On Thu, 14 Nov 2013, Ulf Hansson wrote: > > Bear in mind that drivers _cannot_ rely on runtime PM to inactivate a > > device during system suspend. The user can always prevent a device > > from going into runtime suspend by writing "on" to the > > /sys/.../power/control file. > > Good that you brought this up. From my point of view I think the sysfs > for runtime PM could be debated whether it should exist at all, at > least in it's current form. What other form would you suggest? > Anyway, if userspace decides to prevent runtime_suspend, I guess it > will have take the consequences for it as well. :-) Right now, those consequences don't include also preventing the device from going to low power during system system. What would you do if you had a buggy device, where you knew it couldn't handle runtime suspend? If you still wanted to put the whole system to sleep, you'd be stuck. > So as a way forward, I am thinking of a similar approach as you > suggested with the "generic" suspend_late. But instead add a new > runtime PM API, which intent is to let drivers to specify for PM core, > if it should care to prevent the runtime suspend from happen during > system system - or not. Could that work? I don't see what good it would do. Instead of adding a new flag, why not just let drivers point their .suspend_late methods to the new generic function? That would accomplish almost the same thing without changing the API. (Actually, it would be superior. The generic suspend_late approach will work even if the user writes "on" to /sys/.../power/control, whereas your approach won't work.) Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
