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

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
   3#define _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
   4
   5#include <asm/types.h>
   6#include <asm/bitsperlong.h>
   7
   8/**
   9 * __ffs - find first bit in word.
  10 * @word: The word to search
  11 *
  12 * Undefined if no bit exists, so code should check against 0 first.
  13 */
  14static __always_inline unsigned long __ffs(unsigned long word)
  15{
  16        int num = 0;
  17
  18#if __BITS_PER_LONG == 64
  19        if ((word & 0xffffffff) == 0) {
  20                num += 32;
  21                word >>= 32;
  22        }
  23#endif
  24        if ((word & 0xffff) == 0) {
  25                num += 16;
  26                word >>= 16;
  27        }
  28        if ((word & 0xff) == 0) {
  29                num += 8;
  30                word >>= 8;
  31        }
  32        if ((word & 0xf) == 0) {
  33                num += 4;
  34                word >>= 4;
  35        }
  36        if ((word & 0x3) == 0) {
  37                num += 2;
  38                word >>= 2;
  39        }
  40        if ((word & 0x1) == 0)
  41                num += 1;
  42        return num;
  43}
  44
  45#endif /* _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_ */
  46