Re: warnings from validate_blend_mode_for_alpha_formats() in next-20260715

[Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>]

Hi,

this is not a linux-next-only issue any more: 860e748bddcc came in with the
drm-next pull of the 7.3 merge window, so it now warns on plain mainline. Here
it fires 16 times on every boot - 8 per GPU, on the 4 primary and 4 cursor
planes of each of the two cards in this machine:

  [PLANE:44:plane-0] pixel format with alpha exposed but blend mode not setup
  WARNING: drivers/gpu/drm/drm_mode_config.c:872 at drm_mode_config_validate+0xa16/0x13b0

I ran into it on 7.2.0-2709dd5ae32f, bisected it to 860e748bddcc and confirmed
by reverting that commit, before I found this thread. Hardware:
0000:03:00.0 Navi 31 (DCN 3.2) and 0000:0f:00.0 Raphael iGPU (DCN 3.1.5).

Nobody has put this on regzbot yet, so:

#regzbot introduced: 860e748bddcc
#regzbot title: drm: WARNING at drm_mode_config_validate() for planes exposing alpha without a blend mode property
#regzbot monitor: https://lore.kernel.org/all/20260813143605.106104-1-mwen@igalia.com/

Status as far as I can see it: Melissa Wen's v3 series (monitored above) fixes
amdgpu for both DCN and DCE, has Reviewed-by from Alex Hung and Tested-by from
Daniel Wheeler, and I tested it here too - the warnings are gone on both GPUs.
It is in neither linux-next nor amd-staging-drm-next so far. 271e90eb5f9f
("drm: use drm_warn() in validate_blend_mode_for_alpha_formats()") turns the
splat into a plain warning and went to drm-next on 2026-08-20 as part of
drm-misc-next-fixes-2026-08-20, but has not reached mainline either. Other
drivers are being fixed in separate threads (imx dcss, rockchip, vkms).

Since this was introduced during the 7.3 merge window, the fixes should land
in 7.3 rather than wait for the next one.

-- 
Thanks,
Mikhail