1 /*
2 * Safe Encapsulated USB Serial Driver
3 *
4 * Copyright (C) 2010 Johan Hovold <jhovold@gmail.com>
5 * Copyright (C) 2001 Lineo
6 * Copyright (C) 2001 Hewlett-Packard
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * By:
14 * Stuart Lynne <sl@lineo.com>, Tom Rushworth <tbr@lineo.com>
15 */
16
17 /*
18 * The encapsultaion is designed to overcome difficulties with some USB
19 * hardware.
20 *
21 * While the USB protocol has a CRC over the data while in transit, i.e. while
22 * being carried over the bus, there is no end to end protection. If the
23 * hardware has any problems getting the data into or out of the USB transmit
24 * and receive FIFO's then data can be lost.
25 *
26 * This protocol adds a two byte trailer to each USB packet to specify the
27 * number of bytes of valid data and a 10 bit CRC that will allow the receiver
28 * to verify that the entire USB packet was received without error.
29 *
30 * Because in this case the sender and receiver are the class and function
31 * drivers there is now end to end protection.
32 *
33 * There is an additional option that can be used to force all transmitted
34 * packets to be padded to the maximum packet size. This provides a work
35 * around for some devices which have problems with small USB packets.
36 *
37 * Assuming a packetsize of N:
38 *
39 * 0..N-2 data and optional padding
40 *
41 * N-2 bits 7-2 - number of bytes of valid data
42 * bits 1-0 top two bits of 10 bit CRC
43 * N-1 bottom 8 bits of 10 bit CRC
44 *
45 *
46 * | Data Length | 10 bit CRC |
47 * + 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 | 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 +
48 *
49 * The 10 bit CRC is computed across the sent data, followed by the trailer
50 * with the length set and the CRC set to zero. The CRC is then OR'd into
51 * the trailer.
52 *
53 * When received a 10 bit CRC is computed over the entire frame including
54 * the trailer and should be equal to zero.
55 *
56 * Two module parameters are used to control the encapsulation, if both are
57 * turned of the module works as a simple serial device with NO
58 * encapsulation.
59 *
60 * See linux/drivers/usbd/serial_fd for a device function driver
61 * implementation of this.
62 *
63 */
64
65
66 #include <linux/kernel.h>
67 #include <linux/errno.h>
68 #include <linux/gfp.h>
69 #include <linux/init.h>
70 #include <linux/tty.h>
71 #include <linux/tty_driver.h>
72 #include <linux/tty_flip.h>
73 #include <linux/module.h>
74 #include <linux/spinlock.h>
75 #include <linux/uaccess.h>
76 #include <linux/usb.h>
77 #include <linux/usb/serial.h>
78
79
80 #ifndef CONFIG_USB_SERIAL_SAFE_PADDED
81 #define CONFIG_USB_SERIAL_SAFE_PADDED 0
82 #endif
83
84 static bool debug;
85 static bool safe = 1;
86 static bool padded = CONFIG_USB_SERIAL_SAFE_PADDED;
87
88 #define DRIVER_VERSION "v0.1"
89 #define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com, Johan Hovold <jhovold@gmail.com>"
90 #define DRIVER_DESC "USB Safe Encapsulated Serial"
91
92 MODULE_AUTHOR(DRIVER_AUTHOR);
93 MODULE_DESCRIPTION(DRIVER_DESC);
94 MODULE_LICENSE("GPL");
95
96 static __u16 vendor; /* no default */
97 static __u16 product; /* no default */
98 module_param(vendor, ushort, 0);
99 MODULE_PARM_DESC(vendor, "User specified USB idVendor (required)");
100 module_param(product, ushort, 0);
101 MODULE_PARM_DESC(product, "User specified USB idProduct (required)");
102
103 module_param(debug, bool, S_IRUGO | S_IWUSR);
104 MODULE_PARM_DESC(debug, "Debug enabled or not");
105
106 module_param(safe, bool, 0);
107 MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");
108
109 module_param(padded, bool, 0);
110 MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off");
111
112 #define CDC_DEVICE_CLASS 0x02
113
114 #define CDC_INTERFACE_CLASS 0x02
115 #define CDC_INTERFACE_SUBCLASS 0x06
116
117 #define LINEO_INTERFACE_CLASS 0xff
118
119 #define LINEO_INTERFACE_SUBCLASS_SAFENET 0x01
120 #define LINEO_SAFENET_CRC 0x01
121 #define LINEO_SAFENET_CRC_PADDED 0x02
122
123 #define LINEO_INTERFACE_SUBCLASS_SAFESERIAL 0x02
124 #define LINEO_SAFESERIAL_CRC 0x01
125 #define LINEO_SAFESERIAL_CRC_PADDED 0x02
126
127
128 #define MY_USB_DEVICE(vend, prod, dc, ic, isc) \
129 .match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
130 USB_DEVICE_ID_MATCH_DEV_CLASS | \
131 USB_DEVICE_ID_MATCH_INT_CLASS | \
132 USB_DEVICE_ID_MATCH_INT_SUBCLASS, \
133 .idVendor = (vend), \
134 .idProduct = (prod),\
135 .bDeviceClass = (dc),\
136 .bInterfaceClass = (ic), \
137 .bInterfaceSubClass = (isc),
138
139 static struct usb_device_id id_table[] = {
140 {MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Itsy */
141 {MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Calypso */
142 {MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Iris */
143 {MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */
144 {MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */
145 {MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */
146 {MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Sharp tmp */
147 /* extra null entry for module vendor/produc parameters */
148 {MY_USB_DEVICE(0, 0, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},
149 {} /* terminating entry */
150 };
151
152 MODULE_DEVICE_TABLE(usb, id_table);
153
154 static struct usb_driver safe_driver = {
155 .name = "safe_serial",
156 .probe = usb_serial_probe,
157 .disconnect = usb_serial_disconnect,
158 .id_table = id_table,
159 };
160
161 static const __u16 crc10_table[256] = {
162 0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
163 0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
164 0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
165 0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
166 0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
167 0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
168 0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
169 0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
170 0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
171 0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
172 0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
173 0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
174 0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
175 0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
176 0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
177 0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
178 0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
179 0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
180 0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
181 0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
182 0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
183 0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
184 0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
185 0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
186 0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
187 0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
188 0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
189 0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
190 0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
191 0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
192 0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
193 0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
194 };
195
196 #define CRC10_INITFCS 0x000 /* Initial FCS value */
197 #define CRC10_GOODFCS 0x000 /* Good final FCS value */
198 #define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))
199
200 /**
201 * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
202 * @sp: pointer to buffer
203 * @len: number of bytes
204 * @fcs: starting FCS
205 *
206 * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
207 * new 10 bit FCS.
