Custom AT command support in ModemManager

[Aleksander Morgado]

>>>>> I just realized you're working with a MBIM modem. So the "No AT
>>>>> port available to run command" may actually mean there is no AT
>>>>> port detected in the modem. Are you able to see a TTY listed in the
>>>>> "System/ports" entry when you do "mmcli -m 0"?
>>>
>>> No, I do not see TTY listed. Snippet of "mmcli -m 0" below -
>>>
>>>   Hardware |   manufacturer: 'Generic'
>>>            |              model: 'MBIM [1BC7:1204]'
>>>            |            revision: '17.01.571'
>>>            |       supported: 'gsm-umts, lte'
>>>            |             current: 'gsm-umts, lte'
>>>            | equipment id: '35323806113733'
>>>   -------------------------
>>>   System   |         device: '/sys/devices/platform/soc/soc:internal-regs/d005e000.usb/usb1/1-1'
>>>            |              drivers: 'cdc_mbim'
>>>            |                plugin: 'Generic'
>>>            |   primary port: 'cdc-wdm0'
>>>            |                  ports: 'cdc-wdm0 (mbim), wwan0 (net)'
>>>
>>
>> So the modem doesn't expose any AT capable TTY in this mode? Is there
>> any /dev/ttyUSBX exposed that we may not be probing correctly?
>>
>>>
>>>>Also, we'd generally discourage enabling custom AT commands in most situations.  Instead, we'd like to learn more about your use-case and see if we can come up with a more >generic way to do >what you want to do.  It may well be the case that what you want to do has an analogue in the other protocols like MBIM and QMI, and thus we could expose >that functionality generically via D-Bus >rather than doing one-off things for specific modems.
>>>
>>> One of the custom (vendor) AT commands is to switch the firmware (i.e. reboot using a different firmware) on the LTE modem based on the SIM card information (operator type).  Another one (#USBCFG) is to change the USB configuration mode (such as, enable MBIM) on the modem device.
>>>
>>
>>> Is there a configuration mode that has MBIM+AT? You may want to use
>>> that one instead of the one you currently have, which doesn't seem to
>>> expose any AT capable TTY.
>
>>1204 composition indeed has serial ports, but the PID is missing in option kernel driver.
>
> I tried this manually -  echo 1bc7 1204 > /sys/bus/usb-serial/drivers/option1/new_id  -
> and this exposes the tty ports for AT.
>
> mmcli -m 0 (snippet)
>   -------------------------
>   System   |         device: '/sys/devices/platform/soc/soc:internal-regs/d005e000.usb/usb1/1-1'
>            |                 drivers: 'option, cdc_mbim'
>            |                   plugin: 'Generic'
>            |      primary port: 'cdc-wdm0'
>            |                     ports: 'ttyUSB0 (qcdm), ttyUSB3 (at), ttyUSB4 (at), wwan0 (net), cdc-wdm0 (mbim)'
>   -------------------------
>
> However, I have to restart ModemManager with --debug option to be able to send AT commands via mmcli (mmcli -m 0 --command="AT").
> Is debug mode always required?
>

We currently enforce that, yes. The Command() API is only enabled in debug mode.

-- 
Aleksander
https://aleksander.es