drm/virtio: Add pixel blend mode property to cursor plane

The cursor plane exposes a format with an alpha channel
(DRM_FORMAT_ARGB8888) without a pixel blend mode property. Since
commit 860e748bdd ("drm: ensure blend mode supported if pixel
format with alpha exposed") this triggers a warning during
drm_mode_config_validate():

[    0.649020] ------------[ cut here ]------------
[    0.649040] [PLANE:36:plane-1] pixel format with alpha exposed but blend mode not setup
[    0.649081] WARNING: drivers/gpu/drm/drm_mode_config.c:872 at drm_mode_config_validate
......
[    0.649761] Call trace:
[    0.649764]  drm_mode_config_validate+0x398/0x558 [drm] (P)
[    0.649912]  drm_dev_register+0x1cc/0x2a0 [drm]
[    0.650058]  virtio_gpu_probe+0xd4/0x1c0 [virtio_gpu]
[    0.650088]  virtio_dev_probe+0x1c8/0x310
......
[    0.650261] ---[ end trace 0000000000000000 ]---

Create the property with the only supported blend mode,
DRM_MODE_BLEND_PREMULTI, which is also the property's default and
matches what userspace had to assume before the property existed.

Fixes: 860e748bdd ("drm: ensure blend mode supported if pixel format with alpha exposed")
Reported-by: Ye Liu <liuye@kylinos.cn>
Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patch.msgid.link/20260828090123.784944-1-oushixiong1025@163.com
This commit is contained in:
Shixiong Ou 2026-08-28 17:01:23 +08:00 • committed by Dmitry Osipenko
commit 6947b78df4