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

From: Thomas Zimmermann <tzimmermann@suse.de>
To: daniel@ffwll.ch, airlied@linux.ie, mripard@kernel.org,
	maarten.lankhorst@linux.intel.com, javierm@redhat.com,
	noralf@tronnes.org, christian.koenig@amd.com
Cc: Thomas Zimmermann <tzimmermann@suse.de>, dri-devel@lists.freedesktop.org
Subject: [PATCH v2 0/5] drm: Ignore non-existing color planes in helpers
Date: Tue, 17 May 2022 13:33:22 +0200	[thread overview]
Message-ID: <20220517113327.26919-1-tzimmermann@suse.de> (raw)

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.

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

[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 (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(-)

-- 
2.36.1