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 11:04:54 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	"Darrick J. Wong" <djwong@...ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	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

Hi Darrick,

On Mon, 10 Nov 2008 17:01:32 -0800, Darrick J. Wong wrote:
> 
> Create a helper macro to divide two numbers and round the result to the
> nearest whole number.  This is a helper macro for hwmon drivers that
> want to convert incoming sysfs values per standard hwmon practice, though
> the macro itself can be used by anyone.
> 
> Signed-off-by: Darrick J. Wong <djwong@...ibm.com>
> ---
> 
>  include/linux/kernel.h |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> 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));	\
> +}							\
> +)
>  
>  #define _RET_IP_		(unsigned long)__builtin_return_address(0)
>  #define _THIS_IP_  ({ __label__ __here; __here: (unsigned long)&&__here; })
> 

I don't get why you implement this as a macro rather than an inline
function? A function would look much better.

-- 
Jean Delvare
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