It is sometimes unable to find DELL WWAN module.

[Franz Hsieh]

I have a DELL WWAN module (DW5580) on my platform. Normally it could be detect and used in Ubuntu 16.04 daily image. However it is sometimes unusable and can not be detected.

After debugging, we found there is an upstream patch that can fix the issue:

  https://cgit.freedesktop.org/ModemManager/ModemManager/commit/?id=8a386218690aeff7e2c923a14f91da7bbc046ed2

Please merge the fix to modem manager to fix the issue.

Ubuntu Xenial (daily image)
Release: 16.04
modemmanager:
  Installed: 1.4.12-1ubuntu1
  Candidate: 1.4.12-1ubuntu1
  Version table:
 *** 1.4.12-1ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status

* 2017-06-20 Update details for SRU

[Impact]

DELL WWAN module (DW5580) is sometimes unusable and can not be detected by ModemManager.

The fix consisted in the correct initialization of a "retry" variable in modem's probing. Without this initialization, the "retry" variable might assume random big values, forcing the modem to retry the same step a semi-infinite number of times.

[Test Case]

1. Start/restart the ModemManager service with debug messages enabled

    a. Open ModemManager.service file and add the flag --debug to the ExecStart entry

        ExecStart=/usr/local/sbin/ModemManager --debug

    b. run systemctl daemon-reload
    c. run systemctl restart Modemmanager

2. Connect Dell WWAN module DW5580 (if the modem is integrated, skip this step)
3. Open ModemManager logs:

    journalctl -fu ModemManager

4. ModemManager logs show that the service is continuously sending AT
    command "AT+CGMI" preventing the modem to be recognized

[Regression Potential]

Considering the nature of the fix (a variable that was not initialized), I can not think of a real potential regression and the patch has been tested and showed no issues so far.

[Ara Pulido (ara)]

Please, add the modemmanager package to the bug.

Also, does this reproduces in Yakkety?

[Carlo Lobrano (c-lobrano)]

Hi,

I'm the author of the patch above, just to note that while in Yakkety the package seems to contain the same bug (at least according to the diff from 1.4.12-1ubuntu2 (in Ubuntu) to 1.6.0-1), the fix is included in ModemManager 1.6.4 which has been released in Zesty

[Sebastien Bacher (seb128)]

Thanks, closing the bug since it's fixed in the current Ubuntu version. It looks like a good SRU candidate for xenial though, could somebody make the bug SRU compliant (https://wiki.ubuntu.com/StableReleaseUpdates)? It basically needs a test case section which can be used for the SRU verifcation and nominate for xenial when it's done?

[Carlo Lobrano (c-lobrano)]

I can try to do it for sure

[Carlo Lobrano (c-lobrano)]

Updated the description with the information requested in SRU template