linux-kernel - Re: [PATCH 2/3] rtc: __rtc_read

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Date:	Wed, 1 Apr 2015 05:21:13 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Aaro Koskinen <aaro.koskinen@....fi>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] rtc: __rtc_read_time: reduce log level

On 28/03/2015 at 23:09:35 +0200, Aaro Koskinen wrote :
> __rtc_read_time logs should be debug logs instead of error logs.
> 
> For example, when the RTC clock is not set, it's not really useful
> to print a kernel error log every time someone tries to read the clock:
> 
> 	~ # hwclock -r
> 	[  604.508263] rtc rtc0: read_time: fail to read
> 	hwclock: RTC_RD_TIME: Invalid argument
> 
> If there's a real error, it's likely that lower level or higher level
> code will tell it anyway. Make these logs debug logs, and also print
> the error code for the read failure.
> 

That actually may be the only error message printed for some failures.
Some RTCs don't print anything in case of error in their .read_time()
and there are in-kernel users of rtc_read_time that simply bail out
without printing anything or have a trace that is already at the debug
level.

I would agree that this would need a better harmonization and I guess we
can do that for now. I'll try to fix the in-kernel cases.

> Signed-off-by: Aaro Koskinen <aaro.koskinen@....fi>
Acked-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>

> ---
>  drivers/rtc/interface.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
> index 37215cf..c786818 100644
> --- a/drivers/rtc/interface.c
> +++ b/drivers/rtc/interface.c
> @@ -31,13 +31,14 @@ static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
>  		memset(tm, 0, sizeof(struct rtc_time));
>  		err = rtc->ops->read_time(rtc->dev.parent, tm);
>  		if (err < 0) {
> -			dev_err(&rtc->dev, "read_time: fail to read\n");
> +			dev_dbg(&rtc->dev, "read_time: fail to read: %d\n",
> +				err);
>  			return err;
>  		}
>  
>  		err = rtc_valid_tm(tm);
>  		if (err < 0)
> -			dev_err(&rtc->dev, "read_time: rtc_time isn't valid\n");
> +			dev_dbg(&rtc->dev, "read_time: rtc_time isn't valid\n");
>  	}
>  	return err;
>  }
> -- 
> 2.2.0
> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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