backlight: Allow drivers to update the core, and generate events on changes

Certain hardware will send us events when the backlight brightness
changes. Add a function to update the value in the core, and
additionally send a uevent so that userspace can pop up appropriate
UI. The uevents are flagged depending on whether the update originated
in the kernel or from userspace, making it easier to only display UI
at the appropriate time.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 79ca2da81c8..0f5f57858a2 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)