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| author | Guenter Roeck <linux@roeck-us.net> | 2012-08-25 04:25:01 +0400 |
|---|---|---|
| committer | Guenter Roeck <linux@roeck-us.net> | 2012-09-02 05:58:09 +0400 |
| commit | b6d86d3d6d6e4c9b588d81615c81b5a8292b62ed (patch) | |
| tree | 814c4ba720911beba197b610d4bd4559a26c3e96 | |
| parent | 4cbe5a555fa58a79b6ecbb6c531b8bab0650778d (diff) | |
| download | linux-b6d86d3d6d6e4c9b588d81615c81b5a8292b62ed.tar.xz | |
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 <linux@roeck-us.net>
Acked-by: Jean Delvare <khali@linux-fr.org>
| -rw-r--r-- | include/linux/kernel.h | 12 |
1 files changed, 10 insertions, 2 deletions
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)); \ } \ ) |