[RFC PATCH 1/3] of: Parse OF graph into graph structure

[Philipp Zabel]

This patch adds a function of_graph_populate() that parses the complete
device tree for port and endpoint nodes and stores them in a graph structure.
The internal graph structure is not exported, the API still uses struct
device_node pointers as handles.
At the same time, of_graph_get_next_endpoint is changed to drop the reference
count of its prev parameter, so it can be used in a for_each_endpoint_of_node
macro, which is added to conveniently iterate over all endpoints of a node.

Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
---
 drivers/of/base.c        | 403 ++++++++++++++++++++++++++++++++++++++---------
 include/linux/of_graph.h |  12 ++
 2 files changed, 337 insertions(+), 78 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index fd4b9c2..abfc462 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -28,7 +28,70 @@
 
 #include "of_private.h"
 
+/**
+ * struct of_graph_entity - In-kernel representation of a node with ports
+ *
+ * @of_node: The corresponding device node in the device tree.
+ * @list: List head in the global graph entity list.
+ * @ports: List of ports contained in this entity.
+ *
+ * This is a shortcut directly containing a list of pe-parsed ports, whether
+ * they are contained in a 'ports' subnode, or whether they are direct children
+ * of the device node. While the of_graph_entity usually will correspond to a
+ * struct device with the same of_node, this is not always the case.
+ */
+struct of_graph_entity {
+	struct device_node *of_node;
+	struct list_head list;
+	struct list_head ports;
+};
+
+/**
+ * struct of_graph_port - In-kernel representation of a port node
+ *
+ * @of_node: The corresponding port node in the device tree.
+ * @parent: The in-kernel representation of the parent device_node.
+ *	This is either a direct parent of the of_node, or its grandparent,
+ *	if the parent is a 'ports' node.
+ * @list: List head in the parent entity 'ports' list.
+ * @endpoints: List of endpoints contained in this port.
+ * @id: Index of the port in the device_node, set by the 'reg' property.
+ */
+struct of_graph_port {
+	struct device_node *of_node;
+	struct of_graph_entity *parent;
+	struct list_head list;
+	struct list_head endpoints;
+	int id;
+};
+
+/**
+ * struct of_graph_endpoint - In-kernel representation of an endpoint node
+ *
+ * @of_node: The corresponding endpoint node in the device tree.
+ * @parent: The in-kernel port representation of the parent port node.
+ * @list: List head in the parent port 'endpoints' list.
+ * @global_list: List head in the global endpoint list.
+ * @remote_node: Remote endpoint node, which either is pointed to by the local
+ *	'remote-endpoint' phandle property, or which points to the
+ *	local endpoint node this way.
+ * @remote_endpoint: Pointer to remote in-kernel endpoint representation after
+ *	linking of endpoint nodes.
+ * @id: Index of the endpoint in the port, set by the 'reg' property.
+ */
+struct of_graph_endpoint {
+	struct device_node *of_node;
+	struct of_graph_port *parent;
+	struct list_head list;
+	struct list_head global_list;
+	struct device_node *remote_node;
+	struct of_graph_endpoint *remote_endpoint;
+	int id;
+};
+
 LIST_HEAD(aliases_lookup);
+LIST_HEAD(entity_list);
+LIST_HEAD(endpoint_list);
 
 struct device_node *of_allnodes;
 EXPORT_SYMBOL(of_allnodes);
@@ -1984,6 +2047,32 @@ struct device_node *of_find_next_cache_node(const struct device_node *np)
 	return NULL;
 }
 
+static struct of_graph_entity *__of_graph_lookup_entity(
+					const struct device_node *node)
+{
+	struct of_graph_entity *entity;
+
+	list_for_each_entry(entity, &entity_list, list) {
+		if (entity->of_node == node)
+			return entity;
+	}
+
+	return NULL;
+}
+
+static struct of_graph_endpoint *__of_graph_lookup_endpoint(
+					const struct device_node *node)
+{
+	struct of_graph_endpoint *endpoint;
+
+	list_for_each_entry(endpoint, &endpoint_list, global_list) {
+		if (endpoint->of_node == node)
+			return endpoint;
+	}
+
+	return NULL;
+}
+
 /**
  * of_graph_parse_endpoint() - parse common endpoint node properties
  * @node: pointer to endpoint device_node
@@ -1994,22 +2083,17 @@ struct device_node *of_find_next_cache_node(const struct device_node *np)
 int of_graph_parse_endpoint(const struct device_node *node,
 			    struct of_endpoint *endpoint)
 {
-	struct device_node *port_node = of_get_parent(node);
-
-	WARN_ONCE(!port_node, "%s(): endpoint %s has no parent node\n",
-		  __func__, node->full_name);
+	struct of_graph_endpoint *ep;
 
 	memset(endpoint, 0, sizeof(*endpoint));
 
