handle_msg
.handle_msg = ff800_handle_midi_msg,
.handle_msg = ff400_handle_msg,
.handle_msg = latter_handle_midi_msg,
ff->spec->protocol->handle_msg(ff, (unsigned int)offset, buf, length, tstamp);
ff->async_handler.address_callback = handle_msg;
void (*handle_msg)(struct snd_ff *ff, unsigned int offset, const __le32 *buf,