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 26Subsystem-wide refactorings 27=========================== 28 29Remove custom dumb_map_offset implementations 30--------------------------------------------- 31 32All GEM based drivers should be using drm_gem_create_mmap_offset() instead. 33Audit each individual driver, make sure it'll work with the generic 34implementation (there's lots of outdated locking leftovers in various 35implementations), and then remove it. 36 37Contact: Daniel Vetter, respective driver maintainers 38 39Level: Intermediate 40 41Convert existing KMS drivers to atomic modesetting 42-------------------------------------------------- 43 443.19 has the atomic modeset interfaces and helpers, so drivers can now be 45converted over. Modern compositors like Wayland or Surfaceflinger on Android 46really want an atomic modeset interface, so this is all about the bright 47future. 48 49There is a conversion guide for atomic and all you need is a GPU for a 50non-converted driver (again virtual HW drivers for KVM are still all 51suitable). 52 53As part of this drivers also need to convert to universal plane (which means 54exposing primary & cursor as proper plane objects). But that's much easier to 55do by directly using the new atomic helper driver callbacks. 56 57Contact: Daniel Vetter, respective driver maintainers 58 59Level: Advanced 60 61Clean up the clipped coordination confusion around planes 62--------------------------------------------------------- 63 64We have a helper to get this right with drm_plane_helper_check_update(), but 65it's not consistently used. This should be fixed, preferrably in the atomic 66helpers (and drivers then moved over to clipped coordinates). Probably the 67helper should also be moved from drm_plane_helper.c to the atomic helpers, to 68avoid confusion - the other helpers in that file are all deprecated legacy 69helpers. 70 71Contact: Ville Syrjälä, Daniel Vetter, driver maintainers 72 73Level: Advanced 74 75Improve plane atomic_check helpers 76---------------------------------- 77 78Aside from the clipped coordinates right above there's a few suboptimal things 79with the current helpers: 80 81- drm_plane_helper_funcs->atomic_check gets called for enabled or disabled 82 planes. At best this seems to confuse drivers, worst it means they blow up 83 when the plane is disabled without the CRTC. The only special handling is 84 resetting values in the plane state structures, which instead should be moved 85 into the drm_plane_funcs->atomic_duplicate_state functions. 86 87- Once that's done, helpers could stop calling ->atomic_check for disabled 88 planes. 89 90- Then we could go through all the drivers and remove the more-or-less confused 91 checks for plane_state->fb and plane_state->crtc. 92 93Contact: Daniel Vetter 94 95Level: Advanced 96 97Convert early atomic drivers to async commit helpers 98---------------------------------------------------- 99 100For the first year the atomic modeset helpers didn't support asynchronous / 101nonblocking commits, and every driver had to hand-roll them. This is fixed 102now, but there's still a pile of existing drivers that easily could be 103converted over to the new infrastructure. 104 105One issue with the helpers is that they require that drivers handle completion 106events for atomic commits correctly. But fixing these bugs is good anyway. 107 108Somewhat related is the legacy_cursor_update hack, which should be replaced with 109the new atomic_async_check/commit functionality in the helpers in drivers that 110still look at that flag. 111 112Contact: Daniel Vetter, respective driver maintainers 113 114Level: Advanced 115 116Fallout from atomic KMS 117----------------------- 118 119``drm_atomic_helper.c`` provides a batch of functions which implement legacy 120IOCTLs on top of the new atomic driver interface. Which is really nice for 121gradual conversion of drivers, but unfortunately the semantic mismatches are 122a bit too severe. So there's some follow-up work to adjust the function 123interfaces to fix these issues: 124 125* atomic needs the lock acquire context. At the moment that's passed around 126 implicitly with some horrible hacks, and it's also allocate with 127 ``GFP_NOFAIL`` behind the scenes. All legacy paths need to start allocating 128 the acquire context explicitly on stack and then also pass it down into 129 drivers explicitly so that the legacy-on-atomic functions can use them. 130 131 Except for some driver code this is done. This task should be finished by 132 adding WARN_ON(!drm_drv_uses_atomic_modeset) in drm_modeset_lock_all(). 