On Wed, 7 Nov 2012, Rafael J. Wysocki wrote: > On Wednesday, November 07, 2012 12:17:02 PM Alan Stern wrote: > > On Wed, 7 Nov 2012, Rafael J. Wysocki wrote: > > > > > > The PCI subsystem assumes that > > > > driverless devices are not in use, so they are disabled for runtime PM > > > > and marked as suspended. This is not appropriate for VGA devices, > > > > which can indeed be used without a driver. > > > > > > > > I'm not sure what the best solution is. Maybe we should Ying's > > > > proposal a step farther: > > > > > > > > Make pm_runtime_set_suspended() fail if runtime PM is > > > > forbidden. > > > > > > > > Make pm_runtime_forbid() call pm_runtime_set_active() > > > > (and do a runtime resume of the parent) if disable_depth > 0. > > > > > > I'd prefer this one. > > > > That wasn't meant to be a choice. The first item is close to what the > > original patch did; I was suggesting that we should adopt all three > > items. > > OK, I need to think about this a bit more, then. > > The problem seems to be that our initial assumption, ie. that driverless > devices won't be in use, is not satisfied in the relevant case. It may > not be satisfied in more cases like this, I suppose, but so far we don't > really know.
Right. The reasoning behind my proposal goes like this: When there's no driver, the subsystem can let userspace directly control the device's power level through the power/control attribute. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
