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Re: [PATCH] rtc: ds1685: Remove superfluous checks for out-of-range u8 v

To: Geert Uytterhoeven <geert@linux-m68k.org>, Alessandro Zummo <a.zummo@towertech.it>, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] rtc: ds1685: Remove superfluous checks for out-of-range u8 values
From: Joshua Kinard <kumba@gentoo.org>
Date: Wed, 18 Feb 2015 08:22:30 -0500
Cc: rtc-linux@googlegroups.com, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
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On 02/18/2015 05:44, Geert Uytterhoeven wrote:
> drivers/rtc/rtc-ds1685.c: In function ‘ds1685_rtc_read_alarm’:
> drivers/rtc/rtc-ds1685.c:402: warning: comparison is always true due to 
> limited range of data type
> drivers/rtc/rtc-ds1685.c:409: warning: comparison is always true due to 
> limited range of data type
> drivers/rtc/rtc-ds1685.c:416: warning: comparison is always true due to 
> limited range of data type
> drivers/rtc/rtc-ds1685.c: In function ‘ds1685_rtc_set_alarm’:
> drivers/rtc/rtc-ds1685.c:475: warning: comparison is always true due to 
> limited range of data type
> drivers/rtc/rtc-ds1685.c:478: warning: comparison is always true due to 
> limited range of data type
> drivers/rtc/rtc-ds1685.c:481: warning: comparison is always true due to 
> limited range of data type
> 
> u8 cannot contain a value larger than 0xff, hence drop the checks.
> Wrapping the checks in unlikely() indicated some sense of humor, though ;-)
> 
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Actually, I think I was operating in -pedantic mode the night I added those
checks.  Good catch, thanks!

Acked-by: Joshua Kinard <kumba@gentoo.org>


> ---
>  drivers/rtc/rtc-ds1685.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-ds1685.c b/drivers/rtc/rtc-ds1685.c
> index 8c3bfcb115b78731..5077078a9305b9d5 100644
> --- a/drivers/rtc/rtc-ds1685.c
> +++ b/drivers/rtc/rtc-ds1685.c
> @@ -399,21 +399,21 @@ ds1685_rtc_read_alarm(struct device *dev, struct 
> rtc_wkalrm *alrm)
>        * of this RTC chip.  We check for it anyways in case support is
>        * added in the future.
>        */
> -     if (unlikely((seconds >= 0xc0) && (seconds <= 0xff)))
> +     if (unlikely(seconds >= 0xc0))
>               alrm->time.tm_sec = -1;
>       else
>               alrm->time.tm_sec = ds1685_rtc_bcd2bin(rtc, seconds,
>                                                      RTC_SECS_BCD_MASK,
>                                                      RTC_SECS_BIN_MASK);
>  
> -     if (unlikely((minutes >= 0xc0) && (minutes <= 0xff)))
> +     if (unlikely(minutes >= 0xc0))
>               alrm->time.tm_min = -1;
>       else
>               alrm->time.tm_min = ds1685_rtc_bcd2bin(rtc, minutes,
>                                                      RTC_MINS_BCD_MASK,
>                                                      RTC_MINS_BIN_MASK);
>  
> -     if (unlikely((hours >= 0xc0) && (hours <= 0xff)))
> +     if (unlikely(hours >= 0xc0))
>               alrm->time.tm_hour = -1;
>       else
>               alrm->time.tm_hour = ds1685_rtc_bcd2bin(rtc, hours,
> @@ -472,13 +472,13 @@ ds1685_rtc_set_alarm(struct device *dev, struct 
> rtc_wkalrm *alrm)
>        * field, and we only support four fields.  We put the support
>        * here anyways for the future.
>        */
> -     if (unlikely((seconds >= 0xc0) && (seconds <= 0xff)))
> +     if (unlikely(seconds >= 0xc0))
>               seconds = 0xff;
>  
> -     if (unlikely((minutes >= 0xc0) && (minutes <= 0xff)))
> +     if (unlikely(minutes >= 0xc0))
>               minutes = 0xff;
>  
> -     if (unlikely((hours >= 0xc0) && (hours <= 0xff)))
> +     if (unlikely(hours >= 0xc0))
>               hours = 0xff;
>  
>       alrm->time.tm_mon       = -1;
> 


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