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Date: Thu, 12 Dec 2013 17:40:22 +0000 From: Will Deacon <will.deacon@....com> To: linux-kernel@...r.kernel.org Cc: torvalds@...ux-foundation.org, viro@...iv.linux.org.uk, Will Deacon <will.deacon@....com> Subject: [PATCH v2 2/2] word-at-a-time: provide generic big-endian zero_bytemask implementation Whilst architectures may be able to do better than this (which they can, by simply defining their own macro), this is a generic stab at a zero_bytemask implementation for the asm-generic, big-endian word-at-a-time implementation. On arm64, a clz instruction is used to implement the fls efficiently. Signed-off-by: Will Deacon <will.deacon@....com> --- include/asm-generic/word-at-a-time.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/asm-generic/word-at-a-time.h b/include/asm-generic/word-at-a-time.h index 3f21f1b72e45..d3909effd725 100644 --- a/include/asm-generic/word-at-a-time.h +++ b/include/asm-generic/word-at-a-time.h @@ -49,4 +49,12 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct return (val + c->high_bits) & ~rhs; } +#ifndef zero_bytemask +#ifdef CONFIG_64BIT +#define zero_bytemask(mask) (~0ul << fls64(mask)) +#else +#define zero_bytemask(mask) (~0ul << fls(mask)) +#endif /* CONFIG_64BIT */ +#endif /* zero_bytemask */ + #endif /* _ASM_WORD_AT_A_TIME_H */ -- 1.8.2.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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