swab.h 1.4 KB

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  1. /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
  2. /*
  3. * arch/arm/include/asm/byteorder.h
  4. *
  5. * ARM Endian-ness. In little endian mode, the data bus is connected such
  6. * that byte accesses appear as:
  7. * 0 = d0...d7, 1 = d8...d15, 2 = d16...d23, 3 = d24...d31
  8. * and word accesses (data or instruction) appear as:
  9. * d0...d31
  10. *
  11. * When in big endian mode, byte accesses appear as:
  12. * 0 = d24...d31, 1 = d16...d23, 2 = d8...d15, 3 = d0...d7
  13. * and word accesses (data or instruction) appear as:
  14. * d0...d31
  15. */
  16. #ifndef _UAPI__ASM_ARM_SWAB_H
  17. #define _UAPI__ASM_ARM_SWAB_H
  18. #include <linux/compiler.h>
  19. #include <linux/types.h>
  20. #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
  21. # define __SWAB_64_THRU_32__
  22. #endif
  23. #if !defined(__KERNEL__) || __LINUX_ARM_ARCH__ < 6
  24. static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
  25. {
  26. __u32 t;
  27. #ifndef __thumb__
  28. if (!__builtin_constant_p(x)) {
  29. /*
  30. * The compiler needs a bit of a hint here to always do the
  31. * right thing and not screw it up to different degrees
  32. * depending on the gcc version.
  33. */
  34. asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
  35. } else
  36. #endif
  37. t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
  38. x = (x << 24) | (x >> 8); /* mov r0,r0,ror #8 */
  39. t &= ~0x00FF0000; /* bic r1,r1,#0x00FF0000 */
  40. x ^= (t >> 8); /* eor r0,r0,r1,lsr #8 */
  41. return x;
  42. }
  43. #define __arch_swab32 __arch_swab32
  44. #endif
  45. #endif /* _UAPI__ASM_ARM_SWAB_H */