net/usb: Add Samsung Kalmia driver for Samsung GT-B3730

Introducing driver for the network port of Samsung Kalmia based USB LTE modems.
It has also an ACM interface that previous patches associates with the "option"
module. To access those interfaces, the modem must first be switched from modem
mode using a tool like usb_modeswitch.

As the proprietary protocol has been discovered by watching the MS Windows driver
behavior, there might be errors in the protocol handling, but stable and fast
connection has been established for hours with Norwegian operator NetCom that
distributes this modem with their LTE/4G subscription.

More and updated information about how to use this driver is available here:

http://www.draisberghof.de/usb_modeswitch/bb/viewtopic.php?t=465
https://github.com/mkotsbak/Samsung-GT-B3730-linux-driver

Signed-off-by: Marius B. Kotsbak <marius@kotsbak.com>
Signed-off-by: David S. Miller <davem@conan.davemloft.net>

drivers/net/usb/Kconfig

@@ -385,6 +385,16 @@ config USB_NET_CX82310_ETH
 	  router with USB ethernet port. This driver is for routers only,
 	  it will not work with ADSL modems (use cxacru driver instead).
 
+config USB_NET_KALMIA
+	tristate "Samsung Kalmia based LTE USB modem"
+	depends on USB_USBNET
+	help
+	  Choose this option if you have a Samsung Kalmia based USB modem
+	  as Samsung GT-B3730.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called kalmia.
+
 config USB_HSO
 	tristate "Option USB High Speed Mobile Devices"
 	depends on USB && RFKILL

drivers/net/usb/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_USB_NET_MCS7830)	+= mcs7830.o
 obj-$(CONFIG_USB_USBNET)	+= usbnet.o
 obj-$(CONFIG_USB_NET_INT51X1)	+= int51x1.o
 obj-$(CONFIG_USB_CDC_PHONET)	+= cdc-phonet.o
+obj-$(CONFIG_USB_NET_KALMIA)	+= kalmia.o
 obj-$(CONFIG_USB_IPHETH)	+= ipheth.o
 obj-$(CONFIG_USB_SIERRA_NET)	+= sierra_net.o
 obj-$(CONFIG_USB_NET_CX82310_ETH)	+= cx82310_eth.o

