Will this work for NVidia cards immediately (I'm using the Dell Studio XPS 13 m1340), or will we have to wait for a new driver from NVidia to implement this?
At the start of the month we talked about GPU switching coming to Linux in a crude form that allowed notebooks with dual GPUs (one being a low-power, low-performance integrated chip and the other being the more performance-oriented GPU that's power hungry) to be switched from without the need for a reboot in Linux. This initial work was just a collection of hacks by David Airlie and it required VT switching after killing the X Server, etc. It also didn't power down the unused GPU. However, as the days passed, this code did more and delayed GPU switching came too.
The Linux GPU switching (a.k.a. "Hybrid Graphics") still isn't as clean of a solution as what can be found with the Windows 7 support where GPUs can be switched between in real-time, but that's because of limitations with the current X.Org Server. However, with the Linux 2.6.33 kernel having just been released, David is hoping to finish off this work that he calls "vga_switcheroo" and to push it into the mainline Linux kernel.
The vga_switcheroo kernel code is now up to its 13th revision with some of the later changes being ATRM support for the Radeon BIOS, a fix for resuming the Intel GPU, and avoid putting an already inactive GPU through suspend-and-resume. David Airlie talked about the revival of this work on his blog. This Red Hat engineer has also started pushing patches on the DRI development list as well as the Linux kernel mailing list.
Assuming some of the remaining issues are cleared up in this code, GPU switching in the form of vga_switcheroo should be here with the Linux 2.6.34 kernel release.