include/asm-generic/bitops/__ffs.h

   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  */
  13 static __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_ */