133 134* A bunch of the vtable hooks are now in the wrong place: DRM has a split 135 between core vfunc tables (named ``drm_foo_funcs``), which are used to 136 implement the userspace ABI. And then there's the optional hooks for the 137 helper libraries (name ``drm_foo_helper_funcs``), which are purely for 138 internal use. Some of these hooks should be move from ``_funcs`` to 139 ``_helper_funcs`` since they are not part of the core ABI. There's a 140 ``FIXME`` comment in the kerneldoc for each such case in ``drm_crtc.h``. 141 142Contact: Daniel Vetter 143 144Level: Intermediate 145 146Get rid of dev->struct_mutex from GEM drivers 147--------------------------------------------- 148 149``dev->struct_mutex`` is the Big DRM Lock from legacy days and infested 150everything. Nowadays in modern drivers the only bit where it's mandatory is 151serializing GEM buffer object destruction. Which unfortunately means drivers 152have to keep track of that lock and either call ``unreference`` or 153``unreference_locked`` depending upon context. 154 155Core GEM doesn't have a need for ``struct_mutex`` any more since kernel 4.8, 156and there's a GEM object ``free`` callback for any drivers which are 157entirely ``struct_mutex`` free. 158 159For drivers that need ``struct_mutex`` it should be replaced with a driver- 160private lock. The tricky part is the BO free functions, since those can't 161reliably take that lock any more. Instead state needs to be protected with 162suitable subordinate locks or some cleanup work pushed to a worker thread. For 163performance-critical drivers it might also be better to go with a more 164fine-grained per-buffer object and per-context lockings scheme. Currently only 165the ``msm`` and `i915` drivers use ``struct_mutex``. 166 167Contact: Daniel Vetter, respective driver maintainers 168 169Level: Advanced 170 171Convert logging to drm_* functions with drm_device paramater 172------------------------------------------------------------ 173 174For drivers which could have multiple instances, it is necessary to 175differentiate between which is which in the logs. Since DRM_INFO/WARN/ERROR 176don't do this, drivers used dev_info/warn/err to make this differentiation. We 177now have drm_* variants of the drm print functions, so we can start to convert 178those drivers back to using drm-formatted specific log messages. 179 180Before you start this conversion please contact the relevant maintainers to make 181sure your work will be merged - not everyone agrees that the DRM dmesg macros 182are better. 183 184Contact: Sean Paul, Maintainer of the driver you plan to convert 185 186Level: Starter 187 188Convert drivers to use simple modeset suspend/resume 189---------------------------------------------------- 190 191Most drivers (except i915 and nouveau) that use 192drm_atomic_helper_suspend/resume() can probably be converted to use 193drm_mode_config_helper_suspend/resume(). Also there's still open-coded version 194of the atomic suspend/resume code in older atomic modeset drivers. 195 196Contact: Maintainer of the driver you plan to convert 197 198Level: Intermediate 199 200Convert drivers to use drm_fbdev_generic_setup() 201------------------------------------------------ 202 203Most drivers can use drm_fbdev_generic_setup(). Driver have to implement 204atomic modesetting and GEM vmap support. Historically, generic fbdev emulation 205expected the framebuffer in system memory or system-like memory. By employing 206struct dma_buf_map, drivers with frambuffers in I/O memory can be supported 207as well. 208 209Contact: Maintainer of the driver you plan to convert 210 211Level: Intermediate 212 213Reimplement functions in drm_fbdev_fb_ops without fbdev 214------------------------------------------------------- 215 216A number of callback functions in drm_fbdev_fb_ops could benefit from 217being rewritten without dependencies on the fbdev module. Some of the 218helpers could further benefit from using struct dma_buf_map instead of 219raw pointers. 220 221Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter 222 223Level: Advanced 224 225 226drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup 227----------------------------------------------------------------- 228 229A lot more drivers could be switched over to the drm_gem_framebuffer helpers. 230Various hold-ups: 231 232- Need to switch over to the generic dirty tracking code using 233 drm_atomic_helper_dirtyfb first (e.g. qxl). 234 235- Need to switch to drm_fbdev_generic_setup(), otherwise a lot of the custom fb 236 setup code can't be deleted. 