mode, a combination of <variablelist> <varlistentry> <term>DRM_CONNECTOR_POLL_HPD</term> <listitem><para> The connector generates hotplug events and doesn't need to be periodically polled. The CONNECT and DISCONNECT flags must not be set together with the HPD flag. </para></listitem> </varlistentry> <varlistentry> <term>DRM_CONNECTOR_POLL_CONNECT</term> <listitem><para> Periodically poll the connector for connection. </para></listitem> </varlistentry> <varlistentry> <term>DRM_CONNECTOR_POLL_DISCONNECT</term> <listitem><para> Periodically poll the connector for disconnection. </para></listitem> </varlistentry> </variablelist> Set to 0 for connectors that don't support connection status discovery. </para></listitem> </varlistentry> </variablelist> <para> The connector is then registered with a call to <function>drm_connector_init</function> with a pointer to the connector functions and a connector type, and exposed through sysfs with a call to <function>drm_sysfs_connector_add</function>. </para> <para> Supported connector types are <itemizedlist> <listitem>DRM_MODE_CONNECTOR_VGA</listitem> <listitem>DRM_MODE_CONNECTOR_DVII</listitem> <listitem>DRM_MODE_CONNECTOR_DVID</listitem> <listitem>DRM_MODE_CONNECTOR_DVIA</listitem> <listitem>DRM_MODE_CONNECTOR_Composite</listitem> <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem> <listitem>DRM_MODE_CONNECTOR_LVDS</listitem> <listitem>DRM_MODE_CONNECTOR_Component</listitem> <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem> <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem> <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem> <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem> <listitem>DRM_MODE_CONNECTOR_TV</listitem> <listitem>DRM_MODE_CONNECTOR_eDP</listitem> <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem> </itemizedlist> </para> <para> Connectors must be attached to an encoder to be used. For devices that map connectors to encoders 1:1, the connector should be attached at initialization time with a call to <function>drm_mode_connector_attach_encoder</function>. The driver must also set the <structname>drm_connector</structname> <structfield>encoder</structfield> field to point to the attached encoder. </para> <para> Finally, drivers must initialize the connectors state change detection with a call to <function>drm_kms_helper_poll_init</function>. If at least one connector is pollable but can't generate hotplug interrupts (indicated by the DRM_CONNECTOR_POLL_CONNECT and DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will automatically be queued to periodically poll for changes. Connectors that can generate hotplug interrupts must be marked with the DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must call <function>drm_helper_hpd_irq_event</function>. The function will queue a delayed work to check the state of all connectors, but no periodic polling will be done. </para> </sect3> <sect3> <title>Connector Operations</title> <note><para> Unless otherwise state, all operations are mandatory. </para></note> <sect4> <title>DPMS</title> <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis> <para> The DPMS operation sets the power state of a connector. The mode argument is one of <itemizedlist> <listitem><para>DRM_MODE_DPMS_ON</para></listitem> <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem> <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem> <listitem><para>DRM_MODE_DPMS_OFF</para></listitem> </itemizedlist> </para> <para> In all but DPMS_ON mode the encoder to which the connector is attached should put the display in low-power mode by driving its signals appropriately. If more than one connector is attached to the encoder care should be taken not to change the power state of other displays as a side effect. Low-power mode should be propagated to the encoders and CRTCs when all related connectors are put in low-power mode. </para> </sect4> <sect4> <title>Modes</title> <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width, uint32_t max_height);</synopsis> <para> Fill the mode list with all supported modes for the connector. If the <parameter>max_width</parameter> and <parameter>max_height</parameter> arguments are non-zero, the implementation must ignore all modes wider than <parameter>max_width</parameter> or higher than <parameter>max_height</parameter>. </para> <para> The connector must also fill in this operation its <structfield>display_info</structfield> <structfield>width_mm</structfield> and <structfield>height_mm</structfield> fields with the connected display physical size in millimeters. The fields should be set to 0 if the value isn't known or is not applicable (for instance for projector devices). </para> </sect4> <sect4> <title>Connection Status</title> <para> The connection status is updated through polling or hotplug events when supported (see <xref linkend="drm-kms-connector-polled"/>). The status value is reported to userspace through ioctls and must not be used inside the driver, as it only gets initialized by a call to <function>drm_mode_getconnector</function> from userspace. </para> <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector, bool force);</synopsis> <para> Check to see if anything is attached to the connector. The <parameter>force</parameter> parameter is set to false whilst polling or to