EHCI_SQTD_SIZE
err = usb_allocmem(&sc->sc_bus, EHCI_SQTD_SIZE*EHCI_SQTD_CHUNK,
offs = i * EHCI_SQTD_SIZE;
#define EHCI_SQTD_CHUNK (EHCI_PAGE_SIZE / EHCI_SQTD_SIZE)