drivers/net/usb/kalmia.c

@@ -0,0 +1,384 @@
+/*
+ * USB network interface driver for Samsung Kalmia based LTE USB modem like the
+ * Samsung GT-B3730 and GT-B3710.
+ *
+ * Copyright (C) 2011 Marius Bjoernstad Kotsbak <marius@kotsbak.com>
+ *
+ * Sponsored by Quicklink Video Distribution Services Ltd.
+ *
+ * Based on the cdc_eem module.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/ctype.h>
+#include <linux/ethtool.h>
+#include <linux/workqueue.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/crc32.h>
+#include <linux/usb/cdc.h>
+#include <linux/usb/usbnet.h>
+#include <linux/gfp.h>
+
+/*
+ * The Samsung Kalmia based LTE USB modems have a CDC ACM port for modem control
+ * handled by the "option" module and an ethernet data port handled by this
+ * module.
+ *
+ * The stick must first be switched into modem mode by usb_modeswitch
+ * or similar tool. Then the modem gets sent two initialization packets by
+ * this module, which gives the MAC address of the device. User space can then
+ * connect the modem using AT commands through the ACM port and then use
+ * DHCP on the network interface exposed by this module. Network packets are
+ * sent to and from the modem in a proprietary format discovered after watching
+ * the behavior of the windows driver for the modem.
+ *
+ * More information about the use of the modem is available in usb_modeswitch
+ * forum and the project page:
+ *
+ * http://www.draisberghof.de/usb_modeswitch/bb/viewtopic.php?t=465
+ * https://github.com/mkotsbak/Samsung-GT-B3730-linux-driver
+ */
+
+/* #define	DEBUG */
+/* #define	VERBOSE */
+
+#define KALMIA_HEADER_LENGTH 6
+#define KALMIA_ALIGN_SIZE 4
+#define KALMIA_USB_TIMEOUT 10000
+
+/*-------------------------------------------------------------------------*/
+
+static int
+kalmia_send_init_packet(struct usbnet *dev, u8 *init_msg, u8 init_msg_len,
+	u8 *buffer, u8 expected_len)
+{
+	int act_len;
+	int status;
+
+	netdev_dbg(dev->net, "Sending init packet");
+
+	status = usb_bulk_msg(dev->udev, usb_sndbulkpipe(dev->udev, 0x02),
+		init_msg, init_msg_len, &act_len, KALMIA_USB_TIMEOUT);
+	if (status != 0) {
+		netdev_err(dev->net,
+			"Error sending init packet. Status %i, length %i\n",
+			status, act_len);
+		return status;
+	}
+	else if (act_len != init_msg_len) {
+		netdev_err(dev->net,
+			"Did not send all of init packet. Bytes sent: %i",
+			act_len);
+	}
+	else {
+		netdev_dbg(dev->net, "Successfully sent init packet.");
+	}
+
+	status = usb_bulk_msg(dev->udev, usb_rcvbulkpipe(dev->udev, 0x81),
+		buffer, expected_len, &act_len, KALMIA_USB_TIMEOUT);
+
+	if (status != 0)
+		netdev_err(dev->net,
+			"Error receiving init result. Status %i, length %i\n",
+			status, act_len);
+	else if (act_len != expected_len)
+		netdev_err(dev->net, "Unexpected init result length: %i\n",
+			act_len);
+
+	return status;
+}
+
+static int
+kalmia_init_and_get_ethernet_addr(struct usbnet *dev, u8 *ethernet_addr)
+{
+	char init_msg_1[] =
+		{ 0x57, 0x50, 0x04, 0x00, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00,
+		0x00, 0x00 };
+	char init_msg_2[] =
+		{ 0x57, 0x50, 0x04, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0xf4,
+		0x00, 0x00 };
+	char receive_buf[28];
+	int status;
+
+	status = kalmia_send_init_packet(dev, init_msg_1, sizeof(init_msg_1)
+		/ sizeof(init_msg_1[0]), receive_buf, 24);
+	if (status != 0)
+		return status;
+
+	status = kalmia_send_init_packet(dev, init_msg_2, sizeof(init_msg_2)
+		/ sizeof(init_msg_2[0]), receive_buf, 28);
+	if (status != 0)
+		return status;
+
+	memcpy(ethernet_addr, receive_buf + 10, ETH_ALEN);
+
+	return status;
+}
+
+static int
