Re: [PATCH v2 0/5] drm: Ignore non-existing color planes in helpers

[Christian König]

Am 17.05.22 um 13:33 schrieb Thomas Zimmermann:
Some DRM helpers assume that all potential color planes of a framebuffer
are available; even if the color format didn't specify them. Non-existing
planes are silently ignored. This behavior is inconsistent with other
helpers and apparently leads to subtle bugs with uninitialized GEM buffer
mappings. [1]
Change all affected code to look at the framebuffer format's number of
color planes and only process these planes. The update has been discussed
in [2] before.

Tested with GEM SHMEM helpers on simpledrm and with GEM VRAM helpers on
ast.

I'm not deep enough into all the details for a full review, but feel 
free to add an Acked-by: Christian König <christian.koe...@amd.com> to 
the series.

Thanks,
Christian.


v2:
        * refactor GEM VRAM code before fixing it (Javier)
        * print more error information in #1 (Javier)
        * commit-message fixes (Javier)

[1] 
https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fdri-devel%2F20210730183511.20080-1-tzimmermann%40suse.de%2FT%2F%23md0172b10bb588d8f20f4f456e304f08d2a4505f7&amp;data=05%7C01%7Cchristian.koenig%40amd.com%7Cc512a92c206f4af0691108da37f915a1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637883840259373791%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=6fXRY%2BWlo1I47tcuRHiamAZ9JGM%2FHaYTfyGnxNrqUts%3D&amp;reserved=0
[2] 
https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fdri-devel%2F877dc0d9-c6c6-022c-20d8-14b33e863934%40suse.de%2F&amp;data=05%7C01%7Cchristian.koenig%40amd.com%7Cc512a92c206f4af0691108da37f915a1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637883840259373791%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=6iFYw5EtQNaSiPrHIAawBw87lj6M66o7j0ADY0ipifs%3D&amp;reserved=0

Thomas Zimmermann (5):
   drm/gem: Share code between drm_gem_fb_{begin,end}_cpu_access()
   drm/gem: Ignore color planes that are unused by framebuffer format
   drm/gem-vram: Share code between GEM VRAM's _{prepare,cleanup}_fb()
   drm/gem-vram: Ignore planes that are unused by framebuffer format
   drm/gem: Warn on trying to use a non-existing framebuffer plane

  drivers/gpu/drm/drm_gem_atomic_helper.c      |   6 +-
  drivers/gpu/drm/drm_gem_framebuffer_helper.c | 104 +++++++++----------
  drivers/gpu/drm/drm_gem_vram_helper.c        |  54 ++++++----
  include/drm/drm_gem_framebuffer_helper.h     |  10 +-
  4 files changed, 92 insertions(+), 82 deletions(-)