[PATCH v5 1/6] of_graph: add of_graph_get_local_port()

[Dmitry Osipenko <digetx@gmail.com>]

In some case, like a DRM display code for example, it's useful to silently
check whether port node exists at all in a device-tree before proceeding
with parsing the graph.

This patch adds of_graph_get_local_port() which returns pointer to a local
port node, or NULL if graph isn't specified in a device-tree for a given
device node.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/of/property.c    | 32 +++++++++++++++++++++++---------
 include/linux/of_graph.h |  7 +++++++
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index 252e4f600155..5dbeccaabb86 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
 	 * parent port node.
 	 */
 	if (!prev) {
-		struct device_node *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);
-
+		port = of_graph_get_local_port(parent);
 		if (!port) {
 			pr_err("graph: no port node found in %pOF\n", parent);
 			return NULL;
@@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
 }
 EXPORT_SYMBOL(of_graph_get_remote_port);
 
+/**
+ * of_graph_get_local_port() - get local port node
+ * @node: pointer to a local endpoint device_node
+ *
+ * Return: First local port node associated with local endpoint node linked
+ *	   to @node. Use of_node_put() on it when done.
+ */
+struct device_node *of_graph_get_local_port(const struct device_node *node)
+{
+	struct device_node *ports, *port;
+
+	ports = of_get_child_by_name(node, "ports");
+	if (ports)
+		node = ports;
+
+	port = of_get_child_by_name(node, "port");
+	of_node_put(ports);
+
+	return port;
+}
+EXPORT_SYMBOL(of_graph_get_local_port);
+
 int of_graph_get_endpoint_count(const struct device_node *np)
 {
 	struct device_node *endpoint;
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index 01038a6aade0..1fdeb72c7765 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -54,6 +54,7 @@ struct device_node *of_graph_get_remote_port_parent(
 struct device_node *of_graph_get_remote_port(const struct device_node *node);
 struct device_node *of_graph_get_remote_node(const struct device_node *node,
 					     u32 port, u32 endpoint);
+struct device_node *of_graph_get_local_port(const struct device_node *node);
 #else
 
 static inline int of_graph_parse_endpoint(const struct device_node *node,
@@ -116,6 +117,12 @@ static inline struct device_node *of_graph_get_remote_node(
 	return NULL;
 }
 
+static inline struct device_node *of_graph_get_local_port(
+					const struct device_node *node)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_OF */
 
 #endif /* __LINUX_OF_GRAPH_H */
-- 
2.26.0