true when checking the connector due to user request. <parameter>force</parameter> can be used by the driver to avoid expensive, destructive operations during automated probing. </para> <para> Return connector_status_connected if something is connected to the connector, connector_status_disconnected if nothing is connected and connector_status_unknown if the connection state isn't known. </para> <para> Drivers should only return connector_status_connected if the connection status has really been probed as connected. Connectors that can't detect the connection status, or failed connection status probes, should return connector_status_unknown. </para> </sect4> <sect4> <title>Miscellaneous</title> <itemizedlist> <listitem> <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis> <para> Destroy the connector when not needed anymore. See <xref linkend="drm-kms-init"/>. </para> </listitem> </itemizedlist> </sect4> </sect3> </sect2> <sect2> <title>Cleanup</title> <para> The DRM core manages its objects' lifetime. When an object is not needed anymore the core calls its destroy function, which must clean up and free every resource allocated for the object. Every <function>drm_*_init</function> call must be matched with a corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs (<function>drm_crtc_cleanup</function>), planes (<function>drm_plane_cleanup</function>), encoders (<function>drm_encoder_cleanup</function>) and connectors (<function>drm_connector_cleanup</function>). Furthermore, connectors that have been added to sysfs must be removed by a call to <function>drm_sysfs_connector_remove</function> before calling <function>drm_connector_cleanup</function>. </para> <para> Connectors state change detection must be cleanup up with a call to <function>drm_kms_helper_poll_fini</function>. </para> </sect2> <sect2> <title>Output discovery and initialization example</title> <programlisting><![CDATA[ |
2d2ef8227 drm: add initial ... |
1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 |
void intel_crt_init(struct drm_device *dev) { struct drm_connector *connector; struct intel_output *intel_output; intel_output = kzalloc(sizeof(struct intel_output), GFP_KERNEL); if (!intel_output) return; connector = &intel_output->base; drm_connector_init(dev, &intel_output->base, &intel_crt_connector_funcs, DRM_MODE_CONNECTOR_VGA); drm_encoder_init(dev, &intel_output->enc, &intel_crt_enc_funcs, DRM_MODE_ENCODER_DAC); drm_mode_connector_attach_encoder(&intel_output->base, &intel_output->enc); /* Set up the DDC bus. */ intel_output->ddc_bus = intel_i2c_create(dev, GPIOA, "CRTDDC_A"); if (!intel_output->ddc_bus) { dev_printk(KERN_ERR, &dev->pdev->dev, "DDC bus registration " "failed. "); return; } intel_output->type = INTEL_OUTPUT_ANALOG; connector->interlace_allowed = 0; connector->doublescan_allowed = 0; drm_encoder_helper_add(&intel_output->enc, &intel_crt_helper_funcs); drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); drm_sysfs_connector_add(connector); |
9cad9c95d Documentation: Do... |
1643 1644 1645 1646 1647 1648 1649 1650 |
}]]></programlisting> <para> In the example above (taken from the i915 driver), a CRTC, connector and encoder combination is created. A device-specific i2c bus is also created for fetching EDID data and performing monitor detection. Once the process is complete, the new connector is registered with sysfs to make its properties available to applications. </para> |
2d2ef8227 drm: add initial ... |
1651 |
</sect2> |
065a50ed3 drm/doc: integrat... |
1652 1653 1654 1655 |
<sect2> <title>KMS API Functions</title> !Edrivers/gpu/drm/drm_crtc.c </sect2> |
2d2ef8227 drm: add initial ... |
1656 |
</sect1> |
e4949f297 drm/doc: Helpers ... |
1657 |
<!-- Internals: kms helper functions --> |
2d2ef8227 drm: add initial ... |
1658 1659 |
<sect1> |
e4949f297 drm/doc: Helpers ... |
1660 |
<title>Mode Setting Helper Functions</title> |
2d2ef8227 drm: add initial ... |
1661 |
<para> |
9cad9c95d Documentation: Do... |
1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 |
The CRTC, encoder and connector functions provided by the drivers implement the DRM API. They're called by the DRM core and ioctl handlers to handle device state changes and configuration request. As implementing those functions often requires logic not specific to drivers, mid-layer helper functions are available to avoid duplicating boilerplate code. </para> <para> The DRM core contains one mid-layer implementation. The mid-layer provides implementations of several CRTC, encoder and connector functions (called from the top of the mid-layer) that pre-process requests and call lower-level functions provided by the driver (at the bottom of the mid-layer). For instance, the <function>drm_crtc_helper_set_config</function> function can be used to fill the struct <structname>drm_crtc_funcs</structname> <structfield>set_config</structfield> field. When called, it will split the <methodname>set_config</methodname> operation in smaller, simpler operations and call the driver to handle them. |
2d2ef8227 drm: add initial ... |
1679 1680 |
</para> <para> |
9cad9c95d Documentation: Do... |
1681 1682 1683 1684 1685 1686 1687 1688 1689 |
