todo.rst (28569B)
1.. _todo: 2 3========= 4TODO list 5========= 6 7This section contains a list of smaller janitorial tasks in the kernel DRM 8graphics subsystem useful as newbie projects. Or for slow rainy days. 9 10Difficulty 11---------- 12 13To make it easier task are categorized into different levels: 14 15Starter: Good tasks to get started with the DRM subsystem. 16 17Intermediate: Tasks which need some experience with working in the DRM 18subsystem, or some specific GPU/display graphics knowledge. For debugging issue 19it's good to have the relevant hardware (or a virtual driver set up) available 20for testing. 21 22Advanced: Tricky tasks that need fairly good understanding of the DRM subsystem 23and graphics topics. Generally need the relevant hardware for development and 24testing. 25 26Expert: Only attempt these if you've successfully completed some tricky 27refactorings already and are an expert in the specific area 28 29Subsystem-wide refactorings 30=========================== 31 32Remove custom dumb_map_offset implementations 33--------------------------------------------- 34 35All GEM based drivers should be using drm_gem_create_mmap_offset() instead. 36Audit each individual driver, make sure it'll work with the generic 37implementation (there's lots of outdated locking leftovers in various 38implementations), and then remove it. 39 40Contact: Daniel Vetter, respective driver maintainers 41 42Level: Intermediate 43 44Convert existing KMS drivers to atomic modesetting 45-------------------------------------------------- 46 473.19 has the atomic modeset interfaces and helpers, so drivers can now be 48converted over. Modern compositors like Wayland or Surfaceflinger on Android 49really want an atomic modeset interface, so this is all about the bright 50future. 51 52There is a conversion guide for atomic and all you need is a GPU for a 53non-converted driver (again virtual HW drivers for KVM are still all 54suitable). 55 56As part of this drivers also need to convert to universal plane (which means 57exposing primary & cursor as proper plane objects). But that's much easier to 58do by directly using the new atomic helper driver callbacks. 59 60Contact: Daniel Vetter, respective driver maintainers 61 62Level: Advanced 63 64Clean up the clipped coordination confusion around planes 65--------------------------------------------------------- 66 67We have a helper to get this right with drm_plane_helper_check_update(), but 68it's not consistently used. This should be fixed, preferrably in the atomic 69helpers (and drivers then moved over to clipped coordinates). Probably the 70helper should also be moved from drm_plane_helper.c to the atomic helpers, to 71avoid confusion - the other helpers in that file are all deprecated legacy 72helpers. 73 74Contact: Ville Syrjälä, Daniel Vetter, driver maintainers 75 76Level: Advanced 77 78Improve plane atomic_check helpers 79---------------------------------- 80 81Aside from the clipped coordinates right above there's a few suboptimal things 82with the current helpers: 83 84- drm_plane_helper_funcs->atomic_check gets called for enabled or disabled 85 planes. At best this seems to confuse drivers, worst it means they blow up 86 when the plane is disabled without the CRTC. The only special handling is 87 resetting values in the plane state structures, which instead should be moved 88 into the drm_plane_funcs->atomic_duplicate_state functions. 89 90- Once that's done, helpers could stop calling ->atomic_check for disabled 91 planes. 92 93- Then we could go through all the drivers and remove the more-or-less confused 94 checks for plane_state->fb and plane_state->crtc. 95 96Contact: Daniel Vetter 97 98Level: Advanced 99 100Convert early atomic drivers to async commit helpers 101---------------------------------------------------- 102 103For the first year the atomic modeset helpers didn't support asynchronous / 104nonblocking commits, and every driver had to hand-roll them. This is fixed 105now, but there's still a pile of existing drivers that easily could be 106converted over to the new infrastructure. 107 108One issue with the helpers is that they require that drivers handle completion 109events for atomic commits correctly. But fixing these bugs is good anyway. 