LXR linux/include/asm-generic/bitops/_

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _ASM_GENERIC_BITOPS___FFS_H_
   3#define _ASM_GENERIC_BITOPS___FFS_H_
   4
   5#include <asm/types.h>
   6
   7/**
   8 * __ffs - find first bit in word.
   9 * @word: The word to search
  10 *
  11 * Undefined if no bit exists, so code should check against 0 first.
  12 */
  13static __always_inline unsigned long __ffs(unsigned long word)
  14{
  15        int num = 0;
  16
  17#if BITS_PER_LONG == 64
  18        if ((word & 0xffffffff) == 0) {
  19                num += 32;
  20                word >>= 32;
  21        }
  22#endif
  23        if ((word & 0xffff) == 0) {
  24                num += 16;
  25                word >>= 16;
  26        }
  27        if ((word & 0xff) == 0) {
  28                num += 8;
  29                word >>= 8;
  30        }
  31        if ((word & 0xf) == 0) {
  32                num += 4;
  33                word >>= 4;
  34        }
  35        if ((word & 0x3) == 0) {
  36                num += 2;
  37                word >>= 2;
  38        }
  39        if ((word & 0x1) == 0)
  40                num += 1;
  41        return num;
  42}
  43
  44#endif /* _ASM_GENERIC_BITOPS___FFS_H_ */
  45