Re: [PATCH 0/4] drm: Ignore non-existing color planes in helpers

["Noralf Trønnes" <noralf@tronnes.org>]

Den 09.05.2022 10.15, skrev 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.
> 

Tested with drm/gud, now there's only one UBSAN warning:

Tested-by: Noralf Trønnes <noralf@tronnes.org>

I was hoping to get some time to give a review, but it doesn't look like
I'm able to do that.

Noralf.


> [1] https://lore.kernel.org/dri-devel/20210730183511.20080-1-tzimmermann@suse.de/T/#md0172b10bb588d8f20f4f456e304f08d2a4505f7
> [2] https://lore.kernel.org/dri-devel/877dc0d9-c6c6-022c-20d8-14b33e863934@suse.de/
> 
> Thomas Zimmermann (4):
>   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: 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 | 103 +++++++++----------
>  drivers/gpu/drm/drm_gem_vram_helper.c        |  36 ++++---
>  include/drm/drm_gem_framebuffer_helper.h     |  10 +-
>  4 files changed, 81 insertions(+), 74 deletions(-)
> 
> 
> base-commit: b0b93865a24c910fcbfa6e6fa0955fae930a56d3