linux-kernel - Re: [RFC v3 3/3] of: Make of_find_node_by

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Date:	Fri, 14 Mar 2014 16:39:38 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Grant Likely <grant.likely@...aro.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
	David Daney <david.daney@...ium.com>
Subject: Re: [RFC v3 3/3] of: Make of_find_node_by_path() handle /aliases

On Fri, Mar 14, 2014 at 12:11 PM, Grant Likely <grant.likely@...aro.org> wrote:
> Make of_find_node_by_path() handle aliases as prefixes. To make this
> work the name search is refactored to search by path component instead
> of by full string. This should be a more efficient search, and it makes
> it possible to start a search at a subnode of a tree.
>
> Signed-off-by: David Daney <david.daney@...ium.com>
> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@...sulko.com>
> [grant.likely: Rework to not require allocating at runtime]
> Signed-off-by: Grant Likely <grant.likely@...aro.org>

I should have read the comments before trying to figure out why you
had that "pointless" recursion...

Acked-by: Rob Herring <robh@...nel.org>

> ---
>  drivers/of/base.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 56 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 7083fad079a6..b8b673526dbd 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -770,9 +770,38 @@ struct device_node *of_get_child_by_name(const struct device_node *node,
>  }
>  EXPORT_SYMBOL(of_get_child_by_name);
>
> +static struct device_node *__of_find_node_by_path(struct device_node *parent,
> +                                               const char *path)
> +{
> +       struct device_node *child;
> +       int len = strchrnul(path, '/') - path;
> +
> +       if (!len)
> +               return parent;
> +
> +       for_each_child_of_node(parent, child) {
> +               const char *name = strrchr(child->full_name, '/');
> +               if (WARN(!name, "malformed device_node %s\n", child->full_name))
> +                       continue;
> +               name++;
> +               if (strncmp(path, name, len) == 0 && (strlen(name) == len))
> +                       return child;
> +       }
> +       return NULL;
> +}
> +
>  /**
>   *     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.
> + *
> + *     Valid paths:
> + *             /foo/bar        Full path
> + *             foo             Valid alias
> + *             foo/bar         Valid alias + relative path
>   *
>   *     Returns a node pointer with refcount incremented, use
>   *     of_node_put() on it when done.
> @@ -780,13 +809,36 @@ EXPORT_SYMBOL(of_get_child_by_name);
>  struct device_node *of_find_node_by_path(const char *path)
>  {
>         struct device_node *np = of_allnodes;
> +       struct property *pp;
>         unsigned long flags;
>
> +       /* The path could begin with an alias */
> +       if (*path != '/') {
> +               char *p = strchrnul(path, '/');
> +               int len = p - path;
> +
> +               /* of_aliases must not be NULL */
> +               if (!of_aliases)
> +                       return NULL;
> +
> +               np = NULL;
> +               for_each_property_of_node(of_aliases, pp) {
> +                       if (strlen(pp->name) == len && !strncmp(pp->name, path, len)) {
> +                               np = of_find_node_by_path(pp->value);
> +                               break;
> +                       }
> +               }
> +               if (!np)
> +                       return NULL;
> +               path = p;
> +       }
> +
> +       /* Step down the tree matching path components */
>         raw_spin_lock_irqsave(&devtree_lock, flags);
> -       for (; np; np = np->allnext) {
> -               if (np->full_name && (of_node_cmp(np->full_name, path) == 0)
> -                   && of_node_get(np))
> -                       break;
> +       while (np && *path == '/') {
> +               path++; /* Increment past '/' delimiter */
> +               np = __of_find_node_by_path(np, path);
> +               path = strchrnul(path, '/');
>         }
>         raw_spin_unlock_irqrestore(&devtree_lock, flags);
>         return np;
> --
> 1.8.3.2
>
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