linux/kernel.h: fix DIV_ROUND_CLOSEST to support negative divisors
authorNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Fri, 24 Feb 2017 23:01:01 +0000 (15:01 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 25 Feb 2017 01:46:57 +0000 (17:46 -0800)
commit4f5901f5a6724f4ed1641e4a94978c5039a1f8c4
treeec5f0c5a8485b040defd3a2247656b6524645f07
parente4afd2e5567fc5d59988025f7528f9b4794d86a5
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>
include/linux/kernel.h