root/include/asm-generic/bitops/__ffs.h

INCLUDED FROM

DEFINITIONS

1. __ffs

#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 __always_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_ */