drm/vkms: Advertise PREMULTI blend mode

[PATCH] [PATCH] drm/vkms: Advertise PREMULTI blend mode

Posted by Michail Tatas 5 days, 2 hours ago

Since we only support pre-multiplied alpha blend mode,
advertise that, otherwise validate_blend_mode_for_alpha_formats()
will throw a WARN.

Reported-by: syzbot+6245cb95ae707991bffa@syzkaller.appspotmail.com
Signed-off-by: Michail Tatas <michail.tatas@gmail.com>
---

syzbot link: https://syzkaller.appspot.com/bug?extid=6245cb95ae707991bffa

 drivers/gpu/drm/vkms/vkms_plane.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
index 68cb2a3335e6..a2e5ebee729a 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -246,6 +246,12 @@ struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
 					  DRM_COLOR_YCBCR_BT601,
 					  DRM_COLOR_YCBCR_FULL_RANGE);
 
+	/* Since our composer only supports pre-multiplied alpha,
+	 * advertise only the PREMULTI blend mode.
+	 */
+	drm_plane_create_blend_mode_property(&plane->base,
+					BIT(DRM_MODE_BLEND_PREMULTI));
+
 	if (vkms_config_plane_get_default_pipeline(plane_cfg))
 		vkms_initialize_colorops(&plane->base);
 
-- 
2.43.0

Re: [PATCH] [PATCH] drm/vkms: Advertise PREMULTI blend mode

Posted by Louis Chauvet 2 days, 11 hours ago


On 7/20/26 02:17, Michail Tatas wrote:
> Since we only support pre-multiplied alpha blend mode,
> advertise that, otherwise validate_blend_mode_for_alpha_formats()
> will throw a WARN.
> 
> Reported-by: syzbot+6245cb95ae707991bffa@syzkaller.appspotmail.com
> Signed-off-by: Michail Tatas <michail.tatas@gmail.com>

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>

> ---
> 
> syzbot link: https://syzkaller.appspot.com/bug?extid=6245cb95ae707991bffa
> 
>   drivers/gpu/drm/vkms/vkms_plane.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> index 68cb2a3335e6..a2e5ebee729a 100644
> --- a/drivers/gpu/drm/vkms/vkms_plane.c
> +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> @@ -246,6 +246,12 @@ struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
>   					  DRM_COLOR_YCBCR_BT601,
>   					  DRM_COLOR_YCBCR_FULL_RANGE);
>   
> +	/* Since our composer only supports pre-multiplied alpha,
> +	 * advertise only the PREMULTI blend mode.
> +	 */
> +	drm_plane_create_blend_mode_property(&plane->base,
> +					BIT(DRM_MODE_BLEND_PREMULTI));
> +
>   	if (vkms_config_plane_get_default_pipeline(plane_cfg))
>   		vkms_initialize_colorops(&plane->base);
>

Re: [PATCH] [PATCH] drm/vkms: Advertise PREMULTI blend mode

Posted by Joshua Peisach 2 days, 12 hours ago

On Sun Jul 19, 2026 at 8:17 PM EDT, Michail Tatas wrote:
> Since we only support pre-multiplied alpha blend mode,
> advertise that, otherwise validate_blend_mode_for_alpha_formats()
> will throw a WARN.
>
> Reported-by: syzbot+6245cb95ae707991bffa@syzkaller.appspotmail.com
> Signed-off-by: Michail Tatas <michail.tatas@gmail.com>
> ---
>
> syzbot link: https://syzkaller.appspot.com/bug?extid=6245cb95ae707991bffa
>
>  drivers/gpu/drm/vkms/vkms_plane.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> index 68cb2a3335e6..a2e5ebee729a 100644
> --- a/drivers/gpu/drm/vkms/vkms_plane.c
> +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> @@ -246,6 +246,12 @@ struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
>  					  DRM_COLOR_YCBCR_BT601,
>  					  DRM_COLOR_YCBCR_FULL_RANGE);
>  
> +	/* Since our composer only supports pre-multiplied alpha,
> +	 * advertise only the PREMULTI blend mode.
> +	 */
> +	drm_plane_create_blend_mode_property(&plane->base,
> +					BIT(DRM_MODE_BLEND_PREMULTI));
> +
>  	if (vkms_config_plane_get_default_pipeline(plane_cfg))
>  		vkms_initialize_colorops(&plane->base);
>  

Hi,

Unfortunately, this still causes the warning on my machine. In my
config CONFIG_DRM_VKMS is not set.

-Josh

Re: [PATCH] [PATCH] drm/vkms: Advertise PREMULTI blend mode

Posted by Joshua Peisach 2 days, 11 hours ago

On Wed Jul 22, 2026 at 10:40 AM EDT, Joshua Peisach wrote:
>
> Hi,
>
> Unfortunately, this still causes the warning on my machine. In my
> config CONFIG_DRM_VKMS is not set.
>
> -Josh

Sorry, disregard. This was meant to be a fix for just VKMS. I was lead
here by syzkaller thinking it would fix it for all.

-Josh