While waiting for MBIM support

[Bjørn Mork <bjorn mork no>]

I was hoping to help finishing the MM MBIM support, but have to realize
that available spare time is insufficient...  And with no one sponsoring
Aleksander's work I guess MBIM just will have to wait.

This means that we should ensure that MBIM devices continue to work
using whatever legacy mode they have.  There are several issues here:

1) devices like the Sierra Wireless MC7710 using multiple
  configurations, where the first interface of the legacy configuration
  is vendor specific.  The Linux kernel (USB core) will select the MBIM
  configuration by default because non-vendor-specific configurations
  are preferred.

  Could be worked around using udev rules

2) devices like the Huawei E367, using multiple configurations to
  support legacy modeswitching and MBIM.  The Linux kernel will select
  the modeswitching configuration because it is first and has a proper
  class (mass-storage).  But usb_modeswitch will switch to the MBIM
  configuration instead of traditional modeswitching if the cdc_mbim
  driver is available

  Could be worked around using usb_modeswitch config

3) devices like the Ericsson H5321gw, having NCM compatible MBIM
 interfaces using different altsettings.

 Could be forced to NCM by setting the cdc_ncm parameter "prefer_mbim"
 (new in Linux v3.8.5/v3.9) to false.

I believe MM should implement the suggested workarounds until it
supports MBIM.  This will ensure that MM works with these MBIM devices,
using legacy modes. And it enables us to switch to MBIM when MM is ready
for that.



Bjørn