include/asm-arm/byteorder.h

   1 /*
   2  *  linux/include/asm-arm/byteorder.h
   3  *
   4  * ARM Endian-ness.  In little endian mode, the data bus is connected such
   5  * that byte accesses appear as:
   6  *  0 = d0...d7, 1 = d8...d15, 2 = d16...d23, 3 = d24...d31
   7  * and word accesses (data or instruction) appear as:
   8  *  d0...d31
   9  *
  10  * When in big endian mode, byte accesses appear as:
  11  *  0 = d24...d31, 1 = d16...d23, 2 = d8...d15, 3 = d0...d7
  12  * and word accesses (data or instruction) appear as:
  13  *  d0...d31
  14  */
  15 #ifndef __ASM_ARM_BYTEORDER_H
  16 #define __ASM_ARM_BYTEORDER_H
  17
  18 #include <linux/compiler.h>
  19 #include <asm/types.h>
  20
  21 static inline __attribute_const__ __u32 ___arch__swab32(__u32 x)
  22 {
  23         __u32 t;
  24
  25 #ifndef __thumb__
  26         if (!__builtin_constant_p(x)) {
  27                 /*
  28                  * The compiler needs a bit of a hint here to always do the
  29                  * right thing and not screw it up to different degrees
  30                  * depending on the gcc version.
  31                  */
  32                 asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
  33         } else
  34 #endif
  35                 t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
  36
  37         x = (x << 24) | (x >> 8);               /* mov r0,r0,ror #8      */
  38         t &= ~0x00FF0000;                       /* bic r1,r1,#0x00FF0000 */
  39         x ^= (t >> 8);                          /* eor r0,r0,r1,lsr #8   */
  40
  41         return x;
  42 }
  43
  44 #define __arch__swab32(x) ___arch__swab32(x)
  45
  46 #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
  47 #  define __BYTEORDER_HAS_U64__
  48 #  define __SWAB_64_THRU_32__
  49 #endif
  50
  51 #ifdef __ARMEB__
  52 #include <linux/byteorder/big_endian.h>
  53 #else
  54 #include <linux/byteorder/little_endian.h>
  55 #endif
  56
  57 #endif
  58