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

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Message-ID: <20140129191232.GC13185@psi-dev26.jf.intel.com>
Date:	Wed, 29 Jan 2014 11:12:32 -0800
From:	David Cohen <david.a.cohen@...ux.intel.com>
To:	"xinhui.pan" <xinhuix.pan@...el.com>
Cc:	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 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.

Br, David

> >>
> >> just like drivers/tty/serial/mfd.c::serial_hsu_runtime_idle() is doing ?
> >>
> >> -- 
> >> balbi
> > 
> > 
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