diff options
author | Jiri Kosina <jkosina@suse.cz> | 2012-10-28 19:28:52 +0100 |
---|---|---|
committer | Jiri Kosina <jkosina@suse.cz> | 2012-10-28 19:29:19 +0100 |
commit | 3bd7bf1f0fe14f591c089ae61bbfa9bd356f178a (patch) | |
tree | 0058693cc9e70b7461dae551f8a19aff2efd13ca /include/asm-generic/bitops/count_zeros.h | |
parent | f16f84937d769c893492160b1a8c3672e3992beb (diff) | |
parent | e657e078d3dfa9f96976db7a2b5fd7d7c9f1f1a6 (diff) |
Merge branch 'master' into for-next
Sync up with Linus' tree to be able to apply Cesar's patch
against newer version of the code.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'include/asm-generic/bitops/count_zeros.h')
-rw-r--r-- | include/asm-generic/bitops/count_zeros.h | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/count_zeros.h b/include/asm-generic/bitops/count_zeros.h new file mode 100644 index 00000000000..97520d21fe6 --- /dev/null +++ b/include/asm-generic/bitops/count_zeros.h @@ -0,0 +1,57 @@ +/* Count leading and trailing zeros functions + * + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#ifndef _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ +#define _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ + +#include <asm/bitops.h> + +/** + * count_leading_zeros - Count the number of zeros from the MSB back + * @x: The value + * + * Count the number of leading zeros from the MSB going towards the LSB in @x. + * + * If the MSB of @x is set, the result is 0. + * If only the LSB of @x is set, then the result is BITS_PER_LONG-1. + * If @x is 0 then the result is COUNT_LEADING_ZEROS_0. + */ +static inline int count_leading_zeros(unsigned long x) +{ + if (sizeof(x) == 4) + return BITS_PER_LONG - fls(x); + else + return BITS_PER_LONG - fls64(x); +} + +#define COUNT_LEADING_ZEROS_0 BITS_PER_LONG + +/** + * count_trailing_zeros - Count the number of zeros from the LSB forwards + * @x: The value + * + * Count the number of trailing zeros from the LSB going towards the MSB in @x. + * + * If the LSB of @x is set, the result is 0. + * If only the MSB of @x is set, then the result is BITS_PER_LONG-1. + * If @x is 0 then the result is COUNT_TRAILING_ZEROS_0. + */ +static inline int count_trailing_zeros(unsigned long x) +{ +#define COUNT_TRAILING_ZEROS_0 (-1) + + if (sizeof(x) == 4) + return ffs(x); + else + return (x != 0) ? __ffs(x) : COUNT_TRAILING_ZEROS_0; +} + +#endif /* _ASM_GENERIC_BITOPS_COUNT_ZEROS_H_ */ |