No Backlight Control with NVIDIA GeForce 9400M

Hi,

I just installed Alpine 3.7 on my old Macbook Pro

Specs:
Apple MacBook Pro 15" late 2008 (5,1)
GPU: NVIDIA GeForce 9600M GT, NVIDIA GeForce 9400M

Installing Alpine went really well (I never enjoyed installing Linux that much)

However the backlight of the screen is stuck on the lowest level, which is unusable during the day
and there seems to be no way to change that.

/sys/class/backlight exists but is empty. The fn Keys won't work.
xbacklight tells me that there is not output it can use.

Has anyone installed Alpine on a Macbook with NVIDIA cards?

best regards