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 <[email protected]> Cc: Andy Shevchenko <[email protected]> Cc: Yury Norov <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Rasmus Villemoes <[email protected]> --- 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
