[PATCH 4.2.y-ckt 021/305] USB: qcserial: Fix support for HP lt4112 LTE/HSPA+ Gobi 4G Modem

[Kamal Mostafa]

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn at mork.no>

commit 59536da34513c594af2a6fd35ba65ea45b6960a1 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 at immerda.ch>
Tested-by: Martin Hauke <mardnh at gmx.de>
Fixes: e7181d005e84 ("USB: qcserial: Add support for HP lt4112 LTE/HSPA+ Gobi 4G Modem")
Signed-off-by: Bjørn Mork <bjorn at mork.no>
Signed-off-by: Johan Hovold <johan at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/serial/qcserial.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/serial/qcserial.c b/drivers/usb/serial/qcserial.c
index 514fa91..293b27a 100644
--- a/drivers/usb/serial/qcserial.c
+++ b/drivers/usb/serial/qcserial.c
@@ -216,6 +216,10 @@ static int qcprobe(struct usb_serial *serial, const struct usb_device_id *id)
 	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;
+
 	nintf = serial->dev->actconfig->desc.bNumInterfaces;
 	dev_dbg(dev, "Num Interfaces = %d\n", nintf);
 	ifnum = intf->desc.bInterfaceNumber;
-- 
1.9.1