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