Comment 36 for bug 1218547

The next step that I'd like to take here is to look at what is in "/sys/class/backlight", both without using the boot param "acpi_backlight=vendor" and with it . To see what we might need to do in order to get one backlight interface working, we need to know what others exist. Without the boot param, I'd expect that we'd see intel_backlight, possibly an nvidia brightness, and acpi_video0. With the boot param, acpi_video0 should be replaced with a vendor specific backlight.

Another quick thing that would be very helpful in guiding us to the root of the problem is to try running the following as root "/bin/echo 0 > /sys/class/backlight/intel_backlight/brightness" this will possibly cause acpi_video0 to function properly, and therefore the brightness keys should also function as expected. If this fixes the issue, it will need to be reentered after a shutdown or a wake from suspend, but I think there is an upstart script somewhere that could be tweaked to do that.

Also, as a last thought for right now, what version of either nouveau or the proprietary nvidia drivers are you using?