drm/vkms: Support setting custom background color

Make use of the BACKGROUND_COLOR CRTC property when filling the
background during blending.  It already defaults to solid black.

Since the internal representation of the pixel color in VKMS relies on
16 bits of precision, use the newly introduced DRM_ARGB64_GET{R|G|B}()
helpers to access the individual components of the background color
property, which is compliant with DRM_FORMAT_ARGB16161616.

It's worth noting the alpha component is ignored, hence non-opaque
background colors are not supported.

Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Diederik de Haas <diederik@cknow-tech.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://patch.msgid.link/20260303-rk3588-bgcolor-v8-3-fee377037ad1@collabora.com
Signed-off-by: Daniel Stone <daniels@collabora.com>

0 files changed, 0 insertions, 0 deletions