Some questions about qmi/wwan

Aleksander Morgado aleksander at
Sun Jul 27 05:11:52 PDT 2014

On Sat, Jul 26, 2014 at 11:25 PM, E:V:A <xdae3v3a at> wrote:
>> On Fri, 2014-07-25 at 19:17 +0200, Marco wrote:
>>> - Once the kernel module is loaded, I get two /dev/cdc-wdm devices (0 and
>>> 1). What are those for? The one that seems to be working with qmicli is
>>> /dev/cdc-wdm1. I also get two network interfaces, wwp0s20u6 and
>>> wwp0s20u6i3, the second one is the one that I can use dhcp client with and
>>> get an IP. Which is the purpose of the other one?
>> I'll leave that to Bjorn and Aleksander, but on some devices there is a
>> second non-operative QMI configuration.  Could be a firmware quirk.
> Hmm, I'm not sure that's it. On most Qulacomm modems, there are a
> (large) number of "debug" interfaces that can be enumerated. However,
> it is far from clear what they all do and how to use them. We know
> this from studying the Gobi phone equivalents of the Snapdragon S4
> family (that include MSM8960 etc.) For example different intefaces are
> (often) used for GPS, Emergency Download Mode (firmware updates etc)
> and RF debug output that is used by proprietary software like QPST and
> QXDM. These often appears as sockets on and inside Androids. But as
> separate USB devices on the outside. So any additional information
> that can shed some light on what these devies do, would be very
> welcome.

In Sierra MC73XX (also in newer MC71XX) interfaces 8 and 10 are both
QMI+WWAN, with different setups as I said in a previous email. There's
also interface 13, which exposes kind of what it could look like a
QMI+WWAN pair, but we ended up blacklisting that one in the kernel
driver because we couldn't make it talk QMI at all. That interface, we
don't know what's for.

>>> - The device has an integrated GPS (PDS in qmi-speak). I understand that,
>>> currently, with libqmi it is not possible to use it (or at least I see no
>>> pds-* options in qmicli 1.10.0, which is the version I'm using). Is that
>>> right?
>> qmicli doesn't have support for that, but programs like ModemManager use
>> libqmi to provide it.
> What would it take to implement this? What is needed?

libqmi supports the PDS location service; I just didn't got around
implementing the corresponding qmicli commands as I directly did the
integration in ModemManager. So with ModemManager you can already get
location info (there's even an A-GPS branch), it's just the qmicli
commands missing. What is needed? Free time and fix other higher
priorities :) Patches welcome, of course ;)


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