Hi,

after upgrading to the latest unstable version of modemmanager to 1.18.4-1, the
Sierra Wireless EM7455 Qualcomm Snapdragon X7 LTE-A in my Lenovo Thinkpad T470
stopped working.

I have a rough idea, what's going on, but not enough insight into mm
to actually fix it properly (see below)

What I see as user:

After booting or resume from suspend, the modem seems to get available
after a few seconds and network-manager tries to start my usual connection.
This fails immediately and the only visible thing is a flashing Dock-Icon
of network-manager.

At the same time, the system journal is flooded with this type
of messages in high frequency:

22:04:52 NetworkManager[1133]: <info>  [1643231092.2962] modem["cdc-wdm1"]: modem state changed, 'disabled' --> 'enabling' (reason: user-requested)
22:04:52 ModemManager[1180]: <info>  [modem0] state changed (enabling -> disabled)
22:04:52 NetworkManager[1133]: <info>  [1643231092.2968] modem["cdc-wdm1"]: modem state changed, 'enabling' --> 'disabled' (reason: unknown)
22:04:52 NetworkManager[1133]: <info>  [1643231092.2969] device (cdc-wdm1): state change: prepare -> disconnected (reason 'user-requested', sys-iface-state: 'managed')
22:04:52 NetworkManager[1133]: <info>  [1643231092.2980] policy: auto-activating connection 'T-Mobile IPv6 only' (...)
22:04:52 NetworkManager[1133]: <info>  [1643231092.2985] device (cdc-wdm1): Activation: starting connection '...)
22:04:52 NetworkManager[1133]: <info>  [1643231092.2986] device (cdc-wdm1): state change: disconnected -> prepare naged')
22:04:52 ModemManager[1180]: <info>  [modem0] simple connect started...
22:04:52 ModemManager[1180]: <info>  [modem0] simple connect state (3/8): enable
22:04:52 ModemManager[1180]: <info>  [modem0] state changed (disabled -> enabling)
22:04:52 ModemManager[1180]: <warn>  [modem0] MBIM protocol error: NotOpened
22:04:52 ModemManager[1180]: <warn>  [modem0] MBIM protocol error: NotOpened
22:04:52 ModemManager[1180]: <warn>  [modem0] couldn't enable interface: 'Invalid transition'

mmcli lists the modem as:

Argh! Nevermind, just figured it out.

It's actually documented in the original NEWS file, but it's
not very obvious to the user, why suddenly the modem disappears.

This is the solution:

ln -sft /etc/ModemManager/fcc-unlock.d
/usr/share/ModemManager/fcc-unlock.available.d/*

and it's also documented quite nicely on the modemmanager.org
website. Maybe debian should add a prominent Warning, because
this will break modemmanager heavily for a lot of non-technical
people:

------------------------- cite from NEWS.gz ---------------------------

ModemManager 1.18.4
-------------------------------------------

  * A new FCC unlock operation management via external scripts is
introduced,
    which will avoid to automatically unlock FCC locked devices unless
the user
    has configured the operation manually, or unless an official
vendor-provided
    FCC unlock tool is found in the system.

    Please refer to the following URL for full details:
https://modemmanager.org/docs/modemmanager/fcc-unlock/

    The following changes should be taken into account by distribution
packagers:
    ** A set of FCC unlock scripts named as the specific vendor 'vid'
will be
       installed in ${datadir}/ModemManager/fcc-unlock.available.d.
    ** A set of symlinks is created named as the specific device
'vid:pid', and
       pointing to the per-vendor 'vid' files, in the same location inside
       ${datadir}.
    ** A new ${sysconfdir}/ModemManager/fcc-unlock.d directory is
created, where
       users will manually install additional symlinks to the scripts
shipped in
       ${datadir}.
    ** A new ${libdir}/ModemManager/fcc-unlock.d directory is created, where
       vendors will install their own official FCC unlock tools.
    ** Both fcc-unlock.d directories should be empty on a new install,
and their
       contents (if any) should not be removed on ModemManager upgrades.

-----------------------------------------------------------------------

Have a nice weekend.
Bjørn

Hi Bjørn,

Thanks for investigating! Since you know exactly what you were looking
for do you want to draft something for NEWS.Debian / README.Debian and
submit this at
https://salsa.debian.org/DebianOnMobile-team/modemmanager ? That would be great.

Cheers,
 -- Guido