fwmem_xfer_req
xfer = fwmem_xfer_req(fwdev, sc, spd, 0, 0, (void*)hand);
xfer = fwmem_xfer_req(fwdev, sc, spd, 0, roundup2(len, 4), (void*)hand);
xfer = fwmem_xfer_req(fwdev, sc, spd, len, 0, (void*)hand);
xfer = fwmem_xfer_req(fwdev, (char *)sc, spd, 0, 4, (void*)hand);