-	endpoint->local_node = node;
-	/*
-	 * It doesn't matter whether the two calls below succeed.
-	 * If they don't then the default value 0 is used.
-	 */
-	of_property_read_u32(port_node, "reg", &endpoint->port);
-	of_property_read_u32(node, "reg", &endpoint->id);
+	ep = __of_graph_lookup_endpoint(node);
+	if (!ep || !ep->parent)
+		return -EINVAL;
 
-	of_node_put(port_node);
+	endpoint->local_node = ep->of_node;
+	endpoint->port = ep->parent->id;
+	endpoint->id = ep->id;
 
 	return 0;
 }
@@ -2017,75 +2101,63 @@ EXPORT_SYMBOL(of_graph_parse_endpoint);
 
 /**
  * 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
  *
- * Return: An 'endpoint' node pointer with refcount incremented. Refcount
- * of the passed @prev node is not decremented, the caller have to use
- * of_node_put() on it when done.
+ * Return: An 'endpoint' node pointer with refcount incremented. The caller
+ * has to use of_node_put() on it when done.
  */
 struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
-					struct device_node *prev)
+					       struct device_node *prev)
 {
-	struct device_node *endpoint;
-	struct device_node *port = NULL;
+	struct of_graph_entity *entity;
+	struct of_graph_port *port;
+	struct of_graph_endpoint *endpoint = NULL;
 
 	if (!parent)
 		return NULL;
 
 	if (!prev) {
-		struct device_node *node;
-		/*
-		 * It's the first call, we have to find a port subnode
-		 * within this node or within an optional 'ports' node.
-		 */
-		node = of_get_child_by_name(parent, "ports");
-		if (node)
-			parent = node;
+		/* It's the first call, we have to find the first port. */
+		entity = __of_graph_lookup_entity(parent);
+		if (WARN_ONCE(!entity || list_empty(&entity->ports),
+				"%s(): no ports specified for %s\n",
+				__func__, parent->full_name))
+			return NULL;
 
-		port = of_get_child_by_name(parent, "port");
+		port = list_first_entry(&entity->ports,
+					struct of_graph_port, list);
+	} else {
+		endpoint = __of_graph_lookup_endpoint(prev);
+		of_node_put(prev);
+		if (WARN_ONCE(!endpoint, "%s(): endpoint %s not in global list\n",
+			      __func__, prev->full_name))
+			return NULL;
+		port = endpoint->parent;
+	}
 
-		if (port) {
-			/* Found a port, get an endpoint. */
-			endpoint = of_get_next_child(port, NULL);
-			of_node_put(port);
+	entity = port->parent;
+	list_for_each_entry_from(port, &entity->ports, list) {
+		if (!endpoint) {
+			endpoint = list_first_entry(&port->endpoints,
+					struct of_graph_endpoint, list);
+		} else if (endpoint != list_last_entry(&port->endpoints,
+					struct of_graph_endpoint, list)) {
+			endpoint = list_next_entry(endpoint, list);
 		} else {
+			/*
+			 * The previous endpoint is the port's last one,
+			 * continue with the next port.
+			 */
 			endpoint = NULL;
+			continue;
 		}
 
-		if (!endpoint)
-			pr_err("%s(): no endpoint nodes specified for %s\n",
-			       __func__, parent->full_name);
-		of_node_put(node);
-
-		return endpoint;
+		return of_node_get(endpoint->of_node);
 	}
 
-	port = of_get_parent(prev);
-	if (WARN_ONCE(!port, "%s(): endpoint %s has no parent node\n",
-		      __func__, prev->full_name))
-		return NULL;
-
-	/* Avoid dropping prev node refcount to 0. */
-	of_node_get(prev);
-	endpoint = of_get_next_child(port, prev);
-	if (endpoint) {
-		of_node_put(port);
-		return endpoint;
-	}
-
-	/* No more endpoints under this port, try the next one. */
-	do {
-		port = of_get_next_child(parent, port);
-		if (!port)
-			return NULL;
-	} while (of_node_cmp(port->name, "port"));
-
-	/* Pick up the first endpoint in this port. */
-	endpoint = of_get_next_child(port, NULL);
-	of_node_put(port);
-
-	return endpoint;
+	return NULL;
 }
 EXPORT_SYMBOL(of_graph_get_next_endpoint);
 
