lkml.org 
[lkml]   [2011]   [May]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH v4 2/6] of: Make of_find_node_by_path() traverse /aliases for relative paths.
On Fri, May 20, 2011 at 03:25:39PM -0700, David Daney wrote:
> 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 | 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
>


\
 
 \ /
  Last update: 2011-05-27 04:51    [from the cache]
©2003-2011 Jasper Spaans. Advertise on this site