summaryrefslogtreecommitdiffstats
path: root/drivers/usb/serial/safe_serial.c
blob: ba895989d8c4b89231cf34a431e7f894a5ab4268 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
/*
 * Safe Encapsulated USB Serial Driver
 *
 *      Copyright (C) 2010 Johan Hovold <jhovold@gmail.com>
 *      Copyright (C) 2001 Lineo
 *      Copyright (C) 2001 Hewlett-Packard
 *
 *	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.
 *
 * By:
 *      Stuart Lynne <sl@lineo.com>, Tom Rushworth <tbr@lineo.com>
 */

/*
 * The encapsultaion is designed to overcome difficulties with some USB
 * hardware.
 *
 * While the USB protocol has a CRC over the data while in transit, i.e. while
 * being carried over the bus, there is no end to end protection. If the
 * hardware has any problems getting the data into or out of the USB transmit
 * and receive FIFO's then data can be lost.
 *
 * This protocol adds a two byte trailer to each USB packet to specify the
 * number of bytes of valid data and a 10 bit CRC that will allow the receiver
 * to verify that the entire USB packet was received without error.
 *
 * Because in this case the sender and receiver are the class and function
 * drivers there is now end to end protection.
 *
 * There is an additional option that can be used to force all transmitted
 * packets to be padded to the maximum packet size. This provides a work
 * around for some devices which have problems with small USB packets.
 *
 * Assuming a packetsize of N:
 *
 *      0..N-2  data and optional padding
 *
 *      N-2     bits 7-2 - number of bytes of valid data
 *              bits 1-0 top two bits of 10 bit CRC
 *      N-1     bottom 8 bits of 10 bit CRC
 *
 *
 *      | Data Length       | 10 bit CRC                                |
 *      + 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 | 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 +
 *
 * The 10 bit CRC is computed across the sent data, followed by the trailer
 * with the length set and the CRC set to zero. The CRC is then OR'd into
 * the trailer.
 *
 * When received a 10 bit CRC is computed over the entire frame including
 * the trailer and should be equal to zero.
 *
 * Two module parameters are used to control the encapsulation, if both are
 * turned of the module works as a simple serial device with NO
 * encapsulation.
 *
 * See linux/drivers/usbd/serial_fd for a device function driver
 * implementation of this.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>


#ifndef CONFIG_USB_SERIAL_SAFE_PADDED
#define CONFIG_USB_SERIAL_SAFE_PADDED 0
#endif

static bool safe = 1;
static bool padded = CONFIG_USB_SERIAL_SAFE_PADDED;

#define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com, Johan Hovold <jhovold@gmail.com>"
#define DRIVER_DESC "USB Safe Encapsulated Serial"

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

module_param(safe, bool, 0);
MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");

module_param(padded, bool, 0);
MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off");

#define CDC_DEVICE_CLASS                        0x02

#define CDC_INTERFACE_CLASS                     0x02
#define CDC_INTERFACE_SUBCLASS                  0x06

#define LINEO_INTERFACE_CLASS                   0xff

#define LINEO_INTERFACE_SUBCLASS_SAFENET        0x01
#define LINEO_SAFENET_CRC                       0x01
#define LINEO_SAFENET_CRC_PADDED                0x02

#define LINEO_INTERFACE_SUBCLASS_SAFESERIAL     0x02
#define LINEO_SAFESERIAL_CRC                    0x01
#define LINEO_SAFESERIAL_CRC_PADDED             0x02


#define MY_USB_DEVICE(vend, prod, dc, ic, isc) \
	.match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
		       USB_DEVICE_ID_MATCH_DEV_CLASS | \
		       USB_DEVICE_ID_MATCH_INT_CLASS | \
		       USB_DEVICE_ID_MATCH_INT_SUBCLASS, \
	.idVendor = (vend), \
	.idProduct = (prod),\
	.bDeviceClass = (dc),\
	.bInterfaceClass = (ic), \
	.bInterfaceSubClass = (isc),

static struct usb_device_id id_table[] = {
	{MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},	/* Itsy */
	{MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},	/* Calypso */
	{MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},	/* Iris */
	{MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},	/* Collie */
	{MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},	/* Collie */
	{MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},	/* Collie */
	{MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},	/* Sharp tmp */
	{}			/* terminating entry  */
};

