def getRawReportDescriptor(self):
        """
        Return a binary string containing the raw HID report descriptor.
        """
        descriptor = _hidraw_report_descriptor()
        size = ctypes.c_uint()
        self._ioctl(_HIDIOCGRDESCSIZE, size, True)
        descriptor.size = size
        self._ioctl(_HIDIOCGRDESC, descriptor, True)
        return b''.join(chr(x) for x in descriptor.value[:size.value])