To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>, <function>drm_encoder_helper_add</function> and <function>drm_connector_helper_add</function> functions to install their mid-layer bottom operations handlers, and fill the <structname>drm_crtc_funcs</structname>, <structname>drm_encoder_funcs</structname> and <structname>drm_connector_funcs</structname> structures with pointers to the mid-layer top API functions. Installing the mid-layer bottom operation handlers is best done right after registering the corresponding KMS object. |
2d2ef8227 drm: add initial ... |
1690 1691 |
</para> <para> |
9cad9c95d Documentation: Do... |
1692 1693 1694 |
The mid-layer is not split between CRTC, encoder and connector operations. To use it, a driver must provide bottom functions for all of the three KMS entities. |
2d2ef8227 drm: add initial ... |
1695 |
</para> |
9cad9c95d Documentation: Do... |
1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 |
<sect2> <title>Helper Functions</title> <itemizedlist> <listitem> <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis> <para> The <function>drm_crtc_helper_set_config</function> helper function is a CRTC <methodname>set_config</methodname> implementation. It first tries to locate the best encoder for each connector by calling the connector <methodname>best_encoder</methodname> helper operation. </para> <para> After locating the appropriate encoders, the helper function will call the <methodname>mode_fixup</methodname> encoder and CRTC helper operations to adjust the requested mode, or reject it completely in which case an error will be returned to the application. If the new configuration after mode adjustment is identical to the current configuration the helper function will return without performing any other operation. </para> <para> If the adjusted mode is identical to the current mode but changes to the frame buffer need to be applied, the <function>drm_crtc_helper_set_config</function> function will call the CRTC <methodname>mode_set_base</methodname> helper operation. If the adjusted mode differs from the current mode, or if the <methodname>mode_set_base</methodname> helper operation is not provided, the helper function performs a full mode set sequence by calling the <methodname>prepare</methodname>, <methodname>mode_set</methodname> and <methodname>commit</methodname> CRTC and encoder helper operations, in that order. </para> </listitem> <listitem> <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis> <para> The <function>drm_helper_connector_dpms</function> helper function is a connector <methodname>dpms</methodname> implementation that tracks power state of connectors. To use the function, drivers must provide <methodname>dpms</methodname> helper operations for CRTCs and encoders to apply the DPMS state to the device. </para> <para> The mid-layer doesn't track the power state of CRTCs and encoders. The <methodname>dpms</methodname> helper operations can thus be called with a mode identical to the currently active mode. </para> </listitem> <listitem> <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector, uint32_t maxX, uint32_t maxY);</synopsis> <para> The <function>drm_helper_probe_single_connector_modes</function> helper function is a connector <methodname>fill_modes</methodname> implementation that updates the connection status for the connector and then retrieves a list of modes by calling the connector <methodname>get_modes</methodname> helper operation. </para> <para> The function filters out modes larger than <parameter>max_width</parameter> and <parameter>max_height</parameter> if specified. It then calls the connector <methodname>mode_valid</methodname> helper operation for each mode in the probed list to check whether the mode is valid for the connector. </para> </listitem> </itemizedlist> </sect2> <sect2> <title>CRTC Helper Operations</title> <itemizedlist> <listitem id="drm-helper-crtc-mode-fixup"> <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc, const struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode);</synopsis> <para> Let CRTCs adjust the requested mode or reject it completely. This operation returns true if the mode is accepted (possibly after being adjusted) or false if it is rejected. </para> <para> The <methodname>mode_fixup</methodname> operation should reject the mode if it can't reasonably use it. The definition of "reasonable" is currently fuzzy in this context. One possible behaviour would be to set the adjusted mode to the panel timings when a fixed-mode panel is used with hardware capable of scaling. Another behaviour would be to accept any input mode and adjust it to the closest mode supported by the hardware (FIXME: This needs to be clarified). </para> </listitem> <listitem> <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y, struct drm_framebuffer *old_fb)</synopsis> <para> Move the CRTC on the current frame buffer (stored in <literal>crtc->fb</literal>) to position (x,y). Any of the frame buffer, x position or y position may have been modified. </para> <para> This helper operation is optional. If not provided, the <function>drm_crtc_helper_set_config</function> function will fall back to the <methodname>mode_set</methodname> helper operation. </para> <note><para> FIXME: Why are x and y passed as arguments, as they can be accessed through <literal>crtc->x</literal> and <literal>crtc->y</literal>? </para></note> </listitem> <listitem> <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis> <para> Prepare