Hi Adam,

1. Which platform?

* little-endian
ARM

* big-endian
MIPS

2. The atomic element size is 16-bit?
No idea about this question.

3. Maybe you should take a look at __be32 and __le32.

* little-endian
# 1 "arch/arm/include/asm/types.h" 1
# 1 "include/asm-generic/int-ll64.h" 1
# 17 "include/asm-generic/int-ll64.h"
typedef __signed__ char __s8;
typedef unsigned char __u8;

typedef __signed__ short __s16;
typedef unsigned short __u16;

typedef __signed__ int __s32;
typedef unsigned int __u32;

# 168 "include/linux/types.h"
typedef __u16 __le16;
typedef __u16 __be16;
typedef __u32 __le32;
typedef __u32 __be32;


* big-endian
# 21 "arch/mips/include/asm/types.h"
# 1 "include/asm-generic/int-ll64.h" 1
# 17 "include/asm-generic/int-ll64.h"
typedef __signed__ char __s8;
typedef unsigned char __u8;

typedef __signed__ short __s16;
typedef unsigned short __u16;

typedef __signed__ int __s32;
typedef unsigned int __u32;

# 168 "include/linux/types.h"
typedef __u16 __le16;
typedef __u16 __be16;
typedef __u32 __le32;
typedef __u32 __be32;


I'm using Linux 2.6.30.

Regards,
GC


2011/8/24 Adam Lee [off-list ref]:

On Tue, Aug 09, 2011 at 03:25:52PM +0800, ??? wrote:

quoted

Please tell me the difference between using unsigned short and __be16 to
declear a variable in a data structure.
For example, in include/net/inet_sock.h, struct inet_sock is decleared as

struct inet_sock {
        __be16                  inet_dport;
};

not

struct inet_sock {
        unsigned short                  inet_dport;
};

I think it has something to do with endianness. But I see that both __le16 and
__be16 are unsigned short when using gcc with -E option for little-endian and
big-endian platform. Can someone give me more information?

* little-endian
typedef unsigned short __u16;
typedef __u16 __le16;
typedef __u16 __be16;

* big-endian
typedef unsigned short __u16;
typedef __u16 __le16;
typedef __u16 __be16;

Which platform? The atomic element size is 16-bit? Maybe you should take
a look at __be32 and __le32.

FYI: This is in the kernel types.h

----
#ifdef __CHECKER__
#define __bitwise__ __attribute__((bitwise))
#else
#define __bitwise__
#endif
#ifdef __CHECK_ENDIAN__
#define __bitwise __bitwise__
#else
#define __bitwise
#endif

typedef __u16 __bitwise __le16;
typedef __u16 __bitwise __be16;
----

--
Regards,
Adam Lee
--------------------------------------------------
E-mail: adam8157 at gmail.com
Website: http://www.adam8157.info
--------------------------------------------------