linux-kernel - Re: [RFC][PATCH 6/8] PM / Sleep: Implement opportunistic sleep

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Message-Id: <201205040024.37008.rjw@sisk.pl>
Date:	Fri, 4 May 2012 00:24:36 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	NeilBrown <neilb@...e.de>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>, markgross@...gnar.org,
	Matthew Garrett <mjg@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 6/8] PM / Sleep: Implement opportunistic sleep

On Friday, May 04, 2012, Arve Hjønnevåg wrote:
> On Thu, May 3, 2012 at 3:20 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > On Thursday, May 03, 2012, Arve Hjønnevåg wrote:
> >> On Thu, May 3, 2012 at 6:28 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> >> > On Thursday, May 03, 2012, Arve Hjønnevåg wrote:
> >> >> On Thu, Apr 26, 2012 at 2:52 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> >> >> ...
> >> >> > From: Rafael J. Wysocki <rjw@...k.pl>
> >> >> > Subject: PM / Sleep: Implement opportunistic sleep, v2
> >> >> >
> >> >> > Introduce a mechanism by which the kernel can trigger global
> >> >> > transitions to a sleep state chosen by user space if there are no
> >> >> > active wakeup sources.
> >> >> >
> >> >> > It consists of a new sysfs attribute, /sys/power/autosleep, that
> >> >> > can be written one of the strings returned by reads from
> >> >> > /sys/power/state, an ordered workqueue and a work item carrying out
> >> >> > the "suspend" operations.  If a string representing the system's
> >> >> > sleep state is written to /sys/power/autosleep, the work item
> >> >> > triggering transitions to that state is queued up and it requeues
> >> >> > itself after every execution until user space writes "off" to
> >> >> > /sys/power/autosleep.
> >> >> >
> >> >>
> >> >> This does not work. Writing something other than "off" disabled auto
> >> >> suspend for me.
> >> >
> >> > My bad, sorry about that.
> >> >
> >> >> ...
> >> >> > +static ssize_t autosleep_store(struct kobject *kobj,
> >> >> > +                              struct kobj_attribute *attr,
> >> >> > +                              const char *buf, size_t n)
> >> >> > +{
> >> >> > +       suspend_state_t state = decode_state(buf, n);
> >> >> > +       int error;
> >> >> > +
> >> >> > +       if (state == PM_SUSPEND_ON
> >> >> > +           && !(strncmp(buf, "off", 3) && strncmp(buf, "off\n", 4)))
> >> >> > +               return -EINVAL;
> >> >>
> >> >> Did you mean:
> >> >>       if (state == PM_SUSPEND_ON
> >> >>           && strcmp(buf, "off") && strcmp(buf, "off\n"))
> >> >>               return -EINVAL;
> >> >
> >> >
> >> > Yes, I did.
> >> >
> >> > I'll add the following as an incremental patch on top of the series.
> >> >
> >> > Thanks,
> >> > Rafael
> >> >
> >> > ---
> >> >  kernel/power/main.c |    2 +-
> >> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >> >
> >> > Index: linux/kernel/power/main.c
> >> > ===================================================================
> >> > --- linux.orig/kernel/power/main.c
> >> > +++ linux/kernel/power/main.c
> >> > @@ -422,7 +422,7 @@ static ssize_t autosleep_store(struct ko
> >> >        int error;
> >> >
> >> >        if (state == PM_SUSPEND_ON
> >> > -           && !(strncmp(buf, "off", 3) && strncmp(buf, "off\n", 4)))
> >> > +           && strncmp(buf, "off", 3) && strncmp(buf, "off\n", 4))
> >> >                return -EINVAL;
> >> >
> >> >        error = pm_autosleep_set_state(state);
> >>
> >> You still use strncmp here, so anything that starts with "off" is
> >> allowed (and the second strncmp is redundant).
> >
> > Good point.  So I'm going to add the patch below after all.
> > OK to add your sign-off to it?
> >
> 
> Yes.

OK, done.
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