the CRTC for mode setting. This operation is called after validating the requested mode. Drivers use it to perform device-specific operations required before setting the new mode. </para> </listitem> <listitem> <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode, int x, int y, struct drm_framebuffer *old_fb);</synopsis> <para> Set a new mode, position and frame buffer. Depending on the device requirements, the mode can be stored internally by the driver and applied in the <methodname>commit</methodname> operation, or programmed to the hardware immediately. </para> <para> The <methodname>mode_set</methodname> operation returns 0 on success or a negative error code if an error occurs. </para> </listitem> <listitem> <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis> <para> Commit a mode. This operation is called after setting the new mode. Upon return the device must use the new mode and be fully operational. </para> </listitem> </itemizedlist> </sect2> <sect2> <title>Encoder Helper Operations</title> <itemizedlist> <listitem> <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder, const struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode);</synopsis> <note><para> FIXME: The mode argument be const, but the i915 driver modifies mode->clock in <function>intel_dp_mode_fixup</function>. </para></note> <para> Let encoders adjust the requested mode or reject it completely. This operation returns true if the mode is accepted (possibly after being adjusted) or false if it is rejected. See the <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper operation</link> for an explanation of the allowed adjustments. </para> </listitem> <listitem> <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis> <para> Prepare the encoder for mode setting. This operation is called after validating the requested mode. Drivers use it to perform device-specific operations required before setting the new mode. </para> </listitem> <listitem> <synopsis>void (*mode_set)(struct drm_encoder *encoder, struct drm_display_mode *mode, struct drm_display_mode *adjusted_mode);</synopsis> <para> Set a new mode. Depending on the device requirements, the mode can be stored internally by the driver and applied in the <methodname>commit</methodname> operation, or programmed to the hardware immediately. </para> </listitem> <listitem> <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis> <para> Commit a mode. This operation is called after setting the new mode. Upon return the device must use the new mode and be fully operational. </para> </listitem> </itemizedlist> </sect2> <sect2> <title>Connector Helper Operations</title> <itemizedlist> <listitem> <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis> <para> Return a pointer to the best encoder for the connecter. Device that map connectors to encoders 1:1 simply return the pointer to the associated encoder. This operation is mandatory. </para> </listitem> <listitem> <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis> <para> Fill the connector's <structfield>probed_modes</structfield> list by parsing EDID data with <function>drm_add_edid_modes</function> or calling <function>drm_mode_probed_add</function> directly for every supported mode and return the number of modes it has detected. This operation is mandatory. </para> <para> When adding modes manually the driver creates each mode with a call to <function>drm_mode_create</function> and must fill the following fields. <itemizedlist> <listitem> <synopsis>__u32 type;</synopsis> <para> Mode type bitmask, a combination of <variablelist> <varlistentry> <term>DRM_MODE_TYPE_BUILTIN</term> <listitem><para>not used?</para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_TYPE_CLOCK_C</term> <listitem><para>not used?</para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_TYPE_CRTC_C</term> <listitem><para>not used?</para></listitem> </varlistentry> <varlistentry> <term> DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector </term> <listitem> <para>not used?</para> </listitem> </varlistentry> <varlistentry> <term>DRM_MODE_TYPE_DEFAULT</term> <listitem><para>not used?</para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_TYPE_USERDEF</term> <listitem><para>not used?</para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_TYPE_DRIVER</term> <listitem> <para> The mode has been created by the driver (as opposed to to user-created modes). </para> </listitem> </varlistentry> </variablelist> Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred mode. </para> </listitem> <listitem> <synopsis>__u32 clock;</synopsis> <para>Pixel clock frequency in kHz unit</para> </listitem> <listitem> <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal; __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis> <para>Horizontal and vertical timing information</para> <screen><![CDATA[ Active Front Sync Back Region Porch Porch <-----------------------><----------------><-------------><--------------> //////////////////////| ////////////////////// | ////////////////////// |.................. ................ _______________ <----- [hv]display -----> <------------- [hv]sync_start ------------> <--------------------- [hv]sync_end ---------------------> <-------------------------------- [hv]total -----------------------------> ]]></screen> </listitem> <listitem> <synopsis>__u16 hskew; __u16 vscan;</synopsis> <para>Unknown</para> </listitem> <listitem> <synopsis>__u32 flags;</synopsis> <para> Mode flags, a combination of <variablelist> <varlistentry> <term>DRM_MODE_FLAG_PHSYNC</term> <listitem><para> Horizontal sync is active high </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_NHSYNC</term> <listitem><para> Horizontal sync is active low </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_PVSYNC</term> <listitem><para> Vertical sync is active high </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_NVSYNC</term> <listitem><para> Vertical sync is active low </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_INTERLACE</term> <listitem><para> Mode is interlaced </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_DBLSCAN</term> <listitem><para> Mode uses doublescan </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_CSYNC</term> <listitem><para> Mode uses composite sync </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_PCSYNC</term> <listitem><para> Composite sync is active high </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_NCSYNC</term> <listitem><para> Composite sync is active low </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_HSKEW</term> <listitem><para> hskew provided (not used?) </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_BCAST</term> <listitem><para> not used? </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_PIXMUX</term> <listitem><para> not used? </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_DBLCLK</term> <listitem><para> not used? </para></listitem> </varlistentry> <varlistentry> <term>DRM_MODE_FLAG_CLKDIV2</term> <listitem><para> ? </para></listitem> </varlistentry> </variablelist> </para> <para> Note that modes marked with the INTERLACE or DBLSCAN flags will be filtered out by <function>drm_helper_probe_single_connector_modes</function> if the connector's <structfield>interlace_allowed</structfield> or <structfield>doublescan_allowed</structfield> field is set to 0. </para> </listitem> <listitem> <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis> <para> Mode name. The driver must call <function>drm_mode_set_name</function> to fill the mode name from <structfield>hdisplay</structfield>, <structfield>vdisplay</structfield> and interlace flag after filling the corresponding fields. </para> </listitem> </itemizedlist> </para> <para> The <structfield>vrefresh</structfield> value is computed by <function>drm_helper_probe_single_connector_modes</function>. </para> <para> When parsing EDID data, <function>drm_add_edid_modes</function> fill the connector <structfield>display_info</structfield> <structfield>width_mm</structfield> and <structfield>height_mm</structfield> fields. When creating modes manually the <methodname>get_modes</methodname> helper operation must set the <structfield>display_info</structfield> <structfield>width_mm</structfield> and <structfield>height_mm</structfield> fields if they haven't been set already (for instance at initilization time when a fixed-size panel is attached to the connector). The mode <structfield>width_mm</structfield> and <structfield>height_mm</structfield> fields are only used internally during EDID parsing and should not be set when creating modes manually. </para> </listitem> <listitem> <synopsis>int (*mode_valid)(struct drm_connector *connector, struct drm_display_mode *mode);</synopsis> <para> Verify whether a mode is valid for the connector. Return MODE_OK for supported modes and one of the enum drm_mode_status values (MODE_*) for unsupported modes. This operation is mandatory. </para> <para> As the mode rejection reason is currently not used beside for immediately removing the unsupported mode, an implementation can return MODE_BAD regardless of the exact reason why the mode is not valid. </para> <note><para> Note that the <methodname>mode_valid</methodname> helper operation is only called for modes detected by the device, and <emphasis>not</emphasis> for modes set by the user through the CRTC <methodname>set_config</methodname> operation. </para></note> </listitem> </itemizedlist> </sect2> |
0d4ed4c8f drm/doc: integrat... |
2142 2143 2144 2145 |
<sect2> <title>Modeset Helper Functions Reference</title> !Edrivers/gpu/drm/drm_crtc_helper.c </sect2> |
d0ddc0338 drm/doc: integrat... |
2146 2147 2148 2149 |
<sect2> <title>fbdev Helper Functions Reference</title> !Pdrivers/gpu/drm/drm_fb_helper.c fbdev helpers !Edrivers/gpu/drm/drm_fb_helper.c |
207fd3297 drm/fb-helper: im... |
2150 |
!Iinclude/drm/drm_fb_helper.h |
d0ddc0338 drm/doc: integrat... |
2151 |
</sect2> |
28164fdad drm/doc: add new ... |
2152 2153 2154 2155 2156 2157 |
<sect2> <title>Display Port Helper Functions Reference</title> !Pdrivers/gpu/drm/drm_dp_helper.c dp helpers !Iinclude/drm/drm_dp_helper.h !Edrivers/gpu/drm/drm_dp_helper.c </sect2> |
5e308591a drm: Add EDID hel... |
2158 2159 2160 2161 |
<sect2> <title>EDID Helper Functions Reference</title> !Edrivers/gpu/drm/drm_edid.c </sect2> |
2d2ef8227 drm: add initial ... |
2162 |
</sect1> |
9cad9c95d Documentation: Do... |
2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 |
