Re: [PATCH v2] drm: Guard DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Hello,

On 7/2/26 10:16, Robert Mader wrote:
> The client cap is currently advertised unconditionally, even for drivers
> that do not support plane color pipelines. If clients supporting the later,
> 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>
> 
> ---
> 
> Changes in v2:
>  - Replace the driver feature with a simple check (suggested by Maarten
>    Lankhorst <maarten.lankhorst@linux.intel.com>)
>  - Expand the commit message slightly and change the title
> ---
>  drivers/gpu/drm/drm_ioctl.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index e2df4becce62..b2c0234eaf14 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -373,13 +373,26 @@ 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;
> +
> +		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;
> +
>  		if (!file_priv->atomic)
>  			return -EINVAL;
>  		if (req->value > 1)
>  			return -EINVAL;
>  		file_priv->plane_color_pipeline = req->value;
>  		break;
> +	}

Perhaps put the most specific check (is there a plane with color pipeline?)
last, and return -EINVAL, as that is the default before
DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE was added.

Kind regards,
~Maarten Lankhorst