Merge branch 'bugzilla-13671' into release

drivers/acpi/video.c

@@ -1979,6 +1979,10 @@ acpi_video_switch_brightness(struct acpi_video_device *device, int event)
 	unsigned long long level_current, level_next;
 	int result = -EINVAL;
 
+	/* no warning message if acpi_backlight=vendor is used */
+	if (!acpi_video_backlight_support())
+		return 0;
+
 	if (!device->brightness)
 		goto out;