Date: Tue, 26 Apr 2011 13:57:45 -0700
From: Greg KH <gregkh@suse.de>
To: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, MyungJoo Ham <myungjoo.ham@samsung.com>,
        linux-pm@lists.linux-foundation.org, Len Brown <len.brown@intel.com>,
        "Jean Delvare (PC drivers core)" <khali@linux-fr.org>,
        "Ben Dooks (embedded platforms)" <ben-linux@fluff.org>,
        kyungmin.park@samsung.com, myungjoo.ham@gmail.com,
        LKML <linux-kernel@vger.kernel.org>,
        Alan Stern <stern@rowland.harvard.edu>
Subject: Re: [RFC PATCH v2 1/3] PM / Core: suspend_again callback for device
 PM.
Message-ID: <20110426205745.GB20381@suse.de>
References: <1303288106-2965-1-git-send-email-myungjoo.ham@samsung.com>
 <1303781471-2477-1-git-send-email-myungjoo.ham@samsung.com>
 <201104261347.21811.rjw@sisk.pl>
 <20110426131737.GA13597@suse.de>
 <20110426203853.GC27140@elf.ucw.cz>
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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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