On Saturday, September 04, 2010, Alan Stern wrote: > On Sat, 4 Sep 2010, Rafael J. Wysocki wrote: > > > > while. (There's also a notion of an "energy break-even" time.) > > > > That's correct, but people are considering using PM QoS for this purpose. > > When applied to an individual device, it can be considered a runtime-PM > concept. Ultimately these two separate things will have to cooperate > somehow... Indeed. > > > Until now, a subsystem or driver wanting to do this has had to handle > > > all the details on its own: keeping track of when the device was last > > > used, computing how long the device should remain idle, allowing the > > > user to set the idle-delay value, and so on. The patch merely moves > > > all these pesky details into the PM core. > > > > That's fine, but I think there are situations in which las_busy/suspend_delay > > are simply not useful. > > That's why it's off by default and there are function calls by which a > subsystem/driver can turn it on and off. In general, I don't expect > these changes to happen very frequently. At least, no more frequently > than the user changes the card in a card reader or changes the network > cable going to an Ethernet adapter. They may not be frequent, but that doesn't mean the way to handle them correctly in a driver needs to be complicated. :-) > > > That's why I think using "autosuspend" in the name isn't so good. > > > This stuff is centered around the idea of implementing delays, not > > > automatically suspending. > > > > That depends on what you mean by "automatic suspending". To me, "automatic > > suspend" means exactly "suspend after certain period of inactivity", but there > > are other situations in which runtime PM is applicable (eg. the "cable not > > present" case). > > What the patch provides could more accurately be described as "don't > allow suspend until a certain period of inactivity has elapsed". That > isn't the same as "suspend after a certain period of inactivity". OK, so in the context of my other message, I think we need these types of helpers: (1) "suspend X ms from now" (2) "suspend X ms from now if the device has been inactive for Y ms" where Y is set by user space (and X may be 0). To me, the both of them make sense. Thanks, Rafael -- 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
