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

Arve Hjønnevåg
2009-02-03T00:08:19Z

On Mon, Feb 2, 2009 at 3:51 PM, Nigel Cunningham
<ncunningham@crca.org.au> wrote:
>> 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.

Early-suspend was easier to add to the kernel, and easier for us to
use from user-space.

> 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.

You are describing suspend.

>> 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.

I don't think leaving a device on should prevent us from using
suspend. Wakeup from suspend is already supported. If wakeup is
enabled for a device, it needs to be in a power state that can support
wakeup (whether this is its lowest power state or not).

--
Arve Hjønnevåg