Acer-WMI: fingers off backlight if video.ko is serving this functionality

Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Carlos Corbacho <carlos@strangeworlds.co.uk>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/misc/acer-wmi.c b/drivers/misc/acer-wmi.c
index 0532a2d..94c9f911 100644
--- a/drivers/misc/acer-wmi.c
+++ b/drivers/misc/acer-wmi.c
@@ -1297,6 +1297,12 @@
 
 	set_quirks();
 
+	if (!acpi_video_backlight_support() && has_cap(ACER_CAP_BRIGHTNESS)) {
+		interface->capability &= ~ACER_CAP_BRIGHTNESS;
+		printk(ACER_INFO "Brightness must be controlled by "
+		       "generic video driver\n");
+	}
+
 	if (platform_driver_register(&acer_platform_driver)) {
 		printk(ACER_ERR "Unable to register platform driver.\n");
 		goto error_platform_register;