linux-kernel - Re: [PATCH] of: Make of_find_node_by

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Message-ID: <CACxGe6uceSmCznZxh5NoWTRTMCnN-nNi2NH9PLPx5C4O5Y7G7w@mail.gmail.com>
Date:	Wed, 19 Mar 2014 21:00:55 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Cc:	Rob Herring <robherring2@...il.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Matt Porter <matt.porter@...aro.org>,
	Koen Kooi <koen@...inion.thruhere.net>,
	Alison Chaiken <Alison_Chaiken@...tor.com>,
	Dinh Nguyen <dinh.linux@...il.com>,
	Jan Lubbe <jluebbe@...net.de>,
	Alexander Sverdlin <alexander.sverdlin@....com>,
	Michael Stickel <ms@...able.de>,
	Guenter Roeck <linux@...ck-us.net>,
	Dirk Behme <dirk.behme@...il.com>,
	Alan Tull <delicious.quinoa@...il.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Michael Bohan <mbohan@...eaurora.org>,
	Ionut Nicu <ioan.nicu.ext@....com>,
	Michal Simek <monstr@...str.eu>,
	Matt Ranostay <mranostay@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pete Popov <pete.popov@...sulko.com>,
	Dan Malek <dan.malek@...sulko.com>,
	Georgi Vlaev <georgi.vlaev@...sulko.com>
Subject: Re: [PATCH] of: Make of_find_node_by_path() handle /aliases

On Tue, Mar 18, 2014 at 9:52 PM, Pantelis Antoniou
<pantelis.antoniou@...sulko.com> wrote:
> Make of_find_node_by_path() handle aliases as prefixes.
>
> Originally by David Daney <ddaney@...iumnetworks.com>, but
> reworked according to remark by Grant Likely.
>
> Handles all cases without allocating memory as requested by
> Grant Likely <grant.likely@...aro.org>
>
> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@...sulko.com>

I posted a patch that does the same thing with a different method just
a few days ago:

http://www.spinics.net/lists/devicetree/msg26336.html

The above patch also has the advantage of being a more efficient search.

g.

> ---
>  drivers/of/base.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 65 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 7083fad..19bcdb4 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -773,22 +773,83 @@ EXPORT_SYMBOL(of_get_child_by_name);
>  /**
>   *     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.
>   */
>  struct device_node *of_find_node_by_path(const char *path)
>  {
> -       struct device_node *np = of_allnodes;
> +       struct device_node *np = NULL;
> +       int len;
> +       const char *p = NULL;
> +       struct property *prop;
>         unsigned long flags;
>
> +       /* under lock (not very nice) */
>         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))
> +
> +       len = strlen(path);
> +
> +       /* path begins with an alias */
> +       if (path[0] != '/') {
> +
> +               /* now find the relative path (if any)*/
> +               p = strchr(path, '/');
> +               if (p != NULL)
> +                       len = p - path;
> +
> +               /* of_aliases must not be NULL */
> +               if (!of_aliases)
> +                       goto out;
> +
> +               /* find matching alias */
> +               for_each_property_of_node(of_aliases, prop)
> +                       if (strlen(prop->name) == len &&
> +                                       strncmp(prop->name, path, len) == 0)
> +                               break;
> +
> +               /* not found; bail */
> +               if (prop == NULL)
> +                       goto out;
> +
> +               path = prop->value;
> +       }
> +
> +       /* path lookup */
> +       for_each_of_allnodes(np) {
> +
> +               if (!np->full_name)
> +                       continue;
> +
> +               if (p == NULL) {
> +                       /* full component */
> +                       if (strcasecmp(np->full_name, path) != 0)
> +                               continue;
> +               } else {
> +                       /* last component (including '/') */
> +                       if (strncasecmp(np->full_name, path, len) != 0)
> +                               continue;
> +
> +                       if (strcasecmp(np->full_name + len, p) != 0)
> +                               continue;
> +               }
> +
> +               if (of_node_get(np))
>                         break;
>         }
> +
> +out:
>         raw_spin_unlock_irqrestore(&devtree_lock, flags);
> +
>         return np;
>  }
>  EXPORT_SYMBOL(of_find_node_by_path);
> --
> 1.7.12
>
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