The patch titled
Subject: linux/kernel.h: fix DIV_ROUND_CLOSEST to support negative divisors
has been added to the -mm tree. Its filename is
linux-kernelh-fix-div_round_closest-to-support-negative-divisors.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/linux-kernelh-fix-div_round_closest-to-support-negative-divisors.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/linux-kernelh-fix-div_round_closest-to-support-negative-divisors.patch
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From: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
Subject: linux/kernel.h: fix DIV_ROUND_CLOSEST to support negative divisors
While working on a thermal driver I encounter a scenario where the divisor
could be negative, instead of adding local code to handle this I though I
first try to add support for this in DIV_ROUND_CLOSEST.
Add support to DIV_ROUND_CLOSEST for negative divisors if both dividend
and divisor variable types are signed. This should not alter current
behavior for users of the macro as previously negative divisors where not
supported.
Before:
DIV_ROUND_CLOSEST( 59, 4) = 15
DIV_ROUND_CLOSEST( 59, -4) = -14
DIV_ROUND_CLOSEST( -59, 4) = -15
DIV_ROUND_CLOSEST( -59, -4) = 14
After:
DIV_ROUND_CLOSEST( 59, 4) = 15
DIV_ROUND_CLOSEST( 59, -4) = -15
DIV_ROUND_CLOSEST( -59, 4) = -15
DIV_ROUND_CLOSEST( -59, -4) = 15
Link: http://lkml.kernel.org/r/20161222102217.29011-1-niklas.soderlund+renesas@xxxxxxxxxxxx
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kernel.h | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff -puN include/linux/kernel.h~linux-kernelh-fix-div_round_closest-to-support-negative-divisors include/linux/kernel.h
--- a/include/linux/kernel.h~linux-kernelh-fix-div_round_closest-to-support-negative-divisors
+++ a/include/linux/kernel.h
@@ -100,16 +100,18 @@
)
/*
- * Divide positive or negative dividend by positive divisor and round
- * to closest integer. Result is undefined for negative divisors and
- * for negative dividends if the divisor variable type is unsigned.
+ * Divide positive or negative dividend by positive or negative divisor
+ * and round to closest integer. Result is undefined for negative
+ * divisors if dividends variable type is unsigned and for negative
+ * dividends if the divisor variable type is unsigned.
*/
#define DIV_ROUND_CLOSEST(x, divisor)( \
{ \
typeof(x) __x = x; \
typeof(divisor) __d = divisor; \
(((typeof(x))-1) > 0 || \
- ((typeof(divisor))-1) > 0 || (__x) > 0) ? \
+ ((typeof(divisor))-1) > 0 || \
+ (((__x) > 0) == ((__d) > 0))) ? \
(((__x) + ((__d) / 2)) / (__d)) : \
(((__x) - ((__d) / 2)) / (__d)); \
} \
_
Patches currently in -mm which might be from niklas.soderlund+renesas@xxxxxxxxxxxx are
linux-kernelh-fix-div_round_closest-to-support-negative-divisors.patch
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