begin_session
err = begin_session(dg00x);
.begin_session = ff800_begin_session,
.begin_session = ff400_begin_session,
.begin_session = latter_begin_session,
err = ff->spec->protocol->begin_session(ff, rate);
int (*begin_session)(struct snd_ff *ff, unsigned int rate);
err = begin_session(motu);
err = begin_session(tscm);