leds: add led_trigger_rename function

Implements a "led_trigger_rename" function to rename a trigger with
proper locking.

This assumes that led name was originally allocated in non-constant
storage.
Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com>
Cc: Kurt Van Dijck <kurt.van.dijck@eia.be>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

drivers/leds/led-triggers.c

@@ -166,6 +166,19 @@ void led_trigger_set_default(struct led_classdev *led_cdev)
 }
 EXPORT_SYMBOL_GPL(led_trigger_set_default);
 
+void led_trigger_rename_static(const char *name, struct led_trigger *trig)
+{
+	/* new name must be on a temporary string to prevent races */
+	BUG_ON(name == trig->name);
+
+	down_write(&triggers_list_lock);
+	/* this assumes that trig->name was originaly allocated to
+	 * non constant storage */
+	strcpy((char *)trig->name, name);
+	up_write(&triggers_list_lock);
+}
+EXPORT_SYMBOL_GPL(led_trigger_rename_static);
+
 /* LED Trigger Interface */
 
 int led_trigger_register(struct led_trigger *trig)

include/linux/leds.h

@@ -139,6 +139,24 @@ extern void led_blink_set_oneshot(struct led_classdev *led_cdev,
 extern void led_set_brightness(struct led_classdev *led_cdev,
 			       enum led_brightness brightness);
 
+/**
+ * led_trigger_rename_static - rename a trigger
+ * @name: the new trigger name
+ * @trig: the LED trigger to rename
+ *
+ * Change a LED trigger name by copying the string passed in
+ * name into current trigger name, which MUST be large
+ * enough for the new string.
+ *
+ * Note that name must NOT point to the same string used
+ * during LED registration, as that could lead to races.
+ *
+ * This is meant to be used on triggers with statically
+ * allocated name.
+ */
+extern void led_trigger_rename_static(const char *name,
+				      struct led_trigger *trig);
+
 /*
  * LED Triggers
  */