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| author | Akinobu Mita <mita@miraclelinux.com> | 2006-03-26 11:39:08 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-26 18:57:10 +0200 |
| commit | c1226a005ec400e966f4993dfcc0e99fd7baa6a1 (patch) | |
| tree | 7c69ee952fae6209b7e760c1b7de83e2d9f05d25 /include/asm-generic | |
| parent | [PATCH] bitops: generic __{,test_and_}{set,clear,change}_bit() and test_bit() (diff) | |
| download | linux-c1226a005ec400e966f4993dfcc0e99fd7baa6a1.tar.xz linux-c1226a005ec400e966f4993dfcc0e99fd7baa6a1.zip | |
[PATCH] bitops: generic __ffs()
This patch introduces the C-language equivalent of the function: unsigned long
__ffs(unsigned long word);
In include/asm-generic/bitops/__ffs.h
This code largely copied from: include/asm-sparc/bitops.h
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/bitops/__ffs.h | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/__ffs.h b/include/asm-generic/bitops/__ffs.h new file mode 100644 index 000000000000..9a3274aecf83 --- /dev/null +++ b/include/asm-generic/bitops/__ffs.h @@ -0,0 +1,43 @@ +#ifndef _ASM_GENERIC_BITOPS___FFS_H_ +#define _ASM_GENERIC_BITOPS___FFS_H_ + +#include <asm/types.h> + +/** + * __ffs - find first bit in word. + * @word: The word to search + * + * Undefined if no bit exists, so code should check against 0 first. + */ +static inline unsigned long __ffs(unsigned long word) +{ + int num = 0; + +#if BITS_PER_LONG == 64 + if ((word & 0xffffffff) == 0) { + num += 32; + word >>= 32; + } +#endif + if ((word & 0xffff) == 0) { + num += 16; + word >>= 16; + } + if ((word & 0xff) == 0) { + num += 8; + word >>= 8; + } + if ((word & 0xf) == 0) { + num += 4; + word >>= 4; + } + if ((word & 0x3) == 0) { + num += 2; + word >>= 2; + } + if ((word & 0x1) == 0) + num += 1; + return num; +} + +#endif /* _ASM_GENERIC_BITOPS___FFS_H_ */ |