USB: qcserial: Fix support for HP lt4112 LTE/HSPA+ Gobi 4G Modem

commit 59536da3 upstream.

The DEVICE_HWI type was added under the faulty assumption that Huawei
devices based on Qualcomm chipsets and firmware use the static USB
interface numbering known from Gobi devices.  But this model does
not apply to Huawei devices like the HP branded lt4112 (Huawei me906e).
Huawei firmwares will dynamically assign interface numbers. Functions
are renumbered when the firmware is reconfigured.

Fix by changing the DEVICE_HWI type to use a simplified version
of Huawei's subclass + protocol scheme: Blacklisting known network
interface combinations and assuming the rest are serial.
Reported-and-tested-by: Muri Nicanor <muri+libqmi@immerda.ch>
Tested-by: Martin Hauke <mardnh@gmx.de>
Fixes: e7181d00 ("USB: qcserial: Add support for HP lt4112 LTE/HSPA+ Gobi 4G Modem")
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/usb/serial/qcserial.c

@@ -212,6 +212,10 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
 	__u8 ifnum;
 	int altsetting = -1;
 
+	/* we only support vendor specific functions */
+	if (intf->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC)
+		goto done;
+
 	/* we only support vendor specific functions */
 	if (intf->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC)
 		goto done;