Re: [RFC][PATCH 00/11] Android PM extensions

[Nigel Cunningham <ncunningham@crca.org.au>]

Hi.

On Mon, 2009-02-02 at 15:21 -0800, Arve Hjønnevåg wrote:
> On Mon, Feb 2, 2009 at 1:47 PM, Nigel Cunningham
> <ncunningham@crca.org.au> wrote:
> > It sounds to me like all of this stuff is just power management of
> > individual devices, which should be done through the sysfs interface and
> > completely unrelated to /sys/power/state.
> 
> It is easier for us to add a hook to the individual drivers than to
> maintain a list of devices in user-space. Also, last time I checked,
> the only way to disable individual devices was through a deprecated
> interface. Is there a new way to do this?

Not as far as I know, but I understood that we weren't focusing on what
currently exists, but on what ought to exist to properly support what
you're after, in a generic enough way to be useful to others as well.

> > I'm putting the talk about
> > suspending the CPU in this box too because it sounds like the desire is
> > to stop the CPU without necessarily suspending other devices such as
> > transmitters - sort of a CPU freq state where the frequency is 0.
> 
> Is this different from idle?

Well, I'm imagining a state that is more than just idle - where, as you
say, processes don't run until some sort of wakeup event occurs.

> > That said, if suspend to ram is what they really want for 'auto-mem',
> > what you're suggesting sounds good to me.
> 
> Suspend gives us two advantages over idle. All threads are frozen
> which means that an app that is using too much cpu time no longer
> drains the battery. And, the monotonic clock stops.

Do you want to leave any devices on while in this state? If not, okay -
suspend to ram sounds right. If yes, I think you want to take
leave /sys/power/disk alone and go along the lines of run-time power
management instead.

Regards,

Nigel

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