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[RFC PATCH v5 2/6] of: Make of_find_node_by_path() traverse /aliases for

To: linux-mips@linux-mips.org, ralf@linux-mips.org, devicetree-discuss@lists.ozlabs.org, grant.likely@secretlab.ca, linux-kernel@vger.kernel.org
Subject: [RFC PATCH v5 2/6] of: Make of_find_node_by_path() traverse /aliases for relative paths.
From: David Daney <ddaney@caviumnetworks.com>
Date: Mon, 6 Jun 2011 12:19:42 -0700
Cc: David Daney <ddaney@caviumnetworks.com>
In-reply-to: <1307387986-27069-1-git-send-email-ddaney@caviumnetworks.com>
References: <1307387986-27069-1-git-send-email-ddaney@caviumnetworks.com>
Sender: linux-mips-bounce@linux-mips.org
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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