[review] Use AT+CESQ for signal interface in MBIM modems if TTY available

[Aleksander Morgado]

>> > This MR enables support for the "Signal" interface in MBIM modems
>> > if
>> > they expose an AT-capable TTY port and AT+CESQ is supported. If no
>> > AT
>> > port is available in the device, the modem will report no extended
>> > signal capabilities, as it was doing until now for all MBIM modems.
>> >
>> > https://gitlab.freedesktop.org/mobile-broadband/ModemManager/merge_
>> > requests/18
>> >
>>
>> I've closed this MR because I think using the MBIM AT&T extensions
>> service to get the same information fits much better in the MBIM
>> modem
>> object:
>> https://gitlab.freedesktop.org/mobile-broadband/ModemManager/merge_re
>> quests/25
>
> I think that's probably fine for now, though I would bet there will be
> modems that don't implement ATDS and do implement CESQ in the future,
> if they don't exist already.
>

Surprisingly, all Qualcomm and Intel based modems I've tested recently
do support ATDS for signal and location support at least. But yes, we
can always set it up to fallback to CESQ if it isn't supported. Let me
prepare a new patch for that, should be easy.

-- 
Aleksander
https://aleksander.es