Feature phone with 3G modem capability used to work under 1.18 but no longer works under 1.20

[Aleksander Morgado]

Hey Alex,

> >
> > On Mon, Feb 19, 2024 at 2:31 AM Alex Villacís Lasso
> > <a_villacis at palosanto.com> wrote:
> >> El 16/2/24 a las 17:48, Alex Villacís Lasso escribió:
> >>> I have this old phone, a Samsung E3210B pre-Android feature phone that
> >>> I wish to use as a fallback option when (more frequently than I would
> >>> like) my broadband internet service goes down. When using ModemManager
> >>> 1.18.x, I could plug in this phone, and it would expose a single
> >>> /dev/ttyACM0 port for all interactions including AT commands and PPP.
> >>> Then ModemManager could connect to the internet using the port as
> >>> normal, using the "generic" plugin. Now, using ModemManager 1.20.6
> >>> under Fedora 39, the same phone fails (with a timeout) to establish a
> >>> connection using ModemManager. However, it does setup a proper
> >>> connection using wvdial from the command line, even under Fedora 39.
> >>>
> >>> After a while, I managed to perform a git bisect on the code, and
> >>> pinpointed the first commit that breaks my phone, to commit
> >>> 213cd81b3ade35024e2d702e2726273f00344185 "iface-modem-simple: wait for
> >>> packet service 'attach' state in ConnectionStep". However, I am now at
> >>> a bit of a loss at understanding the supposed purpose of this commit.
> >>> Full details are at this bug report:
> >>>
> >>> https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues/743
> >>>
> >>> The patch no longer cleanly reverts under 1.20.x, so I cannot just rip
> >>> it off...
> >>>
> >> I have updated the bug report with a new discovery: ModemManager 1.20
> >> will dial into the phone immediately, if I first manually select some
> >> phone feature that requires Internet access (such as Google Search),
> >> then click OK in the little dialog that ask to connect to the Internet.
> >> However, this manual interaction with the phone should be unnecessary,
> >> because it was not needed with ModemManager 1.18 and is also not needed
> >> when using the phone through wvdial.
> >>
> >> I need a way to tell ModemManager when using this particular phone to
> >> connect, to IGNORE the "searching" status of the GPRS registration and
> >> dial anyway, since the GPRS will be enabled by the very act of dialing
> >> the Internet access sequence. Is there any existing way to do that?
> >>
> > I replied at the issue, I believe your problem would be solved with MM
> > 1.22 and https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/commit/179a800ab64b28f5437c3d06056640f702e68aa5.
> > You may still experience some delay to connect, because MM will first
> > wait some seconds for the attach state to come up automatically, and
> > only otherwise try to send the operation to activate it.
> >
> > Either way, it looks like your device needs a much more relaxed logic
> > in this regard, so fully ignoring the packet service attach state
> > would be a better option probably.
> >
>
> I have updated the bug report. With ModemManager 1.22 on Fedora 40, the
> phone is not even recognized as a valid modem, even though wvdial
> continues to work with it. On a separate machine using Debian Testing
> (Trixie) with the same minor version (1.22) the problem also exists.
>

Would you be able to gather MM debug logs and post them?

-- 
Aleksander