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Another QMI speaking Qualcomm based device, which should be
driven by qmi_wwan, while cdc_ether should ignore it.

Like on other Huawei devices, the wwan function can appear
either as a single vendor specific interface or as a CDC ECM
class function using separate control and data interfaces.
The ECM control interface protocol is 0xff, likely in an
attempt to indicate that vendor specific management is
required.

In addition to the near standard CDC class, Huawei also add
vendor specific AT management commands to their firmwares.
This is probably an attempt to support non-Windows systems
using standard class drivers.  Unfortunately, this part of
the firmware is often buggy.  Linux is much better off using
whatever native vendor specific management protocol the
device offers, and Windows uses, whenever possible. This
means QMI in the case of Qualcomm based devices.

The E1820 has been verified to work fine with QMI.

Matching on interface number is n...