usb_isoc_time_expand
usb_isoc_time_expand(&sc->sc_bus, nframes) +
usb_isoc_time_expand(&sc->sc_bus, nframes) + buf_offset +
(usb_isoc_time_expand(&sc->sc_bus, nframes) + buf_offset +
usb_isoc_time_expand(&sc->sc_bus, nframes) + temp +
usb_isoc_time_expand(&temp.sc->sc_bus, x / 8) +
uint16_t usb_isoc_time_expand(struct usb_bus *bus, uint16_t isoc_time_curr);