<!-- Internals: vertical blanking --> <sect1 id="drm-vertical-blank"> <title>Vertical Blanking</title> <para> Vertical blanking plays a major role in graphics rendering. To achieve tear-free display, users must synchronize page flips and/or rendering to vertical blanking. The DRM API offers ioctls to perform page flips synchronized to vertical blanking and wait for vertical blanking. </para> <para> The DRM core handles most of the vertical blanking management logic, which involves filtering out spurious interrupts, keeping race-free blanking counters, coping with counter wrap-around and resets and keeping use counts. It relies on the driver to generate vertical blanking interrupts and optionally provide a hardware vertical blanking counter. Drivers must implement the following operations. </para> <itemizedlist> <listitem> <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc); void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis> <para> Enable or disable vertical blanking interrupts for the given CRTC. </para> </listitem> <listitem> <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis> <para> Retrieve the value of the vertical blanking counter for the given CRTC. If the hardware maintains a vertical blanking counter its value should be returned. Otherwise drivers can use the <function>drm_vblank_count</function> helper function to handle this operation. </para> </listitem> </itemizedlist> |
2d2ef8227 drm: add initial ... |
2200 |
<para> |
9cad9c95d Documentation: Do... |
2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 |
Drivers must initialize the vertical blanking handling core with a call to <function>drm_vblank_init</function> in their <methodname>load</methodname> operation. The function will set the struct <structname>drm_device</structname> <structfield>vblank_disable_allowed</structfield> field to 0. This will keep vertical blanking interrupts enabled permanently until the first mode set operation, where <structfield>vblank_disable_allowed</structfield> is set to 1. The reason behind this is not clear. Drivers can set the field to 1 after <function>calling drm_vblank_init</function> to make vertical blanking interrupts dynamically managed from the beginning. |
2d2ef8227 drm: add initial ... |
2211 |
</para> |
9cad9c95d Documentation: Do... |
2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 |
<para> Vertical blanking interrupts can be enabled by the DRM core or by drivers themselves (for instance to handle page flipping operations). The DRM core maintains a vertical blanking use count to ensure that the interrupts are not disabled while a user still needs them. To increment the use count, drivers call <function>drm_vblank_get</function>. Upon return vertical blanking interrupts are guaranteed to be enabled. </para> <para> To decrement the use count drivers call <function>drm_vblank_put</function>. Only when the use count drops to zero will the DRM core disable the vertical blanking interrupts after a delay by scheduling a timer. The delay is accessible through the vblankoffdelay module parameter or the <varname>drm_vblank_offdelay</varname> global variable and expressed in milliseconds. Its default value is 5000 ms. </para> <para> When a vertical blanking interrupt occurs drivers only need to call the <function>drm_handle_vblank</function> function to account for the interrupt. </para> <para> Resources allocated by <function>drm_vblank_init</function> must be freed with a call to <function>drm_vblank_cleanup</function> in the driver <methodname>unload</methodname> operation handler. </para> </sect1> <!-- Internals: open/close, file operations and ioctls --> |
2d2ef8227 drm: add initial ... |
2241 |
|
9cad9c95d Documentation: Do... |
2242 2243 |
<sect1> <title>Open/Close, File Operations and IOCTLs</title> |
2d2ef8227 drm: add initial ... |
2244 |
<sect2> |
9cad9c95d Documentation: Do... |
2245 2246 2247 2248 2249 2250 2251 2252 |
<title>Open and Close</title> <synopsis>int (*firstopen) (struct drm_device *); void (*lastclose) (struct drm_device *); int (*open) (struct drm_device *, struct drm_file *); void (*preclose) (struct drm_device *, struct drm_file *); void (*postclose) (struct drm_device *, struct drm_file *);</synopsis> <abstract>Open and close handlers. None of those methods are mandatory. </abstract> |
2d2ef8227 drm: add initial ... |
2253 |
<para> |
9cad9c95d Documentation: Do... |
2254 2255 2256 2257 2258 2259 2260 2261 |
The <methodname>firstopen</methodname> method is called by the DRM core when an application opens a device that has no other opened file handle. Similarly the <methodname>lastclose</methodname> method is called when the last application holding a file handle opened on the device closes it. Both methods are mostly used for UMS (User Mode Setting) drivers to acquire and release device resources which should be done in the <methodname>load</methodname> and <methodname>unload</methodname> methods for KMS drivers. |
2d2ef8227 drm: add initial ... |
2262 2263 |
</para> <para> |
9cad9c95d Documentation: Do... |
2264 2265 2266 2267 |
Note that the <methodname>lastclose</methodname> method is also called at module unload time or, for hot-pluggable devices, when the device is unplugged. The <methodname>firstopen</methodname> and <methodname>lastclose</methodname> calls can thus be unbalanced. |
2d2ef8227 drm: add initial ... |
2268 2269 |
</para> <para> |
9cad9c95d Documentation: Do... |
2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 |
