Re: [RFC PATCH v4 2/6] of: Make of_find_node_by_path() traverse /aliases for relative paths.
From: Grant Likely <hidden>
Date: 2011-05-27 02:48:06
Also in:
linux-mips, lkml
On Fri, May 20, 2011 at 03:25:39PM -0700, David Daney wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- drivers/of/base.c | 48 +++++++++++++++++++++++++++++++++++++++++++++--- 1 files changed, 45 insertions(+), 3 deletions(-)diff --git a/drivers/of/base.c b/drivers/of/base.c index 632ebae..279134b 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c@@ -340,22 +340,64 @@ 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; read_lock(&devtree_lock); - for (; np; np = np->allnext) { + + if (path[0] != '/') { + const char *ps; + aliases = of_find_node_by_path("/aliases"); + if (!aliases) + goto out;
Hmmm, we should probably cache the pointer to this node.
+
+ ps = strchr(path, '/');
+ if (ps) {
+ size_t len = ps - path;
+ alias = kstrndup(path, len, GFP_KERNEL);
+ if (!alias)
+ goto out;
+ path = of_get_property(aliases, alias, NULL);
+ if (!path)
+ goto out;
+
+ len = strlen(path) + strlen(ps) + 1;
+ new_path = kmalloc(len, GFP_KERNEL);
+ if (!new_path)
+ goto out;
+ strcpy(new_path, path);
+ strcat(new_path, ps);
+ path = new_path;
+ } else {
+ path = of_get_property(aliases, path, NULL);
+ }
+ if (!path)
+ goto out;
+ }
Looks about right, but I think it can be a bit more elegant and I think it
should be better documented. Perhaps something like this?
/*
* 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) {
path = new_path = kzalloc(strlen(path) + strlen(ps) + 1, GFP_KERNEL);
if (!path)
goto out;
sprintf(new_path, "%s%s", path, ps);
}
}
/*
* At this point, path now points to the full unaliased path to a node,
* regardless of whether or not it started with an alias
*/
What do you think?
g.
+
+ 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