From c1226a005ec400e966f4993dfcc0e99fd7baa6a1 Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Sun, 26 Mar 2006 01:39:08 -0800 Subject: [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/bitops/__ffs.h | 43 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 include/asm-generic/bitops/__ffs.h (limited to 'include/asm-generic/bitops') 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 + +/** + * __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_ */ -- cgit v1.2.3