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

Alan Stern
2009-02-02T15:05:00Z

On Mon, 2 Feb 2009, Uli Luckas wrote:

> Hi Alan,
> we have had a (userspace) wake-lock implementation on our handyPC devices for
> a couple of years now. So maybe I can shed some light.
>
> The above quote underlines pretty well, where Arve's and your ideas of
> eraly-suspend and wake-locks diverge. And why you are missunderstanding each
> other.
> Arve is always talking about "blanking the screen" because that's what the
> users sees. From the user's perspective the device is "suspended" as soon as
> his user interfaces vanishes. That's probably also why his notions
> of "suspend" and "wake" are not alway following a strict definition.

And that's partly why I have been complaining about the things he
writes. To a kernel programmer, "suspend" has a very specific meaning,
quite different from what it might mean to a user. When Arve posts on
a kernel-oriented mailing list, he should use such words in a way his
readers will understand.

> If the device stays blanked while the user has his 10 min phone conversation,
> then he won't even notice wether the device suspends or not after the call.
> This is the idea. The user does not care for anything they can't see.
>
> Arve is not talking about a laptop that needs to sleep befor it's ventilation
> slot are covered. He is talking about a phone that could well do with only
> blanking it's screen. Except it want's to save battery when ever possible.

The problem is that he's talking about making changes to a kernel that
will be installed in all sorts of machines, from phones all the way up
to supercomputers. When you do this, you have to broaden your point of
view -- your code has to run correctly in all of these settings.

Alan Stern