linux-kernel - Re: [PATCH] rtc: pcf2127: add error message if writing to CLKOUT register fails

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Message-ID: <YehiHJXP23TSREbE@piout.net>
Date:   Wed, 19 Jan 2022 20:10:20 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Hugo Villeneuve <hugo@...ovil.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Hugo Villeneuve <hvilleneuve@...onoff.com>,
        linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: pcf2127: add error message if writing to CLKOUT
 register fails

On 19/01/2022 13:08:45-0500, Hugo Villeneuve wrote:
> On Wed, 19 Jan 2022 18:37:40 +0100
> Alexandre Belloni <alexandre.belloni@...tlin.com> wrote:
> 
> > On 19/01/2022 12:27:39-0500, Hugo Villeneuve wrote:
> > > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > > 
> > > If writing to CLKOUT register fails, the probe operation will be aborted
> > > without a meaningful error message.
> > > 
> > 
> > The current trend is to remove debug messages, please do not add more :)
> 
> Hi,
> If the read operation fails, the probe function will exit silently, and our RTC chip will not work. In that case, if we parse the dmesg logs, I think we  should have an indication that something went wrong.
> 

This is not true, it doesn't fail silently, you'd get:
rtc-pcf2127: probe of 1-0051 failed with error -121

> I had a case where my dev board was not properly plugged-in, and before this patch, I didn't notice it because of the silent abort of the probe function.
> 

Again, not silent.

> > 
> > > Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > > ---
> > >  drivers/rtc/rtc-pcf2127.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
> > > index 3d1f57e54372..823abe2a7147 100644
> > > --- a/drivers/rtc/rtc-pcf2127.c
> > > +++ b/drivers/rtc/rtc-pcf2127.c
> > > @@ -717,8 +717,10 @@ static int pcf2127_probe(struct device *dev, struct regmap *regmap,
> > >  	if (!(val & PCF2127_BIT_CLKOUT_OTPR)) {
> > >  		ret = regmap_set_bits(pcf2127->regmap, PCF2127_REG_CLKOUT,
> > >  				      PCF2127_BIT_CLKOUT_OTPR);
> > > -		if (ret < 0)
> > > +		if (ret < 0) {
> > > +			dev_err(dev, "writing to CLKOUT register failed\n");
> > >  			return ret;
> > > +		}
> > >  
> > >  		msleep(100);
> > >  	}
> > > -- 
> > > 2.30.2
> > > 
> > 
> > -- 
> > Alexandre Belloni, co-owner and COO, Bootlin
> > Embedded Linux and Kernel engineering
> > https://bootlin.com
> > 
> 
> 
> -- 
> Hugo Villeneuve <hugo@...ovil.com>

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com