On Wed, 29 Feb 2012 11:21:04 -0800, David Daney <ddaney.cavm@xxxxxxxxx> wrote:
> From: David Daney <david.daney@xxxxxxxxxx>
>
> 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 <david.daney@xxxxxxxxxx>
> ---
> 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);
> --
> 1.7.2.3
>
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