drm: bridge: Return NULL on error from drm_bridge_get_edid()

The drm_bridge_get_edid() function is documented to return an error
pointer on error. The underlying .get_edid() operation, however, returns
NULL on error, and so do the drm_get_edid() and drm_do_get_edid()
functions upon which .get_edid() is usually implemented. Make
drm_bridge_get_edid() return NULL on error to be consistent.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200526011505.31884-6-laurent.pinchart+renesas@ideasonboard.com

drivers/gpu/drm/bridge/ti-tfp410.c

@@ -51,11 +51,15 @@ static int tfp410_get_modes(struct drm_connector *connector)
 	struct edid *edid;
 	int ret;
 
+	if (dvi->next_bridge->ops & DRM_BRIDGE_OP_EDID) {
 		edid = drm_bridge_get_edid(dvi->next_bridge, connector);
-	if (IS_ERR_OR_NULL(edid)) {
-		if (edid != ERR_PTR(-ENOTSUPP))
+		if (!edid)
 			DRM_INFO("EDID read failed. Fallback to standard modes\n");
+	} else {
+		edid = NULL;
+	}
 
+	if (!edid) {
 		/*
 		 * No EDID, fallback on the XGA standard modes and prefer a mode
 		 * pretty much anything can handle.

drivers/gpu/drm/drm_bridge.c

@@ -1086,16 +1086,16 @@ EXPORT_SYMBOL_GPL(drm_bridge_get_modes);
  *
  * If the bridge supports output EDID retrieval, as reported by the
  * DRM_BRIDGE_OP_EDID bridge ops flag, call &drm_bridge_funcs.get_edid to
- * get the EDID and return it. Otherwise return ERR_PTR(-ENOTSUPP).
+ * get the EDID and return it. Otherwise return NULL.
  *
  * RETURNS:
- * The retrieved EDID on success, or an error pointer otherwise.
+ * The retrieved EDID on success, or NULL otherwise.
  */
 struct edid *drm_bridge_get_edid(struct drm_bridge *bridge,
 				 struct drm_connector *connector)
 {
 	if (!(bridge->ops & DRM_BRIDGE_OP_EDID))
-		return ERR_PTR(-ENOTSUPP);
+		return NULL;
 
 	return bridge->funcs->get_edid(bridge, connector);
 }