of: Add of_graph_get_port_by_id function

This patch adds a function to get a port device tree node by port id,
or reg property value.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

2 files changed, 39 insertions, 0 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 05b20f1cca7b..6398b9ca9157 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2081,6 +2081,38 @@ int of_graph_parse_endpoint(const struct device_node *node,
 EXPORT_SYMBOL(of_graph_parse_endpoint);
 
 /**
+ * of_graph_get_port_by_id() - get the port matching a given id
+ * @parent: pointer to the parent device node
+ * @id: id of the port
+ *
+ * Return: A 'port' node pointer with refcount incremented. The caller
+ * has to use of_node_put() on it when done.
+ */
+struct device_node *of_graph_get_port_by_id(struct device_node *parent, u32 id)
+{
+        struct device_node *node, *port;
+
+        node = of_get_child_by_name(parent, "ports");
+        if (node)
+                parent = node;
+
+        for_each_child_of_node(parent, port) {
+                u32 port_id = 0;
+
+                if (of_node_cmp(port->name, "port") != 0)
+                        continue;
+                of_property_read_u32(port, "reg", &port_id);
+                if (id == port_id)
+                        break;
+        }
+
+        of_node_put(node);
+
+        return port;
+}
+EXPORT_SYMBOL(of_graph_get_port_by_id);
+
+/**
  * of_graph_get_next_endpoint() - get next endpoint node
  * @parent: pointer to the parent device node
  * @prev: previous endpoint node, or NULL to get first
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index e43442efcbe5..3c1c95a39e0c 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -40,6 +40,7 @@ struct of_endpoint {
 #ifdef CONFIG_OF
 int of_graph_parse_endpoint(const struct device_node *node,
                                 struct of_endpoint *endpoint);
+struct device_node *of_graph_get_port_by_id(struct device_node *node, u32 id);
 struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
                                         struct device_node *previous);
 struct device_node *of_graph_get_remote_port_parent(
@@ -53,6 +54,12 @@ static inline int of_graph_parse_endpoint(const struct device_node *node,
         return -ENOSYS;
 }
 
+static inline struct device_node *of_graph_get_port_by_id(
+                                        struct device_node *node, u32 id)
+{
+        return NULL;
+}
+
 static inline struct device_node *of_graph_get_next_endpoint(
                                         const struct device_node *parent,
                                         struct device_node *previous)