I wish I could find something in Linux that would allow me to reduce the backlight brightness on my old MacBook Pro [4,1 model, I think]. I've tried a million

I wish I could find something in Linux that would allow me to reduce the backlight brightness on my old MacBook Pro [4,1 model, I think]. I've tried a million widgets and hacks but that ol' thing just keeps shining out at full brightness. Shame really as, otherwise –running a light Linux environment– it would make a decent emergency spare machine.