110 111Somewhat related is the legacy_cursor_update hack, which should be replaced with 112the new atomic_async_check/commit functionality in the helpers in drivers that 113still look at that flag. 114 115Contact: Daniel Vetter, respective driver maintainers 116 117Level: Advanced 118 119Fallout from atomic KMS 120----------------------- 121 122``drm_atomic_helper.c`` provides a batch of functions which implement legacy 123IOCTLs on top of the new atomic driver interface. Which is really nice for 124gradual conversion of drivers, but unfortunately the semantic mismatches are 125a bit too severe. So there's some follow-up work to adjust the function 126interfaces to fix these issues: 127 128* atomic needs the lock acquire context. At the moment that's passed around 129 implicitly with some horrible hacks, and it's also allocate with 130 ``GFP_NOFAIL`` behind the scenes. All legacy paths need to start allocating 131 the acquire context explicitly on stack and then also pass it down into 132 drivers explicitly so that the legacy-on-atomic functions can use them. 133 134 Except for some driver code this is done. This task should be finished by 135 adding WARN_ON(!drm_drv_uses_atomic_modeset) in drm_modeset_lock_all(). 136 137* A bunch of the vtable hooks are now in the wrong place: DRM has a split 138 between core vfunc tables (named ``drm_foo_funcs``), which are used to 139 implement the userspace ABI. And then there's the optional hooks for the 140 helper libraries (name ``drm_foo_helper_funcs``), which are purely for 141 internal use. Some of these hooks should be move from ``_funcs`` to 142 ``_helper_funcs`` since they are not part of the core ABI. There's a 143 ``FIXME`` comment in the kerneldoc for each such case in ``drm_crtc.h``. 144 145Contact: Daniel Vetter 146 147Level: Intermediate 148 149Get rid of dev->struct_mutex from GEM drivers 150--------------------------------------------- 151 152``dev->struct_mutex`` is the Big DRM Lock from legacy days and infested 153everything. Nowadays in modern drivers the only bit where it's mandatory is 154serializing GEM buffer object destruction. Which unfortunately means drivers 155have to keep track of that lock and either call ``unreference`` or 156``unreference_locked`` depending upon context. 157 158Core GEM doesn't have a need for ``struct_mutex`` any more since kernel 4.8, 159and there's a GEM object ``free`` callback for any drivers which are 160entirely ``struct_mutex`` free. 161 162For drivers that need ``struct_mutex`` it should be replaced with a driver- 163private lock. The tricky part is the BO free functions, since those can't 164reliably take that lock any more. Instead state needs to be protected with 165suitable subordinate locks or some cleanup work pushed to a worker thread. For 166performance-critical drivers it might also be better to go with a more 167fine-grained per-buffer object and per-context lockings scheme. Currently only 168the ``msm`` and `i915` drivers use ``struct_mutex``. 169 170Contact: Daniel Vetter, respective driver maintainers 171 172Level: Advanced 173 174Move Buffer Object Locking to dma_resv_lock() 175--------------------------------------------- 176 177Many drivers have their own per-object locking scheme, usually using 178mutex_lock(). This causes all kinds of trouble for buffer sharing, since 179depending which driver is the exporter and importer, the locking hierarchy is 180reversed. 181 182To solve this we need one standard per-object locking mechanism, which is 183dma_resv_lock(). This lock needs to be called as the outermost lock, with all 184other driver specific per-object locks removed. The problem is tha rolling out 185the actual change to the locking contract is a flag day, due to struct dma_buf 186buffer sharing. 187 188Level: Expert 189 190Convert logging to drm_* functions with drm_device paramater 191------------------------------------------------------------ 192 193For drivers which could have multiple instances, it is necessary to 194differentiate between which is which in the logs. Since DRM_INFO/WARN/ERROR 195don't do this, drivers used dev_info/warn/err to make this differentiation. We 196now have drm_* variants of the drm print functions, so we can start to convert 197those drivers back to using drm-formatted specific log messages. 198 199Before you start this conversion please contact the relevant maintainers to make 200sure your work will be merged - not everyone agrees that the DRM dmesg macros 201are better. 