Re: Brightness control not working with nVidia driver
If that works for you, I think you have a different problem.
First, the nvidia-setting brightness doesn't change the backlight intensity; it changes the image brightness (washing it out).
Second, at least in my case (/proc/acpi/toshiba/lcd), the /proc acpi interface to the video is not operational. The same problem exists with the new video interface (/sys/class/backlight/toshiba/brightness). It accepts a value, but does not change the backlight intensity.