option: Improve Quectel EP06 detection

[Johan Hovold <johan@kernel.org>]

On Sat, Sep 08, 2018 at 02:57:54PM +0200, Kristian Evensen wrote:
> The Quectel EP06 (and EM06/EG06) LTE modem supports updating the USB
> configuration, without the VID/PID or configuration number changing.
> When the configuration is updated and interfaces are added/removed, the
> interface numbers are updated. This causes our current code for matching
> EP06 not to work as intended, as the assumption about reserved
> interfaces no longer holds. If for example the diagnostic (first)
> interface is removed, option will (try to) bind to the QMI interface.
> 
> This patch improves EP06 detection by replacing the current match with
> two matches, and those matches check class, subclass and protocol as
> well as VID and PID. The diag interface exports class, subclass and
> protocol as 0xff. For the other serial interfaces, class is 0xff and
> subclass and protocol are both 0x0.
> 
> The modem can export the following devices and always in this order:
> diag, nmea, at, ppp. qmi and adb. This means that diag can only ever be
> interface 0, and interface numbers 1-5 should be marked as reserved. The
> three other serial devices can have interface numbers 0-3, but I have
> not marked any interfaces as reserved. The reason is that the serial
> devices are the only interfaces exported by the device where subclass
> and protocol is 0x0.
> 
> QMI exports the same class, subclass and protocol values as the diag
> interface. However, the two interfaces have different number of
> endpoints, QMI has three and diag two. I have added a check for number
> of interfaces if VID/PID matches the EP06, and we ignore the device if
> number of interfaces equals three (and subclass is set).
> 
> Signed-off-by: Kristian Evensen <kristian.evensen@gmail.com>

What a mess.

Please provide the output of usb-devices (or lsusb -v) for both
"configurations". How do you update the configuration by the way?

Thanks,
Johan