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