237 238- Many drivers wrap drm_gem_fb_create() only to check for valid formats. For 239 atomic drivers we could check for valid formats by calling 240 drm_plane_check_pixel_format() against all planes, and pass if any plane 241 supports the format. For non-atomic that's not possible since like the format 242 list for the primary plane is fake and we'd therefor reject valid formats. 243 244- Many drivers subclass drm_framebuffer, we'd need a embedding compatible 245 version of the varios drm_gem_fb_create functions. Maybe called 246 drm_gem_fb_create/_with_dirty/_with_funcs as needed. 247 248Contact: Daniel Vetter 249 250Level: Intermediate 251 252Clean up mmap forwarding 253------------------------ 254 255A lot of drivers forward gem mmap calls to dma-buf mmap for imported buffers. 256And also a lot of them forward dma-buf mmap to the gem mmap implementations. 257There's drm_gem_prime_mmap() for this now, but still needs to be rolled out. 258 259Contact: Daniel Vetter 260 261Level: Intermediate 262 263Generic fbdev defio support 264--------------------------- 265 266The defio support code in the fbdev core has some very specific requirements, 267which means drivers need to have a special framebuffer for fbdev. The main 268issue is that it uses some fields in struct page itself, which breaks shmem 269gem objects (and other things). To support defio, affected drivers require 270the use of a shadow buffer, which may add CPU and memory overhead. 271 272Possible solution would be to write our own defio mmap code in the drm fbdev 273emulation. It would need to fully wrap the existing mmap ops, forwarding 274everything after it has done the write-protect/mkwrite trickery: 275 276- In the drm_fbdev_fb_mmap helper, if we need defio, change the 277 default page prots to write-protected with something like this:: 278 279 vma->vm_page_prot = pgprot_wrprotect(vma->vm_page_prot); 280 281- Set the mkwrite and fsync callbacks with similar implementions to the core 282 fbdev defio stuff. These should all work on plain ptes, they don't actually 283 require a struct page. uff. These should all work on plain ptes, they don't 284 actually require a struct page. 285 286- Track the dirty pages in a separate structure (bitfield with one bit per page 287 should work) to avoid clobbering struct page. 288 289Might be good to also have some igt testcases for this. 290 291Contact: Daniel Vetter, Noralf Tronnes 292 293Level: Advanced 294 295Garbage collect fbdev scrolling acceleration 296-------------------------------------------- 297 298Scroll acceleration is disabled in fbcon by hard-wiring p->scrollmode = 299SCROLL_REDRAW. There's a ton of code this will allow us to remove: 300 301- lots of code in fbcon.c 302 303- a bunch of the hooks in fbcon_ops, maybe the remaining hooks could be called 304 directly instead of the function table (with a switch on p->rotate) 305 306- fb_copyarea is unused after this, and can be deleted from all drivers 307 308Note that not all acceleration code can be deleted, since clearing and cursor 309support is still accelerated, which might be good candidates for further 310deletion projects. 311 312Contact: Daniel Vetter 313 314Level: Intermediate 315 316idr_init_base() 317--------------- 318 319DRM core&drivers uses a lot of idr (integer lookup directories) for mapping 320userspace IDs to internal objects, and in most places ID=0 means NULL and hence 321is never used. Switching to idr_init_base() for these would make the idr more 322efficient. 323 324Contact: Daniel Vetter 325 326Level: Starter 327 328struct drm_gem_object_funcs 329--------------------------- 330 331GEM objects can now have a function table instead of having the callbacks on the 332DRM driver struct. This is now the preferred way. Callbacks in drivers have been 333converted, except for struct drm_driver.gem_prime_mmap. 334 335Level: Intermediate 336 337Use DRM_MODESET_LOCK_ALL_* helpers instead of boilerplate 338--------------------------------------------------------- 339 340For cases where drivers are attempting to grab the modeset locks with a local 341acquire context. Replace the boilerplate code surrounding 342drm_modeset_lock_all_ctx() with DRM_MODESET_LOCK_ALL_BEGIN() and 343DRM_MODESET_LOCK_ALL_END() instead. 344 345This should also be done for all places where drm_modeset_lock_all() is still 346used. 347 348As a reference, take a look at the conversions already completed in drm core. 349 350Contact: Sean Paul, respective driver maintainers 351 352Level: Starter 353 354Rename CMA helpers to DMA helpers 355--------------------------------- 356 357CMA (standing for contiguous memory allocator) is really a bit an accident of 358what these were used for first, a much better name would be DMA helpers. In the 359text these should even be called coherent DMA memory helpers (so maybe CDM, but 360no one knows what that means) since underneath they just use dma_alloc_coherent. 