Comment 8 for bug 1016896

 I'll try to report the bug but I'm not sure where and if they care enough to fix it, my real hopes are in you! ;)

For the workaround, the most solid way I can think to determine if a GPU is active or not is looking for "VGA controller" near to it in lspci.

----------------------------
DISCRETE ENABLED
----------------------------
lspci -vnnn | grep VGA
00:02.0 VGA compatible controller [0300]: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0116] (rev 09) (prog-if 00 [VGA controller])
01:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI Whistler XT [AMD Radeon HD 6700M Series] [1002:6740] (prog-if 00 [VGA controller])

----------------------------
DISCRETE DISABLED
----------------------------
lspci -vnnn | grep VGA
00:02.0 VGA compatible controller [0300]: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0116] (rev 09) (prog-if 00 [VGA controller])
01:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI Whistler XT [AMD Radeon HD 6700M Series] [1002:6740] (rev ff) (prog-if ff)

from the command output in my laptop is clear that the intel integrated VGA is never really disabled (from other literature we know that in any case it routes the VGA signal to the monitor), so the most solid evidence is that "VGA controller", not present on a disabled GPU.

Hope this helps and thanks again for looking into that :)