+kalmia_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+	u8 status;
+	u8 ethernet_addr[ETH_ALEN];
+
+	/* Don't bind to AT command interface */
+	if (intf->cur_altsetting->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC)
+		return -EINVAL;
+
+	dev->in = usb_rcvbulkpipe(dev->udev, 0x81 & USB_ENDPOINT_NUMBER_MASK);
+	dev->out = usb_sndbulkpipe(dev->udev, 0x02 & USB_ENDPOINT_NUMBER_MASK);
+	dev->status = NULL;
+
+	dev->net->hard_header_len += KALMIA_HEADER_LENGTH;
+	dev->hard_mtu = 1400;
+	dev->rx_urb_size = dev->hard_mtu * 10; // Found as optimal after testing
+
+	status = kalmia_init_and_get_ethernet_addr(dev, ethernet_addr);
+
+	if (status < 0) {
+		usb_set_intfdata(intf, NULL);
+		usb_driver_release_interface(driver_of(intf), intf);
+		return status;
+	}
+
+	memcpy(dev->net->dev_addr, ethernet_addr, ETH_ALEN);
+	memcpy(dev->net->perm_addr, ethernet_addr, ETH_ALEN);
+
+	return status;
+}
+
+static struct sk_buff *
+kalmia_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
+{
+	struct sk_buff *skb2 = NULL;
+	u16 content_len;
+	unsigned char *header_start;
+	unsigned char ether_type_1, ether_type_2;
+	u8 remainder, padlen = 0;
+
+	if (!skb_cloned(skb)) {
+		int headroom = skb_headroom(skb);
+		int tailroom = skb_tailroom(skb);
+
+		if ((tailroom >= KALMIA_ALIGN_SIZE) && (headroom
+			>= KALMIA_HEADER_LENGTH))
+			goto done;
+
+		if ((headroom + tailroom) > (KALMIA_HEADER_LENGTH
+			+ KALMIA_ALIGN_SIZE)) {
+			skb->data = memmove(skb->head + KALMIA_HEADER_LENGTH,
+				skb->data, skb->len);
+			skb_set_tail_pointer(skb, skb->len);
+			goto done;
+		}
+	}
+
+	skb2 = skb_copy_expand(skb, KALMIA_HEADER_LENGTH,
+		KALMIA_ALIGN_SIZE, flags);
+	if (!skb2)
+		return NULL;
+
+	dev_kfree_skb_any(skb);
+	skb = skb2;
+
+	done: header_start = skb_push(skb, KALMIA_HEADER_LENGTH);
+	ether_type_1 = header_start[KALMIA_HEADER_LENGTH + 12];
+	ether_type_2 = header_start[KALMIA_HEADER_LENGTH + 13];
+
+	netdev_dbg(dev->net, "Sending etherType: %02x%02x", ether_type_1,
+		ether_type_2);
+
+	/* According to empiric data for data packages */
+	header_start[0] = 0x57;
+	header_start[1] = 0x44;
+	content_len = skb->len - KALMIA_HEADER_LENGTH;
+	header_start[2] = (content_len & 0xff); /* low byte */
+	header_start[3] = (content_len >> 8); /* high byte */
+
+	header_start[4] = ether_type_1;
+	header_start[5] = ether_type_2;
+
+	/* Align to 4 bytes by padding with zeros */
+	remainder = skb->len % KALMIA_ALIGN_SIZE;
+	if (remainder > 0) {
+		padlen = KALMIA_ALIGN_SIZE - remainder;
+		memset(skb_put(skb, padlen), 0, padlen);
+	}
+
+	netdev_dbg(
+		dev->net,
+		"Sending package with length %i and padding %i. Header: %02x:%02x:%02x:%02x:%02x:%02x.",
+		content_len, padlen, header_start[0], header_start[1],
+		header_start[2], header_start[3], header_start[4],
+		header_start[5]);
+
+	return skb;
+}
+
+static int
+kalmia_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
+{
+	/*
+	 * Our task here is to strip off framing, leaving skb with one
+	 * data frame for the usbnet framework code to process.
+	 */
+	const u8 HEADER_END_OF_USB_PACKET[] =
+		{ 0x57, 0x5a, 0x00, 0x00, 0x08, 0x00 };
+	const u8 EXPECTED_UNKNOWN_HEADER_1[] =
+		{ 0x57, 0x43, 0x1e, 0x00, 0x15, 0x02 };
+	const u8 EXPECTED_UNKNOWN_HEADER_2[] =
+		{ 0x57, 0x50, 0x0e, 0x00, 0x00, 0x00 };
+	u8 i = 0;
+
+	/* incomplete header? */
+	if (skb->len < KALMIA_HEADER_LENGTH)
+		return 0;
+
+	do {
+		struct sk_buff *skb2 = NULL;
+		u8 *header_start;
+		u16 usb_packet_length, ether_packet_length;
+		int is_last;
+
+		header_start = skb->data;
+
+		if (unlikely(header_start[0] != 0x57 || header_start[1] != 0x44)) {
