[media] v4l: of: Support empty port nodes

Empty port nodes are allowed but currently unsupported as the
v4l2_of_get_next_endpoint() function assumes that all port nodes have at
least an endpoint. Fix this.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/v4l2-core/v4l2-of.c

@@ -166,43 +166,51 @@ struct device_node *v4l2_of_get_next_endpoint(const struct device_node *parent,
 					struct device_node *prev)
 {
 	struct device_node *endpoint;
-	struct device_node *port = NULL;
+	struct device_node *port;
 
 	if (!parent)
 		return NULL;
 
+	/*
+	 * Start by locating the port node. If no previous endpoint is specified
+	 * search for the first port node, otherwise get the previous endpoint
+	 * parent port node.
+	 */
 	if (!prev) {
 		struct device_node *node;
-		/*
-		 * It's the first call, we have to find a port subnode
-		 * within this node or within an optional 'ports' node.
-		 */
+
 		node = of_get_child_by_name(parent, "ports");
 		if (node)
 			parent = node;
 
 		port = of_get_child_by_name(parent, "port");
+		of_node_put(node);
 
-		if (port) {
-			/* Found a port, get an endpoint. */
-			endpoint = of_get_next_child(port, NULL);
-			of_node_put(port);
-		} else {
-			endpoint = NULL;
-		}
-
-		if (!endpoint)
-			pr_err("%s(): no endpoint nodes specified for %s\n",
+		if (!port) {
+			pr_err("%s(): no port node found in %s\n",
 			       __func__, parent->full_name);
-		of_node_put(node);
+			return NULL;
+		}
 	} else {
 		port = of_get_parent(prev);
-		if (!port)
+		if (!port) {
 			/* Hm, has someone given us the root node ?... */
 			return NULL;
+		}
 
-		/* Avoid dropping prev node refcount to 0. */
+		/*
+		 * Avoid dropping prev node refcount to 0 when getting the next
+		 * child below.
+		 */
 		of_node_get(prev);
+	}
+
+	while (1) {
+		/*
+		 * Now that we have a port node, get the next endpoint by
+		 * getting the next child. If the previous endpoint is NULL this
+		 * will return the first child.
+		 */
 		endpoint = of_get_next_child(port, prev);
 		if (endpoint) {
 			of_node_put(port);
@@ -210,18 +218,14 @@ struct device_node *v4l2_of_get_next_endpoint(const struct device_node *parent,
 		}
 
 		/* No more endpoints under this port, try the next one. */
+		prev = NULL;
+
 		do {
 			port = of_get_next_child(parent, port);
 			if (!port)
 				return NULL;
 		} while (of_node_cmp(port->name, "port"));
-
-		/* Pick up the first endpoint in this port. */
-		endpoint = of_get_next_child(port, NULL);
-		of_node_put(port);
 	}
-
-	return endpoint;
 }
 EXPORT_SYMBOL(v4l2_of_get_next_endpoint);