linux-kernel - RE: [PATCH] rtc: Modify leap year test for more simpler way

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Date:	Wed, 6 Feb 2013 17:12:55 +0530
From:	Venu Byravarasu <vbyravarasu@...dia.com>
To:	Jonghwa Lee <jonghwa3.lee@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"a.zummo@...ertech.it" <a.zummo@...ertech.it>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>
Subject: RE: [PATCH] rtc: Modify leap year test for more simpler way

By definition, leap year is one, which is a divisible by 4 & 400, excluding multiples of 100s.
Hence I feel this patch is not correct.

Thanks,
Venu


> -----Original Message-----
> From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-
> owner@...r.kernel.org] On Behalf Of Jonghwa Lee
> Sent: Wednesday, February 06, 2013 4:53 PM
> To: linux-kernel@...r.kernel.org
> Cc: a.zummo@...ertech.it; Andrew Morton; rtc-linux@...glegroups.com;
> Jonghwa Lee
> Subject: [PATCH] rtc: Modify leap year test for more simpler way
> 
> Leap year which is multiple of 4, just needed 2 LSB for verifying.
> A year with zero for all thease two bits means that it is leap year.
> 
> Signed-off-by: Jonghwa Lee <jonghwa3.lee@...sung.com>
> ---
>  include/linux/rtc.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/rtc.h b/include/linux/rtc.h
> index 9531845..d662b8d 100644
> --- a/include/linux/rtc.h
> +++ b/include/linux/rtc.h
> @@ -181,7 +181,7 @@ void rtc_timer_do_work(struct work_struct *work);
> 
>  static inline bool is_leap_year(unsigned int year)
>  {
> -	return (!(year % 4) && (year % 100)) || !(year % 400);
> +	return !(year & 0x3);
>  }
> 
>  #ifdef CONFIG_RTC_HCTOSYS_DEVICE
> --
> 1.7.9.5
> 
> --
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