Since commit 860e748bdd ("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: 860e748bdd ("drm: ensure blend mode supported if pixel format with alpha exposed")
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Qinyun Tan <qinyuntan@linux.alibaba.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20260901083234.1828755-3-qinyuntan@linux.alibaba.com
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