202 203Contact: Sean Paul, Maintainer of the driver you plan to convert 204 205Level: Starter 206 207Convert drivers to use simple modeset suspend/resume 208---------------------------------------------------- 209 210Most drivers (except i915 and nouveau) that use 211drm_atomic_helper_suspend/resume() can probably be converted to use 212drm_mode_config_helper_suspend/resume(). Also there's still open-coded version 213of the atomic suspend/resume code in older atomic modeset drivers. 214 215Contact: Maintainer of the driver you plan to convert 216 217Level: Intermediate 218 219Convert drivers to use drm_fbdev_generic_setup() 220------------------------------------------------ 221 222Most drivers can use drm_fbdev_generic_setup(). Driver have to implement 223atomic modesetting and GEM vmap support. Historically, generic fbdev emulation 224expected the framebuffer in system memory or system-like memory. By employing 225struct iosys_map, drivers with frambuffers in I/O memory can be supported 226as well. 227 228Contact: Maintainer of the driver you plan to convert 229 230Level: Intermediate 231 232Reimplement functions in drm_fbdev_fb_ops without fbdev 233------------------------------------------------------- 234 235A number of callback functions in drm_fbdev_fb_ops could benefit from 236being rewritten without dependencies on the fbdev module. Some of the 237helpers could further benefit from using struct iosys_map instead of 238raw pointers. 239 240Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter 241 242Level: Advanced 243 244Benchmark and optimize blitting and format-conversion function 245-------------------------------------------------------------- 246 247Drawing to dispay memory quickly is crucial for many applications' 248performance. 249 250On at least x86-64, sys_imageblit() is significantly slower than 251cfb_imageblit(), even though both use the same blitting algorithm and 252the latter is written for I/O memory. It turns out that cfb_imageblit() 253uses movl instructions, while sys_imageblit apparently does not. This 254seems to be a problem with gcc's optimizer. DRM's format-conversion 255helpers might be subject to similar issues. 256 257Benchmark and optimize fbdev's sys_() helpers and DRM's format-conversion 258helpers. In cases that can be further optimized, maybe implement a different 259algorithm. For micro-optimizations, use movl/movq instructions explicitly. 260That might possibly require architecture-specific helpers (e.g., storel() 261storeq()). 262 263Contact: Thomas Zimmermann <tzimmermann@suse.de> 264 265Level: Intermediate 266 267drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup 268----------------------------------------------------------------- 269 270A lot more drivers could be switched over to the drm_gem_framebuffer helpers. 271Various hold-ups: 272 273- Need to switch over to the generic dirty tracking code using 274 drm_atomic_helper_dirtyfb first (e.g. qxl). 275 276- Need to switch to drm_fbdev_generic_setup(), otherwise a lot of the custom fb 277 setup code can't be deleted. 278 279- Many drivers wrap drm_gem_fb_create() only to check for valid formats. For 280 atomic drivers we could check for valid formats by calling 281 drm_plane_check_pixel_format() against all planes, and pass if any plane 282 supports the format. For non-atomic that's not possible since like the format 283 list for the primary plane is fake and we'd therefor reject valid formats. 284 285- Many drivers subclass drm_framebuffer, we'd need a embedding compatible 286 version of the varios drm_gem_fb_create functions. Maybe called 287 drm_gem_fb_create/_with_dirty/_with_funcs as needed. 288 289Contact: Daniel Vetter 290 291Level: Intermediate 292 293Generic fbdev defio support 294--------------------------- 295 296The defio support code in the fbdev core has some very specific requirements, 297which means drivers need to have a special framebuffer for fbdev. The main 298issue is that it uses some fields in struct page itself, which breaks shmem 299gem objects (and other things). To support defio, affected drivers require 300the use of a shadow buffer, which may add CPU and memory overhead. 