On Fri, 4 May 2007, David Brownell wrote: > > You are describing the difference between ACPI S4 and S5, but I was > > talking about the difference between "normal" poweroff and "hibernate" > > poweroff. There doesn't seem to be any reason why we must always have > > > > hibernate = S4 and normal = S5. > > What the ACPI spec describes for the "Non-Volatile Sleep" is > that either S4 or S5 could match "hibernate" ... but for > a software-controlled "poweroff", only S5 is appropriate. > > That's a reason. Another: pretty much all end-user docs > on this stuff match what ACPI says. > > Lacking compelling reasons to violate specs (like them > being clearly broken), I avoid breaking them. Again you misunderstand. I concede that either S4 or S5 is appropriate for "Non-Volatile Sleep" whereas only S5 is appropriate for software-controlled "poweroff". But who says that hibernate has to use "Non-Volatile Sleep" and normal shutdown has to use software-controlled "poweroff"? Why shouldn't the user be able to do it the other way 'round? > > > Non-ACPI systems can make the same natural distinctions. > > > > On such systems there seems to be even less reason for those equalities > > (or rather, their analogs). > > This is one of those "less is more" things, right? :) > > People doing embedded designs _like_ their flexibility. > > It's common to have multiple power levels. If you mean > that they _could_ give up that flexibility and only use > one of those state analogues, yes they could ... but if > you mean they'd see that as a Good Thing, I doubt it. No, no! That's not what I mean. I'm proposing that we offer the user _more_ flexibility by giving a choice of power levels. The user should be able to choose whether the system uses "Non-Volatile Sleep" vs. software-controlled "poweroff"; the choice shouldn't be dictated by whether or not the system is entering hibernation. > I guess I don't see why you want to throw away all the > work the hardware (and/or software) designers did to > ensure that some key devices use a "retention" mode > in their S4-analogue state. > > Me, I always thought that leveraging those retention > states was a great way to shrink wakeup times and get > more functionality. I can't imagine why you think I proposed anything along those lines. > > > You're suggesting Linux not use the S5 state, essentially. > > > > No, I'm suggesting that the user should be able to control whether Linux > > uses S4 vs. S5 at poweroff time. If the user selected always to use S4 > > then wakeup devices would function in both hibernation and normal > > shutdown. If the user selected always to use S5 then wakeup devices would > > not function in either hibernation or normal shutdown. > > That's a different suggestion, yes. I'm not sure I see any > benefit of that flexibility for "soft off" states though, > especially if it made "off" consume more power. The benefit is that it allows more devices to function as wakeup sources, right? Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
