I am running Ubuntu 15.10 x64 on my Dell M4800 with the lvds connected to the Nvidia K2100M via nvidia-355, as the intel card does not support the 3K screen.
So when I change the screen brightness using hotkeys or within energy settings, it doesn't change anything.
When I change it via xbacklight, it works perfect.
So, what's the difference, and is there a way I can help devs to make it work ootb?
Thanks for your help.