Messages in this thread Patch in this message | | | From | Wei Wang <> | Subject | [PATCH v2] linux/bitmap.h: comments on BITMAP_LAST_WORD_MASK | Date | Fri, 27 Jul 2018 16:03:31 +0800 |
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When "nbits = 0" which means no bits to mask, this macro is expected to return 0, instead of 0xffffffff. Currently, the "nbits = 0" case is avoided by the callers themselves (e.g.__bitmap_intersects, __bitmap_weight). This corner case should be explicitly noted.
This patch simply adds a comment above the macro as a note to users about the corner case.
Signed-off-by: Wei Wang <wei.w.wang@intel.com> Cc: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Yury Norov <ynorov@caviumnetworks.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- include/linux/bitmap.h | 1 + 1 file changed, 1 insertion(+)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 1ee46f4..4e64d1f 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -194,6 +194,7 @@ extern int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp, int nmaskbits); #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1))) +/* "nbits = 0" is not applicable to this macro. Callers should avoid that. */ #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1))) #define small_const_nbits(nbits) \ -- 2.7.4
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