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instead. 36Audit each individual driver, make sure it'll work with the generic 37implementation (there's lots of outdated locking leftovers in various 38implementations), and then remove it. 39 40Contact: Daniel Vetter, respective driver maintainers 41 42Level: Intermediate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 dma_buf_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 dma_buf_map instead of 238raw pointers. 239 240Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter 241 242Level: Advanced 243 244 245drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup 246----------------------------------------------------------------- 247 248A lot more drivers could be switched over to the drm_gem_framebuffer helpers. 249Various hold-ups: 250 251- Need to switch over to the generic dirty tracking code using 252 drm_atomic_helper_dirtyfb first (e.g. qxl). 253 254- Need to switch to drm_fbdev_generic_setup(), otherwise a lot of the custom fb 255 setup code can't be deleted. 256 257- Many drivers wrap drm_gem_fb_create() only to check for valid formats. For 258 atomic drivers we could check for valid formats by calling 259 drm_plane_check_pixel_format() against all planes, and pass if any plane 260 supports the format. For non-atomic that's not possible since like the format 261 list for the primary plane is fake and we'd therefor reject valid formats. 262 263- Many drivers subclass drm_framebuffer, we'd need a embedding compatible 264 version of the varios drm_gem_fb_create functions. Maybe called 265 drm_gem_fb_create/_with_dirty/_with_funcs as needed. 266 267Contact: Daniel Vetter 268 269Level: Intermediate 270 271Clean up mmap forwarding 272------------------------ 273 274A lot of drivers forward gem mmap calls to dma-buf mmap for imported buffers. 275And also a lot of them forward dma-buf mmap to the gem mmap implementations. 276There's drm_gem_prime_mmap() for this now, but still needs to be rolled out. 277 278Contact: Daniel Vetter 279 280Level: Intermediate 281 282Generic fbdev defio support 283--------------------------- 284 285The defio support code in the fbdev core has some very specific requirements, 286which means drivers need to have a special framebuffer for fbdev. The main 287issue is that it uses some fields in struct page itself, which breaks shmem 288gem objects (and other things). To support defio, affected drivers require 289the use of a shadow buffer, which may add CPU and memory overhead. 290 291Possible solution would be to write our own defio mmap code in the drm fbdev 292emulation. It would need to fully wrap the existing mmap ops, forwarding 293everything after it has done the write-protect/mkwrite trickery: 294 295- In the drm_fbdev_fb_mmap helper, if we need defio, change the 296 default page prots to write-protected with something like this:: 297 298 vma->vm_page_prot = pgprot_wrprotect(vma->vm_page_prot); 299 300- Set the mkwrite and fsync callbacks with similar implementions to the core 301 fbdev defio stuff. These should all work on plain ptes, they don't actually 302 require a struct page. uff. These should all work on plain ptes, they don't 303 actually require a struct page. 304 305- Track the dirty pages in a separate structure (bitfield with one bit per page 306 should work) to avoid clobbering struct page. 307 308Might be good to also have some igt testcases for this. 309 310Contact: Daniel Vetter, Noralf Tronnes 311 312Level: Advanced 313 314Garbage collect fbdev scrolling acceleration 315-------------------------------------------- 316 317Scroll acceleration has been disabled in fbcon. Now it works as the old 318SCROLL_REDRAW mode. A ton of code was removed in fbcon.c and the hook bmove was 319removed from fbcon_ops. 320Remaining tasks: 321 322- a bunch of the hooks in fbcon_ops could be removed or simplified by calling 323 directly instead of the function table (with a switch on p->rotate) 324 325- fb_copyarea is unused after this, and can be deleted from all drivers 326 327- after that, fb_copyarea can be deleted from fb_ops in include/linux/fb.h as 328 well as cfb_copyarea 329 330Note that not all acceleration code can be deleted, since clearing and cursor 331support is still accelerated, which might be good candidates for further 332deletion projects. 333 334Contact: Daniel Vetter 335 336Level: Intermediate 337 338idr_init_base() 339--------------- 340 341DRM core&drivers uses a lot of idr (integer lookup directories) for mapping 342userspace IDs to internal objects, and in most places ID=0 means NULL and hence 343is never used. Switching to idr_init_base() for these would make the idr more 344efficient. 