drm/connector: Add a helper to attach the colorspace property

The intel driver uses the same logic to attach the Colorspace property
in multiple places and we'll need it in vc4 too. Let's move that common
code in a helper.

Reviewed-by: Jernej Skrabec <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_connector.c

···
 EXPORT_SYMBOL(drm_connector_attach_hdr_output_metadata_property);
 
 /**
+ * drm_connector_attach_colorspace_property - attach "Colorspace" property
+ * @connector: connector to attach the property on.
+ *
+ * This is used to allow the userspace to signal the output colorspace
+ * to the driver.
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_connector_attach_colorspace_property(struct drm_connector *connector)
+{
+	struct drm_property *prop = connector->colorspace_property;
+
+	drm_object_attach_property(&connector->base, prop, DRM_MODE_COLORIMETRY_DEFAULT);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_connector_attach_colorspace_property);
+
+/**
  * drm_connector_atomic_hdr_metadata_equal - checks if the hdr metadata changed
  * @old_state: old connector state to compare
  * @new_state: new connector state to compare

drivers/gpu/drm/i915/display/intel_connector.c

···
 intel_attach_hdmi_colorspace_property(struct drm_connector *connector)
 {
 	if (!drm_mode_create_hdmi_colorspace_property(connector))
-		drm_object_attach_property(&connector->base,
-					   connector->colorspace_property, 0);
+		drm_connector_attach_colorspace_property(connector);
 }
 
 void
 intel_attach_dp_colorspace_property(struct drm_connector *connector)
 {
 	if (!drm_mode_create_dp_colorspace_property(connector))
-		drm_object_attach_property(&connector->base,
-					   connector->colorspace_property, 0);
+		drm_connector_attach_colorspace_property(connector);
 }

include/drm/drm_connector.h

···
 					       u32 scaling_mode_mask);
 int drm_connector_attach_vrr_capable_property(
 		struct drm_connector *connector);
+int drm_connector_attach_colorspace_property(struct drm_connector *connector);
 int drm_connector_attach_hdr_output_metadata_property(struct drm_connector *connector);
 bool drm_connector_atomic_hdr_metadata_equal(struct drm_connector_state *old_state,
 					     struct drm_connector_state *new_state);