@@ -2099,19 +2171,16 @@ EXPORT_SYMBOL(of_graph_get_next_endpoint);
 struct device_node *of_graph_get_remote_port_parent(
 			       const struct device_node *node)
 {
-	struct device_node *np;
-	unsigned int depth;
+	struct of_graph_port *port;
+	struct of_graph_endpoint *ep  = __of_graph_lookup_endpoint(node);
+	if (!ep || !ep->remote_endpoint)
+		return NULL;
 
-	/* Get remote endpoint node. */
-	np = of_parse_phandle(node, "remote-endpoint", 0);
+	port = ep->remote_endpoint->parent;
+	if (!port || !port->parent)
+		return NULL;
 
-	/* Walk 3 levels up only if there is 'ports' node. */
-	for (depth = 3; depth && np; depth--) {
-		np = of_get_next_parent(np);
-		if (depth == 2 && of_node_cmp(np->name, "ports"))
-			break;
-	}
-	return np;
+	return port->parent->of_node;
 }
 EXPORT_SYMBOL(of_graph_get_remote_port_parent);
 
@@ -2124,12 +2193,190 @@ EXPORT_SYMBOL(of_graph_get_remote_port_parent);
  */
 struct device_node *of_graph_get_remote_port(const struct device_node *node)
 {
-	struct device_node *np;
+	struct of_graph_endpoint *ep;
 