345 346Contact: Daniel Vetter 347 348Level: Starter 349 350struct drm_gem_object_funcs 351--------------------------- 352 353GEM objects can now have a function table instead of having the callbacks on the 354DRM driver struct. This is now the preferred way. Callbacks in drivers have been 355converted, except for struct drm_driver.gem_prime_mmap. 356 357Level: Intermediate 358 359Rename CMA helpers to DMA helpers 360--------------------------------- 361 362CMA (standing for contiguous memory allocator) is really a bit an accident of 363what these were used for first, a much better name would be DMA helpers. In the 364text these should even be called coherent DMA memory helpers (so maybe CDM, but 365no one knows what that means) since underneath they just use dma_alloc_coherent. 366 367Contact: Laurent Pinchart, Daniel Vetter 368 369Level: Intermediate (mostly because it is a huge tasks without good partial 370milestones, not technically itself that challenging) 371 372connector register/unregister fixes 373----------------------------------- 374 375- For most connectors it's a no-op to call drm_connector_register/unregister 376 directly from driver code, drm_dev_register/unregister take care of this 377 already. We can remove all of them. 378 379- For dp drivers it's a bit more a mess, since we need the connector to be 380 registered when calling drm_dp_aux_register. Fix this by instead calling 381 drm_dp_aux_init, and moving the actual registering into a late_register 382 callback as recommended in the kerneldoc. 383 384Level: Intermediate 385 386Remove load/unload callbacks from all non-DRIVER_LEGACY drivers 387--------------------------------------------------------------- 388 389The load/unload callbacks in struct &drm_driver are very much midlayers, plus 390for historical reasons they get the ordering wrong (and we can't fix that) 391between setting up the &drm_driver structure and calling drm_dev_register(). 392 393- Rework drivers to no longer use the load/unload callbacks, directly coding the 394 load/unload sequence into the driver's probe function. 395 396- Once all non-DRIVER_LEGACY drivers are converted, disallow the load/unload 397 callbacks for all modern drivers. 398 399Contact: Daniel Vetter 400 401Level: Intermediate 402 403Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi 404--------------------------------------------------------------- 405 406Once EDID is parsed, the monitor HDMI support information is available through 407drm_display_info.is_hdmi. Many drivers still call drm_detect_hdmi_monitor() to 408retrieve the same information, which is less efficient. 409 410Audit each individual driver calling drm_detect_hdmi_monitor() and switch to 411drm_display_info.is_hdmi if applicable. 412 413Contact: Laurent Pinchart, respective driver maintainers 414 415Level: Intermediate 416 417Consolidate custom driver modeset properties 418-------------------------------------------- 419 420Before atomic modeset took place, many drivers where creating their own 421properties. Among other things, atomic brought the requirement that custom, 422driver specific properties should not be used. 423 424For this task, we aim to introduce core helpers or reuse the existing ones 425if available: 426 427A quick, unconfirmed, examples list. 428 429Introduce core helpers: 430- audio (amdgpu, intel, gma500, radeon) 431- brightness, contrast, etc (armada, nouveau) - overlay only (?) 432- broadcast rgb (gma500, intel) 433- colorkey (armada, nouveau, rcar) - overlay only (?) 434- dither (amdgpu, nouveau, radeon) - varies across drivers 435- underscan family (amdgpu, radeon, nouveau) 436 437Already in core: 438- colorspace (sti) 439- tv format names, enhancements (gma500, intel) 440- tv overscan, margins, etc. (gma500, intel) 441- zorder (omapdrm) - same as zpos (?) 442 443 444Contact: Emil Velikov, respective driver maintainers 445 446Level: Intermediate 447 448Use struct dma_buf_map throughout codebase 449------------------------------------------ 450 451Pointers to shared device memory are stored in struct dma_buf_map. Each 452instance knows whether it refers to system or I/O memory. Most of the DRM-wide 453interface have been converted to use struct dma_buf_map, but implementations 454often still use raw pointers. 455 456The task is to use struct dma_buf_map where it makes sense. 457 458* Memory managers should use struct dma_buf_map for dma-buf-imported buffers. 459* TTM might benefit from using struct dma_buf_map internally. 