linux-kernel - Re: [PATCH 1/4] kernel.h: Implement DIV_ROUND_CLOSEST

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Date:	Mon, 23 Mar 2015 17:04:17 +0000
From:	Javi Merino <javi.merino@....com>
To:	Jeff Epler <jepler@...ythonic.net>
Cc:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	Guenter Roeck <linux@...ck-us.net>, Alex Elder <elder@...e.org>
Subject: Re: [PATCH 1/4] kernel.h: Implement DIV_ROUND_CLOSEST_ULL

On Mon, Mar 23, 2015 at 12:34:04PM +0000, Jeff Epler wrote:
> On Fri, Mar 20, 2015 at 11:14:40AM +0000, Javi Merino wrote:
> > +/*
> > + * Same as above but for u64 dividends.  divisor must be a 32-bit
> > + * number.
> > + */
> > +#define DIV_ROUND_CLOSEST_ULL(x, divisor)(		\
> > +{							\
> > +	unsigned long long _tmp = (x) + (divisor) / 2;	\
> > +	do_div(_tmp, divisor);				\
> > +	_tmp;						\
> > +}							\
> > +)
> 
> The macro evaluates 'divisor' twice.

Good catch.  That needs to be fixed.  I could do the typeof trick that
DIV_ROUND_CLOSEST() does but it's probably better to just create a
static function as Alex Elder suggests.  I'll send a v2 tomorrow with
a static function instead.

Cheers,
Javi

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