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authorNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>2017-02-24 15:01:01 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:57 -0800
commit4f5901f5a6724f4ed1641e4a94978c5039a1f8c4 (patch)
treeec5f0c5a8485b040defd3a2247656b6524645f07 /include
parente4afd2e5567fc5d59988025f7528f9b4794d86a5 (diff)
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 [akpm@linux-foundation.org: fix comment, per Guenter] Link: http://lkml.kernel.org/r/20161222102217.29011-1-niklas.soderlund+renesas@ragnatech.se Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/kernel.h10
1 files changed, 6 insertions, 4 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index cb09238f6d32..4c26dc3a8295 100644
--- a/include/linux/kernel.h
+++ b/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 he dividend 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)); \
} \