1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * USB network interface driver for Samsung Kalmia based LTE USB modem like the
4 * Samsung GT-B3730 and GT-B3710.
5 *
6 * Copyright (C) 2011 Marius Bjoernstad Kotsbak <marius@kotsbak.com>
7 *
8 * Sponsored by Quicklink Video Distribution Services Ltd.
9 *
10 * Based on the cdc_eem module.
11 */
12
13#include <linux/module.h>
14#include <linux/netdevice.h>
15#include <linux/etherdevice.h>
16#include <linux/ctype.h>
17#include <linux/ethtool.h>
18#include <linux/workqueue.h>
19#include <linux/mii.h>
20#include <linux/usb.h>
21#include <linux/crc32.h>
22#include <linux/usb/cdc.h>
23#include <linux/usb/usbnet.h>
24#include <linux/gfp.h>
25
26/*
27 * The Samsung Kalmia based LTE USB modems have a CDC ACM port for modem control
28 * handled by the "option" module and an ethernet data port handled by this
29 * module.
30 *
31 * The stick must first be switched into modem mode by usb_modeswitch
32 * or similar tool. Then the modem gets sent two initialization packets by
33 * this module, which gives the MAC address of the device. User space can then
34 * connect the modem using AT commands through the ACM port and then use
35 * DHCP on the network interface exposed by this module. Network packets are
36 * sent to and from the modem in a proprietary format discovered after watching
37 * the behavior of the windows driver for the modem.
38 *
39 * More information about the use of the modem is available in usb_modeswitch
40 * forum and the project page:
41 *
42 * http://www.draisberghof.de/usb_modeswitch/bb/viewtopic.php?t=465
43 * https://github.com/mkotsbak/Samsung-GT-B3730-linux-driver
44 */
45
46/* #define	DEBUG */
47/* #define	VERBOSE */
48
49#define KALMIA_HEADER_LENGTH 6
50#define KALMIA_ALIGN_SIZE 4
51#define KALMIA_USB_TIMEOUT 10000
52
53/*-------------------------------------------------------------------------*/
54
55static int
56kalmia_send_init_packet(struct usbnet *dev, u8 *init_msg, u8 init_msg_len,
57	u8 *buffer, u8 expected_len)
58{
59	int act_len;
60	int status;
61
62	netdev_dbg(dev->net, "Sending init packet");
63
64	status = usb_bulk_msg(dev->udev, usb_sndbulkpipe(dev->udev, 0x02),
65		init_msg, init_msg_len, &act_len, KALMIA_USB_TIMEOUT);
66	if (status != 0) {
67		netdev_err(dev->net,
68			"Error sending init packet. Status %i\n",
69			status);
70		return status;
71	}
72	else if (act_len != init_msg_len) {
73		netdev_err(dev->net,
74			"Did not send all of init packet. Bytes sent: %i",
75			act_len);
76	}
77	else {
78		netdev_dbg(dev->net, "Successfully sent init packet.");
79	}
80
81	status = usb_bulk_msg(dev->udev, usb_rcvbulkpipe(dev->udev, 0x81),
82		buffer, expected_len, &act_len, KALMIA_USB_TIMEOUT);
83
84	if (status != 0)
85		netdev_err(dev->net,
86			"Error receiving init result. Status %i\n",
87			status);
88	else if (act_len != expected_len)
89		netdev_err(dev->net, "Unexpected init result length: %i\n",
90			act_len);
91
92	return status;
93}
94
95static int
96kalmia_init_and_get_ethernet_addr(struct usbnet *dev, u8 *ethernet_addr)
97{
98	static const char init_msg_1[] =
99		{ 0x57, 0x50, 0x04, 0x00, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00,
100		0x00, 0x00 };
101	static const char init_msg_2[] =
102		{ 0x57, 0x50, 0x04, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0xf4,
103		0x00, 0x00 };
104	static const int buflen = 28;
105	char *usb_buf;
106	int status;
107
