linux-kernel - Re: [PATCH v10 5/6] rtc: max77686: Use ffs() to calculate tm

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Date:	Fri, 19 Sep 2014 12:52:27 -0700
From:	Joe Perches <joe@...ches.com>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Doug Anderson <dianders@...omium.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	rtc-linux@...glegroups.com, linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 5/6] rtc: max77686: Use ffs() to calculate tm_wday

On Fri, 2014-09-19 at 21:27 +0200, Javier Martinez Canillas wrote:
> Hello Joe,

Hello Javier.

> On 09/19/2014 04:39 PM, Joe Perches wrote:
> > On Fri, 2014-09-19 at 12:26 +0200, Javier Martinez Canillas wrote:
> >> The function max77686_rtc_calculate_wday() is used to
> >> calculate the day of the week to be filled in struct
> >> rtc_time but that function only calculates the number
> >> of bits shifted. So the ffs() function can be used to
> >> find the first bit set instead of a special function.
> > 
> > This isn't the same logic.  Perhaps you want fls.
> >
> 
> Right, the removed function has the same logic than fls() - 1 but the value
> stored in data[RTC_WEEKDAY] is:
> 
> data[RTC_WEEKDAY] = 1 << tm->tm_wday;
> 
> so for this particular case, it doesn't matter since ffs() == fls() always.

I didn't look that far.

I just wanted to show that the logic wasn't the same.

Perhaps you can specify that ffs==fls in the changelog.


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