Re: [PATCH v2 2/4] drm/qxl: create blend mode property on primary and cursor 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 qxl primary and cursor planes expose ARGB8888 and
> trip this on driver load.
>
> qxl submits cursors as SPICE_CURSOR_TYPE_ALPHA, which the SPICE
> protocol explicitly defines as a "pre-multiplied ARGB8888 pixmap"
> (Spice Protocol, "Cursor channel definition" section [1]). This
> matches the blend mode userspace has always assumed when the property
> is not attached. Expose a "pixel blend mode" property advertising only
> DRM_MODE_BLEND_PREMULTI to make these semantics explicit and silence
> the warning. The primary plane is the bottom-most plane so its blend
> mode has no visible effect; advertise the same value there for
> consistency. No functional change.
>
> [1] https://www.spice-space.org/spice-protocol.html
>
> Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
> Signed-off-by: Qinyun Tan <qinyuntan@xxxxxxxxxxxxxxxxx>

Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

> ---
> v2: no code change; cite the SPICE protocol definition of the ALPHA
> cursor type in the commit message.
>
>   drivers/gpu/drm/qxl/qxl_display.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/qxl/qxl_display.c b/drivers/gpu/drm/qxl/qxl_display.c
> index 7f4178800afd7..0cd1456cca347 100644
> --- a/drivers/gpu/drm/qxl/qxl_display.c
> +++ b/drivers/gpu/drm/qxl/qxl_display.c
> @@ -30,6 +30,7 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_atomic.h>
>   #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_blend.h>
>   #include <drm/drm_edid.h>
>   #include <drm/drm_encoder.h>
>   #include <drm/drm_framebuffer.h>
> @@ -993,6 +994,9 @@ static struct drm_plane *qxl_create_plane(struct qxl_device *qdev,
>   
>   	drm_plane_helper_add(plane, helper_funcs);
>   
> +	drm_plane_create_blend_mode_property(plane,
> +					     BIT(DRM_MODE_BLEND_PREMULTI));
> +
>   	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)