arch/arm/include/asm/swab.h

   1 /*
   2  *  arch/arm/include/asm/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_SWAB_H
  16 #define __ASM_ARM_SWAB_H
  17
  18 #include <linux/compiler.h>
  19 #include <linux/types.h>
  20
  21 #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
  22 #  define __SWAB_64_THRU_32__
  23 #endif
  24
  25 #if defined(__KERNEL__)
  26 #if __LINUX_ARM_ARCH__ >= 6
  27
  28 static inline __attribute_const__ __u32 __arch_swahb32(__u32 x)
  29 {
  30         __asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x));
  31         return x;
  32 }
  33 #define __arch_swahb32 __arch_swahb32
  34 #define __arch_swab16(x) ((__u16)__arch_swahb32(x))
  35
  36 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
  37 {
  38         __asm__ ("rev %0, %1" : "=r" (x) : "r" (x));
  39         return x;
  40 }
  41 #define __arch_swab32 __arch_swab32
  42
  43 #endif
  44 #endif
  45
  46 #if !defined(__KERNEL__) || __LINUX_ARM_ARCH__ < 6
  47 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
  48 {
  49         __u32 t;
  50
  51 #ifndef __thumb__
  52         if (!__builtin_constant_p(x)) {
  53                 /*
  54                  * The compiler needs a bit of a hint here to always do the
  55                  * right thing and not screw it up to different degrees
  56                  * depending on the gcc version.
  57                  */
  58                 asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
  59         } else
  60 #endif
  61                 t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
  62
  63         x = (x << 24) | (x >> 8);               /* mov r0,r0,ror #8      */
  64         t &= ~0x00FF0000;                       /* bic r1,r1,#0x00FF0000 */
  65         x ^= (t >> 8);                          /* eor r0,r0,r1,lsr #8   */
  66
  67         return x;
  68 }
  69 #define __arch_swab32 __arch_swab32
  70
  71 #endif
  72
  73 #endif