460* Framebuffer copying and blitting helpers should operate on struct dma_buf_map. 461 462Contact: Thomas Zimmermann <tzimmermann@suse.de>, Christian König, Daniel Vetter 463 464Level: Intermediate 465 466 467Core refactorings 468================= 469 470Make panic handling work 471------------------------ 472 473This is a really varied tasks with lots of little bits and pieces: 474 475* The panic path can't be tested currently, leading to constant breaking. The 476 main issue here is that panics can be triggered from hardirq contexts and 477 hence all panic related callback can run in hardirq context. It would be 478 awesome if we could test at least the fbdev helper code and driver code by 479 e.g. trigger calls through drm debugfs files. hardirq context could be 480 achieved by using an IPI to the local processor. 481 482* There's a massive confusion of different panic handlers. DRM fbdev emulation 483 helpers have one, but on top of that the fbcon code itself also has one. We 484 need to make sure that they stop fighting over each another. 485 486* ``drm_can_sleep()`` is a mess. It hides real bugs in normal operations and 487 isn't a full solution for panic paths. We need to make sure that it only 488 returns true if there's a panic going on for real, and fix up all the 489 fallout. 490 491* The panic handler must never sleep, which also means it can't ever 492 ``mutex_lock()``. Also it can't grab any other lock unconditionally, not 493 even spinlocks (because NMI and hardirq can panic too). We need to either 494 make sure to not call such paths, or trylock everything. Really tricky. 495 496* For the above locking troubles reasons it's pretty much impossible to 497 attempt a synchronous modeset from panic handlers. The only thing we could 498 try to achive is an atomic ``set_base`` of the primary plane, and hope that 499 it shows up. Everything else probably needs to be delayed to some worker or 500 something else which happens later on. Otherwise it just kills the box 501 harder, prevent the panic from going out on e.g. netconsole. 502 503* There's also proposal for a simplied DRM console instead of the full-blown 504 fbcon and DRM fbdev emulation. Any kind of panic handling tricks should 505 obviously work for both console, in case we ever get kmslog merged. 506 507Contact: Daniel Vetter 508 509Level: Advanced 510 511Clean up the debugfs support 512---------------------------- 513 514There's a bunch of issues with it: 515 516- The drm_info_list ->show() function doesn't even bother to cast to the drm 517 structure for you. This is lazy. 518 519- We probably want to have some support for debugfs files on crtc/connectors and 520 maybe other kms objects directly in core. There's even drm_print support in 521 the funcs for these objects to dump kms state, so it's all there. And then the 522 ->show() functions should obviously give you a pointer to the right object. 523 524- The drm_info_list stuff is centered on drm_minor instead of drm_device. For 525 anything we want to print drm_device (or maybe drm_file) is the right thing. 526 527- The drm_driver->debugfs_init hooks we have is just an artifact of the old 528 midlayered load sequence. DRM debugfs should work more like sysfs, where you 529 can create properties/files for an object anytime you want, and the core 530 takes care of publishing/unpuplishing all the files at register/unregister 531 time. Drivers shouldn't need to worry about these technicalities, and fixing 532 this (together with the drm_minor->drm_device move) would allow us to remove 533 debugfs_init. 534 535Previous RFC that hasn't landed yet: https://lore.kernel.org/dri-devel/20200513114130.28641-2-wambui.karugax@gmail.com/ 536 537Contact: Daniel Vetter 538 539Level: Intermediate 540 541Object lifetime fixes 542--------------------- 543 544There's two related issues here 545 546- Cleanup up the various ->destroy callbacks, which often are all the same 547 simple code. 548 549- Lots of drivers erroneously allocate DRM modeset objects using devm_kzalloc, 550 which results in use-after free issues on driver unload. This can be serious 551 trouble even for drivers for hardware integrated on the SoC due to 552 EPROBE_DEFERRED backoff. 553 554Both these problems can be solved by switching over to drmm_kzalloc(), and the 555various convenience wrappers provided, e.g. drmm_crtc_alloc_with_planes(), 556drmm_universal_plane_alloc(), ... and so on. 557 558Contact: Daniel Vetter 559 560Level: Intermediate 561 562Remove automatic page mapping from dma-buf importing 563---------------------------------------------------- 564 565When importing dma-bufs, the dma-buf and PRIME frameworks automatically map 566imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and 567drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach() 568even if they never do actual device DMA, but only CPU access through 569dma_buf_vmap(). This is a problem for USB devices, which do not support DMA 570operations. 