301 302Possible solution would be to write our own defio mmap code in the drm fbdev 303emulation. It would need to fully wrap the existing mmap ops, forwarding 304everything after it has done the write-protect/mkwrite trickery: 305 306- In the drm_fbdev_fb_mmap helper, if we need defio, change the 307 default page prots to write-protected with something like this:: 308 309 vma->vm_page_prot = pgprot_wrprotect(vma->vm_page_prot); 310 311- Set the mkwrite and fsync callbacks with similar implementions to the core 312 fbdev defio stuff. These should all work on plain ptes, they don't actually 313 require a struct page. uff. These should all work on plain ptes, they don't 314 actually require a struct page. 315 316- Track the dirty pages in a separate structure (bitfield with one bit per page 317 should work) to avoid clobbering struct page. 318 319Might be good to also have some igt testcases for this. 320 321Contact: Daniel Vetter, Noralf Tronnes 322 323Level: Advanced 324 325idr_init_base() 326--------------- 327 328DRM core&drivers uses a lot of idr (integer lookup directories) for mapping 329userspace IDs to internal objects, and in most places ID=0 means NULL and hence 330is never used. Switching to idr_init_base() for these would make the idr more 331efficient. 332 333Contact: Daniel Vetter 334 335Level: Starter 336 337struct drm_gem_object_funcs 338--------------------------- 339 340GEM objects can now have a function table instead of having the callbacks on the 341DRM driver struct. This is now the preferred way. Callbacks in drivers have been 342converted, except for struct drm_driver.gem_prime_mmap. 343 344Level: Intermediate 345 346Rename CMA helpers to DMA helpers 347--------------------------------- 348 349CMA (standing for contiguous memory allocator) is really a bit an accident of 350what these were used for first, a much better name would be DMA helpers. In the 351text these should even be called coherent DMA memory helpers (so maybe CDM, but 352no one knows what that means) since underneath they just use dma_alloc_coherent. 353 354Contact: Laurent Pinchart, Daniel Vetter 355 356Level: Intermediate (mostly because it is a huge tasks without good partial 357milestones, not technically itself that challenging) 358 359connector register/unregister fixes 360----------------------------------- 361 362- For most connectors it's a no-op to call drm_connector_register/unregister 363 directly from driver code, drm_dev_register/unregister take care of this 364 already. We can remove all of them. 365 366- For dp drivers it's a bit more a mess, since we need the connector to be 367 registered when calling drm_dp_aux_register. Fix this by instead calling 368 drm_dp_aux_init, and moving the actual registering into a late_register 369 callback as recommended in the kerneldoc. 370 371Level: Intermediate 372 373Remove load/unload callbacks from all non-DRIVER_LEGACY drivers 374--------------------------------------------------------------- 375 376The load/unload callbacks in struct &drm_driver are very much midlayers, plus 377for historical reasons they get the ordering wrong (and we can't fix that) 378between setting up the &drm_driver structure and calling drm_dev_register(). 379 380- Rework drivers to no longer use the load/unload callbacks, directly coding the 381 load/unload sequence into the driver's probe function. 382 383- Once all non-DRIVER_LEGACY drivers are converted, disallow the load/unload 384 callbacks for all modern drivers. 385 386Contact: Daniel Vetter 387 388Level: Intermediate 389 390Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi 391--------------------------------------------------------------- 392 393Once EDID is parsed, the monitor HDMI support information is available through 394drm_display_info.is_hdmi. Many drivers still call drm_detect_hdmi_monitor() to 395retrieve the same information, which is less efficient. 396 397Audit each individual driver calling drm_detect_hdmi_monitor() and switch to 398drm_display_info.is_hdmi if applicable. 399 400Contact: Laurent Pinchart, respective driver maintainers 401 402Level: Intermediate 403 404Consolidate custom driver modeset properties 405-------------------------------------------- 406 407Before atomic modeset took place, many drivers where creating their own 408properties. Among other things, atomic brought the requirement that custom, 409driver specific properties should not be used. 410 411For this task, we aim to introduce core helpers or reuse the existing ones 412if available: 413 414A quick, unconfirmed, examples list. 415 416Introduce core helpers: 417- audio (amdgpu, intel, gma500, radeon) 418- brightness, contrast, etc (armada, nouveau) - overlay only (?) 