Subject: [PATCH v3] of: Output devicetree alias names in uevent

From: [email-masked] (Stepan Moskovchenko)
Date: Thu, 6 Dec 2012 14:55:41 -0800

In some situations, userspace may want to resolve a
device by function and logical number (ie, "serial0")
rather than by the base address or full device path. Being
able to resolve a device by alias frees userspace from the
burden of otherwise having to maintain a mapping between
device addresses and their logical assignments on each
platform when multiple instances of the same hardware block
are present in the system.

Although the uevent device attribute contains devicetree
compatible information and the full device path, the uevent
does not list the alises that may have been defined for the
device.

Signed-off-by: Stepan Moskovchenko <[email-masked]>
---
v3: Fix copyright/license message on of_platform.h to match
    the messages in the file the code came from.

I also noticed that some of the comments in the original
header might no longer apply, but I copied the header in
its entirety. I can try to trim these down if you like.

 drivers/of/base.c       |   23 +++--------------------
 drivers/of/device.c     |   17 +++++++++++++++++
 drivers/of/of_private.h |   41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+), 20 deletions(-)
 create mode 100644 drivers/of/of_private.h

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 5806449..715aef2 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -24,32 +24,15 @@
 #include <linux/slab.h>
 #include <linux/proc_fs.h>

-/**
- * struct alias_prop - Alias property in 'aliases' node
- * @link:	List node to link the structure in aliases_lookup list
- * @alias:	Alias property name
- * @np:		Pointer to device_node that the alias stands for
- * @id:		Index value from end of alias name
- * @stem:	Alias string without the index
- *
- * The structure represents one alias property of 'aliases' node as
- * an entry in aliases_lookup list.
- */
-struct alias_prop {
-	struct list_head link;
-	const char *alias;
-	struct device_node *np;
-	int id;
-	char stem[0];
-};
+#include "of_private.h"

-static LIST_HEAD(aliases_lookup);
+LIST_HEAD(aliases_lookup);

 struct device_node *allnodes;
 struct device_node *of_chosen;
 struct device_node *of_aliases;

-static DEFINE_MUTEX(of_aliases_mutex);
+DEFINE_MUTEX(of_aliases_mutex);

 /* use when traversing tree through the allnext, child, sibling,
  * or parent members of struct device_node.
diff --git a/drivers/of/device.c b/drivers/of/device.c
index 4c74e4f..b8d31db 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -8,6 +8,7 @@
 #include <linux/slab.h>

 #include <asm/errno.h>
+#include "of_private.h"

 /**
  * of_match_device - Tell if a struct device matches an of_device_id list
@@ -131,6 +132,7 @@ ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len)
 void of_device_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
 	const char *compat;
+	struct alias_prop *app;
 	int seen = 0, cplen, sl;

 	if ((!dev) || (!dev->of_node))
@@ -153,6 +155,21 @@ void of_device_uevent(struct device *dev, struct kobj_uevent_env *env)
 		seen++;
 	}
 	add_uevent_var(env, "OF_COMPATIBLE_N=%d", seen);
+
+	seen = 0;
+	mutex_lock(&of_aliases_mutex);
+	list_for_each_entry(app, &aliases_lookup, link) {
+		if (dev->of_node == app->np) {
+			add_uevent_var(env, "OF_ALIAS_%d=%s", seen,
+				       app->alias);
+			seen++;
+		}
+	}
+
+	if (seen)
+		add_uevent_var(env, "OF_ALIAS_N=%d", seen);
+
+	mutex_unlock(&of_aliases_mutex);
 }

 int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env)
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
new file mode 100644
index 0000000..b38415c
--- /dev/null
+++ b/drivers/of/of_private.h
@@ -0,0 +1,41 @@
+/*
+ * Procedures for creating, accessing and interpreting the device tree.
+ *
+ * Paul Mackerras	August 1996.
+ * Copyright (C) 1996-2005 Paul Mackerras.
+ *
+ *  Adapted for 64bit PowerPC by Dave Engebretsen and Peter Bergner.
+ *    [email-masked]
+ *
+ *  Adapted for sparc and sparc64 by David S. Miller davem at davemloft.net
+ *
+ *  Reconsolidated from arch/x/kernel/prom.c by Stephen Rothwell and
+ *  Grant Likely.
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+/**
+ * struct alias_prop - Alias property in 'aliases' node
+ * @link:	List node to link the structure in aliases_lookup list
+ * @alias:	Alias property name
+ * @np:		Pointer to device_node that the alias stands for
+ * @id:		Index value from end of alias name
+ * @stem:	Alias string without the index
+ *
+ * The structure represents one alias property of 'aliases' node as
+ * an entry in aliases_lookup list.
+ */
+struct alias_prop {
+	struct list_head link;
+	const char *alias;
+	struct device_node *np;
+	int id;
+	char stem[0];
+};
+
+extern struct mutex of_aliases_mutex;
+extern struct list_head aliases_lookup;
--
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