dt: introduce for_each_available_child_of_node, of_get_next_available_child

Macro for_each_child_of_node() makes it easy to iterate over all of the
children for a given device tree node, including those nodes that are
marked as unavailable (i.e. status = "disabled").

Introduce for_each_available_child_of_node(), which is like
for_each_child_of_node(), but it automatically skips unavailable nodes.
This also requires the introduction of helper function
of_get_next_available_child(), which returns the next available child
node.
Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/of/base.c

@@ -363,6 +363,33 @@ struct device_node *of_get_next_child(const struct device_node *node,
 }
 EXPORT_SYMBOL(of_get_next_child);
 
+/**
+ *	of_get_next_available_child - Find the next available child node
+ *	@node:	parent node
+ *	@prev:	previous child of the parent node, or NULL to get first
+ *
+ *      This function is like of_get_next_child(), except that it
+ *      automatically skips any disabled nodes (i.e. status = "disabled").
+ */
+struct device_node *of_get_next_available_child(const struct device_node *node,
+	struct device_node *prev)
+{
+	struct device_node *next;
+
+	read_lock(&devtree_lock);
+	next = prev ? prev->sibling : node->child;
+	for (; next; next = next->sibling) {
+		if (!of_device_is_available(next))
+			continue;
+		if (of_node_get(next))
+			break;
+	}
+	of_node_put(prev);
+	read_unlock(&devtree_lock);
+	return next;
+}
+EXPORT_SYMBOL(of_get_next_available_child);
+
 /**
  *	of_find_node_by_path - Find a node matching a full OF path
  *	@path:	The full path to match

include/linux/of.h

@@ -190,10 +190,17 @@ extern struct device_node *of_get_parent(const struct device_node *node);
 extern struct device_node *of_get_next_parent(struct device_node *node);
 extern struct device_node *of_get_next_child(const struct device_node *node,
 					     struct device_node *prev);
+extern struct device_node *of_get_next_available_child(
+	const struct device_node *node, struct device_node *prev);
+
 #define for_each_child_of_node(parent, child) \
 	for (child = of_get_next_child(parent, NULL); child != NULL; \
 	     child = of_get_next_child(parent, child))
 
+#define for_each_available_child_of_node(parent, child) \
+	for (child = of_get_next_available_child(parent, NULL); child != NULL; \
+	     child = of_get_next_available_child(parent, child))
+
 static inline int of_get_child_count(const struct device_node *np)
 {
 	struct device_node *child;