Created attachment 108419 [details]
X screen blanks after timeout, but backlight remains on forever. "xset dpms force off" has no effect. "vbetool dpms off" does turn off the backlight. Using nvidia proprietary driver, "xset dpms force off" turns off backlight but then has other issues ( https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-331/+bug/1268151 )
Curiously, and possibly related, "xset s activate" (via ssh and/or using sleep 1) has no effect. It does not blank the screen.
Possibly related, from Xorg.0.log:
[ 27.193] (II) NOUVEAU(0): No DPMS capabilities specified
version: nouveau from kernel 3.16.6-gentoo.
Problem persists on kernel 4.0.5 xorg-server 1.16.4