419- broadcast rgb (gma500, intel) 420- colorkey (armada, nouveau, rcar) - overlay only (?) 421- dither (amdgpu, nouveau, radeon) - varies across drivers 422- underscan family (amdgpu, radeon, nouveau) 423 424Already in core: 425- colorspace (sti) 426- tv format names, enhancements (gma500, intel) 427- tv overscan, margins, etc. (gma500, intel) 428- zorder (omapdrm) - same as zpos (?) 429 430 431Contact: Emil Velikov, respective driver maintainers 432 433Level: Intermediate 434 435Use struct iosys_map throughout codebase 436---------------------------------------- 437 438Pointers to shared device memory are stored in struct iosys_map. Each 439instance knows whether it refers to system or I/O memory. Most of the DRM-wide 440interface have been converted to use struct iosys_map, but implementations 441often still use raw pointers. 442 443The task is to use struct iosys_map where it makes sense. 444 445* Memory managers should use struct iosys_map for dma-buf-imported buffers. 446* TTM might benefit from using struct iosys_map internally. 447* Framebuffer copying and blitting helpers should operate on struct iosys_map. 448 449Contact: Thomas Zimmermann <tzimmermann@suse.de>, Christian König, Daniel Vetter 450 451Level: Intermediate 452 453Review all drivers for setting struct drm_mode_config.{max_width,max_height} correctly 454-------------------------------------------------------------------------------------- 455 456The values in struct drm_mode_config.{max_width,max_height} describe the 457maximum supported framebuffer size. It's the virtual screen size, but many 458drivers treat it like limitations of the physical resolution. 459 460The maximum width depends on the hardware's maximum scanline pitch. The 461maximum height depends on the amount of addressable video memory. Review all 462drivers to initialize the fields to the correct values. 463 464Contact: Thomas Zimmermann <tzimmermann@suse.de> 465 466Level: Intermediate 467 468Request memory regions in all drivers 469------------------------------------- 470 471Go through all drivers and add code to request the memory regions that the 472driver uses. This requires adding calls to request_mem_region(), 473pci_request_region() or similar functions. Use helpers for managed cleanup 474where possible. 475 476Drivers are pretty bad at doing this and there used to be conflicts among 477DRM and fbdev drivers. Still, it's the correct thing to do. 478 479Contact: Thomas Zimmermann <tzimmermann@suse.de> 480 481Level: Starter 482 483 484Core refactorings 485================= 486 487Make panic handling work 488------------------------ 489 490This is a really varied tasks with lots of little bits and pieces: 491 492* The panic path can't be tested currently, leading to constant breaking. The 493 main issue here is that panics can be triggered from hardirq contexts and 494 hence all panic related callback can run in hardirq context. It would be 495 awesome if we could test at least the fbdev helper code and driver code by 496 e.g. trigger calls through drm debugfs files. hardirq context could be 497 achieved by using an IPI to the local processor. 498 499* There's a massive confusion of different panic handlers. DRM fbdev emulation 500 helpers had their own (long removed), but on top of that the fbcon code itself 501 also has one. We need to make sure that they stop fighting over each other. 502 This is worked around by checking ``oops_in_progress`` at various entry points 503 into the DRM fbdev emulation helpers. A much cleaner approach here would be to 504 switch fbcon to the `threaded printk support 505 <https://lwn.net/Articles/800946/>`_. 506 507* ``drm_can_sleep()`` is a mess. It hides real bugs in normal operations and 508 isn't a full solution for panic paths. We need to make sure that it only 509 returns true if there's a panic going on for real, and fix up all the 510 fallout. 511 512* The panic handler must never sleep, which also means it can't ever 513 ``mutex_lock()``. Also it can't grab any other lock unconditionally, not 514 even spinlocks (because NMI and hardirq can panic too). We need to either 515 make sure to not call such paths, or trylock everything. Really tricky. 