arch/arm/include/uapi/asm/swab.h

   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
  19 #include <linux/compiler.h>
  20 #include <linux/types.h>
  21
  22 #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
  23 #  define __SWAB_64_THRU_32__
  24 #endif
  25
  26
  27 #if !defined(__KERNEL__) || __LINUX_ARM_ARCH__ < 6
  28 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
  29 {
  30         __u32 t;
  31
  32 #ifndef __thumb__
  33         if (!__builtin_constant_p(x)) {
  34                 /*
  35                  * The compiler needs a bit of a hint here to always do the
  36                  * right thing and not screw it up to different degrees
  37                  * depending on the gcc version.
  38                  */
  39                 asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
  40         } else
  41 #endif
  42                 t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
  43
  44         x = (x << 24) | (x >> 8);               /* mov r0,r0,ror #8      */
  45         t &= ~0x00FF0000;                       /* bic r1,r1,#0x00FF0000 */
  46         x ^= (t >> 8);                          /* eor r0,r0,r1,lsr #8   */
  47
  48         return x;
  49 }
  50 #define __arch_swab32 __arch_swab32
  51
  52 #endif
  53
  54 #endif /* _UAPI__ASM_ARM_SWAB_H */