208 */
fcs_compute10(unsigned char * sp,int len,__u16 fcs)209 static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
210 {
211 for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
212 return fcs;
213 }
214
safe_process_read_urb(struct urb * urb)215 static void safe_process_read_urb(struct urb *urb)
216 {
217 struct usb_serial_port *port = urb->context;
218 unsigned char *data = urb->transfer_buffer;
219 unsigned char length = urb->actual_length;
220 int actual_length;
221 struct tty_struct *tty;
222 __u16 fcs;
223
224 if (!length)
225 return;
226
227 tty = tty_port_tty_get(&port->port);
228 if (!tty)
229 return;
230
231 if (!safe)
232 goto out;
233
234 fcs = fcs_compute10(data, length, CRC10_INITFCS);
235 if (fcs) {
236 dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
237 goto err;
238 }
239
240 actual_length = data[length - 2] >> 2;
241 if (actual_length > (length - 2)) {
242 dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
243 __func__, actual_length, length);
244 goto err;
245 }
246 dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
247 length = actual_length;
248 out:
249 tty_insert_flip_string(tty, data, length);
250 tty_flip_buffer_push(tty);
251 err:
252 tty_kref_put(tty);
253 }
254
safe_prepare_write_buffer(struct usb_serial_port * port,void * dest,size_t size)255 static int safe_prepare_write_buffer(struct usb_serial_port *port,
256 void *dest, size_t size)
257 {
258 unsigned char *buf = dest;
259 int count;
260 int trailer_len;
261 int pkt_len;
262 __u16 fcs;
263
264 trailer_len = safe ? 2 : 0;
265
266 count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
267 &port->lock);
268 if (!safe)
269 return count;
270
271 /* pad if necessary */
272 if (padded) {
273 pkt_len = size;
274 memset(buf + count, '0', pkt_len - count - trailer_len);
275 } else {
276 pkt_len = count + trailer_len;
277 }
278
279 /* set count */
280 buf[pkt_len - 2] = count << 2;
281 buf[pkt_len - 1] = 0;
282
283 /* compute fcs and insert into trailer */
284 fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
285 buf[pkt_len - 2] |= fcs >> 8;
286 buf[pkt_len - 1] |= fcs & 0xff;
287
288 return pkt_len;
289 }
290
safe_startup(struct usb_serial * serial)291 static int safe_startup(struct usb_serial *serial)
292 {
293 switch (serial->interface->cur_altsetting->desc.bInterfaceProtocol) {
294 case LINEO_SAFESERIAL_CRC:
295 break;
296 case LINEO_SAFESERIAL_CRC_PADDED:
297 padded = 1;
298 break;
299 default:
300 return -EINVAL;
301 }
302 return 0;
303 }
304
305 static struct usb_serial_driver safe_device = {
306 .driver = {
307 .owner = THIS_MODULE,
308 .name = "safe_serial",
309 },
310 .id_table = id_table,
311 .num_ports = 1,
312 .process_read_urb = safe_process_read_urb,
313 .prepare_write_buffer = safe_prepare_write_buffer,
314 .attach = safe_startup,
315 };
316
317 static struct usb_serial_driver * const serial_drivers[] = {
318 &safe_device, NULL
319 };
320
safe_init(void)321 static int __init safe_init(void)
322 {
323 int i;
324
325 printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_VERSION ":"
326 DRIVER_DESC "\n");
327
328 /* if we have vendor / product parameters patch them into id list */
329 if (vendor || product) {
330 printk(KERN_INFO KBUILD_MODNAME ": vendor: %x product: %x\n",
331 vendor, product);
332
333 for (i = 0; i < ARRAY_SIZE(id_table); i++) {
334 if (!id_table[i].idVendor && !id_table[i].idProduct) {
335 id_table[i].idVendor = vendor;
336 id_table[i].idProduct = product;
337 break;
338 }
339 }
340 }
341
342 return usb_serial_register_drivers(&safe_driver, serial_drivers);
343 }
344
safe_exit(void)345 static void __exit safe_exit(void)
346 {
347 usb_serial_deregister_drivers(&safe_driver, serial_drivers);
348 }
349
350 module_init(safe_init);
351 module_exit(safe_exit);
352