On Wed, 26 May 2010, Matthew Garrett wrote: > On Wed, May 26, 2010 at 12:56:33PM -0400, Alan Stern wrote: > > > I don't know how that works. However an easy approach would be to make > > opening the device file (or however the userspace driver gets a > > reference to the device) cause the core to do a pm_runtime_get_sync(), > > with a corresponding pm_runtime_put_sync() when the file is closed. > > No, X is far worse than you think. It's handled by mmap()ping /dev/mem. Can we rely on the forbid/allow mechanism? If userspace never allows runtime suspend for devices like the video controller then there's no problem. Conversely, if a PCI device really doesn't have a driver and isn't used for anything, then by default it should go into a lower power state if userspace allows this. I admit this is a slightly brittle solution, in that it depends on userspace not doing the wrong thing. But the default (runtime PM forbidden) is always safe. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
