[PATCH v2 2/9] of: property: add of_graph_get_next_port_endpoint()

[Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>]

We already have of_graph_get_next_endpoint(), but it is not
intuitive to use.

(X)	node {
(Y)		ports {
			port@0 { endpoint { remote-endpoint = ...; };};
(A1)			port@1 { endpoint { remote-endpoint = ...; };
(A2)				 endpoint { remote-endpoint = ...; };};
(B)			port@2 { endpoint { remote-endpoint = ...; };};
		};
	};

For example, if I want to handle port@1's 2 endpoints (= A1, A2),
I want to use like below

	A1 = of_graph_get_next_endpoint(port1, NULL);
	A2 = of_graph_get_next_endpoint(port1, A1);

But 1st one will be error, because of_graph_get_next_endpoint()
requested "parent" means "node" (X) or "ports" (Y), not "port".
Below are OK

	/* These will be node/ports/port@0/endpoint */
	of_graph_get_next_endpoint(node,  NULL);
	of_graph_get_next_endpoint(ports, NULL);

In other words, we can't handle A1/A2 directly via
of_graph_get_next_endpoint() so far.

There is another non intuitive behavior on of_graph_get_next_endpoint().
In case of if I could get A1 pointer for some way, and if I want to
handle port@1 things, I would like use it like below

	/*
	 * "ep" is now A1, and handle port1 things here,
	 * but we don't know how many endpoints port1 has.
	 *
	 * Because "ep" is non NULL, we can use port1
	 * as of_graph_get_next_endpoint(port1, xxx)
	 */
	do {
		/* do something for port1 specific things here */
	} while (ep = of_graph_get_next_endpoint(port1, ep))

But it also not worked as I expected.
I expect it will be A1 -> A2 -> NULL,
but      it will be A1 -> A2 -> B,    because
of_graph_get_next_endpoint() will fetch "endpoint" beyond the "port".

It is not useful on generic driver like Generic Sound Card.
It uses of_get_next_child() instead for now, but it is not intuitive.
And it doesn't check node name (= "endpoint").

To handle endpoint more intuitive, create of_graph_get_next_port_endpoint()

	of_graph_get_next_port_endpoint(port1, NULL); // A1
	of_graph_get_next_port_endpoint(port1, A1);   // A2
	of_graph_get_next_port_endpoint(port1, A2);   // NULL

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>
---
 drivers/of/property.c    | 22 ++++++++++++++++++++++
 include/linux/of_graph.h | 20 ++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index e4d5dfe70104..dace154baaab 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -695,6 +695,28 @@ struct device_node *of_graph_get_next_port(struct device_node *parent,
 }
 EXPORT_SYMBOL(of_graph_get_next_port);
 
+/**
+ * of_graph_get_next_port_endpoint() - get next endpoint node in port.
+ * If it reached to end of the port, it will return NULL.
+ * @port: pointer to the target port node
+ * @prev: previous endpoint node, or NULL to get first
+ *
+ * Return: An 'endpoint' node pointer with refcount incremented. Refcount
+ * of the passed @prev node is decremented.
+ */
+struct device_node *of_graph_get_next_port_endpoint(const struct device_node *port,
+						    struct device_node *prev)
+{
+	do {
+		prev = of_get_next_child(port, prev);
+		if (!prev)
+			break;
+	} while (!of_node_name_eq(prev, "endpoint"));
+
+	return prev;
+}
+EXPORT_SYMBOL(of_graph_get_next_port_endpoint);
+
 /**
  * of_graph_get_next_endpoint() - get next endpoint node
  * @parent: pointer to the parent device node
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index a6b91577700a..967ee14a1ff3 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -59,6 +59,17 @@ struct of_endpoint {
 	for (child = of_graph_get_next_port(parent, NULL); child != NULL; \
 	     child = of_graph_get_next_port(parent, child))
 
+/**
+ * for_each_of_graph_port_endpoint - iterate over every endpoint in a port node
+ * @parent: parent port node
+ * @child: loop variable pointing to the current endpoint node
+ *
+ * When breaking out of the loop, of_node_put(child) has to be called manually.
+ */
+#define for_each_of_graph_port_endpoint(parent, child)			\
+		for (child = of_graph_get_next_port_endpoint(parent, NULL); child != NULL; \
+		     child = of_graph_get_next_port_endpoint(parent, child))
+
 #ifdef CONFIG_OF
 bool of_graph_is_present(const struct device_node *node);
 int of_graph_parse_endpoint(const struct device_node *node,
@@ -72,6 +83,8 @@ struct device_node *of_graph_get_next_ports(struct device_node *parent,
 					    struct device_node *ports);
 struct device_node *of_graph_get_next_port(struct device_node *parent,
 					   struct device_node *port);
+struct device_node *of_graph_get_next_port_endpoint(const struct device_node *port,
+						    struct device_node *prev);
 struct device_node *of_graph_get_endpoint_by_regs(
 		const struct device_node *parent, int port_reg, int reg);
 struct device_node *of_graph_get_remote_endpoint(
@@ -132,6 +145,13 @@ static inline struct device_node *of_graph_get_next_port(
 	return NULL;
 }
 
+static inline struct device_node *of_graph_get_next_port_endpoint(
+					const struct device_node *parent,
+					struct device_node *previous)
+{
+	return NULL;
+}
+
 static inline struct device_node *of_graph_get_endpoint_by_regs(
 		const struct device_node *parent, int port_reg, int reg)
 {
-- 
2.43.0