linux-kernel - Re: [PATCH 1/2] Create a DIV_ROUND_CLOSEST macro to do division with rounding

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Date:	Tue, 11 Nov 2008 10:51:50 -0800
From:	Joe Perches <joe@...ches.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	lm-sensors <lm-sensors@...sensors.org>
Subject: Re: [PATCH 1/2] Create a DIV_ROUND_CLOSEST macro to do division
 with  rounding

On Tue, 2008-11-11 at 09:07 -0800, Andrew Morton wrote:
> On Tue, 11 Nov 2008 11:04:54 +0100 Jean Delvare <khali@...ux-fr.org> wrote:
> > On Mon, 10 Nov 2008 17:01:32 -0800, Darrick J. Wong wrote:
> > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> > > index fba141d..fb02266 100644
> > > --- a/include/linux/kernel.h
> > > +++ b/include/linux/kernel.h
> > > @@ -48,6 +48,12 @@ extern const char linux_proc_banner[];
> > >  #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
> > >  #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
> > >  #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
> > > +#define DIV_ROUND_CLOSEST(x, divisor)(			\
> > > +{							\
> > > +	typeof(divisor) __divisor = divisor;		\
> > > +	(((x) + ((__divisor) / 2)) / (__divisor));	\
> > > +}							\
> > > +) 
> > I don't get why you implement this as a macro rather than an inline
> > function? A function would look much better.
> The idea is that DIV_ROUND_CLOSEST() can be used with arguments of any
> size (char, short, ...  long long) and will do all the suitable
> promotion and will return a type of the appropriate width and
> signedness.

Perhaps the macro should be placed directly after
DIV_ROUND_UP and should use the same argument naming.

Perhaps HALF_UP is more descriptive and fairly common.
http://java.sun.com/j2se/1.5.0/docs/api/java/math/RoundingMode.html


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