linux-kernel - Re: [RFC] sleepy linux

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Message-ID: <20071229235134.GC17823@ucw.cz>
Date:	Sat, 29 Dec 2007 23:51:34 +0000
From:	Pavel Machek <pavel@....cz>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	kernel list <linux-kernel@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...ts.osdl.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [RFC] sleepy linux

Hi!

> > ... I also don't need to call any suspend() routines, because all the
> > drivers are already suspended, right?
> 
> Well, you have a number of devices which cannot do runtime pm.
> They can do suspend/resume with the whole system. For them these
> operations mean saving/restoring state.
> So for these devices implementing autosuspend makes no sense.
> They would sensibly do only idle/busy detection.

Yep... Let's call busy/idle detection and save/restore state
"autosuspend" for those devices. It does not save any power, but it
can be viewed as "kind-of-suspend". (No, I do not have this kind of
details ready).

> > And yes, I want device activity to prevent s2ram. If user is burning
> > CD, machine should not sleep. If user is actively typing, machine
> 
> In these cases the devices involved should report themselves busy,
> shouldn't they?

Yes.

> > should not sleep. My vision is: screen saver tells kernel keyboard
> > need not be very responsive, at that point keyboard driver can
> > autosuspend the keyboard, and if that was the last device, whole
> > system sleeps.
> 
> We lack a notion of telling devices that they are opened only for
> detecting wakeups. Currently a driver has to assume that an opened
> device has to be fully functional.

Yes, we'll need to add some userland interfaces. No, this will not be
easy.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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