Description:
When using laptop with Nvidia Optimus technology (Thinkpad T520) DVI/HDMI display is hardwired to Nvidia GPU. This causes a problem if you want to use Intel GPU (which uses considerably less power than Nvidia) with secondary display connected when laptop is plugged in or docked. Fortunately with Reverse PRIME you can render images on Intel GPU and just pass it off to Nvidia's output. Unfortunately xf86-video-nouveau 1.0.12-1 does not turn off Nvidia card when secondary display is disconnected which causes additional 10W of battery usage.

Patch was posted to nouveau mailing list on Jun 3 - https://lists.freedesktop.org/archives/nouveau/2016-June/025274.html

I applied the patch and verified it is working - when I disconnect secondary display status of Nvidia card switches to DynOff.


Additional info:
extra/xf86-video-nouveau 1.0.12-1

Steps to reproduce:
- set bios to use Nvidia Optimus and install xf86-video-intel and xf86-video-nouveau drivers
- enable Reverse PRIME: 'xrandr --setprovideroutputsource nouveau Intel'
- enable secondary monitor: 'xrandr --output DP-1-3 --auto --right-of LVDS2'
- check nvidia status with 'cat /sys/kernel/debug/vgaswitcheroo/switch' (should be DynPwr)
- disable Reverse PRIME: 'xrandr --setprovideroutputsource nouveau 0x0'
- check nvidia status again (should be DynOff, but it stays DynPwr)