of: Make of_find_node_by_path() handle /aliases

Make of_find_node_by_path() handle aliases as prefixes. To make this
work the name search is refactored to search by path component instead
of by full string. This should be a more efficient search, and it makes
it possible to start a search at a subnode of a tree.

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[grant.likely: Rework to not require allocating at runtime]
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Grant Likely <grant.likely@linaro.org>

1 files changed, 61 insertions, 6 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 9df50c74162c..e67b308819c9 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -783,23 +783,78 @@ struct device_node *of_get_child_by_name(const struct device_node *node,
 }
 EXPORT_SYMBOL(of_get_child_by_name);
 
+static struct device_node *__of_find_node_by_path(struct device_node *parent,
+                                                const char *path)
+{
+        struct device_node *child;
+        int len = strchrnul(path, '/') - path;
+
+        if (!len)
+                return NULL;
+
+        __for_each_child_of_node(parent, child) {
+                const char *name = strrchr(child->full_name, '/');
+                if (WARN(!name, "malformed device_node %s\n", child->full_name))
+                        continue;
+                name++;
+                if (strncmp(path, name, len) == 0 && (strlen(name) == len))
+                        return child;
+        }
+        return NULL;
+}
+
 /**
  *      of_find_node_by_path - Find a node matching a full OF path
- *      @path:  The full path to match
+ *      @path: Either the full path to match, or if the path does not
+ *             start with '/', the name of a property of the /aliases
+ *             node (an alias).  In the case of an alias, the node
+ *             matching the alias' value will be returned.
+ *
+ *      Valid paths:
+ *              /foo/bar        Full path
+ *              foo             Valid alias
+ *              foo/bar         Valid alias + relative path
  *
  *      Returns a node pointer with refcount incremented, use
  *      of_node_put() on it when done.
  */
 struct device_node *of_find_node_by_path(const char *path)
 {
-        struct device_node *np = of_allnodes;
+        struct device_node *np = NULL;
+        struct property *pp;
         unsigned long flags;
 
+        if (strcmp(path, "/") == 0)
+                return of_node_get(of_allnodes);
+
+        /* The path could begin with an alias */
+        if (*path != '/') {
+                char *p = strchrnul(path, '/');
+                int len = p - path;
+
+                /* of_aliases must not be NULL */
+                if (!of_aliases)
+                        return NULL;
+
+                for_each_property_of_node(of_aliases, pp) {
+                        if (strlen(pp->name) == len && !strncmp(pp->name, path, len)) {
+                                np = of_find_node_by_path(pp->value);
+                                break;
+                        }
+                }
+                if (!np)
+                        return NULL;
+                path = p;
+        }
+
+        /* Step down the tree matching path components */
         raw_spin_lock_irqsave(&devtree_lock, flags);
-        for (; np; np = np->allnext) {
-                if (np->full_name && (of_node_cmp(np->full_name, path) == 0)
-                    && of_node_get(np))
-                        break;
+        if (!np)
+                np = of_node_get(of_allnodes);
+        while (np && *path == '/') {
+                path++; /* Increment past '/' delimiter */
+                np = __of_find_node_by_path(np, path);
+                path = strchrnul(path, '/');
         }
         raw_spin_unlock_irqrestore(&devtree_lock, flags);
         return np;