linux-kernel - Re: [RFC] sleepy linux

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Message-ID: <20071231144447.GD26339@ucw.cz>
Date:	Mon, 31 Dec 2007 14:44:47 +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

On Sun 2007-12-30 17:39:42, Oliver Neukum wrote:
> Am Sonntag, 30. Dezember 2007 00:51:34 schrieb Pavel Machek:
> > 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).
> 
> Well, you probably would have to walk through all devices and check
> all devices are either suspended or can be suspended. That would mean
> struct device has to be extended to show common attributes.
> 
> But what's wrong with calling suspend() the conventional way once you've
> decided to go into sleepy mode?

I'm not sure if it can be done in non-racy way. It is different from
"conventional" suspend(): you can still have userland requests after
this suspend(), and you should abort auto-sleep if you get one. (As
opposed to blocking in system suspend case).
								Pavel

-- 
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