rndis_host: support Novatel Verizon USB730L

Treat the ef/04/01 interface class/subclass/protocol combination used
by the Novatel Verizon USB730L (1410:9030) as a possible RNDIS
interface.

T: Bus=01 Lev=02 Prnt=02 Port=01 Cnt=02 Dev#= 17 Spd=480 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 3
P: Vendor=1410 ProdID=9030 Rev=03.10
S: Manufacturer=Novatel Wireless
S: Product=MiFi USB730L
S: SerialNumber=0123456789ABCDEF
C: #Ifs= 3 Cfg#= 1 Atr=80 MxPwr=500mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=ef(misc ) Sub=04 Prot=01 Driver=rndis_host
I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=rndis_host
I: If#= 2 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid

Once the network interface is brought up, the user just needs to run a
DHCP client to get IP address and routing setup.

As a side note, other Novatel Verizon USB730L models with the same
vid:pid end up exposing a standard ECM interface which doesn't require
any other kernel update to make it work.

Signed-off-by: Aleksander Morgado <[e-mail]>
Reviewed-by: Bjørn Mork <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/usb/cdc_ether.c

···
 		desc->bInterfaceProtocol == 3);
 }
 
+static int is_novatel_rndis(struct usb_interface_descriptor *desc)
+{
+	return (desc->bInterfaceClass == USB_CLASS_MISC &&
+		desc->bInterfaceSubClass == 4 &&
+		desc->bInterfaceProtocol == 1);
+}
+
 #else
 
 #define is_rndis(desc)		0
 #define is_activesync(desc)	0
 #define is_wireless_rndis(desc)	0
+#define is_novatel_rndis(desc)	0
 
 #endif
 
···
 	 */
 	rndis = (is_rndis(&intf->cur_altsetting->desc) ||
 		 is_activesync(&intf->cur_altsetting->desc) ||
-		 is_wireless_rndis(&intf->cur_altsetting->desc));
+		 is_wireless_rndis(&intf->cur_altsetting->desc) ||
+		 is_novatel_rndis(&intf->cur_altsetting->desc));
 
 	memset(info, 0, sizeof(*info));
 	info->control = intf;

drivers/net/usb/rndis_host.c

···
 	/* RNDIS for tethering */
 	USB_INTERFACE_INFO(USB_CLASS_WIRELESS_CONTROLLER, 1, 3),
 	.driver_info = (unsigned long) &rndis_info,
+}, {
+	/* Novatel Verizon USB730L */
+	USB_INTERFACE_INFO(USB_CLASS_MISC, 4, 1),
+	.driver_info = (unsigned long) &rndis_info,
 },
 	{ },		// END
 };