Comment 196 for bug 312756

There is a hack to enable ONLY the discrete video card in ASUS ULXX-VT models, which might be applicable to some similar hardware here;

Changing the SATA operation mode in BIOS from "enhanced" to "compatible" has the side effect of completely disabling the Intel card, and enabling the nVidia g210m card instead.

Unfortunately this setting noticeably slows down times to boot and suspend/resume
but hopefully it is a hint towards a solution that could be triggered from userspace
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I have tried to duplicate this effect, removing the intel device from the PCI bus, by means of the fake PCI hotplug driver:
(with nomodeset kernel option) rmmod i915 && modprobe fakephp && echo 0 > /sys/bus/pci/slots/0000\:00\:02.0/power && modprobe nvidia-current

Yet that still doesn't seem to allow the nvidia card to be used in X;
information in Xorg.0.log looks almost the same as when specifying a BusID for the nvidia card
(either approach shows the X server loading the nvidia drivers, but the nvidia card's PCI ID is listed as the Primary Device when it is the "only" card)

Interestingly, the Intel video card comes back when sending a power-on signal to the _SATA controller_!:
echo 1 > /sys/bus/pci/slots/0000\:00\:1f.2/power

Perhaps someone more familiar with the setpci command could suggest some similar functions to try?

I have seen mention that it may be even possible to change the SATA mode via setpci:
http://www.spinics.net/lists/linux-pci/msg08942.html