361 362Contact: Laurent Pinchart, Daniel Vetter 363 364Level: Intermediate (mostly because it is a huge tasks without good partial 365milestones, not technically itself that challenging) 366 367connector register/unregister fixes 368----------------------------------- 369 370- For most connectors it's a no-op to call drm_connector_register/unregister 371 directly from driver code, drm_dev_register/unregister take care of this 372 already. We can remove all of them. 373 374- For dp drivers it's a bit more a mess, since we need the connector to be 375 registered when calling drm_dp_aux_register. Fix this by instead calling 376 drm_dp_aux_init, and moving the actual registering into a late_register 377 callback as recommended in the kerneldoc. 378 379Level: Intermediate 380 381Remove load/unload callbacks from all non-DRIVER_LEGACY drivers 382--------------------------------------------------------------- 383 384The load/unload callbacks in struct &drm_driver are very much midlayers, plus 385for historical reasons they get the ordering wrong (and we can't fix that) 386between setting up the &drm_driver structure and calling drm_dev_register(). 387 388- Rework drivers to no longer use the load/unload callbacks, directly coding the 389 load/unload sequence into the driver's probe function. 390 391- Once all non-DRIVER_LEGACY drivers are converted, disallow the load/unload 392 callbacks for all modern drivers. 393 394Contact: Daniel Vetter 395 396Level: Intermediate 397 398Replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi 399--------------------------------------------------------------- 400 401Once EDID is parsed, the monitor HDMI support information is available through 402drm_display_info.is_hdmi. Many drivers still call drm_detect_hdmi_monitor() to 403retrieve the same information, which is less efficient. 404 405Audit each individual driver calling drm_detect_hdmi_monitor() and switch to 406drm_display_info.is_hdmi if applicable. 407 408Contact: Laurent Pinchart, respective driver maintainers 409 410Level: Intermediate 411 412Consolidate custom driver modeset properties 413-------------------------------------------- 414 415Before atomic modeset took place, many drivers where creating their own 416properties. Among other things, atomic brought the requirement that custom, 417driver specific properties should not be used. 418 419For this task, we aim to introduce core helpers or reuse the existing ones 420if available: 421 422A quick, unconfirmed, examples list. 423 424Introduce core helpers: 425- audio (amdgpu, intel, gma500, radeon) 426- brightness, contrast, etc (armada, nouveau) - overlay only (?) 427- broadcast rgb (gma500, intel) 428- colorkey (armada, nouveau, rcar) - overlay only (?) 429- dither (amdgpu, nouveau, radeon) - varies across drivers 430- underscan family (amdgpu, radeon, nouveau) 431 432Already in core: 433- colorspace (sti) 434- tv format names, enhancements (gma500, intel) 435- tv overscan, margins, etc. (gma500, intel) 436- zorder (omapdrm) - same as zpos (?) 437 438 439Contact: Emil Velikov, respective driver maintainers 440 441Level: Intermediate 442 443Plumb drm_atomic_state all over 444------------------------------- 445 446Currently various atomic functions take just a single or a handful of 447object states (eg. plane state). While that single object state can 448suffice for some simple cases, we often have to dig out additional 449object states for dealing with various dependencies between the individual 450objects or the hardware they represent. The process of digging out the 451additional states is rather non-intuitive and error prone. 452 453To fix that most functions should rather take the overall 454drm_atomic_state as one of their parameters. The other parameters 455would generally be the object(s) we mainly want to interact with. 456 457For example, instead of 458 459.. code-block:: c 460 461 int (*atomic_check)(struct drm_plane *plane, struct drm_plane_state *state); 462 463we would have something like 464 465.. code-block:: c 466 467 int (*atomic_check)(struct drm_plane *plane, struct drm_atomic_state *state); 468 469The implementation can then trivially gain access to any required object 470state(s) via drm_atomic_get_plane_state(), drm_atomic_get_new_plane_state(), 471drm_atomic_get_old_plane_state(), and their equivalents for 472other object types. 