linux-kernel - Re: [PATCH v2 1/2] linux/kernel.h: Introduce IDIV_ROUND

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Date:	Thu, 30 Aug 2012 16:50:36 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jean Delvare <khali@...ux-fr.org>, lm-sensors@...sensors.org
Subject: Re: [PATCH v2 1/2] linux/kernel.h: Introduce IDIV_ROUND_CLOSEST

On Thu, Aug 30, 2012 at 04:15:32PM -0700, Andrew Morton wrote:
> On Tue, 28 Aug 2012 09:30:55 -0700
> Guenter Roeck <linux@...ck-us.net> wrote:
> 
> > DIV_ROUND_CLOSEST returns a bad result for negative dividends:
> > 	DIV_ROUND_CLOSEST(-2, 2) = 0
> > 
> > Most of the time this does not matter. However, in the hardware monitoring
> > subsystem, it is sometimes used on integers which can be negative (such as
> > temperatures). Introduce new macro IDIV_ROUND_CLOSEST which also supports
> > negative dividends.
> > 
> 
> Can't we just fix DIV_ROUND_CLOSEST?  That will make it a bit slower
> but it's not exactly a speed demon right now.  And fixing
> DIV_ROUND_CLOSEST() might just fix other bugs that we don't know about
> yet.
> 
Sure, fine with me. I'll submit a patch. Let's see who starts screaming.

Guenter
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