Re: [PATCH] drm/pl111: Advertise no pixel blending

[Leandro Ribeiro]

On 8/25/26 7:54 AM, Roshan Kumar wrote:
> Commit 860e748bddcc ("drm: ensure blend mode supported if
> pixel format with alpha exposed") added validation that warns when a
> plane exposes an alpha format without a pixel blend mode property. PL111
> exposes several such formats but does not attach the property.
> 
> The PL110/PL111 controller scans out a single framebuffer and does not
> blend its alpha channel with a background. Advertise
> DRM_MODE_BLEND_PIXEL_NONE to match the existing hardware behavior.
> 
> With panic_on_warn enabled, this warning prevents the syzkaller
> vexpress-a15 manager from booting. The change was tested on current
> master with QEMU 10 and the existing production DTB; the guest reached
> sshd and returned an SSH banner.
> 
> Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
> Link: https://github.com/google/syzkaller/issues/7805
> Signed-off-by: Roshan Kumar <roshaen09@xxxxxxxxx>
> ---
>  drivers/gpu/drm/pl111/pl111_display.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/pl111/pl111_display.c b/drivers/gpu/drm/pl111/pl111_display.c
> index 5d10bc5..758b297 100644
> --- a/drivers/gpu/drm/pl111/pl111_display.c
> +++ b/drivers/gpu/drm/pl111/pl111_display.c
> @@ -15,6 +15,7 @@
>  #include <linux/media-bus-format.h>
>  #include <linux/of_graph.h>
>  
> +#include <drm/drm_blend.h>
>  #include <drm/drm_fb_dma_helper.h>
>  #include <drm/drm_fourcc.h>
>  #include <drm/drm_framebuffer.h>
> @@ -596,5 +597,10 @@ int pl111_display_init(struct drm_device *drm)
>  	if (ret)
>  		return ret;
>  
> +	ret = drm_plane_create_blend_mode_property(&priv->pipe.plane,
> +						   BIT(DRM_MODE_BLEND_PIXEL_NONE));
> +	if (ret)
> +		return ret;
> +

Hello,

Thank you! Looks good to me from the blend-mode requirements
perspective. But I'm not familiar with this driver. So, with this caveat:

Reviewed-by: Leandro Ribeiro <leandro.ribeiro@xxxxxxxxxxxxx>

>  	return 0;
>  }

-- 
Leandro Ribeiro