473 474Additionally many drivers currently access the object->state pointer 475directly in their commit functions. That is not going to work if we 476eg. want to allow deeper commit pipelines as those pointers could 477then point to the states corresponding to a future commit instead of 478the current commit we're trying to process. Also non-blocking commits 479execute locklessly so there are serious concerns with dereferencing 480the object->state pointers without holding the locks that protect them. 481Use of drm_atomic_get_new_plane_state(), drm_atomic_get_old_plane_state(), 482etc. avoids these problems as well since they relate to a specific 483commit via the passed in drm_atomic_state. 484 485Contact: Ville Syrjälä, Daniel Vetter 486 487Level: Intermediate 488 489Use struct dma_buf_map throughout codebase 490------------------------------------------ 491 492Pointers to shared device memory are stored in struct dma_buf_map. Each 493instance knows whether it refers to system or I/O memory. Most of the DRM-wide 494interface have been converted to use struct dma_buf_map, but implementations 495often still use raw pointers. 496 497The task is to use struct dma_buf_map where it makes sense. 498 499* Memory managers should use struct dma_buf_map for dma-buf-imported buffers. 500* TTM might benefit from using struct dma_buf_map internally. 501* Framebuffer copying and blitting helpers should operate on struct dma_buf_map. 502 503Contact: Thomas Zimmermann <tzimmermann@suse.de>, Christian König, Daniel Vetter 504 505Level: Intermediate 506 507 508Core refactorings 509================= 510 511Make panic handling work 512------------------------ 513 514This is a really varied tasks with lots of little bits and pieces: 515 516* The panic path can't be tested currently, leading to constant breaking. The 517 main issue here is that panics can be triggered from hardirq contexts and 518 hence all panic related callback can run in hardirq context. It would be 519 awesome if we could test at least the fbdev helper code and driver code by 520 e.g. trigger calls through drm debugfs files. hardirq context could be 521 achieved by using an IPI to the local processor. 522 523* There's a massive confusion of different panic handlers. DRM fbdev emulation 524 helpers have one, but on top of that the fbcon code itself also has one. We 525 need to make sure that they stop fighting over each another. 526 527* ``drm_can_sleep()`` is a mess. It hides real bugs in normal operations and 528 isn't a full solution for panic paths. We need to make sure that it only 529 returns true if there's a panic going on for real, and fix up all the 530 fallout. 531 532* The panic handler must never sleep, which also means it can't ever 533 ``mutex_lock()``. Also it can't grab any other lock unconditionally, not 534 even spinlocks (because NMI and hardirq can panic too). We need to either 535 make sure to not call such paths, or trylock everything. Really tricky. 536 537* For the above locking troubles reasons it's pretty much impossible to 538 attempt a synchronous modeset from panic handlers. The only thing we could 539 try to achive is an atomic ``set_base`` of the primary plane, and hope that 540 it shows up. Everything else probably needs to be delayed to some worker or 541 something else which happens later on. Otherwise it just kills the box 542 harder, prevent the panic from going out on e.g. netconsole. 543 544* There's also proposal for a simplied DRM console instead of the full-blown 545 fbcon and DRM fbdev emulation. Any kind of panic handling tricks should 546 obviously work for both console, in case we ever get kmslog merged. 547 548Contact: Daniel Vetter 549 550Level: Advanced 551 552Clean up the debugfs support 553---------------------------- 554 555There's a bunch of issues with it: 556 557- The drm_info_list ->show() function doesn't even bother to cast to the drm 558 structure for you. This is lazy. 559 560- We probably want to have some support for debugfs files on crtc/connectors and 561 maybe other kms objects directly in core. There's even drm_print support in 562 the funcs for these objects to dump kms state, so it's all there. And then the 563 ->show() functions should obviously give you a pointer to the right object. 564 565- The drm_info_list stuff is centered on drm_minor instead of drm_device. For 566 anything we want to print drm_device (or maybe drm_file) is the right thing. 567 568- The drm_driver->debugfs_init hooks we have is just an artifact of the old 569 midlayered load sequence. DRM debugfs should work more like sysfs, where you 570 can create properties/files for an object anytime you want, and the core 571 takes care of publishing/unpuplishing all the files at register/unregister 572 time. Drivers shouldn't need to worry about these technicalities, and fixing 573 this (together with the drm_minor->drm_device move) would allow us to remove 574 debugfs_init. 575 576Contact: Daniel Vetter 577 578Level: Intermediate 579 580KMS cleanups 581------------ 582 583Some of these date from the very introduction of KMS in 2008 ... 