The patch titled
Subject: linux/kernel.h: fix warning seen with W=1 due to change in DIV_ROUND_CLOSEST
has been added to the -mm tree. Its filename is
linux-kernelh-fix-warning-seen-with-w=1-due-to-change-in-div_round_closest.patch
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From: Guenter Roeck <linux@xxxxxxxxxxxx>
Subject: linux/kernel.h: fix warning seen with W=1 due to change in DIV_ROUND_CLOSEST
After commit b6d86d3d ("Fix DIV_ROUND_CLOSEST to support negative
dividends"), the following warning is seen if the kernel is compiled with
W=1 (-Wextra):
warning: comparison of unsigned expression >= 0 is always true
The warning is due to the test '((typeof(x))-1) >= 0', which is used to
detect if the variable type is unsigned. Research on the web suggests
that the warning disappears if '>' instead of '>=' is used for the
comparison.
Tests after changing the macro along that line show that the warning is gone,
and that the result is still correct:
i=-4: DIV_ROUND_CLOSEST(i, 2)=-2
i=-3: DIV_ROUND_CLOSEST(i, 2)=-2
i=-2: DIV_ROUND_CLOSEST(i, 2)=-1
i=-1: DIV_ROUND_CLOSEST(i, 2)=-1
i=0: DIV_ROUND_CLOSEST(i, 2)=0
i=1: DIV_ROUND_CLOSEST(i, 2)=1
i=2: DIV_ROUND_CLOSEST(i, 2)=1
i=3: DIV_ROUND_CLOSEST(i, 2)=2
i=4: DIV_ROUND_CLOSEST(i, 2)=2
Code size is the same as before.
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Tested-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Acked-by: Jean Delvare <khali@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kernel.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN include/linux/kernel.h~linux-kernelh-fix-warning-seen-with-w=1-due-to-change-in-div_round_closest include/linux/kernel.h
--- a/include/linux/kernel.h~linux-kernelh-fix-warning-seen-with-w=1-due-to-change-in-div_round_closest
+++ a/include/linux/kernel.h
@@ -91,7 +91,7 @@
{ \
typeof(x) __x = x; \
typeof(divisor) __d = divisor; \
- (((typeof(x))-1) >= 0 || (__x) >= 0) ? \
+ (((typeof(x))-1) > 0 || (__x) > 0) ? \
(((__x) + ((__d) / 2)) / (__d)) : \
(((__x) - ((__d) / 2)) / (__d)); \
} \
_
Patches currently in -mm which might be from linux@xxxxxxxxxxxx are
linux-kernelh-fix-warning-seen-with-w=1-due-to-change-in-div_round_closest.patch
linux-next.patch
drm-i915-optimize-div_round_closest-call.patch
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