Comment 42 for bug 875441

I've got the same problem with ZTE MF636 - modem manager uses ttyUSB2, while it should be ttyUSB3.
I think I found a little simpler solution to this problem, just added one line to /lib/udev/rules.d/77-mm-zte-port-types.rules:

ATTRS{idProduct}=="0033", ENV{.MM_USBIFNUM}=="04", ENV{ID_MM_ZTE_PORT_TYPE_MODEM}="1"
ATTRS{idProduct}=="0033", ENV{.MM_USBIFNUM}=="01", ENV{ID_MM_ZTE_PORT_TYPE_AUX}="1"
# this is what I added
ATTRS{idProduct}=="0033", ENV{.MM_USBIFNUM}=="02", ENV{ID_MM_ZTE_PORT_TYPE_MODEM}="0"

Now modem manager uses proper ttyUSB3 and everything works as expected.
There is one difference I've noticed using lsusb between ttyUSB2 and ttyUSB3 - the last has
Transfer Type Interrupt
and the others have
Transfer Type Bulk
maybe it can be utilized to help modem manager to find right device.

below I send full output of 'lsusb -d 19d2:0033 -v' :

Bus 001 Device 068: ID 19d2:0033 ZTE WCDMA Technologies MSM
Device Descriptor:
  bLength 18
  bDescriptorType 1
  bcdUSB 2.00
  bDeviceClass 0 (Defined at Interface level)
  bDeviceSubClass 0
  bDeviceProtocol 0
  bMaxPacketSize0 64
  idVendor 0x19d2 ZTE WCDMA Technologies MSM
  idProduct 0x0033
  bcdDevice 0.00
  iManufacturer 3 ZTE,Incorporated
  iProduct 2 ZTE CDMA Technologies MSM
  iSerial 4 1234567890ABCDEF
  bNumConfigurations 1
  Configuration Descriptor:
    bLength 9
    bDescriptorType 2
    wTotalLength 131
    bNumInterfaces 5
    bConfigurationValue 1
    iConfiguration 1 ZTE Configuration
    bmAttributes 0xe0
      Self Powered
      Remote Wakeup
    MaxPower 500mA
    Interface Descriptor:
      bLength 9
      bDescriptorType 4
      bInterfaceNumber 0
      bAlternateSetting 0
      bNumEndpoints 2
      bInterfaceClass 255 Vendor Specific Class
      bInterfaceSubClass 255 Vendor Specific Subclass
      bInterfaceProtocol 255 Vendor Specific Protocol
      iInterface 0
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x81 EP 1 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x01 EP 1 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
    Interface Descriptor:
      bLength 9
      bDescriptorType 4
      bInterfaceNumber 1
      bAlternateSetting 0
      bNumEndpoints 2
      bInterfaceClass 255 Vendor Specific Class
      bInterfaceSubClass 255 Vendor Specific Subclass
      bInterfaceProtocol 255 Vendor Specific Protocol
      iInterface 0
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x82 EP 2 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x02 EP 2 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
    Interface Descriptor:
      bLength 9
      bDescriptorType 4
      bInterfaceNumber 2
      bAlternateSetting 0
      bNumEndpoints 2
      bInterfaceClass 255 Vendor Specific Class
      bInterfaceSubClass 255 Vendor Specific Subclass
      bInterfaceProtocol 255 Vendor Specific Protocol
      iInterface 0
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x83 EP 3 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x03 EP 3 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
    Interface Descriptor:
      bLength 9
      bDescriptorType 4
      bInterfaceNumber 3
      bAlternateSetting 0
      bNumEndpoints 2
      bInterfaceClass 8 Mass Storage
      bInterfaceSubClass 6 SCSI
      bInterfaceProtocol 80 Bulk-Only
      iInterface 0
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x04 EP 4 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 0
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x84 EP 4 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 0
    Interface Descriptor:
      bLength 9
      bDescriptorType 4
      bInterfaceNumber 4
      bAlternateSetting 0
      bNumEndpoints 3
      bInterfaceClass 255 Vendor Specific Class
      bInterfaceSubClass 255 Vendor Specific Subclass
      bInterfaceProtocol 255 Vendor Specific Protocol
      iInterface 0
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x85 EP 5 IN
        bmAttributes 3
          Transfer Type Interrupt
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0040 1x 64 bytes
        bInterval 5
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x86 EP 6 IN
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
      Endpoint Descriptor:
        bLength 7
        bDescriptorType 5
        bEndpointAddress 0x05 EP 5 OUT
        bmAttributes 2
          Transfer Type Bulk
          Synch Type None
          Usage Type Data
        wMaxPacketSize 0x0200 1x 512 bytes
        bInterval 32
Device Qualifier (for other device speed):
  bLength 10
  bDescriptorType 6
  bcdUSB 2.00
  bDeviceClass 0 (Defined at Interface level)
  bDeviceSubClass 0
  bDeviceProtocol 0
  bMaxPacketSize0 64
  bNumConfigurations 1
Device Status: 0x0000
  (Bus Powered)