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[RFC PATCH v2 03/12] of: Make of_find_node_by_path() traverse /aliases f

To: linux-mips@linux-mips.org, ralf@linux-mips.org, devicetree-discuss@lists.ozlabs.org, grant.likely@secretlab.ca, linux-kernel@vger.kernel.org
Subject: [RFC PATCH v2 03/12] of: Make of_find_node_by_path() traverse /aliases for relative paths.
From: David Daney <ddaney@caviumnetworks.com>
Date: Fri, 4 Mar 2011 11:42:15 -0800
Cc: David Daney <ddaney@caviumnetworks.com>
In-reply-to: <1299267744-17278-1-git-send-email-ddaney@caviumnetworks.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1299267744-17278-1-git-send-email-ddaney@caviumnetworks.com>
Sender: linux-mips-bounce@linux-mips.org
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>
---

This patch is unchanged from the previous version I send separately.  I
have not forgotten about Grant's feedback, just deferred it to the
next version.

 drivers/of/base.c |   24 +++++++++++++++++++++++-
 1 files changed, 23 insertions(+), 1 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 710b53b..e63da9c 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -340,7 +340,10 @@ 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.
@@ -348,13 +351,32 @@ EXPORT_SYMBOL(of_get_next_child);
 struct device_node *of_find_node_by_path(const char *path)
 {
        struct device_node *np = allnodes;
+       struct device_node *aliases = NULL;
 
        read_lock(&devtree_lock);
+
+       if (path[0] != '/') {
+               aliases = of_find_node_by_path("/aliases");
+               if (!aliases)
+                       goto out;
+               path = of_get_property(aliases, path, NULL);
+               /*
+                * The alias must begin with '/', otherwise we could
+                * get stuck in an endless loop and blow out the
+                * stack.
+                */
+               if (!path || path[0] != '/')
+                       goto out;
+       }
+
        for (; 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);
        return np;
 }
-- 
1.7.2.3


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