From b6d86d3d6d6e4c9b588d81615c81b5a8292b62ed Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Fri, 24 Aug 2012 17:25:01 -0700 Subject: linux/kernel.h: Fix DIV_ROUND_CLOSEST to support negative dividends 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 Acked-by: Jean Delvare --- include/linux/kernel.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 604382143bcf..594b419b7d20 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -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)); \ } \ ) -- cgit v1.2.3