cdc-wdmX interface no longer created after reset

[Bjørn Mork]

Paul Gildea <gildeap at tcd.ie> writes:

> Here is the new output where the cdc-wdm interface is not created:
>
>
> [   34.784426] usb 2-3: New USB device found, idVendor=1199, idProduct=9071
>
> [   34.784428] usb 2-3: New USB device strings: Mfr=1, Product=2,
> SerialNumber=0
> [   34.784430] usb 2-3: Product: MC7455
>
> [   34.784432] usb 2-3: Manufacturer: Sierra Wireless, Incorporated
>
> [   34.786401] qcserial 2-3:1.0: Qualcomm USB modem converter detected
> [   34.786504] usb 2-3: Qualcomm USB modem converter now attached to ttyUSB0
> [   34.787384] qcserial 2-3:1.2: Qualcomm USB modem converter detected
> [   34.787475] usb 2-3: Qualcomm USB modem converter now attached to ttyUSB1
> [   34.788347] qcserial 2-3:1.3: Qualcomm USB modem converter detected
> [   34.788439] usb 2-3: Qualcomm USB modem converter now attached to
> ttyUSB2
>
> The only differences I can see are that the "Product:" has changed and the
> "SerialNumber:" is missing. When I check the device path the Serial file is
> not there. I can connect to the device and send AT commands no problem as
> the USB interfaces are enumerated. Any idea what may have caused this?
> Modem is no longer usable with qmicli, for some reason qmi_wwan is not
> creating the interface?

The only possible reason I see is that there are no RMNET/QMI functions
and no serial number string descriptor.  Please veriy by doing e.g

 lsusb -vd 1199:9071

Both the RMNET functions and the serial number export are controlled by
firmware config.  I cannot explain why the configuration changed, but it
should be easy to fix since you still have AT command access.  Assuming
that there isn't anything more serious wrong here - unexplained NVRAM
changes are not good...  You may want to let Sierra Wireless take a look
at the modem if you have that option.

Please see the documentation of the AT!USBCOMP and AT!CUSTOM commands in
the "AirPrime EM74xx/MC74xx AT Command Reference" for info on how to
change the settings back to normal.  I believe the serial number custom
setting is “USBSERIALENABLE”.



Bjørn