__ffs.h 777 B

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