1. 根目录:
2. include
3. uapi
4. asm-generic
5. swab.h

#ifndef _ASM_GENERIC_SWAB_H
#define _ASM_GENERIC_SWAB_H

#include <asm/bitsperlong.h>

/*
 * 32 bit architectures typically (but not always) want to
 * set __SWAB_64_THRU_32__. In user space, this is only
 * valid if the compiler supports 64 bit data types.
 */

#if __BITS_PER_LONG == 32
#if defined(__GNUC__) && !defined(__STRICT_ANSI__) || defined(__KERNEL__)
#define __SWAB_64_THRU_32__
#endif
#endif

#endif /* _ASM_GENERIC_SWAB_H */