Re: [PATCH v6 2/2] of: Make of_find_node_by_path() traverse /aliases for relative paths.
From: Grant Likely <hidden>
Date: 2012-03-09 01:33:28
Also in:
linux-mips, lkml
On Wed, 29 Feb 2012 11:21:04 -0800, David Daney [off-list ref] wrote:
quoted hunk ↗ jump to hunk
From: David Daney <redacted> 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 | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 62 insertions(+), 3 deletions(-)diff --git a/drivers/of/base.c b/drivers/of/base.c index 5806449..0bbe47c 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c@@ -365,22 +365,81 @@ 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;
All the aliases are already decoded at boot time now. See
of_alias_scan(). Instead of open-coding this, you can add an
of_alias_lookup() function something like this (untested):
const char *of_alias_lookup(const char *alias)
{
struct alias_prop *app;
list_for_each_entry(app, &aliases_lookup, link) {
if (strcmp(app->alias, alias))
return app->np->full_name;
}
return NULL;
}
Then most of the above code disappears. It can instead look like:
ps = strchr(path, '/');
if (path != ps) {
char alias[ps - path + 1];
strncpy(alias, path, ps - path);
alias[ps - path] = '\0';
path = of_alias_lookup(alias);
if (path && ps)
/* Don't forget to free this */
path = kasprintf(GFP_KERNEL, "%s%s", path, ps);
if (!path)
return NULL;
}
g.
+
+ /* 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);
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