[PATCH v2 5/8] of: Add of_graph_get_port_by_id function

[Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
---
Changes since v1:
 - Fixed whitespace in comment
 - Changed id parameter to of_graph_get_port_by_id to u32
 - Simplified of_graph_get_port_by_id as suggested by Laurent,
   making use of port id defaulting to 0 if no "reg" property is given.
---
 drivers/of/base.c        | 26 ++++++++++++++++++++++++++
 include/linux/of_graph.h |  7 +++++++
 2 files changed, 33 insertions(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index a49b5628..b282474 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2053,6 +2053,32 @@ 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 *node, u32 id)
+{
+	struct device_node *port = NULL;
+	u32 port_id = 0;
+
+	while (true) {
+		port = of_get_next_child(node, port);
+		if (!port)
+			return NULL;
+		if (of_node_cmp(port->name, "port") != 0)
+			continue;
+		of_property_read_u32(port, "reg", &port_id);
+		if (id == port_id)
+			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 e43442e..e028e49 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, int id)
+{
+	return NULL;
+}
+
 static inline struct device_node *of_graph_get_next_endpoint(
 					const struct device_node *parent,
 					struct device_node *previous)
-- 
2.1.0

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