Prevent MM form using a specific modem serial port

[Jose, Shijo]

Hello,

I have ModemManager version 1.6.4  running on Yocto and I am using it  to communicate with a Telit LE910 V2 over MBIM.
Along with MM I have running my own process that sends and receives AT commands over one of the serial interfaces (ttyACM0) and so I want to use this port exclusively for my process and not have MM open/read/write to it

How do prevent MM from accessing one or all of the serial ports?

I have tried adding udev rules for MM to ignore only the serial ports but this does not work
KERNEL=="ttyACM*", ENV{ID_MM_DEVICE_IGNORE}="1"

Note that I do want to generate udev events for ttyACM0 since my custom process relies on it to identify an AT capable serial port, however I want MM to avoid using this port.

Snippet of mmcli -m 0 ouput:

  -------------------------
  Hardware |   manufacturer: 'Generic'
           |          model: 'MBIM [1BC7:0032]'
           |       revision: '20.00.502.7-ATT'
          |      supported: 'gsm-umts, lte'
           |        current: 'gsm-umts, lte'
           |   equipment id: '358148061058728'
  -------------------------
  System   |         device: '/sys/devices/platform/soc/soc:internal-regs/d005e000.usb/usb1/1-1'
           |        drivers: 'cdc_acm, cdc_mbim'
           |         plugin: 'Generic'
           |   primary port: 'cdc-wdm0'
           |          ports: 'ttyACM3 (at), cdc-wdm0 (mbim), wwan0 (net), ttyACM0 (at)'


Snippet of udevadm info --export-db:

P: /devices/platform/soc/soc:internal-regs/d005e000.usb/usb1/1-1/1-1:1.0/tty/ttyACM0
N: ttyACM0
S: serial/by-id/usb-Telit_FIH7160_358148061058728-if00
S: serial/by-path/platform-d005e000.usb-usb-0:1:1.0
E: DEVLINKS=/dev/serial/by-path/platform-d005e000.usb-usb-0:1:1.0 /dev/serial/by-id/usb-Telit_FIH7160_358148061058728-if00
E: DEVNAME=/dev/ttyACM0
E: DEVPATH=/devices/platform/soc/soc:internal-regs/d005e000.usb/usb1/1-1/1-1:1.0/tty/ttyACM0
E: ID_BUS=usb
E: ID_MM_CANDIDATE=1
E: ID_MODEL=FIH7160
E: ID_MODEL_ENC=FIH7160
E: ID_MODEL_ID=0032
E: ID_PATH=platform-d005e000.usb-usb-0:1:1.0
E: ID_PATH_TAG=platform-d005e000_usb-usb-0_1_1_0
E: ID_REVISION=1729
E: ID_SERIAL=Telit_FIH7160_358148061058728
E: ID_SERIAL_SHORT=358148061058728
E: ID_TYPE=generic
E: ID_USB_DRIVER=cdc_acm
E: ID_USB_INTERFACES=:020201:0a0000:020d00:020e00:0a0001:0a0002:
E: ID_USB_INTERFACE_NUM=00
E: ID_VENDOR=Telit
E: ID_VENDOR_ENC=Telit
E: ID_VENDOR_ID=1bc7
E: MAJOR=166
E: MINOR=0
E: SUBSYSTEM=tty
E: TAGS=:systemd:
E: USEC_INITIALIZED=2777690

Please let me know if you need more information.

Thanks for your help,
Shijo

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