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Commit c1226a00 authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
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[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: default avatarAkinobu Mita <mita@miraclelinux.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4117b021

include/asm-generic/bitops/__ffs.h

0 → 100644
+43 −0
Original line number Diff line number Diff line 
#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_ */