linux-kernel - Re: [PATCH] gpio-intel-mid: fix the incorrect return of idle callback

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Message-ID: <20140129195230.GC32149@saruman.home>
Date:	Wed, 29 Jan 2014 13:52:30 -0600
From:	Felipe Balbi <balbi@...com>
To:	David Cohen <david.a.cohen@...ux.intel.com>
CC:	"xinhui.pan" <xinhuix.pan@...el.com>, Felipe Balbi <balbi@...com>,
	<linux-kernel@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
	<linus.walleij@...aro.org>, <gnurou@...il.com>,
	<yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH] gpio-intel-mid: fix the incorrect return of idle callback

On Wed, Jan 29, 2014 at 11:12:32AM -0800, David Cohen wrote:
> On Wed, Jan 29, 2014 at 03:23:40PM +0800, xinhui.pan wrote:
> > 
> > 于 2014年01月29日 08:13, David Cohen 写道:
> > > On Tue, Jan 28, 2014 at 12:12:06PM -0600, Felipe Balbi wrote:
> > >> On Tue, Jan 28, 2014 at 09:24:13AM -0800, David Cohen wrote:
> > >>> On Tue, Jan 28, 2014 at 10:49:37AM -0600, Felipe Balbi wrote:
> > >>>> On Tue, Jan 28, 2014 at 04:50:57PM +0800, xinhui.pan wrote:
> > >>>>> From: "xinhui.pan" <xinhuiX.pan@...el.com>
> > >>>>>
> > >>>>> intel_gpio_runtime_idle should return correct error code if it do fail.
> > >>>>> make it more correct even though -EBUSY is the most possible return value.
> > >>>>>
> > >>>>> Signed-off-by: bo.he <bo.he@...el.com>
> > >>>>> Signed-off-by: xinhui.pan <xinhuiX.pan@...el.com>
> > >>>>> ---
> > >>>>>  drivers/gpio/gpio-intel-mid.c |    4 +++-
> > >>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
> > >>>>>
> > >>>>> diff --git a/drivers/gpio/gpio-intel-mid.c b/drivers/gpio/gpio-intel-mid.c
> > >>>>> index d1b50ef..05749a3 100644
> > >>>>> --- a/drivers/gpio/gpio-intel-mid.c
> > >>>>> +++ b/drivers/gpio/gpio-intel-mid.c
> > >>>>> @@ -394,7 +394,9 @@ static const struct irq_domain_ops intel_gpio_irq_ops = {
> > >>>>>  
> > >>>>>  static int intel_gpio_runtime_idle(struct device *dev)
> > >>>>>  {
> > >>>>> -	pm_schedule_suspend(dev, 500);
> > >>>>> +	int err = pm_schedule_suspend(dev, 500);
> > >>>>> +	if (err)
> > >>>>> +		return err;
> > >>>>>  	return -EBUSY;
> > >>>>
> > >>>> wait, is it only me or this would look a lot better as:
> > >>>>
> > >>>> static int intel_gpio_runtime_idle(struct device *dev)
> > >>>> {
> > >>>> 	return pm_schedule_suspend(dev, 500);
> > >>>> }
> > >>>
> > >>> The reply to your suggestion is probably in this commit :)
> > >>>
> > >>> ---
> > >>> commit 45f0a85c8258741d11bda25c0a5669c06267204a
> > >>> Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > >>> Date:   Mon Jun 3 21:49:52 2013 +0200
> > >>>
> > >>>     PM / Runtime: Rework the "runtime idle" helper routine
> > >>> ---
> > >>>
> > >>> We won't return 0 from here.
> > >>
> > >> so you never want to return 0, why don't you, then:
> > >>
> > >> static int intel_gpio_runtime_idle(struct device *dev)
> > >> {
> > >> 	pm_schedule_suspend(dev, 500);
> > >> 	return -EBUSY;
> > >> }
> > > 
> > > That's how it is currently :)
> > > 
> > > But this patch is making the function to return a different code in case
> > > of error. IMHO there is not much fuctional gain with it, but I see
> > > perhaps one extra info for tracing during development.
> > > 
> > > Anyway, I'll let Xinhui to do further comment since he's the author.
> > > 
> > > Br, David
> > > 
> > hi ,David & Balbi
> >   I checked several drivers yesterday to see how they use pm_schedule_suspend 
> > then found one bug in i2c. Also I noticed  gpio. 
> > I think returning a correct error code is important.So I change -EBUSY 
> > to *err*. To be honest,current code works well.
> 
> In my experience, when I'm using fancy things like lauterbach a proper
> error code may save couple of minutes in my life :)
> 
> I keep my ack here.

fair enough, sorry for the noise ;-) It could still be simplified a bit:

	return err ?: -EBUSY;

-- 
balbi

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