Ease testing on /dev/cdc-wdmX where X > 0

[Bjørn Mork]

Dan Williams <dcbw at redhat.com> writes:

> If you're running two APNs, one for your normal data connection and a
> second one for MMS, then I believe you need to use PPP over a free AT
> port to set up the second PDP context for MMS.  Kinda ugly, but hey, so
> is MMS!

Right, that makes sense.  So that's why we'd want more than one wwan
interface then...

I am having a lot of success testing a Sierra Wireless MC7710 module
right now, after finally figuring out how to switch it from (the Sierra
Wireless specific) "Direct IP" mode to "QMI" mode.  There are two
different endpoint configurations available in "QMI" mode.  One of them
looks a lot like the Android rmnet thingy.  It provides 3 QMI/wwan
interfaces which can be configured and used independently.  So you can
connect to 3 different APNs and still use the far more efficient
ethernet emulation mode.

Currently having two connections active (this is *one* LTE module): 


wwan0     Link encap:Ethernet  HWaddr da:56:52:c2:82:87  
          inet addr:10.151.159.163  Bcast:10.151.159.167  Mask:255.255.255.248
          inet6 addr: fe80::d856:52ff:fec2:8287/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:25593 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16581 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:34001391 (32.4 MiB)  TX bytes:6899391 (6.5 MiB)

wwan1     Link encap:Ethernet  HWaddr da:56:52:c2:82:87  
          inet addr:77.16.3.99  Bcast:77.16.3.103  Mask:255.255.255.248
          inet6 addr: fe80::d856:52ff:fec2:8287/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:12065 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7709 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:17986367 (17.1 MiB)  TX bytes:529979 (517.5 KiB)

wwan2     Link encap:Ethernet  HWaddr da:56:52:c2:82:87  
          inet6 addr: fe80::d856:52ff:fec2:8287/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

bjorn at nemi:~$ ls -l /sys/class/net/wwan*/device
lrwxrwxrwx 1 root root 0 Apr 17 17:22 /sys/class/net/wwan0/device -> ../../../4-4:1.8
lrwxrwxrwx 1 root root 0 Apr 17 17:23 /sys/class/net/wwan1/device -> ../../../4-4:1.19
lrwxrwxrwx 1 root root 0 Apr 17 17:25 /sys/class/net/wwan2/device -> ../../../4-4:1.20


Now, the only drawback is that this configuration is not the default and
changing it is password protected and available under NDA only.  So we
cannot really take adavantage of it in general.  But I will try to add
support for both this mode and the default in qmi_wwan.

I have to test this more, but it seems that the "Direct IP" mode using
the sierra_net driver gives about the same performance as PPP.  I.e. not
as good when upstream bandwidth exceeds 10 Mbits/s.  Probably because
stripping the HIP header is quite a lot of work for the module.  Just
look at the otherwise very nice sierra_net driver.  But supporting both
comes for free as the module use different USB product IDs for them.



Bjørn