FCC unlock surprises after upgrading (was: Re: ANN: ModemManager 1.18.4 released)

Bjørn Mork bjorn at mork.no
Fri Dec 31 21:22:10 UTC 2021

Aleksander Morgado <aleksander at aleksander.es> writes:

>  * 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.

Sorry for late comments again, but I'm worrying about the user
experience for those upgrading a previously working system.

I did read this announcement and the discussion about the feature back
in november, and thought it sounded all fine. And I upgraded to 1.18.4
right before christmas when the Debian package showed up.  Still didn't
think much about this, and obviously didn't read out of the NEWS file
that I was supposed to do something...

Now I don't suspend or reboot my laptop often with Corona office and all
that.  But today I did.  And was very surprised when MM failed to
connect after resuming.  Manually trying to enable the modem failed with
a message which didn't immediately ring any bells:

 root at miraculix:/home/bjorn# mmcli -m any -e
 error: couldn't enable the modem: 'GDBus.Error:org.freedesktop.ModemManager1.Error.Core.Retry: Invalid transition'

I must admit that I had to take a detour via AT commands, looking at
AT!PCINFO? to realize that this was a failure to do the FCC unlock. Only
after that did it occur to me that I should read those instructions
again. But that was only because I had seen then before only a few
weeks ago.  I'm not sure everyone else would make the connection.  Or
maybe they would, and I'm the only slow one here :-)

Fixing the problem was of course as simple as

 cd /etc/ModemManager/fcc-unlock.d
 ln -s /usr/share/ModemManager/fcc-unlock.available.d/1199\:9079

and everything worked as expected after that.

I understand that you want/need to make this a concious decision for new
users and modems.  But I wonder if we really have to make it this
difficult for existing users?  After all, I am spoiled by 5+ years of
fully automatic unlock on this laptop/modem. Why should I have to
manually re-enable it now?  Maybe we could accept a script adding the
symlink on upgrades from older MM versions, on systems with an affected
modem?  Or at least a subset of older modems?

Or maybe this isn't a big problem?  After all, it's just a one time
thing.  I only hope people figure it out quicker than me...


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