returns the current inquiry scan interval and window, 
    or -1 on failure

def read_inquiry_scan_activity(sock):
    """returns the current inquiry scan interval and window, 
    or -1 on failure"""
    # save current filter
    old_filter = sock.getsockopt( bluez.SOL_HCI, bluez.HCI_FILTER, 14)

    # Setup socket filter to receive only events related to the
    # read_inquiry_mode command
    flt = bluez.hci_filter_new()
    opcode = bluez.cmd_opcode_pack(bluez.OGF_HOST_CTL, 
            bluez.OCF_READ_INQ_ACTIVITY)
    bluez.hci_filter_set_ptype(flt, bluez.HCI_EVENT_PKT)
    bluez.hci_filter_set_event(flt, bluez.EVT_CMD_COMPLETE);
    bluez.hci_filter_set_opcode(flt, opcode)
    sock.setsockopt( bluez.SOL_HCI, bluez.HCI_FILTER, flt )

    # first read the current inquiry mode.
    bluez.hci_send_cmd(sock, bluez.OGF_HOST_CTL, 
            bluez.OCF_READ_INQ_ACTIVITY )

    pkt = sock.recv(255)

    status,interval,window = struct.unpack("!xxxxxxBHH", pkt)
    interval = bluez.btohs(interval)
    interval = (interval >> 8) | ( (interval & 0xFF) << 8 )
    window = (window >> 8) | ( (window & 0xFF) << 8 )
    if status != 0: mode = -1

    # restore old filter
    sock.setsockopt( bluez.SOL_HCI, bluez.HCI_FILTER, old_filter )
    return interval, window