Confuse with big endian bitwise field

["Li YanBo" <dreamfly281@gmail.com>]

hi all,

I am try  to define a hardware specific struct, it is like below:

struct xxx {
        __be32 pdu_cnt:6;
        __be32 y:3;
        __be32 wep_key:2;
        __be32 uses_wep_key:1;
        __be32 keep_alive:1;
        __be32 buff_tail_addr:19;

        __be32 cts_11g:1;
        __be32 rts_11g:1;
        __be32 x:2;
        __be32 frag_size:12;
        __be32 payload_len:12;
        __be32 frag_num:4;
}

but I am confuse with how to assign the values to the fields
"buff_tail_addr" and "payload_len", I think there  are two ways to
assign values to them, but I don't know which is right?

eg: I declare a variable  struct xxx X;

1: X.buff_tail_addr = 0x3456;                        X.payload_len = 0x20;
2: X.buff_tail_addr = cpu_to_be32(0x3456);    X.payload_len = cpu_to_be16(0x20);

There are two way I think to assign values. Could anyone tell me which
is right or both are wrong? I will be appreciate for any hints, thanks
in advance!

BR

lyb