1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2 /*
3  *  arch/arm/include/asm/byteorder.h
4  *
5  * ARM Endian-ness.  In little endian mode, the data bus is connected such
6  * that byte accesses appear as:
7  *  0 = d0...d7, 1 = d8...d15, 2 = d16...d23, 3 = d24...d31
8  * and word accesses (data or instruction) appear as:
9  *  d0...d31
10  *
11  * When in big endian mode, byte accesses appear as:
12  *  0 = d24...d31, 1 = d16...d23, 2 = d8...d15, 3 = d0...d7
13  * and word accesses (data or instruction) appear as:
14  *  d0...d31
15  */
16 #ifndef _UAPI__ASM_ARM_SWAB_H
17 #define _UAPI__ASM_ARM_SWAB_H
18 
19 #include <linux/compiler.h>
20 #include <linux/types.h>
21 
22 #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
23 #  define __SWAB_64_THRU_32__
24 #endif
25 
26 
27 #if !defined(__KERNEL__) || __LINUX_ARM_ARCH__ < 6
__arch_swab32(__u32 x)28 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
29 {
30 	__u32 t;
31 
32 #ifndef __thumb__
33 	if (!__builtin_constant_p(x)) {
34 		/*
35 		 * The compiler needs a bit of a hint here to always do the
36 		 * right thing and not screw it up to different degrees
37 		 * depending on the gcc version.
38 		 */
39 		asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
40 	} else
41 #endif
42 		t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
43 
44 	x = (x << 24) | (x >> 8);		/* mov r0,r0,ror #8      */
45 	t &= ~0x00FF0000;			/* bic r1,r1,#0x00FF0000 */
46 	x ^= (t >> 8);				/* eor r0,r0,r1,lsr #8   */
47 
48 	return x;
49 }
50 #define __arch_swab32 __arch_swab32
51 
52 #endif
53 
54 #endif /* _UAPI__ASM_ARM_SWAB_H */
55