-	/* Get remote endpoint node. */
-	np = of_parse_phandle(node, "remote-endpoint", 0);
-	if (!np)
+	ep = __of_graph_lookup_endpoint(node);
+	if (!ep || !ep->remote_endpoint || !ep->remote_endpoint->parent)
 		return NULL;
-	return of_get_next_parent(np);
+
+	return ep->remote_endpoint->parent->of_node;
 }
 EXPORT_SYMBOL(of_graph_get_remote_port);
+
+static int of_graph_add_endpoint(struct of_graph_port *port,
+				struct device_node *node)
+{
+	struct of_graph_endpoint *ep = kzalloc(sizeof(*ep), GFP_KERNEL);
+	if (!ep)
+		return -ENOMEM;
+
+	ep->of_node = node;
+	ep->parent = port;
+	of_property_read_u32(node, "reg", &ep->id);
+	ep->remote_node = of_parse_phandle(node, "remote-endpoint", 0);
+
+	list_add_tail(&ep->global_list, &endpoint_list);
+	list_add_tail(&ep->list, &port->endpoints);
+	return 0;
+}
+
+static int of_graph_add_port(struct of_graph_entity *entity,
+				struct device_node *node)
+{
+	struct device_node *child;
+	struct of_graph_port *port = kzalloc(sizeof(*port), GFP_KERNEL);
+	if (!port)
+		return -ENOMEM;
+
+	port->of_node = node;
+	port->parent = entity;
+	of_property_read_u32(node, "reg", &port->id);
+	INIT_LIST_HEAD(&port->endpoints);
+
+	for_each_child_of_node(node, child) {
+		int rc;
+		if (of_node_cmp(child->name, "endpoint") != 0) {
+			pr_warn("%s(): non-endpoint node inside port %s\n",
+				__func__, node->full_name);
+			continue;
+		}
+
+		rc = of_graph_add_endpoint(port, child);
+		if (rc)
+			return rc;
+	}
+
+	list_add_tail(&port->list, &entity->ports);
+	return 0;
+}
+
+/**
+ * of_graph_entity() - parse all ports contained in a node
+ *
+ * @node: The parent node containing the ports.
+ * @child: Either the 'ports' node or the first 'port' node contained in node.
+ * @ports_node: If true, child is a 'ports' node, otherwise it is the first
+ *	'port'.
+ *
+ * This function is given either the 'ports' node or the first 'port' as
+ * second parameter so the parsing that was already done in of_graph_recurse
+ * does not have to be repeated. It parses all ports and collects them in an
+ * of_graph_entity structure that is added to the global entity_list.
+ *
+ * Returns zero on success, an error value otherwise.
+ */
+static int of_graph_add_entity(struct device_node *node,
+				struct device_node *child, bool ports_node)
+{
+	struct device_node *parent = node;
+	struct of_graph_entity *entity;
+	int rc = 0;
+
+	entity = kzalloc(sizeof(*entity), GFP_KERNEL);
+	if (!entity)
+		return -ENOMEM;
+
+	entity->of_node = node;
+	INIT_LIST_HEAD(&entity->ports);
+
+	if (ports_node) {
+		parent = child;
+		child = of_get_next_child(parent, NULL);
+	}
+	while (child) {
+		rc = of_graph_add_port(entity, child);
+		if (rc)
+			return rc;
+
+		do {
+			child = of_get_next_child(parent, child);
+			if (!child)
+				break;
+		} while (of_node_cmp(child->name, "port"));
+	}
+
+	list_add_tail(&entity->list, &entity_list);
+	return 0;
+}
+
+static int of_graph_recurse(struct device_node *node)
+{
+	struct device_node *child;
+	int rc = 0;
+
+	for_each_child_of_node(node, child) {
+		/*
+		 * Find the first 'ports' or 'port' subnode. If one is found,
+		 * parse all ports contained in the node
+		 */
+		if ((of_node_cmp(child->name, "ports") == 0) &&
+		    (!of_find_property(child, "compatible", NULL))) {
+			rc = of_graph_add_entity(node, child, true);
+			break;
+		} else if ((of_node_cmp(child->name, "port") == 0) &&
+			   (!of_find_property(child, "compatible", NULL))) {
+			rc = of_graph_add_entity(node, child, false);
+			break;
+		} else {
+			rc = of_graph_recurse(child);
+		}
+	}
+
+	return rc;
+}
+
+/**
+ * of_graph_populate() - populates the of graph from the device tree
+ *
+ * @root: Root node of the device tree.
+ *
+ * This function scans the device tree for port and endpoint nodes and
+ * generates the of graph from that, linking together endpoints that point
+ * at each other.
+ *
+ * Returns zero on success, an error value otherwise.
+ */
+int of_graph_populate(struct device_node *root)
+{
+	struct of_graph_endpoint *ep1, *ep2;
+	int rc = 0;
+
+	/* Skip if the graph is already populated */
+	if (!list_empty(&endpoint_list))
+		return 0;
+
+	root = root ? of_node_get(root) : of_find_node_by_path("/");
+
+	/* Parse device tree */
+	rc = of_graph_recurse(root);
+	if (rc)
+		return rc;
+
+	/* Connect endpoints */
+	list_for_each_entry(ep1, &endpoint_list, global_list) {
+		ep2 = ep1;
+		list_for_each_entry_continue(ep2, &endpoint_list, global_list) {
+			struct of_graph_endpoint *from, *to;
+
+			if (ep1->remote_node) {
+				from = ep1;
+				to = ep2;
+			} else {
+				from = ep2;
+				to = ep1;
+			}
+			if (from->remote_node &&
+			    from->remote_node == to->of_node) {
+				WARN_ON(to->remote_node &&
+					to->remote_node != from->of_node);
+				to->remote_node = from->of_node;
+				to->remote_endpoint = from;
+				from->remote_endpoint = to;
+			}
+		}
+	}
+
+	of_node_put(root);
+	return rc;
+}
+EXPORT_SYMBOL(of_graph_populate);
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index befef42..b6dd55b 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -26,6 +26,10 @@ struct of_endpoint {
 	const struct device_node *local_node;
 };
 
+#define for_each_endpoint_of_node(dn, ep) \
+	for (ep = of_graph_get_next_endpoint(dn, NULL); ep != NULL; \
+	     ep = of_graph_get_next_endpoint(dn, ep))
+
 #ifdef CONFIG_OF
 int of_graph_parse_endpoint(const struct device_node *node,
 				struct of_endpoint *endpoint);
@@ -34,6 +38,9 @@ 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_populate(struct device_node *root);
+
 #else
 
 static inline int of_graph_parse_endpoint(const struct device_node *node,
@@ -61,6 +68,11 @@ static inline struct device_node *of_graph_get_remote_port(
 	return NULL;
 }
 
+static inline int of_graph_populate(struct device_node *root)
+{
+	return -ENOSYS;
+}
+
 #endif /* CONFIG_OF */
 
 #endif /* __LINUX_OF_GRAPH_H */
-- 
1.9.0

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