drm: Guard DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE

The client cap is currently advertised unconditionally, even for drivers
that do not support plane color pipelines. If clients supporting the latter,
like Wayland compositors or tools like drm_info, enable the client cap on
such drivers they will be left without both color pipeline and the legacy
properties COLOR_ENCODING and COLOR_RANGE, effectively breaking YUV->RGB
conversion support.

Prevent that by only marking the cap supported if there are actually planes
with color pipelines.

Note: while the color pipeline replacement for the legacy properties is
still under review (1), we can assume that it will work as a drop-in
replacement. That means any plane on any hardware currently supporting
the legacy properties will be able to offer a functionally equal color
pipeline and there will be no technical reason keep using the legacy
properties if both the driver and the client support the new API.

[1] https://lore.kernel.org/dri-devel/20260623164812.81110-1-harry.wentland@amd.com/

Signed-off-by: Robert Mader <robert.mader@collabora.com>
Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Fixes: 179ab8e7d7b3 ("drm/colorop: Introduce DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE")
Link: https://patch.msgid.link/20260703073230.19982-1-robert.mader@collabora.com
Suggested-by: Maarten Lankhorst <dev@lankhorst.se>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index e2df4becce629a0d7766bed94da0a5183f728e74..9039a39c43243ab59c9abcc43aeafd3a60b93178 100644 (file)
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -373,13 +373,25 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
                        return -EINVAL;
                file_priv->supports_virtualized_cursor_plane = req->value;
                break;
-       case DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE:
+       case DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE: {
+               struct drm_plane *plane;
+               bool has_plane_with_color_pipeline = false;
+
                if (!file_priv->atomic)
                        return -EINVAL;
                if (req->value > 1)
                        return -EINVAL;
+               drm_for_each_plane(plane, dev) {
+                       if (plane->color_pipeline_property) {
+                               has_plane_with_color_pipeline = true;
+                               break;
+                       }
+               }
+               if (!has_plane_with_color_pipeline)
+                       return -EOPNOTSUPP;
                file_priv->plane_color_pipeline = req->value;
                break;
+       }
        default:
                return -EINVAL;
        }