kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-11-10 20:48:12 +00:00
Code Issues Releases Packages Activity

drm/pl111: drop alpha formats the hardware cannot scan out

Browse source 
The PL110/PL111 controller scans out a single framebuffer and never
blends its alpha channel with anything. In every pixel-format table
each alpha-carrying entry (ARGB/ABGR in 8888, 1555 and 4444) maps to
exactly the same register configuration as its XRGB/XBGR counterpart,
so the alpha byte was never used by the hardware.

Commit 860e748bdd ("drm: ensure blend mode supported if pixel format
with alpha exposed") added validation that warns when a plane exposes
alpha formats without a pixel blend mode property, and PL111 does exactly
that. With panic_on_warn enabled the warning prevents the syzkaller
vexpress-a15 manager from booting.

Drivers should not report formats they do not support, so remove the
alpha formats from all variant tables: the generic PL110, PL111 and
Nomadik tables in pl111_drv.c and the board-specific Integrator, IM-PD1,
Versatile and RealView/Versatile-Express tables in pl111_versatile.c,
plus the now dead case labels in the display setup and the Versatile
syscon connector switch, instead of advertising a blend mode property.
Behavior is unchanged for userspace that picks an XRGB/XBGR/RGB format;
alpha-picking clients fall back to the identical X variant.

Link: https://github.com/google/syzkaller/issues/7805
Fixes: 860e748bdd ("drm: ensure blend mode supported if pixel format with alpha exposed")
Signed-off-by: Roshan Kumar <roshaen09@gmail.com>

Changes in v2: drop the alpha formats entirely instead of advertising a
DRM_MODE_BLEND_PIXEL_NONE property, per review feedback from Thomas
Zimmermann. Leandro's Reviewed-by from v1 is not carried as the
approach changed.

Changes in v3: v2 missed the board-specific variant tables in
pl111_versatile.c (Integrator, IM-PD1, Versatile, RealView and
Versatile Express), which still exposed alpha formats and would fall
through to the WARN_ONCE default in pl111_display_enable() on those
boards. Pointed out by the sashiko AI reviewer.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://github.com/google/syzkaller/issues/7805
Signed-off-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20260910192526.137057-1-roshaen09@gmail.com
This commit is contained in:
Roshan Kumar 2026-09-11 00:55:26 +05:30 • committed by Linus Walleij
commit 9d4c982195
3 changed files with 0 additions and 40 deletions
Download patch file Download diff file Expand all files Collapse all files