108	usb_buf = kmalloc(buflen, GFP_DMA | GFP_KERNEL);
109	if (!usb_buf)
110		return -ENOMEM;
111
112	memcpy(usb_buf, init_msg_1, 12);
113	status = kalmia_send_init_packet(dev, usb_buf, ARRAY_SIZE(init_msg_1),
114					 usb_buf, 24);
115	if (status != 0)
116		goto out;
117
118	memcpy(usb_buf, init_msg_2, 12);
119	status = kalmia_send_init_packet(dev, usb_buf, ARRAY_SIZE(init_msg_2),
120					 usb_buf, 28);
121	if (status != 0)
122		goto out;
123
124	memcpy(ethernet_addr, usb_buf + 10, ETH_ALEN);
125out:
126	kfree(usb_buf);
127	return status;
128}
129
130static int
131kalmia_bind(struct usbnet *dev, struct usb_interface *intf)
132{
133	int status;
134	u8 ethernet_addr[ETH_ALEN];
135
136	/* Don't bind to AT command interface */
137	if (intf->cur_altsetting->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC)
138		return -EINVAL;
139
140	dev->in = usb_rcvbulkpipe(dev->udev, 0x81 & USB_ENDPOINT_NUMBER_MASK);
141	dev->out = usb_sndbulkpipe(dev->udev, 0x02 & USB_ENDPOINT_NUMBER_MASK);
142	dev->status = NULL;
143
144	dev->net->hard_header_len += KALMIA_HEADER_LENGTH;
145	dev->hard_mtu = 1400;
146	dev->rx_urb_size = dev->hard_mtu * 10; // Found as optimal after testing
147
148	status = kalmia_init_and_get_ethernet_addr(dev, ethernet_addr);
149	if (status)
150		return status;
151
152	eth_hw_addr_set(dev->net, ethernet_addr);
153
154	return status;
155}
156
157static struct sk_buff *
158kalmia_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
159{
160	struct sk_buff *skb2 = NULL;
161	u16 content_len;
162	unsigned char *header_start;
163	unsigned char ether_type_1, ether_type_2;
164	u8 remainder, padlen = 0;
165
166	if (!skb_cloned(skb)) {
167		int headroom = skb_headroom(skb);
168		int tailroom = skb_tailroom(skb);
169
170		if ((tailroom >= KALMIA_ALIGN_SIZE) && (headroom
171			>= KALMIA_HEADER_LENGTH))
172			goto done;
173
174		if ((headroom + tailroom) > (KALMIA_HEADER_LENGTH
175			+ KALMIA_ALIGN_SIZE)) {
176			skb->data = memmove(skb->head + KALMIA_HEADER_LENGTH,
177				skb->data, skb->len);
178			skb_set_tail_pointer(skb, skb->len);
179			goto done;
180		}
181	}
182
183	skb2 = skb_copy_expand(skb, KALMIA_HEADER_LENGTH,
184		KALMIA_ALIGN_SIZE, flags);
185	if (!skb2)
186		return NULL;
187
188	dev_kfree_skb_any(skb);
189	skb = skb2;
190
191done:
192	header_start = skb_push(skb, KALMIA_HEADER_LENGTH);
193	ether_type_1 = header_start[KALMIA_HEADER_LENGTH + 12];
194	ether_type_2 = header_start[KALMIA_HEADER_LENGTH + 13];
195
196	netdev_dbg(dev->net, "Sending etherType: %02x%02x", ether_type_1,
197		ether_type_2);
198
199	/* According to empiric data for data packages */
200	header_start[0] = 0x57;
201	header_start[1] = 0x44;
202	content_len = skb->len - KALMIA_HEADER_LENGTH;
203
204	put_unaligned_le16(content_len, &header_start[2]);
205	header_start[4] = ether_type_1;
206	header_start[5] = ether_type_2;
207
208	/* Align to 4 bytes by padding with zeros */
209	remainder = skb->len % KALMIA_ALIGN_SIZE;
210	if (remainder > 0) {
211		padlen = KALMIA_ALIGN_SIZE - remainder;
212		skb_put_zero(skb, padlen);
213	}
214
215	netdev_dbg(dev->net,
216		"Sending package with length %i and padding %i. Header: %6phC.",
217		content_len, padlen, header_start);
218
219	return skb;
220}
221
222static int
223kalmia_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
224{
225	/*
226	 * Our task here is to strip off framing, leaving skb with one
227	 * data frame for the usbnet framework code to process.