MODULE_DEVICE_TABLE(usb, id_table);

static const __u16 crc10_table[256] = {
	0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
	0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
	0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
	0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
	0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
	0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
	0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
	0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
	0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
	0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
	0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
	0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
	0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
	0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
	0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
	0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
	0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
	0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
	0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
	0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
	0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
	0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
	0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
	0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
	0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
	0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
	0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
	0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
	0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
	0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
	0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
	0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
};

#define CRC10_INITFCS     0x000	/* Initial FCS value */
#define CRC10_GOODFCS     0x000	/* Good final FCS value */
#define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))

/**
 * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
 * @sp: pointer to buffer
 * @len: number of bytes
 * @fcs: starting FCS
 *
 * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
 * new 10 bit FCS.
 */
static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
{
	for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
	return fcs;
}

static void safe_process_read_urb(struct urb *urb)
{
	struct usb_serial_port *port = urb->context;
	unsigned char *data = urb->transfer_buffer;
	unsigned char length = urb->actual_length;
	int actual_length;
	__u16 fcs;

	if (!length)
		return;

	if (!safe)
		goto out;

	fcs = fcs_compute10(data, length, CRC10_INITFCS);
	if (fcs) {
		dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
		return;
	}

	actual_length = data[length - 2] >> 2;
	if (actual_length > (length - 2)) {
		dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
				__func__, actual_length, length);
		return;
	}
	dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
	length = actual_length;
out:
	tty_insert_flip_string(&port->port, data, length);
	tty_flip_buffer_push(&port->port);
}

static int safe_prepare_write_buffer(struct usb_serial_port *port,
						void *dest, size_t size)
{
	unsigned char *buf = dest;
	int count;
	int trailer_len;
	int pkt_len;
	__u16 fcs;

	trailer_len = safe ? 2 : 0;

	count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
								&port->lock);
	if (!safe)
		return count;

	/* pad if necessary */
	if (padded) {
		pkt_len = size;
		memset(buf + count, '0', pkt_len - count - trailer_len);
	} else {
		pkt_len = count + trailer_len;
	}

	/* set count */
	buf[pkt_len - 2] = count << 2;
	buf[pkt_len - 1] = 0;

	/* compute fcs and insert into trailer */
	fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
	buf[pkt_len - 2] |= fcs >> 8;
	buf[pkt_len - 1] |= fcs & 0xff;

	return pkt_len;
}

static int safe_startup(struct usb_serial *serial)
{
	struct usb_interface_descriptor	*desc;

	if (serial->dev->descriptor.bDeviceClass != CDC_DEVICE_CLASS)
		return -ENODEV;

	desc = &serial->interface->cur_altsetting->desc;

	if (desc->bInterfaceClass != LINEO_INTERFACE_CLASS)
		return -ENODEV;
	if (desc->bInterfaceSubClass != LINEO_INTERFACE_SUBCLASS_SAFESERIAL)
		return -ENODEV;

	switch (desc->bInterfaceProtocol) {
	case LINEO_SAFESERIAL_CRC:
		break;
	case LINEO_SAFESERIAL_CRC_PADDED:
		padded = 1;
		break;
	default:
		return -EINVAL;
	}
	return 0;
}

static struct usb_serial_driver safe_device = {
	.driver = {
		.owner =	THIS_MODULE,
		.name =		"safe_serial",
	},
	.id_table =		id_table,
	.num_ports =		1,
	.process_read_urb =	safe_process_read_urb,
	.prepare_write_buffer =	safe_prepare_write_buffer,
	.attach =		safe_startup,
};

static struct usb_serial_driver * const serial_drivers[] = {
	&safe_device, NULL
};

module_usb_serial_driver(serial_drivers, id_table);