linux-kernel - Re: [PATCH] RTC: rtc_time_to

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Message-ID: <4820E0C6.10309@gmail.com>
Date:	Wed, 07 May 2008 02:50:46 +0400
From:	Dmitri Vorobiev <dmitri.vorobiev@...il.com>
To:	"Maciej W. Rozycki" <macro@...ux-mips.org>
CC:	Alessandro Zummo <a.zummo@...ertech.it>,
	Andrew Morton <akpm@...ux-foundation.org>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RTC: rtc_time_to_tm: use unsigned arithmetic

Maciej W. Rozycki пишет:
>  The input argument to rtc_time_to_tm() is unsigned as well as are members
> of the output structure.  However signed arithmetic is used within for
> calculations leading to incorrect results for input values outside the
> signed positive range.  If this happens the time of day returned is out of
> range.
> 
>  Found the problem when fiddling with the RTC and the driver where year
> was set to an unexpectedly large value like 2070, e.g.:
> 
> rtc0: setting system clock to 2070-01-01 1193046:71582832:26 UTC (3155760954)
> 
> while it should be:
> 
> rtc0: setting system clock to 2070-01-01 00:15:54 UTC (3155760954)
> 
> Changing types to unsigned fixes the problem.
> 
> Signed-off-by: Maciej W. Rozycki <macro@...ux-mips.org>
> ---
>  Tested on 64-bit MIPS.  Please apply.
> 
>   Maciej
> 
> patch-2.6.26-rc1-20080505-rtc-time-unsigned-11
> diff -up --recursive --new-file linux-2.6.26-rc1-20080505.macro/drivers/rtc/rtc-lib.c linux-2.6.26-rc1-20080505/drivers/rtc/rtc-lib.c
> --- linux-2.6.26-rc1-20080505.macro/drivers/rtc/rtc-lib.c	2007-07-10 04:56:26.000000000 +0000
> +++ linux-2.6.26-rc1-20080505/drivers/rtc/rtc-lib.c	2008-05-05 02:37:38.000000000 +0000
> @@ -51,7 +51,7 @@ EXPORT_SYMBOL(rtc_year_days);
>   */
>  void rtc_time_to_tm(unsigned long time, struct rtc_time *tm)
>  {
> -	register int days, month, year;
> +	register unsigned int days, month, year;

Does it make any sense to use the `register' keyword nowadays?

Dmitri
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