The <methodname>open</methodname> method is called every time the device is opened by an application. Drivers can allocate per-file private data in this method and store them in the struct <structname>drm_file</structname> <structfield>driver_priv</structfield> field. Note that the <methodname>open</methodname> method is called before <methodname>firstopen</methodname>. </para> <para> The close operation is split into <methodname>preclose</methodname> and <methodname>postclose</methodname> methods. Drivers must stop and cleanup all per-file operations in the <methodname>preclose</methodname> method. For instance pending vertical blanking and page flip events must be cancelled. No per-file operation is allowed on the file handle after returning from the <methodname>preclose</methodname> method. </para> <para> Finally the <methodname>postclose</methodname> method is called as the last step of the close operation, right before calling the <methodname>lastclose</methodname> method if no other open file handle exists for the device. Drivers that have allocated per-file private data in the <methodname>open</methodname> method should free it here. </para> <para> The <methodname>lastclose</methodname> method should restore CRTC and plane properties to default value, so that a subsequent open of the device will not inherit state from the previous user. |
2d2ef8227 drm: add initial ... |
2296 2297 |
</para> </sect2> |
2d2ef8227 drm: add initial ... |
2298 |
<sect2> |
9cad9c95d Documentation: Do... |
2299 2300 2301 |
<title>File Operations</title> <synopsis>const struct file_operations *fops</synopsis> <abstract>File operations for the DRM device node.</abstract> |
2d2ef8227 drm: add initial ... |
2302 |
<para> |
9cad9c95d Documentation: Do... |
2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 |
Drivers must define the file operations structure that forms the DRM userspace API entry point, even though most of those operations are implemented in the DRM core. The <methodname>open</methodname>, <methodname>release</methodname> and <methodname>ioctl</methodname> operations are handled by <programlisting> .owner = THIS_MODULE, .open = drm_open, .release = drm_release, .unlocked_ioctl = drm_ioctl, #ifdef CONFIG_COMPAT .compat_ioctl = drm_compat_ioctl, #endif </programlisting> |
2d2ef8227 drm: add initial ... |
2317 2318 |
</para> <para> |
9cad9c95d Documentation: Do... |
2319 2320 2321 2322 |
Drivers that implement private ioctls that requires 32/64bit compatibility support must provide their own <methodname>compat_ioctl</methodname> handler that processes private ioctls and calls <function>drm_compat_ioctl</function> for core ioctls. |
2d2ef8227 drm: add initial ... |
2323 2324 |
</para> <para> |
9cad9c95d Documentation: Do... |
2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 |
The <methodname>read</methodname> and <methodname>poll</methodname> operations provide support for reading DRM events and polling them. They are implemented by <programlisting> .poll = drm_poll, .read = drm_read, .fasync = drm_fasync, .llseek = no_llseek, </programlisting> </para> <para> The memory mapping implementation varies depending on how the driver manages memory. Pre-GEM drivers will use <function>drm_mmap</function>, while GEM-aware drivers will use <function>drm_gem_mmap</function>. See <xref linkend="drm-gem"/>. <programlisting> .mmap = drm_gem_mmap, </programlisting> </para> <para> No other file operation is supported by the DRM API. </para> </sect2> <sect2> <title>IOCTLs</title> <synopsis>struct drm_ioctl_desc *ioctls; int num_ioctls;</synopsis> <abstract>Driver-specific ioctls descriptors table.</abstract> <para> Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls descriptors table is indexed by the ioctl number offset from the base value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the table entries. </para> <para> <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting> <para> <parameter>ioctl</parameter> is the ioctl name. Drivers must define the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number offset from DRM_COMMAND_BASE and the ioctl number respectively. The first macro is private to the device while the second must be exposed to userspace in a public header. </para> <para> <parameter>func</parameter> is a pointer to the ioctl handler function compatible with the <type>drm_ioctl_t</type> type. <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data, struct drm_file *file_priv);</programlisting> </para> <para> <parameter>flags</parameter> is a bitmask combination of the following values. It restricts how the ioctl is allowed to be called. <itemizedlist> <listitem><para> DRM_AUTH - Only authenticated callers allowed </para></listitem> <listitem><para> DRM_MASTER - The ioctl can only be called on the master file handle </para></listitem> <listitem><para> DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed </para></listitem> <listitem><para> DRM_CONTROL_ALLOW - The ioctl can only be called on a control device </para></listitem> <listitem><para> DRM_UNLOCKED - The ioctl handler will be called without locking the DRM global mutex </para></listitem> </itemizedlist> </para> |
2d2ef8227 drm: add initial ... |
2398 2399 |
</para> </sect2> |
2d2ef8227 drm: add initial ... |
2400 2401 2402 2403 2404 |
</sect1> <sect1> <title>Command submission & fencing</title> <para> |
