Re: [PATCH v2 4/4] drm/vboxvideo: create blend mode property on planes

[Thomas Zimmermann]

Am 01.09.26 um 10:32 schrieb Qinyun Tan:
> Since commit 860e748bddcc ("drm: ensure blend mode supported if pixel
> format with alpha exposed"), drm_mode_config_validate() warns when a
> plane exposes an alpha pixel format but not the "pixel blend mode"
> property. Both the vboxvideo primary and cursor planes expose ARGB8888
> and trip this on driver load.
>
> VirtualBox draws the cursor through the host windowing system, which
> treats the guest-supplied pointer shape as straight
> (non-pre-multiplied) alpha: the host frontend loads the pixels
> verbatim into an unpremultiplied ARGB image before handing them to the
> host cursor APIs. This corresponds to DRM_MODE_BLEND_COVERAGE. Expose
> a "pixel blend mode" property advertising only DRM_MODE_BLEND_COVERAGE
> to make these semantics explicit and silence the warning. The primary
> plane's alpha channel is ignored by the host (opaque blit) and it is
> the bottom-most plane anyway; advertise the same value there for
> consistency.
>
> Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
> Signed-off-by: Qinyun Tan <qinyuntan@xxxxxxxxxxxxxxxxx>

Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

> ---
> v2: advertise DRM_MODE_BLEND_COVERAGE instead of PREMULTI after
> checking how the VirtualBox host composites the pointer shape.
>
>   drivers/gpu/drm/vboxvideo/vbox_mode.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/vboxvideo/vbox_mode.c b/drivers/gpu/drm/vboxvideo/vbox_mode.c
> index 8e4e5fc9d3c5a..3c41238a82685 100644
> --- a/drivers/gpu/drm/vboxvideo/vbox_mode.c
> +++ b/drivers/gpu/drm/vboxvideo/vbox_mode.c
> @@ -15,6 +15,7 @@
>   
>   #include <drm/drm_atomic.h>
>   #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_blend.h>
>   #include <drm/drm_edid.h>
>   #include <drm/drm_fb_helper.h>
>   #include <drm/drm_fourcc.h>
> @@ -540,6 +541,9 @@ static struct drm_plane *vbox_create_plane(struct vbox_private *vbox,
>   
>   	drm_plane_helper_add(plane, helper_funcs);
>   
> +	drm_plane_create_blend_mode_property(plane,
> +					     BIT(DRM_MODE_BLEND_COVERAGE));
> +
>   	return plane;
>   
>   free_plane:

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)