From mboxrd@z Thu Jan 1 00:00:00 1970 From: Akinobu Mita Date: Wed, 01 Feb 2006 09:02:31 +0000 Subject: [patch 07/44] generic __ffs() Message-Id: <20060201090322.698909000@localhost.localdomain> List-Id: References: <20060201090224.536581000@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-kernel@vger.kernel.org Cc: Russell King , Ian Molton , David Howells , Hirokazu Takata , Greg Ungerer , linux-mips@linux-mips.org, linuxsh-dev@lists.sourceforge.net, linuxsh-shmedia-dev@lists.sourceforge.net, sparclinux@vger.kernel.org, ultralinux@vger.kernel.org, Miles Bader , Akinobu Mita 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 include/asm-generic/bitops/__ffs.h | 43 +++++++++++++++++++++++++++++++++++++ 1 files changed, 43 insertions(+) Index: 2.6-git/include/asm-generic/bitops/__ffs.h =================================--- /dev/null +++ 2.6-git/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_ */ --