fw_open_isodma
int fw_open_isodma(struct firewire_comm *, int);
i = fw_open_isodma(fc, /* tx */1);
i = fw_open_isodma(fc, /* tx */0);
fwe->dma_ch = fw_open_isodma(fc, /* tx */0);
fwip->dma_ch = fw_open_isodma(fc, /* tx */0);