Comment 8 for bug 428910

The patch does not apply cleanly to 2.6.31-11-generic, some minor tweaks are required.

The backlight controls now work partially.

Direct write to /sys/devices/virtual/backlight/acpi_video0/brightness yields correct results, i.e. I can set backlight level properly by writing 1..9 to that file, great!

However when I am trying to use the hardware buttons it behaves as:

1. brightness is at 9, pressing brightness-up once - brightness is at 9
2. brightness is at 9, pressing brightness-up again - screen is dimmed and acpi_video0/brightness shows 1
3. pressing brightness-up again brings the screen to the max brightness, acpi_video0/brightness shows 9

So it is possible to use only 2 values, 1 and 9 when operating via keyboard.

I am attaching both the patch and kernel module, in case someone wants to play with the code on their hardware.