backlight: introduce backlight_device_registered
Introduce a new API for modules to query if a specific type of backlight
device has been registered. This is useful for some backlight device
provider module (e.g. ACPI video) to know if a native control
interface(e.g. the interface created by i915) is available and then do
things accordingly (e.g. avoid registering its own on Win8 systems).
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 53b7794..5f9cd96 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -100,6 +100,9 @@
/* The framebuffer notifier block */
struct notifier_block fb_notif;
+ /* list entry of all registered backlight devices */
+ struct list_head entry;
+
struct device dev;
};
@@ -123,6 +126,7 @@
struct backlight_device *bd);
extern void backlight_force_update(struct backlight_device *bd,
enum backlight_update_reason reason);
+extern bool backlight_device_registered(enum backlight_type type);
#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)