static __always_inline __u32 __be32_to_cpup(const __be32 p), include/uapi/linux/byteorder/little_endian.h
{
return __swab32p((__u32 )p);
}

static __always_inline __u32 __swab32p(const __u32 _p), include/uapi/linux/swab.h
{
#ifdef __arch_swab32p
return __arch_swab32p(p);
#else
return __swab32(_p);

endif

}

ifdef HAVE_BUILTIN_BSWAP32 (include/uapi/linux/swab.h)

define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))

else

define __swab32(x)

(__builtin_constant_p((__u32)(x)) ?
constantswab32(x) :
fswab32(x))

endif

static inline attribute_const __u32 __fswab32(__u32 val), include/uapi/linux/swab.h
{

if defined(__arch_swab32)

return __arch_swab32(val);

else

return ___constant_swab32(val);

endif

}

define constantswab32(x) ((u32)(

(((__u32)(x) & (__u32)0x000000ffUL) << 24) |
(((__u32)(x) & (__u32)0x0000ff00UL) << 8) |
(((__u32)(x) & (__u32)0x00ff0000UL) >> 8) |
(((__u32)(x) & (__u32)0xff000000UL) >> 24)))

2.2 如果cpu为大端序
static __always_inline __u32 __be32_to_cpup(const __be32 _p), include/uapi/linux/byteorder/big_endian.h
{
return (__force __u32)_p;
}

Original: https://www.cnblogs.com/dakewei/p/13848569.html
Author: Jello
Title: 在linux内核中为什么解析设备树时会使用be32_to_cpup()接口？