Some WWAN LTE/3G devices based on chipsets from Qualcomm provide
near standard CDC ECM interfaces in addition to the usual serial
interfaces.   The Huawei E392/E398 are examples of such devices.

These typically cannot be fully configured using AT commands
over a serial interface.  It is necessary to speak the proprietary
Qualcomm MSM Interface (QMI) protocol to the device to enable the
ethernet proxy functionality.

The devices embed the QMI protocol in CDC on the control interface,
using standard CDC commands and notifications. The do not otherwise
use CDC commands for the ethernet function.  This driver does
therefore not need access to any other aspects of the control
interface than the descriptors attached to it.

Another driver, cdc-wdm, will provide userspace access to the
QMI protocol independently of this driver.  To facilitate this,
this driver avoids binding to the control interface, and uses
only the associated data interface after parsing the common CDC
functional descriptors on the control interface.

You will want both the cdc-wdm and option drivers as companions to
this driver, to have full access to all interfaces and protocols
exported by the device.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>