+			if (!memcmp(header_start, EXPECTED_UNKNOWN_HEADER_1,
+				sizeof(EXPECTED_UNKNOWN_HEADER_1)) || !memcmp(
+				header_start, EXPECTED_UNKNOWN_HEADER_2,
+				sizeof(EXPECTED_UNKNOWN_HEADER_2))) {
+				netdev_dbg(
+					dev->net,
+					"Received expected unknown frame header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
+					header_start[0], header_start[1],
+					header_start[2], header_start[3],
+					header_start[4], header_start[5],
+					skb->len - KALMIA_HEADER_LENGTH);
+			}
+			else {
+				netdev_err(
+					dev->net,
+					"Received unknown frame header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
+					header_start[0], header_start[1],
+					header_start[2], header_start[3],
+					header_start[4], header_start[5],
+					skb->len - KALMIA_HEADER_LENGTH);
+				return 0;
+			}
+		}
+		else
+			netdev_dbg(
+				dev->net,
+				"Received header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
+				header_start[0], header_start[1], header_start[2],
+				header_start[3], header_start[4], header_start[5],
+				skb->len - KALMIA_HEADER_LENGTH);
+
+		/* subtract start header and end header */
+		usb_packet_length = skb->len - (2 * KALMIA_HEADER_LENGTH);
+		ether_packet_length = header_start[2] + (header_start[3] << 8);
+		skb_pull(skb, KALMIA_HEADER_LENGTH);
+
+		/* Some small packets misses end marker */
+		if (usb_packet_length < ether_packet_length) {
+			ether_packet_length = usb_packet_length
+				+ KALMIA_HEADER_LENGTH;
+			is_last = true;
+		}
+		else {
+			netdev_dbg(dev->net, "Correct package length #%i", i
+				+ 1);
+
+			is_last = (memcmp(skb->data + ether_packet_length,
+				HEADER_END_OF_USB_PACKET,
+				sizeof(HEADER_END_OF_USB_PACKET)) == 0);
+			if (!is_last) {
+				header_start = skb->data + ether_packet_length;
+				netdev_dbg(
+					dev->net,
+					"End header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
+					header_start[0], header_start[1],
+					header_start[2], header_start[3],
+					header_start[4], header_start[5],
+					skb->len - KALMIA_HEADER_LENGTH);
+			}
+		}
+
+		if (is_last) {
+			skb2 = skb;
+		}
+		else {
+			skb2 = skb_clone(skb, GFP_ATOMIC);
+			if (unlikely(!skb2))
+				return 0;
+		}
+
+		skb_trim(skb2, ether_packet_length);
+
+		if (is_last) {
+			return 1;
+		}
+		else {
+			usbnet_skb_return(dev, skb2);
+			skb_pull(skb, ether_packet_length);
+		}
+
+		i++;
+	}
+	while (skb->len);
+
+	return 1;
+}
+
+static const struct driver_info kalmia_info = {
+	.description = "Samsung Kalmia LTE USB dongle",
+	.flags = FLAG_WWAN,
+	.bind = kalmia_bind,
+	.rx_fixup = kalmia_rx_fixup,
+	.tx_fixup = kalmia_tx_fixup
+};
+
+/*-------------------------------------------------------------------------*/
+
+static const struct usb_device_id products[] = {
+	/* The unswitched USB ID, to get the module auto loaded: */
+	{ USB_DEVICE(0x04e8, 0x689a) },
+	/* The stick swithed into modem (by e.g. usb_modeswitch): */
+	{ USB_DEVICE(0x04e8, 0x6889),
+		.driver_info = (unsigned long) &kalmia_info, },
+	{ /* EMPTY == end of list */} };
+MODULE_DEVICE_TABLE( usb, products);
+
+static struct usb_driver kalmia_driver = {
+	.name = "kalmia",
+	.id_table = products,
+	.probe = usbnet_probe,
+	.disconnect = usbnet_disconnect,
+	.suspend = usbnet_suspend,
+	.resume = usbnet_resume
+};
+
+static int __init kalmia_init(void)
+{
+	return usb_register(&kalmia_driver);
+}
+module_init( kalmia_init);
+
+static void __exit kalmia_exit(void)
+{
+	usb_deregister(&kalmia_driver);
+}
+module_exit( kalmia_exit);
+
+MODULE_AUTHOR("Marius Bjoernstad Kotsbak <marius@kotsbak.com>");
+MODULE_DESCRIPTION("Samsung Kalmia USB network driver");
+MODULE_LICENSE("GPL");