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 __ASM_ARM_SWAB_H
17#define __ASM_ARM_SWAB_H
18
19
20#include <linux/types.h>
21
22#if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
23#  define __SWAB_64_THRU_32__
24#endif
25
26
27static __inline__  __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
52#endif /* __ASM_ARM_SWAB_H */