228	 */
229	static const u8 HEADER_END_OF_USB_PACKET[] =
230		{ 0x57, 0x5a, 0x00, 0x00, 0x08, 0x00 };
231	static const u8 EXPECTED_UNKNOWN_HEADER_1[] =
232		{ 0x57, 0x43, 0x1e, 0x00, 0x15, 0x02 };
233	static const u8 EXPECTED_UNKNOWN_HEADER_2[] =
234		{ 0x57, 0x50, 0x0e, 0x00, 0x00, 0x00 };
235	int i = 0;
236
237	/* incomplete header? */
238	if (skb->len < KALMIA_HEADER_LENGTH)
239		return 0;
240
241	do {
242		struct sk_buff *skb2 = NULL;
243		u8 *header_start;
244		u16 usb_packet_length, ether_packet_length;
245		int is_last;
246
247		header_start = skb->data;
248
249		if (unlikely(header_start[0] != 0x57 || header_start[1] != 0x44)) {
250			if (!memcmp(header_start, EXPECTED_UNKNOWN_HEADER_1,
251				sizeof(EXPECTED_UNKNOWN_HEADER_1)) || !memcmp(
252				header_start, EXPECTED_UNKNOWN_HEADER_2,
253				sizeof(EXPECTED_UNKNOWN_HEADER_2))) {
254				netdev_dbg(dev->net,
255					"Received expected unknown frame header: %6phC. Package length: %i\n",
256					header_start,
257					skb->len - KALMIA_HEADER_LENGTH);
258			}
259			else {
260				netdev_err(dev->net,
261					"Received unknown frame header: %6phC. Package length: %i\n",
262					header_start,
263					skb->len - KALMIA_HEADER_LENGTH);
264				return 0;
265			}
266		}
267		else
268			netdev_dbg(dev->net,
269				"Received header: %6phC. Package length: %i\n",
270				header_start, skb->len - KALMIA_HEADER_LENGTH);
271
272		/* subtract start header and end header */
273		usb_packet_length = skb->len - (2 * KALMIA_HEADER_LENGTH);
274		ether_packet_length = get_unaligned_le16(&header_start[2]);
275		skb_pull(skb, KALMIA_HEADER_LENGTH);
276
277		/* Some small packets misses end marker */
278		if (usb_packet_length < ether_packet_length) {
279			ether_packet_length = usb_packet_length
280				+ KALMIA_HEADER_LENGTH;
281			is_last = true;
282		}
283		else {
284			netdev_dbg(dev->net, "Correct package length #%i", i
285				+ 1);
286
287			is_last = (memcmp(skb->data + ether_packet_length,
288				HEADER_END_OF_USB_PACKET,
289				sizeof(HEADER_END_OF_USB_PACKET)) == 0);
290			if (!is_last) {
291				header_start = skb->data + ether_packet_length;
292				netdev_dbg(dev->net,
293					"End header: %6phC. Package length: %i\n",
294					header_start,
295					skb->len - KALMIA_HEADER_LENGTH);
296			}
297		}
298
299		if (is_last) {
300			skb2 = skb;
301		}
302		else {
303			skb2 = skb_clone(skb, GFP_ATOMIC);
304			if (unlikely(!skb2))
305				return 0;
306		}
307
308		skb_trim(skb2, ether_packet_length);
309
310		if (is_last) {
311			return 1;
312		}
313		else {
314			usbnet_skb_return(dev, skb2);
315			skb_pull(skb, ether_packet_length);
316		}
317
318		i++;
319	}
320	while (skb->len);
321
322	return 1;
323}
324
325static const struct driver_info kalmia_info = {
326	.description = "Samsung Kalmia LTE USB dongle",
327	.flags = FLAG_WWAN,
328	.bind = kalmia_bind,
329	.rx_fixup = kalmia_rx_fixup,
330	.tx_fixup = kalmia_tx_fixup
331};
332
333/*-------------------------------------------------------------------------*/
334
335static const struct usb_device_id products[] = {
336	/* The unswitched USB ID, to get the module auto loaded: */
337	{ USB_DEVICE(0x04e8, 0x689a) },
338	/* The stick switched into modem (by e.g. usb_modeswitch): */
339	{ USB_DEVICE(0x04e8, 0x6889),
340		.driver_info = (unsigned long) &kalmia_info, },
341	{ /* EMPTY == end of list */} };
342MODULE_DEVICE_TABLE( usb, products);
343
344static struct usb_driver kalmia_driver = {
345	.name = "kalmia",
346	.id_table = products,
347	.probe = usbnet_probe,
348	.disconnect = usbnet_disconnect,
349	.suspend = usbnet_suspend,
350	.resume = usbnet_resume,
351	.disable_hub_initiated_lpm = 1,
352};
353
354module_usb_driver(kalmia_driver);
355
356MODULE_AUTHOR("Marius Bjoernstad Kotsbak <marius@kotsbak.com>");
357MODULE_DESCRIPTION("Samsung Kalmia USB network driver");
358MODULE_LICENSE("GPL");
359