static int usb_serial_initfn(USBDevice *dev)
{
    USBSerialState *s = DO_UPCAST(USBSerialState, dev, dev);
    s->dev.speed = USB_SPEED_FULL;
    qemu_chr_add_handlers(s->cs, usb_serial_can_read, usb_serial_read,
                          usb_serial_event, s);
    usb_serial_handle_reset(dev);
    return 0;