net/usb: Ethernet quirks for the LG-VL600 4G modem

This adds a driver for the CDC Ethernet part of this modem.  The
device's ID is blacklisted in cdc_ether.c and is white-listed in
this new driver because of the quirks needed to make it useful.
The modem's firmware exposes a CDC ACM port for modem control and a
CDC Ethernet port for network data.  The descriptors look fine but
both ports actually are some sort of multiplexers requiring non-
standard headers added/removed from every packet or they get
ignored.  All information is based on a usb traffic log from a
Windows machine.

On the Verizon 4G network I've seen speeds up to 1.1MB/s so far with
this driver, a speed-o-meter site reports 16.2Mbps/10.5Mbps.
Userspace scripts are required to talk to the CDC ACM port.
Signed-off-by: Andrzej Zaborowski <balrogg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/Kconfig

@@ -433,4 +433,19 @@ config USB_SIERRA_NET
 	  To compile this driver as a module, choose M here: the
 	  module will be called sierra_net.
 
+config USB_VL600
+	tristate "LG VL600 modem dongle"
+	depends on USB_NET_CDCETHER
+	select USB_ACM
+	help
+	  Select this if you want to use an LG Electronics 4G/LTE usb modem
+	  called VL600.  This driver only handles the ethernet
+	  interface exposed by the modem firmware.  To establish a connection
+	  you will first need a userspace program that sends the right
+	  command to the modem through its CDC ACM port, and most
+	  likely also a DHCP client.  See this thread about using the
+	  4G modem from Verizon:
+
+	  http://ubuntuforums.org/showpost.php?p=10589647&postcount=17
+
 endmenu

drivers/net/usb/Makefile

@@ -27,4 +27,5 @@ obj-$(CONFIG_USB_IPHETH)	+= ipheth.o
 obj-$(CONFIG_USB_SIERRA_NET)	+= sierra_net.o
 obj-$(CONFIG_USB_NET_CX82310_ETH)	+= cx82310_eth.o
 obj-$(CONFIG_USB_NET_CDC_NCM)	+= cdc_ncm.o
+obj-$(CONFIG_USB_VL600)		+= lg-vl600.o
 

drivers/net/usb/cdc_ether.c

@@ -378,7 +378,7 @@ static void dumpspeed(struct usbnet *dev, __le32 *speeds)
 		   __le32_to_cpu(speeds[1]) / 1000);
 }
 
-static void cdc_status(struct usbnet *dev, struct urb *urb)
+void usbnet_cdc_status(struct usbnet *dev, struct urb *urb)
 {
 	struct usb_cdc_notification	*event;
 
@@ -418,8 +418,9 @@ static void cdc_status(struct usbnet *dev, struct urb *urb)
 		break;
 	}
 }
+EXPORT_SYMBOL_GPL(usbnet_cdc_status);
 
-static int cdc_bind(struct usbnet *dev, struct usb_interface *intf)
+int usbnet_cdc_bind(struct usbnet *dev, struct usb_interface *intf)
 {
 	int				status;
 	struct cdc_state		*info = (void *) &dev->data;
@@ -441,6 +442,7 @@ static int cdc_bind(struct usbnet *dev, struct usb_interface *intf)
 	 */
 	return 0;
 }
+EXPORT_SYMBOL_GPL(usbnet_cdc_bind);
 
 static int cdc_manage_power(struct usbnet *dev, int on)
 {
@@ -452,18 +454,18 @@ static const struct driver_info	cdc_info = {
 	.description =	"CDC Ethernet Device",
 	.flags =	FLAG_ETHER,
 	// .check_connect = cdc_check_connect,
-	.bind =		cdc_bind,
+	.bind =		usbnet_cdc_bind,
 	.unbind =	usbnet_cdc_unbind,
-	.status =	cdc_status,
+	.status =	usbnet_cdc_status,
 	.manage_power =	cdc_manage_power,
 };
 
 static const struct driver_info mbm_info = {
 	.description =	"Mobile Broadband Network Device",
 	.flags =	FLAG_WWAN,
-	.bind = 	cdc_bind,
+	.bind =		usbnet_cdc_bind,
 	.unbind =	usbnet_cdc_unbind,
-	.status =	cdc_status,
+	.status =	usbnet_cdc_status,
 	.manage_power =	cdc_manage_power,
 };
 
@@ -560,6 +562,13 @@ static const struct usb_device_id	products [] = {
 	.driver_info		= 0,
 },
 
+/* LG Electronics VL600 wants additional headers on every frame */
+{
+	USB_DEVICE_AND_INTERFACE_INFO(0x1004, 0x61aa, USB_CLASS_COMM,
+			USB_CDC_SUBCLASS_ETHERNET, USB_CDC_PROTO_NONE),
+	.driver_info		= 0,
+},
+
 /*
  * WHITELIST!!!
  *

drivers/net/usb/usbnet.c

@@ -387,8 +387,12 @@ static int rx_submit (struct usbnet *dev, struct urb *urb, gfp_t flags)
 static inline void rx_process (struct usbnet *dev, struct sk_buff *skb)
 {
 	if (dev->driver_info->rx_fixup &&
-	    !dev->driver_info->rx_fixup (dev, skb))
-		goto error;
+	    !dev->driver_info->rx_fixup (dev, skb)) {
+		/* With RX_ASSEMBLE, rx_fixup() must update counters */
+		if (!(dev->driver_info->flags & FLAG_RX_ASSEMBLE))
+			dev->net->stats.rx_errors++;
+		goto done;
+	}
 	// else network stack removes extra byte if we forced a short packet
 
 	if (skb->len) {
@@ -401,8 +405,8 @@ static inline void rx_process (struct usbnet *dev, struct sk_buff *skb)
 	}
 
 	netif_dbg(dev, rx_err, dev->net, "drop\n");
-error:
 	dev->net->stats.rx_errors++;
+done:
 	skb_queue_tail(&dev->done, skb);
 }
 

include/linux/usb/usbnet.h

@@ -102,6 +102,7 @@ struct driver_info {
  * Affects statistic (counters) and short packet handling.
  */
 #define FLAG_MULTI_PACKET	0x1000
+#define FLAG_RX_ASSEMBLE	0x2000	/* rx packets may span >1 frames */
 
 	/* init device ... can sleep, or cause probe() failure */
 	int	(*bind)(struct usbnet *, struct usb_interface *);
@@ -172,7 +173,9 @@ struct cdc_state {
 };
 
 extern int usbnet_generic_cdc_bind(struct usbnet *, struct usb_interface *);
+extern int usbnet_cdc_bind(struct usbnet *, struct usb_interface *);
 extern void usbnet_cdc_unbind(struct usbnet *, struct usb_interface *);
+extern void usbnet_cdc_status(struct usbnet *, struct urb *);
 
 /* CDC and RNDIS support the same host-chosen packet filters for IN transfers */
 #define	DEFAULT_FILTER	(USB_CDC_PACKET_TYPE_BROADCAST \