Re:GSM modem enable failed: (32) Failed to find a usable modem character set

[van Schelve <public van-schelve de>]

Hi,

> Hi,
>   I had been trying to connect my SAMSUNG Mobile USB Modem. I had the
> same problem. I could successfully hack Networkmanager and Modemmanager
> to support my device.
>  

My problem became bit more complex. I checked the specific laptop a bit
more.
I removed the SIM card and put it into my mobile phone to verify if the
SIM is OK. Everything was fine there. So I put it back into the laptop.
Now I cannot reproduce the error any more on that system!

Anyway. As I told before, we are currently in rollout of a big number
of Linux
Systems (~5000) using NetworkManager. They are all the same model:
Lenovo Thinkpad T61
with an embedded Sierra Modem MC8775. This should be perfectly
supported by.

In the last days I'm getting more and more error reports from our user
helpdesk
because our users in the field are running into big issues when they
using the 
internal modem.

I have divided the several reports (currently we are getting about 20
per day)
into these categories:

1. The user is not able to bring up the system-connection:
In this situation the user is trying to establish a broadband
connection by selecting
the system-connection in nm-applet. It looks like that the connection
will be initialized 
but at the end the user is getting a connection error (like "...
disconnected" or "... 
failed"). Sometimes it helps to disable the modem using the rfkill
switch. Our support staff
found some log entries in syslog like "carrier lost" or "failed to find
a usable modem 
character set" have a look

2. The connection is up but no data transfer is possible
The user is able to establish a mobile connection. The ppp0 interface
get's an ip and I can 
see the login on my central radius server. But no IP communication is
possible. I have seen 
the situation today with one customer in the field. He had a connection
based on EDGE but I was
not able to ping the remote system.

3. The modem is not recognized by modemmanager.
The user cannot establish the mobile connection because it is not in
the list. He has to use the
hw-rfkill switch in front of his laptop to powercycle the modem. Then
the modem-manager is able
to find the modem and the connection is in the nm-applet list.

> My guess is that your 3g based modem not supported by currently
> available modem manager plug-ins and generic GSM plug-in is not working
> for you.
> If you really want to support the modem  you can roll your own and hack
> it. Just comment out few places where modem manager checks for the best
> character set; so that it works fine even if it is  horrid, and
> evil.(Just what I did- It may not be right way)

At the end this might be a solution. But I don't believe that the
existing 
sierra_plugin is so broken. 

> 
> For debugging, you can make following arrangements. 
> 1.Remove NM from upstart -Otherwise it keep on re-spawning and makes
> difficult to debug 
> 2.Kill NM - stop  currently running instance 
> 3.Kill modem manager
> 4.Launch modem manager on a debugger with break points (may be
> mm-generic-gsm.c: mm_generic_gsm_enable_complete a good place to start)
> 5.Launch NM on separate terminal with --no-daemon

A more generic debug option in network-manager / modem-manager would be
very helpful. The problem is that all the systems are spread all over 
germany. So I cannot debug them in your suggested way. I need to use
the
distribution specific upstart job for starting the components in debug
mode.

Currently I'm trying to find a way doing this in upstart. But It's not
so
easy. A more generic debug option would be very helpful (see my last
post:
http://mail.gnome.org/archives/networkmanager-list/2010-September/msg00036.html)

> 
> All the best
I really need it!

> -shakthi
HG