linux-kernel - Re: [PATCH] driver/rtc/class.c: check the error after rtc_read

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Date:	Thu, 24 Jul 2014 01:49:44 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Hyogi Gim <hyogi.gim@....com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH] driver/rtc/class.c: check the error after rtc_read_time()

On Thursday, July 24, 2014 01:47:57 AM Rafael J. Wysocki wrote:
> On Wednesday, July 23, 2014 02:56:34 PM Andrew Morton wrote:
> > On Tue, 15 Jul 2014 17:25:23 +0900 Hyogi Gim <hyogi.gim@....com> wrote:
> > 
> > > In rtc_suspend() and rtc_resume(), the error after rtc_read_time() is not
> > > checked. If rtc device fail to read time, we cannot guarantee the following
> > > process.
> > > 
> > > Add the verification code for returned rtc_read_time() error.
> > > 
> > > ...
> > >
> > > --- a/drivers/rtc/class.c
> > > +++ b/drivers/rtc/class.c
> > > @@ -53,6 +53,7 @@ static int rtc_suspend(struct device *dev)
> > >  	struct rtc_device	*rtc = to_rtc_device(dev);
> > >  	struct rtc_time		tm;
> > >  	struct timespec		delta, delta_delta;
> > > +	int err;
> > >  
> > >  	if (has_persistent_clock())
> > >  		return 0;
> > > @@ -61,7 +62,12 @@ static int rtc_suspend(struct device *dev)
> > >  		return 0;
> > >  
> > >  	/* snapshot the current RTC and system time at suspend*/
> > > -	rtc_read_time(rtc, &tm);
> > > +	err = rtc_read_time(rtc, &tm);
> > > +	if (err < 0) {
> > > +		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
> > > +		return 0;
> > > +	}
> > 
> > OK, it makes no sense to go ahead and set the system time from a
> > garbage rtc_time.
> > 
> > But I'm wondering if we should propagate the error back to the
> > rtc_suspend() caller.  What does the PM core do if a particular
> > device's ->suspend or ->resume fails?
> 
> It aborts the suspend.

I mean, if ->suspend fails, the suspend is aborted.

If ->resume fails, on the other hand, we cannot do much more than logging
an error message.

Rafael

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