a5294e01f DocBook/drm: `(de... |
2405 |
This should cover a few device-specific command submission |
2d2ef8227 drm: add initial ... |
2406 2407 2408 |
implementations. </para> </sect1> |
9cad9c95d Documentation: Do... |
2409 |
<!-- Internals: suspend/resume --> |
2d2ef8227 drm: add initial ... |
2410 |
<sect1> |
9cad9c95d Documentation: Do... |
2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 |
<title>Suspend/Resume</title> <para> The DRM core provides some suspend/resume code, but drivers wanting full suspend/resume support should provide save() and restore() functions. These are called at suspend, hibernate, or resume time, and should perform any state save or restore required by your device across suspend or hibernate states. </para> <synopsis>int (*suspend) (struct drm_device *, pm_message_t state); int (*resume) (struct drm_device *);</synopsis> |
2d2ef8227 drm: add initial ... |
2421 |
<para> |
9cad9c95d Documentation: Do... |
2422 2423 2424 2425 |
Those are legacy suspend and resume methods. New driver should use the power management interface provided by their bus type (usually through the struct <structname>device_driver</structname> dev_pm_ops) and set these methods to NULL. |
2d2ef8227 drm: add initial ... |
2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 |
</para> </sect1> <sect1> <title>DMA services</title> <para> This should cover how DMA mapping etc. is supported by the core. These functions are deprecated and should not be used. </para> </sect1> </chapter> |
9cad9c95d Documentation: Do... |
2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 |
<!-- TODO - Add a glossary - Document the struct_mutex catch-all lock - Document connector properties - Why is the load method optional? - What are drivers supposed to set the initial display state to, and how? Connector's DPMS states are not initialized and are thus equal to DRM_MODE_DPMS_ON. The fbcon compatibility layer calls drm_helper_disable_unused_functions(), which disables unused encoders and CRTCs, but doesn't touch the connectors' DPMS state, and drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers that don't implement (or just don't use) fbcon compatibility need to call those functions themselves? - KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset() around mode setting. Should this be done in the DRM core? - vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset() call and never set back to 0. It seems to be safe to permanently set it to 1 in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as well. This should be investigated. - crtc and connector .save and .restore operations are only used internally in drivers, should they be removed from the core? - encoder mid-layer .save and .restore operations are only used internally in drivers, should they be removed from the core? - encoder mid-layer .detect operation is only used internally in drivers, should it be removed from the core? --> |
2d2ef8227 drm: add initial ... |
2465 2466 2467 2468 2469 2470 2471 |
<!-- External interfaces --> <chapter id="drmExternals"> <title>Userland interfaces</title> <para> The DRM core exports several interfaces to applications, generally intended to be used through corresponding libdrm |
a5294e01f DocBook/drm: `(de... |
2472 |
wrapper functions. In addition, drivers export device-specific |
7f0925aca DocBook/drm: `dev... |
2473 |
interfaces for use by userspace drivers & device-aware |
2d2ef8227 drm: add initial ... |
2474 2475 2476 2477 2478 2479 2480 2481 |
applications through ioctls and sysfs files. </para> <para> External interfaces include: memory mapping, context management, DMA operations, AGP management, vblank control, fence management, memory management, and output management. </para> <para> |
bcd3cfc12 DocBook/drm: Clea... |
2482 2483 |
Cover generic ioctls and sysfs layout here. We only need high-level info, since man pages should cover the rest. |
2d2ef8227 drm: add initial ... |
2484 |
</para> |
9cad9c95d Documentation: Do... |
2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 |
<!-- External: vblank handling --> <sect1> <title>VBlank event handling</title> <para> The DRM core exposes two vertical blank related ioctls: <variablelist> <varlistentry> <term>DRM_IOCTL_WAIT_VBLANK</term> <listitem> <para> This takes a struct drm_wait_vblank structure as its argument, and it is used to block or request a signal when a specified vblank event occurs. </para> </listitem> </varlistentry> <varlistentry> <term>DRM_IOCTL_MODESET_CTL</term> <listitem> <para> This should be called by application level drivers before and after mode setting, since on many devices the vertical blank counter is reset at that time. Internally, the DRM snapshots the last vblank count when the ioctl is called with the _DRM_PRE_MODESET command, so that the counter won't go backwards (which is dealt with when _DRM_POST_MODESET is used). </para> </listitem> </varlistentry> </variablelist> <!--!Edrivers/char/drm/drm_irq.c--> </para> </sect1> |
2d2ef8227 drm: add initial ... |
2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 |
</chapter> <!-- API reference --> <appendix id="drmDriverApi"> <title>DRM Driver API</title> <para> Include auto-generated API reference here (need to reference it from paragraphs above too). </para> </appendix> </book> |