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drm: ensure blend mode supported if pixel format with alpha exposed

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Before "drm/drm_blend: allow blend mode property without PREMULTI",
userspace would have to assume that only PREMULTI was supported by
drivers that didn't expose the blend mode property. But now userspace
shouldn't rely on that, as they can't count with drivers always
supporting PREMULTI.

Warn if a driver exposes pixel formats with alpha but doesn't expose the
blend mode property. This way userspace doesn't have to guess. Drivers
triggering this warning must be fixed.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Link: https://patch.msgid.link/20260526181700.25310-3-leandro.ribeiro@collabora.com
Signed-off-by: Daniel Stone <daniels@collabora.com>
This commit is contained in:
Leandro Ribeiro
2026-05-26 15:17:00 -03:00
committed by Daniel Stone
parent 9813e158d1
commit 860e748bdd
1 changed files with 21 additions and 0 deletions
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21
drivers/gpu/drm/drm_mode_config.c
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@@ -857,6 +857,25 @@ static void validate_encoder_possible_crtcs(struct drm_encoder *encoder)
encoder->possible_crtcs, crtc_mask);
}
static void validate_blend_mode_for_alpha_formats(struct drm_plane *plane)
{
const struct drm_format_info *fmt;
u32 i;
/* blend mode property supported, no need to check anything */
if (plane->blend_mode_property)
return;
for (i = 0; i < plane->format_count; i++) {
fmt = drm_format_info(plane->format_types[i]);
if (fmt->has_alpha) {
WARN(1, "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup",
plane->base.id, plane->name);
break;
}
}
}
void drm_mode_config_validate(struct drm_device *dev)
{
struct drm_encoder *encoder;
@@ -915,6 +934,8 @@ void drm_mode_config_validate(struct drm_device *dev)
drm_for_each_plane(plane, dev) {
if (plane->type == DRM_PLANE_TYPE_PRIMARY)
num_primary++;
validate_blend_mode_for_alpha_formats(plane);
}
WARN(num_primary != dev->mode_config.num_crtc,