571 572To fix the issue, automatic page mappings should be removed from the 573buffer-sharing code. Fixing this is a bit more involved, since the import/export 574cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over 575this problem for USB devices by fishing out the USB host controller device, as 576long as that supports DMA. Otherwise importing can still needlessly fail. 577 578Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter 579 580Level: Advanced 581 582 583Better Testing 584============== 585 586Enable trinity for DRM 587---------------------- 588 589And fix up the fallout. Should be really interesting ... 590 591Level: Advanced 592 593Make KMS tests in i-g-t generic 594------------------------------- 595 596The i915 driver team maintains an extensive testsuite for the i915 DRM driver, 597including tons of testcases for corner-cases in the modesetting API. It would 598be awesome if those tests (at least the ones not relying on Intel-specific GEM 599features) could be made to run on any KMS driver. 600 601Basic work to run i-g-t tests on non-i915 is done, what's now missing is mass- 602converting things over. For modeset tests we also first need a bit of 603infrastructure to use dumb buffers for untiled buffers, to be able to run all 604the non-i915 specific modeset tests. 605 606Level: Advanced 607 608Extend virtual test driver (VKMS) 609--------------------------------- 610 611See the documentation of :ref:`VKMS <vkms>` for more details. This is an ideal 612internship task, since it only requires a virtual machine and can be sized to 613fit the available time. 614 615Level: See details 616 617Backlight Refactoring 618--------------------- 619 620Backlight drivers have a triple enable/disable state, which is a bit overkill. 621Plan to fix this: 622 6231. Roll out backlight_enable() and backlight_disable() helpers everywhere. This 624 has started already. 6252. In all, only look at one of the three status bits set by the above helpers. 6263. Remove the other two status bits. 627 628Contact: Daniel Vetter 629 630Level: Intermediate 631 632Driver Specific 633=============== 634 635AMD DC Display Driver 636--------------------- 637 638AMD DC is the display driver for AMD devices starting with Vega. There has been 639a bunch of progress cleaning it up but there's still plenty of work to be done. 640 641See drivers/gpu/drm/amd/display/TODO for tasks. 642 643Contact: Harry Wentland, Alex Deucher 644 645Bootsplash 646========== 647 648There is support in place now for writing internal DRM clients making it 649possible to pick up the bootsplash work that was rejected because it was written 650for fbdev. 651 652- [v6,8/8] drm/client: Hack: Add bootsplash example 653 https://patchwork.freedesktop.org/patch/306579/ 654 655- [RFC PATCH v2 00/13] Kernel based bootsplash 656 https://lore.kernel.org/r/20171213194755.3409-1-mstaudt@suse.de 657 658Contact: Sam Ravnborg 659 660Level: Advanced 661 662Outside DRM 663=========== 664 665Convert fbdev drivers to DRM 666---------------------------- 667 668There are plenty of fbdev drivers for older hardware. Some hardware has 669become obsolete, but some still provides good(-enough) framebuffers. The 670drivers that are still useful should be converted to DRM and afterwards 671removed from fbdev. 672 673Very simple fbdev drivers can best be converted by starting with a new 674DRM driver. Simple KMS helpers and SHMEM should be able to handle any 675existing hardware. The new driver's call-back functions are filled from 676existing fbdev code. 677 678More complex fbdev drivers can be refactored step-by-step into a DRM 679driver with the help of the DRM fbconv helpers. [1] These helpers provide 680the transition layer between the DRM core infrastructure and the fbdev 681driver interface. Create a new DRM driver on top of the fbconv helpers, 682copy over the fbdev driver, and hook it up to the DRM code. Examples for 683several fbdev drivers are available at [1] and a tutorial of this process 684available at [2]. The result is a primitive DRM driver that can run X11 685and Weston. 686 687 - [1] https://gitlab.freedesktop.org/tzimmermann/linux/tree/fbconv 688 - [2] https://gitlab.freedesktop.org/tzimmermann/linux/blob/fbconv/drivers/gpu/drm/drm_fbconv_helper.c 689 690Contact: Thomas Zimmermann <tzimmermann@suse.de> 691 692Level: Advanced 693