Re: RE: on-ness

Pavel Machek
2006-04-24T21:32:45Z

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On Po 24-04-06 14:04:40, David Brownell wrote:
>
> > > > > Uh. Not /sys/power/state. But /sys/devices/...../power/{[a],[b],[c]} where
> > > > > [a], [b] and [c] need sensible names.
> > > >
> > > > Well, "on" could have one defined meaning. Maybe it's the only option
> > > > available, until drivers add intelligence. I don't see any problem
> > > > with the other names being system-specific, since it's rather unlikely
> > > > that a PCI_D3hot state will ever appear on most embedded ARM boxes.
> > > > And if any userspace code tries to set power states, it had darn well
> > > > better understand exactly what's going on.
> > >
> > > Yes. However if a network managing userspace code wants to set the power
> > > conusmption of a WLAN device to the lowest possible setting, it shouldn't
> > > need a configuration file specific for each platform.
> >
> > I'd say that "on" and "off" are well defined.
>
> Are they? Does "off" imply the device will have been reset the next
> time it goes to "on"? If not, there would seem to be two "off" states.
> Or maybe more ... PCI_D0 is probably "on", but all of the other PCI
> device states seem to be variants of "off", not of "on".

I'd say "off" is as low as possible, perhaps including device reset.

> And for that matter, "on" doesn't seem to me to imply anything more
> than "full functionality from external POV". That doesn't necessarily
> imply "full power-on", and in fact it'd be better if it were using the
> lowest power state(s) available. That state might be compatible with
> certain system sleep states, or not, depending on the device's
> workload.

Agreed.

> > For certain classes (like ethernet), other states may be common
> > between platforms, too, like "off-with-WOL".
>
> Actually the wakeup characteristics are orthogonal, there are per-device
> bits controlling whether a device can and should do the wakeup. We don't
> for example treat "PCI_D3hot with wakeup" as a distinct state.

Ok, "off-with-WOL" was example. Hopefully there's better example.
Pavel
--
Thanks for all the (sleeping) penguins.