release/src-rt-6.x/linux/linux-2.6/include/asm-generic/bitops/__ffs.h

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