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linux/kernel.h: Fix DIV_ROUND_CLOSEST to support negative dividends

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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, DIV_ROUND_CLOSEST is sometimes used on integers which can be
negative (such as temperatures).

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
Guenter Roeck 2012-08-24 17:25:01 -07:00
commit b6d86d3d6d
1 changed files with 10 additions and 2 deletions
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12
include/linux/kernel.h
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@ -82,10 +82,18 @@
__x - (__x % (y)); \
} \
)
/*
* Divide positive or negative dividend by positive divisor and round
* to closest integer. Result is undefined for negative divisors.
*/
#define DIV_ROUND_CLOSEST(x, divisor)( \
{ \
typeof(divisor) __divisor = divisor; \
(((x) + ((__divisor) / 2)) / (__divisor)); \
typeof(x) __x = x; \
typeof(divisor) __d = divisor; \
(((typeof(x))-1) >= 0 || (__x) >= 0) ? \
(((__x) + ((__d) / 2)) / (__d)) : \
(((__x) - ((__d) / 2)) / (__d)); \
} \
)