diff -u xserver-xorg-video-intel-2.9.1/src/drmmode_display.c xserver-xorg-video-intel-2.9.1/src/drmmode_display.c
--- xserver-xorg-video-intel-2.9.1/src/drmmode_display.c
+++ xserver-xorg-video-intel-2.9.1/src/drmmode_display.c
@@ -95,6 +95,7 @@
     "asus-laptop",
     "eeepc",
     "thinkpad_screen",
+    "mbp_backlight",
     "acpi_video1",
     "acpi_video0",
     "fujitsu-laptop",