[PATCH] of: Implement of_graph_register_endpoint

[Philipp Zabel]

This patch adds a function that lets drivers register their endpoints in a
global list. Newly registered endpoints are compared against known endpoints
to check if a connection should be made. If so, the driver is notified via
a simple callback.

Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
---
 drivers/of/base.c        | 69 +++++++++++++++++++++++++++++++++++++++++++++---
 include/linux/of_graph.h | 20 +++++++++++++-
 2 files changed, 84 insertions(+), 5 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index ebb001a..77ae54a 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -29,6 +29,7 @@
 #include "of_private.h"
 
 LIST_HEAD(aliases_lookup);
+LIST_HEAD(endpoint_list);
 
 struct device_node *of_allnodes;
 EXPORT_SYMBOL(of_allnodes);
@@ -2002,6 +2003,7 @@ int of_graph_parse_endpoint(const struct device_node *node,
 	memset(endpoint, 0, sizeof(*endpoint));
 
 	endpoint->local_node = node;
+	endpoint->remote_node = of_parse_phandle(node, "remote-endpoint", 0);
 	/*
 	 * It doesn't matter whether the two calls below succeed.
 	 * If they don't then the default value 0 is used.
@@ -2126,6 +2128,19 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
 }
 EXPORT_SYMBOL(of_graph_get_next_endpoint);
 
+static struct of_endpoint *__of_graph_lookup_endpoint(
+				const struct device_node *node)
+{
+	struct of_endpoint *ep;
+
+	list_for_each_entry(ep, &endpoint_list, list) {
+		if (ep->local_node == node)
+			return ep;
+	}
+
+	return NULL;
+}
+
 /**
  * of_graph_get_remote_port_parent() - get remote port's parent node
  * @node: pointer to a local endpoint device_node
@@ -2136,11 +2151,15 @@ EXPORT_SYMBOL(of_graph_get_next_endpoint);
 struct device_node *of_graph_get_remote_port_parent(
 			       const struct device_node *node)
 {
+	struct of_endpoint *ep;
 	struct device_node *np;
 	unsigned int depth;
 
 	/* Get remote endpoint node. */
-	np = of_parse_phandle(node, "remote-endpoint", 0);
+	ep = __of_graph_lookup_endpoint(node);
+	if (!ep || !ep->remote_node)
+		return NULL;
+	np = ep->remote_node;
 
 	/* Walk 3 levels up only if there is 'ports' node */
 	for (depth = 3; depth && np; depth--) {
@@ -2163,13 +2182,14 @@ EXPORT_SYMBOL(of_graph_get_remote_port_parent);
  */
 struct device_node *of_graph_get_remote_port(const struct device_node *node)
 {
+	struct of_endpoint *ep;
 	struct device_node *np;
 
 	/* Get remote endpoint node. */
-	np = of_parse_phandle(node, "remote-endpoint", 0);
-	if (!np)
+	ep = __of_graph_lookup_endpoint(node);
+	if (!ep || !ep->remote_node)
 		return NULL;
-	np = of_get_next_parent(np);
+	np = of_get_next_parent(ep->remote_node);
 	if (of_node_cmp(np->name, "port")) {
 		of_node_put(np);
 		return NULL;
@@ -2177,3 +2197,44 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
 	return np;
 }
 EXPORT_SYMBOL(of_graph_get_remote_port);
+
+int of_graph_register_endpoint(const struct device_node *node,
+		void (*cb)(struct of_endpoint *ep, void *data), void *data)
+{
+	struct of_endpoint *remote_ep, *ep = kmalloc(sizeof(*ep), GFP_KERNEL);
+	if (!ep)
+		return -ENOMEM;
+
+	of_graph_parse_endpoint(node, ep);
+	ep->callback = cb;
+	ep->data = data;
+
+	list_add(&ep->list, &endpoint_list);
+
+	list_for_each_entry(remote_ep, &endpoint_list, list) {
+		struct of_endpoint *from, *to;
+		if (ep->remote_node) {
+			from = ep;
+			to = remote_ep;
+		} else {
+			from = remote_ep;
+			to = ep;
+		}
+		if (from->remote_node &&
+		    from->remote_node == to->local_node) {
+			WARN_ON(to->remote_node &&
+				to->remote_node != from->local_node);
+			to->remote_node = from->local_node;
+			to->remote_ep = from;
+			from->remote_ep = to;
+			if (from->callback)
+				from->callback(from, from->data);
+			if (to->callback)
+				to->callback(to, to->data);
+			return 0;
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(of_graph_register_endpoint);
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index 3a3c5a9..f00ac4e 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -23,7 +23,14 @@
 struct of_endpoint {
 	unsigned int port;
 	unsigned int id;
-	const struct device_node *local_node;
+	struct device_node *local_node;
+	struct device_node *remote_node;
+	struct of_endpoint *remote_ep;
+
+	/* Internal use only */
+	struct list_head list;
+	void (*callback)(struct of_endpoint *ep, void *data);
+	void *data;
 };
 
 #ifdef CONFIG_OF
@@ -35,6 +42,10 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
 struct device_node *of_graph_get_remote_port_parent(
 					const struct device_node *node);
 struct device_node *of_graph_get_remote_port(const struct device_node *node);
+
+int of_graph_register_endpoint(const struct device_node *ep_node,
+				void (*cb)(struct of_endpoint *ep, void *data),
+				void *data);
 #else
 
 static inline int of_graph_parse_endpoint(const struct device_node *node,
@@ -68,6 +79,13 @@ static inline struct device_node *of_graph_get_remote_port(
 	return NULL;
 }
 
+static inline int of_graph_register_endpoint(const struct device_node *ep_node,
+				void (*cb)(struct of_endpoint *ep, void *data),
+				void *data);
+{
+	return -ENOSYS;
+}
+
 #endif /* CONFIG_OF */
 
 #endif /* __LINUX_OF_GRAPH_H */
-- 
1.9.0


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