LXR linux/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
  28static 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 */
  55