584 585- Make ->funcs and ->helper_private vtables optional. There's a bunch of empty 586 function tables in drivers, but before we can remove them we need to make sure 587 that all the users in helpers and drivers do correctly check for a NULL 588 vtable. 589 590- Cleanup up the various ->destroy callbacks. A lot of them just wrapt the 591 drm_*_cleanup implementations and can be removed. Some tack a kfree() at the 592 end, for which we could add drm_*_cleanup_kfree(). And then there's the (for 593 historical reasons) misnamed drm_primary_helper_destroy() function. 594 595Level: Intermediate 596 597Better Testing 598============== 599 600Enable trinity for DRM 601---------------------- 602 603And fix up the fallout. Should be really interesting ... 604 605Level: Advanced 606 607Make KMS tests in i-g-t generic 608------------------------------- 609 610The i915 driver team maintains an extensive testsuite for the i915 DRM driver, 611including tons of testcases for corner-cases in the modesetting API. It would 612be awesome if those tests (at least the ones not relying on Intel-specific GEM 613features) could be made to run on any KMS driver. 614 615Basic work to run i-g-t tests on non-i915 is done, what's now missing is mass- 616converting things over. For modeset tests we also first need a bit of 617infrastructure to use dumb buffers for untiled buffers, to be able to run all 618the non-i915 specific modeset tests. 619 620Level: Advanced 621 622Extend virtual test driver (VKMS) 623--------------------------------- 624 625See the documentation of :ref:`VKMS <vkms>` for more details. This is an ideal 626internship task, since it only requires a virtual machine and can be sized to 627fit the available time. 628 629Contact: Daniel Vetter 630 631Level: See details 632 633Backlight Refactoring 634--------------------- 635 636Backlight drivers have a triple enable/disable state, which is a bit overkill. 637Plan to fix this: 638 6391. Roll out backlight_enable() and backlight_disable() helpers everywhere. This 640 has started already. 6412. In all, only look at one of the three status bits set by the above helpers. 6423. Remove the other two status bits. 643 644Contact: Daniel Vetter 645 646Level: Intermediate 647 648Driver Specific 649=============== 650 651AMD DC Display Driver 652--------------------- 653 654AMD DC is the display driver for AMD devices starting with Vega. There has been 655a bunch of progress cleaning it up but there's still plenty of work to be done. 656 657See drivers/gpu/drm/amd/display/TODO for tasks. 658 659Contact: Harry Wentland, Alex Deucher 660 661Bootsplash 662========== 663 664There is support in place now for writing internal DRM clients making it 665possible to pick up the bootsplash work that was rejected because it was written 666for fbdev. 667 668- [v6,8/8] drm/client: Hack: Add bootsplash example 669 https://patchwork.freedesktop.org/patch/306579/ 670 671- [RFC PATCH v2 00/13] Kernel based bootsplash 672 https://lkml.org/lkml/2017/12/13/764 673 674Contact: Sam Ravnborg 675 676Level: Advanced 677 678Outside DRM 679=========== 680 681Convert fbdev drivers to DRM 682---------------------------- 683 684There are plenty of fbdev drivers for older hardware. Some hwardware has 685become obsolete, but some still provides good(-enough) framebuffers. The 686drivers that are still useful should be converted to DRM and afterwards 687removed from fbdev. 688 689Very simple fbdev drivers can best be converted by starting with a new 690DRM driver. Simple KMS helpers and SHMEM should be able to handle any 691existing hardware. The new driver's call-back functions are filled from 692existing fbdev code. 693 694More complex fbdev drivers can be refactored step-by-step into a DRM 695driver with the help of the DRM fbconv helpers. [1] These helpers provide 696the transition layer between the DRM core infrastructure and the fbdev 697driver interface. Create a new DRM driver on top of the fbconv helpers, 698copy over the fbdev driver, and hook it up to the DRM code. Examples for 699several fbdev drivers are available at [1] and a tutorial of this process 700available at [2]. The result is a primitive DRM driver that can run X11 701and Weston. 702 703 - [1] https://gitlab.freedesktop.org/tzimmermann/linux/tree/fbconv 704 - [2] https://gitlab.freedesktop.org/tzimmermann/linux/blob/fbconv/drivers/gpu/drm/drm_fbconv_helper.c 705 706Contact: Thomas Zimmermann <tzimmermann@suse.de> 707 708Level: Advanced 709