Quectel EG21 modem QMI connection works but MM fallbacks to ttyUSB2 as primary port

[Aleksander Morgado]

Hey Rafal!

> Jan  1 04:51:00 zubrOS ModemManager[342]: <debug> [000017460.859237] [filter]   cdc-wdm devices allowed:    yes
> Jan  1 04:51:35 zubrOS kernel: [   54.178239] qmi_wwan_q 1-1:1.4: cdc-wdm0: USB WDM device

I saw your merge request and replied about that there, the problem you
had with ModemManager not detecting the cdc-wdm port as a QMI port was
indeed the kernel driver name, "qmi_wwan_q" vs "qmi_wwan":
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/406

It's really unfortunate that the vendors try to push their own
modified kernel drivers, instead of making sure the upstream one is
properly up to date to support their modules. There should be no
reason for that to happen, and we shouldn't enforce that approach in
ModemManager.

@Carl Yin(殷张成) what is the reason for Quectel to suggest using a
custom modified "qmi_wwan_q" driver instead of suggesting to use the
upstream default one? How can we help solve this?

-- 
Aleksander
https://aleksander.es