linux-kernel - Re: [RFC][PATCH 0/8] PM: Implement autosleep and "wake locks"

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Date:	Mon, 13 Feb 2012 16:11:24 -0800
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	markgross@...gnar.org, NeilBrown <neilb@...e.de>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Matthew Garrett <mjg@...hat.com>,
	Greg KH <greg@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [RFC][PATCH 0/8] PM: Implement autosleep and "wake locks"

On Sun, Feb 12, 2012 at 1:32 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Sunday, February 12, 2012, mark gross wrote:
>> On Fri, Feb 10, 2012 at 01:44:10AM +0100, Rafael J. Wysocki wrote:
> [...]
>> > I'd like us and Android to use the same low-level data structures for power
>> > management and the same API eventually, at least for drivers.  This is not
>> > the case at the moment and it's actively hurting us as a project quite a bit.
>> > If Android needs to add patches on top of whatever we have to get the desired
>> > functionality, I'm fine with that, as long as they don't require drivers to use
>> > APIs that are incompatible with the mainline.  Insisting that Android should
>> > use a user-space-based autosleep implementation wouldn't help at all, because
>> > realistically this isn't going to happen.
>>
>> why not?  I don't think having the PMS explicitly acknowledge a wake
>> event is a big ask at all.
>
> I'd like to hear what the Android people think about that, but somehow it seems
> to me they won't like it. :-)
>

Correct.

The android power manager service does not handle wake events and
therefore does not know when it is safe to acknowledge a wake event
(assuming this acknowledgement re-triggers suspend). Other components
handle the event and only notify the power manager if the event should
change a state (e.g. turn the screen on). Some wake events, like the
alarm used for battery monitoring, don't signal user space at all if
the user visible state did not change. Other wake events are processed
by lower level user-space services than the system-server where the
power manager runs.

-- 
Arve Hjønnevåg
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