On Sat, 15 Aug 2009, Rafael J. Wysocki wrote: > > > Why don't we add a flag indicating whether or not the device is allowed to > > > be power managed at run time, something like runtime_forbidden, that the > > > user space will be able to set through sysfs? > > > > I think even having a runtime_wakeup flag (which defaults to on) would > > be sufficient. > > Perhaps it would, but then unsetting runtime_wakeup would effectively disable > runtime PM for devices that need it to be power managed at run time (probably > all input devices). Also there may be situations in which user space may > really want to disable runtime PM for some devices (think of broken hardware > for one example). It sounds like there are really three choices here, and the decision should largely be left up to the user: 1. don't use runtime PM, 2. allow runtime PM but disable remote wakeup, 3. allow runtime PM with remote wakeup enabled. Now, a driver may say "I can't do my job without remote wakeup". Such a driver would refuse to do runtime_suspend in case 2. But otherwise we should follow the preference of the user. The only remaining question is how to expose this in sysfs in a way that won't be confusing and that won't be confused with the "wakeup" attribute. One possibility is to use the "level" attribute introduced in USB; possible levels are "on" (no runtime PM) and "auto" (runtime PM allowed). Then a new "runtime_wakeup" attribute could contain nothing (if wakeup is not available), "enabled", or "disabled". 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
