of: Add helpers for finding device nodes which have a given property

This commit adds a routine for finding a device node which has a
certain property.  The contents of the property are not taken into
account, merely the presence or absence of the property.

Based on that routine, we add a for_each_ macro for iterating over all
nodes that have a certain property.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 41 insertions, 0 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 7c79e94a35ea..4f884a358a7b 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -329,6 +329,41 @@ struct device_node *of_find_compatible_node(struct device_node *from,
 EXPORT_SYMBOL(of_find_compatible_node);
 
 /**
+ *      of_find_node_with_property - Find a node which has a property with
+ *                                   the given name.
+ *      @from:          The node to start searching from or NULL, the node
+ *                      you pass will not be searched, only the next one
+ *                      will; typically, you pass what the previous call
+ *                      returned. of_node_put() will be called on it
+ *      @prop_name:     The name of the property to look for.
+ *
+ *      Returns a node pointer with refcount incremented, use
+ *      of_node_put() on it when done.
+ */
+struct device_node *of_find_node_with_property(struct device_node *from,
+        const char *prop_name)
+{
+        struct device_node *np;
+        struct property *pp;
+
+        read_lock(&devtree_lock);
+        np = from ? from->allnext : allnodes;
+        for (; np; np = np->allnext) {
+                for (pp = np->properties; pp != 0; pp = pp->next) {
+                        if (of_prop_cmp(pp->name, prop_name) == 0) {
+                                of_node_get(np);
+                                goto out;
+                        }
+                }
+        }
+out:
+        of_node_put(from);
+        read_unlock(&devtree_lock);
+        return np;
+}
+EXPORT_SYMBOL(of_find_node_with_property);
+
+/**
  * of_match_node - Tell if an device_node has a matching of_match structure
  *      @matches:       array of of device match structures to search in
  *      @node:          the of device structure to match against
diff --git a/include/linux/of.h b/include/linux/of.h
index e2488f5e7cb2..6a7efa242f5e 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -57,6 +57,12 @@ extern struct device_node *of_get_next_child(const struct device_node *node,
         for (child = of_get_next_child(parent, NULL); child != NULL; \
              child = of_get_next_child(parent, child))
 
+extern struct device_node *of_find_node_with_property(
+        struct device_node *from, const char *prop_name);
+#define for_each_node_with_property(dn, prop_name) \
+        for (dn = of_find_node_with_property(NULL, prop_name); dn; \
+             dn = of_find_node_with_property(dn, prop_name))
+
 extern struct property *of_find_property(const struct device_node *np,
                                          const char *name,
                                          int *lenp);