2 files changed, 48 insertions, 0 deletions

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 157057c79ca3..6e1446ae7f52 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -73,6 +73,26 @@ static inline void backlight_unregister_fb(struct backlight_device *bd)
 }
 #endif /* CONFIG_FB */
 
+static void backlight_generate_event(struct backlight_device *bd,
+				     enum backlight_update_reason reason)
+{
+	char *envp[2];
+
+	switch (reason) {
+	case BACKLIGHT_UPDATE_SYSFS:
+		envp[0] = "SOURCE=sysfs";
+		break;
+	case BACKLIGHT_UPDATE_HOTKEY:
+		envp[0] = "SOURCE=hotkey";
+		break;
+	default:
+		envp[0] = "SOURCE=unknown";
+		break;
+	}
+	envp[1] = NULL;
+	kobject_uevent_env(&bd->dev.kobj, KOBJ_CHANGE, envp);
+}
+
 static ssize_t backlight_show_power(struct device *dev,
 		struct device_attribute *attr,char *buf)
 {
@@ -142,6 +162,8 @@ static ssize_t backlight_store_brightness(struct device *dev,
 	}
 	mutex_unlock(&bd->ops_lock);
 
+	backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
+
 	return rc;
 }
 
@@ -214,6 +236,25 @@ static struct device_attribute bl_device_attributes[] = {
 };
 
 /**
+ * backlight_force_update - tell the backlight subsystem that hardware state
+ *   has changed
+ * @bd: the backlight device to update
+ *
+ * Updates the internal state of the backlight in response to a hardware event,
+ * and generate a uevent to notify userspace
+ */
+void backlight_force_update(struct backlight_device *bd,
+			    enum backlight_update_reason reason)
+{
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops && bd->ops->get_brightness)
+		bd->props.brightness = bd->ops->get_brightness(bd);
+	mutex_unlock(&bd->ops_lock);
+	backlight_generate_event(bd, reason);
+}
+EXPORT_SYMBOL(backlight_force_update);
+
+/**
  * backlight_device_register - create and register a new object of
  *   backlight_device class.
  * @name: the name of the new object(must be the same as the name of the
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 79ca2da81c87..0f5f57858a23 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -27,6 +27,11 @@
  * Any other use of the locks below is probably wrong.
  */
 
+enum backlight_update_reason {
+	BACKLIGHT_UPDATE_HOTKEY,
+	BACKLIGHT_UPDATE_SYSFS,
+};
+
 struct backlight_device;
 struct fb_info;
 
@@ -100,6 +105,8 @@ static inline void backlight_update_status(struct backlight_device *bd)
 extern struct backlight_device *backlight_device_register(const char *name,
 	struct device *dev, void *devdata, struct backlight_ops *ops);
 extern void backlight_device_unregister(struct backlight_device *bd);
+extern void backlight_force_update(struct backlight_device *bd,
+				   enum backlight_update_reason reason);
 
 #define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)