Understanding Modem Manager

[Bjørn Mork]

Dan Williams <dcbw at redhat.com> writes:

> On Thu, 2013-12-19 at 09:12 +0100, Bjørn Mork wrote:
>> Marc Murphy <marcmltd at marcm.co.uk> writes:
>> 
>> > For the Sierra I have the commands required and the MC8705 uses the AT interface on USB3 and the NMEA stream on USB2
>> 
>> the ttyUSBx names are dynamically allocated, They will change if you
>> e.g.  plug in two devices or reconfigure the modem to use a different
>> set of ports.
>> 
>> But Sierra use static USB interface numbers on many of their modems.
>> For example: interface #7 is DirectIP - most of the time...  Maybe the
>> NMEA port also has a static interface number?  At least for some of the
>> Sierra devices.
>
> That can change depending on the firmware configuration, unfortunately.
> Older devices have AT!MXPORTMAP, AT!MAPUART, AT!NVMUXMODE, and AT!
> NVENGPS.

Yes, I don't know anything about these.

> For newer devices, you change the configuration with AT!UDUSBCOMP which
> takes a single integer argument that selects a specific USB port
> configuration from a set table of configurations.  AT!CUSTOM can be used
> to enable/disable various ports from those configurations too.

But each function still keeps its static interface number, don't they?
So you get spurious numbering with large holes here and there.  Not
quite according to the USB2 spec, but it works fine.

Linux warns about such numbering, so you'll see things like this in the
log: 

[110109.084227] usb 5-4: new high-speed USB device number 97 using ehci-pci
[110109.219710] usb 5-4: config 1 has an invalid interface number: 8 but max is 5
[110109.219727] usb 5-4: config 1 has an invalid interface number: 19 but max is 5
[110109.219736] usb 5-4: config 1 has an invalid interface number: 20 but max is 5
[110109.219745] usb 5-4: config 1 has no interface number 1
[110109.219753] usb 5-4: config 1 has no interface number 4
[110109.219761] usb 5-4: config 1 has no interface number 5
[110109.221047] usb 5-4: config 2 has an invalid interface number: 12 but max is 1
[110109.221058] usb 5-4: config 2 has an invalid interface number: 13 but max is 1
[110109.221068] usb 5-4: config 2 has an invalid interface number: 13 but max is 1
[110109.221076] usb 5-4: config 2 has no interface number 0
[110109.221084] usb 5-4: config 2 has no interface number 1
[110109.223580] usb 5-4: New USB device found, idVendor=1199, idProduct=68a2
[110109.223596] usb 5-4: New USB device strings: Mfr=4, Product=3, SerialNumber=5
[110109.223606] usb 5-4: Product: MC7710
[110109.223614] usb 5-4: Manufacturer: Sierra Wireless, Incorporated


I believe the interface #1, which is missing in both configurations, is
some disabled serial function.  Note that the serial interfaces #2 and
#3 still kept their number in cfg #1


Bjørn