516 517* A clean solution would be an entirely separate panic output support in KMS, 518 bypassing the current fbcon support. See `[PATCH v2 0/3] drm: Add panic handling 519 <https://lore.kernel.org/dri-devel/20190311174218.51899-1-noralf@tronnes.org/>`_. 520 521* Encoding the actual oops and preceding dmesg in a QR might help with the 522 dread "important stuff scrolled away" problem. See `[RFC][PATCH] Oops messages 523 transfer using QR codes 524 <https://lore.kernel.org/lkml/1446217392-11981-1-git-send-email-alexandru.murtaza@intel.com/>`_ 525 for some example code that could be reused. 526 527Contact: Daniel Vetter 528 529Level: Advanced 530 531Clean up the debugfs support 532---------------------------- 533 534There's a bunch of issues with it: 535 536- The drm_info_list ->show() function doesn't even bother to cast to the drm 537 structure for you. This is lazy. 538 539- We probably want to have some support for debugfs files on crtc/connectors and 540 maybe other kms objects directly in core. There's even drm_print support in 541 the funcs for these objects to dump kms state, so it's all there. And then the 542 ->show() functions should obviously give you a pointer to the right object. 543 544- The drm_info_list stuff is centered on drm_minor instead of drm_device. For 545 anything we want to print drm_device (or maybe drm_file) is the right thing. 546 547- The drm_driver->debugfs_init hooks we have is just an artifact of the old 548 midlayered load sequence. DRM debugfs should work more like sysfs, where you 549 can create properties/files for an object anytime you want, and the core 550 takes care of publishing/unpuplishing all the files at register/unregister 551 time. Drivers shouldn't need to worry about these technicalities, and fixing 552 this (together with the drm_minor->drm_device move) would allow us to remove 553 debugfs_init. 554 555Previous RFC that hasn't landed yet: https://lore.kernel.org/dri-devel/20200513114130.28641-2-wambui.karugax@gmail.com/ 556 557Contact: Daniel Vetter 558 559Level: Intermediate 560 561Object lifetime fixes 562--------------------- 563 564There's two related issues here 565 566- Cleanup up the various ->destroy callbacks, which often are all the same 567 simple code. 568 569- Lots of drivers erroneously allocate DRM modeset objects using devm_kzalloc, 570 which results in use-after free issues on driver unload. This can be serious 571 trouble even for drivers for hardware integrated on the SoC due to 572 EPROBE_DEFERRED backoff. 573 574Both these problems can be solved by switching over to drmm_kzalloc(), and the 575various convenience wrappers provided, e.g. drmm_crtc_alloc_with_planes(), 576drmm_universal_plane_alloc(), ... and so on. 577 578Contact: Daniel Vetter 579 580Level: Intermediate 581 582Remove automatic page mapping from dma-buf importing 583---------------------------------------------------- 584 585When importing dma-bufs, the dma-buf and PRIME frameworks automatically map 586imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and 587drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach() 588even if they never do actual device DMA, but only CPU access through 589dma_buf_vmap(). This is a problem for USB devices, which do not support DMA 590operations. 591 592To fix the issue, automatic page mappings should be removed from the 593buffer-sharing code. Fixing this is a bit more involved, since the import/export 594cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over 595this problem for USB devices by fishing out the USB host controller device, as 596long as that supports DMA. Otherwise importing can still needlessly fail. 597 598Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter 599 600Level: Advanced 601 602 603Better Testing 604============== 605 606Add unit tests using the Kernel Unit Testing (KUnit) framework 607-------------------------------------------------------------- 608 609The `KUnit <https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html>`_ 610provides a common framework for unit tests within the Linux kernel. Having a 611test suite would allow to identify regressions earlier. 612 613A good candidate for the first unit tests are the format-conversion helpers in 614``drm_format_helper.c``. 