Re: [PATCH 2/2] drm/verisilicon: set blend mode for the cursor plane

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The cursor plane's blend mode property is created supporting only COVERAGE, but the default atomic state initialization sets it to PREMULTI, causing atomic commits to fail.
--

commit 8e0ec23e99807ff97fec9437ae15ac650e658045
Author: Icenowy Zheng <zhengxingda@iscas.ac.cn>

drm/verisilicon: set blend mode for the cursor plane

This commit adds a fixed COVERAGE blend mode property for the cursor plane,
as blend mode properties are now required to expose pixel formats with alpha.

> diff --git a/drivers/gpu/drm/verisilicon/vs_cursor_plane.c b/drivers/gpu/drm/verisilicon/vs_cursor_plane.c
> index fa4f601dd0c87..36e3664373fa1 100644
> --- a/drivers/gpu/drm/verisilicon/vs_cursor_plane.c
> +++ b/drivers/gpu/drm/verisilicon/vs_cursor_plane.c
[ ... ]
> @@ -268,5 +269,7 @@ struct drm_plane *vs_cursor_plane_init(struct drm_device *drm_dev,
>  
>  	drm_plane_helper_add(plane, &vs_cursor_plane_helper_funcs);
>  
> +	drm_plane_create_blend_mode_property(plane,
> +					     BIT(DRM_MODE_BLEND_COVERAGE));

[Severity: High]
Will this cause atomic commits to fail during state restoration?

Looking at the plane setup, vs_cursor_plane_funcs uses the default
drm_atomic_helper_plane_reset() hook, which unconditionally initializes the
plane state's pixel_blend_mode to DRM_MODE_BLEND_PREMULTI.

Because this property is created supporting only DRM_MODE_BLEND_COVERAGE,
there is a mismatch with the initial state. When userspace queries the
initial state, it reads PREMULTI. If it attempts to write this state back
during an atomic commit (for instance, during a VT switch in a compositor),
the commit will fail with -EINVAL since PREMULTI is not in the supported
blend mode enum list.

>  	return plane;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260901171703.1161592-1-zhengxingda@iscas.ac.cn?part=2