HFCUSB_D_TX
if (fifon >= HFCUSB_D_TX)
if ((fifon == HFCUSB_D_TX) && (hw->protocol == ISDN_P_NT_S0)
if (i == HFCUSB_D_TX)
start_isoc_chain(hw->fifos + HFCUSB_D_TX,
hw->fifos[HFCUSB_D_TX].dch = &hw->dch;