linux-kernel - Re: [RFC PATCH v2 1/3] PM / Core: suspend

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Message-ID: <20110426205745.GB20381@suse.de>
Date:	Tue, 26 Apr 2011 13:57:45 -0700
From:	Greg KH <gregkh@...e.de>
To:	Pavel Machek <pavel@....cz>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	linux-pm@...ts.linux-foundation.org,
	Len Brown <len.brown@...el.com>,
	"Jean Delvare (PC drivers core)" <khali@...ux-fr.org>,
	"Ben Dooks (embedded platforms)" <ben-linux@...ff.org>,
	kyungmin.park@...sung.com, myungjoo.ham@...il.com,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [RFC PATCH v2 1/3] PM / Core: suspend_again callback for device
 PM.

On Tue, Apr 26, 2011 at 10:38:53PM +0200, Pavel Machek wrote:
> Hi!
> 
> > > To conclude, I'm not sure about the approach.  In particular, I'm not sure
> > > if the benefit is worth the effort and the resulting complications (ie. the
> > > possibility of having to deal with wakeup signals not requested by user
> > > space) seem to be a bit too far reaching.
> > > 
> > > Greg, what do you think?
> > 
> > I agree with you in that I don't think that this type of feature is
> > valid at the moment.
> 
> Our current "solution" is low level suspend code on Zaurus directly
> looking at charger state and doing the "wakeup or not" decision by hand. 
> 
> > I don't understand why our current situation doesn't work, what are we
> > lacking that is needed for these systems that we have not seen
> > before?
> 
> It works, but it is ugly; and it seems samsung now needs similar
> hacks.
> 
> > What is the root problem that this is trying to solve?
> 
> It is trying to fix machines that need to run periodic kernel tasks
> even when user asked them to sleep. Zaurus needs to periodicaly wake
> up to be able to charge battery in s2ram state, for example.

That sounds like a bug in userspace you are trying to work around.  Why
not solve it there first?

thanks,

greg k-h
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