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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