615 616Contact: Javier Martinez Canillas <javierm@redhat.com> 617 618Level: Intermediate 619 620Enable trinity for DRM 621---------------------- 622 623And fix up the fallout. Should be really interesting ... 624 625Level: Advanced 626 627Make KMS tests in i-g-t generic 628------------------------------- 629 630The i915 driver team maintains an extensive testsuite for the i915 DRM driver, 631including tons of testcases for corner-cases in the modesetting API. It would 632be awesome if those tests (at least the ones not relying on Intel-specific GEM 633features) could be made to run on any KMS driver. 634 635Basic work to run i-g-t tests on non-i915 is done, what's now missing is mass- 636converting things over. For modeset tests we also first need a bit of 637infrastructure to use dumb buffers for untiled buffers, to be able to run all 638the non-i915 specific modeset tests. 639 640Level: Advanced 641 642Extend virtual test driver (VKMS) 643--------------------------------- 644 645See the documentation of :ref:`VKMS <vkms>` for more details. This is an ideal 646internship task, since it only requires a virtual machine and can be sized to 647fit the available time. 648 649Level: See details 650 651Backlight Refactoring 652--------------------- 653 654Backlight drivers have a triple enable/disable state, which is a bit overkill. 655Plan to fix this: 656 6571. Roll out backlight_enable() and backlight_disable() helpers everywhere. This 658 has started already. 6592. In all, only look at one of the three status bits set by the above helpers. 6603. Remove the other two status bits. 661 662Contact: Daniel Vetter 663 664Level: Intermediate 665 666Driver Specific 667=============== 668 669AMD DC Display Driver 670--------------------- 671 672AMD DC is the display driver for AMD devices starting with Vega. There has been 673a bunch of progress cleaning it up but there's still plenty of work to be done. 674 675See drivers/gpu/drm/amd/display/TODO for tasks. 676 677Contact: Harry Wentland, Alex Deucher 678 679vmwgfx: Replace hashtable with Linux' implementation 680---------------------------------------------------- 681 682The vmwgfx driver uses its own hashtable implementation. Replace the 683code with Linux' implementation and update the callers. It's mostly a 684refactoring task, but the interfaces are different. 685 686Contact: Zack Rusin, Thomas Zimmermann <tzimmermann@suse.de> 687 688Level: Intermediate 689 690Bootsplash 691========== 692 693There is support in place now for writing internal DRM clients making it 694possible to pick up the bootsplash work that was rejected because it was written 695for fbdev. 696 697- [v6,8/8] drm/client: Hack: Add bootsplash example 698 https://patchwork.freedesktop.org/patch/306579/ 699 700- [RFC PATCH v2 00/13] Kernel based bootsplash 701 https://lore.kernel.org/r/20171213194755.3409-1-mstaudt@suse.de 702 703Contact: Sam Ravnborg 704 705Level: Advanced 706 707Outside DRM 708=========== 709 710Convert fbdev drivers to DRM 711---------------------------- 712 713There are plenty of fbdev drivers for older hardware. Some hardware has 714become obsolete, but some still provides good(-enough) framebuffers. The 715drivers that are still useful should be converted to DRM and afterwards 716removed from fbdev. 717 718Very simple fbdev drivers can best be converted by starting with a new 719DRM driver. Simple KMS helpers and SHMEM should be able to handle any 720existing hardware. The new driver's call-back functions are filled from 721existing fbdev code. 722 723More complex fbdev drivers can be refactored step-by-step into a DRM 724driver with the help of the DRM fbconv helpers. [1] These helpers provide 725the transition layer between the DRM core infrastructure and the fbdev 726driver interface. Create a new DRM driver on top of the fbconv helpers, 727copy over the fbdev driver, and hook it up to the DRM code. Examples for 728several fbdev drivers are available at [1] and a tutorial of this process 729available at [2]. The result is a primitive DRM driver that can run X11 730and Weston. 731 732 - [1] https://gitlab.freedesktop.org/tzimmermann/linux/tree/fbconv 733 - [2] https://gitlab.freedesktop.org/tzimmermann/linux/blob/fbconv/drivers/gpu/drm/drm_fbconv_helper.c 734 735Contact: Thomas Zimmermann <tzimmermann@suse.de> 736 737Level: Advanced