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Subject[RFC PATCH v5 2/6] of: Make of_find_node_by_path() traverse /aliases for relative paths.
Date
Currently all paths passed to of_find_node_by_path() must begin with a
'/', indicating a full path to the desired node.

Augment the look-up code so that if a path does *not* begin with '/',
the path is used as the name of an /aliases property. The value of
this alias is then used as the full node path to be found.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
---
drivers/of/base.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 62 insertions(+), 3 deletions(-)
diff --git a/drivers/of/base.c b/drivers/of/base.c
index 632ebae..4165084 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -340,22 +340,81 @@ EXPORT_SYMBOL(of_get_next_child);

/**
* 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.
*
* 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 = allnodes;
+ struct device_node *np = NULL;
+ struct device_node *aliases = NULL;
+ char *alias = NULL;
+ char *new_path = NULL;
+ char *ps;

read_lock(&devtree_lock);
- for (; np; np = np->allnext) {
+
+ /*
+ * The following code has three possibilities:
+ * 1) '/' at start of string; path == ps; (based at root)
+ * 2) '/' at offset in string; path < ps; (relative to alias)
+ * 3) '/' not found; ps == NULL; (alias only)
+ *
+ * If ps != path, then it is either a pure alias (ps == NULL),
+ * or an alias with a relative path (path < ps). Either way,
+ * look up the path pointed to by the alias.
+ */
+ ps = strchr(path, '/');
+ if (path != ps) {
+ aliases = of_find_node_by_path("/aliases");
+ if (!aliases)
+ goto out;
+
+ /*
+ * Duplicate the alias part of the string so it can be
+ * NULL terminated.
+ */
+ alias = kstrndup(path,
+ ps ? (ps - path) : strlen(path), GFP_KERNEL);
+ if (!alias)
+ goto out;
+ path = of_get_property(aliases, alias, NULL);
+ if (!path || path[0] != '/')
+ goto out;
+
+ /* If ps is not NULL, then there is a relative path to append */
+ if (ps) {
+ new_path = kzalloc(strlen(path) + strlen(ps) + 1,
+ GFP_KERNEL);
+ if (!new_path)
+ goto out;
+
+ sprintf(new_path, "%s%s", path, ps);
+ path = new_path;
+ }
+ }
+
+ /*
+ * At this point, path now points to the full unaliased path
+ * to a node, regardless of whether or not it started with an
+ * alias.
+ */
+
+ for (np = allnodes; np; np = np->allnext) {
if (np->full_name && (of_node_cmp(np->full_name, path) == 0)
&& of_node_get(np))
break;
}
+out:
+ if (aliases)
+ of_node_put(aliases);
read_unlock(&devtree_lock);
+ kfree(alias);
+ kfree(new_path);
return np;
}
EXPORT_SYMBOL(of_find_node_by_path);
--
1.7.2.3


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