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
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 */