source: src/linux/universal/linux-3.18/drivers/usb/serial/safe_serial.c @ 31869

Last change on this file since 31869 was 31869, checked in by brainslayer, 4 months ago

update

File size: 10.0 KB
Line 
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
66
67#include <linux/kernel.h>
68#include <linux/errno.h>
69#include <linux/gfp.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
84static bool safe = 1;
85static bool padded = CONFIG_USB_SERIAL_SAFE_PADDED;
86
87#define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com, Johan Hovold <jhovold@gmail.com>"
88#define DRIVER_DESC "USB Safe Encapsulated Serial"
89
90MODULE_AUTHOR(DRIVER_AUTHOR);
91MODULE_DESCRIPTION(DRIVER_DESC);
92MODULE_LICENSE("GPL");
93
94module_param(safe, bool, 0);
95MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");
96
97module_param(padded, bool, 0);
98MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off");
99
100#define CDC_DEVICE_CLASS                        0x02
101
102#define CDC_INTERFACE_CLASS                     0x02
103#define CDC_INTERFACE_SUBCLASS                  0x06
104
105#define LINEO_INTERFACE_CLASS                   0xff
106
107#define LINEO_INTERFACE_SUBCLASS_SAFENET        0x01
108#define LINEO_SAFENET_CRC                       0x01
109#define LINEO_SAFENET_CRC_PADDED                0x02
110
111#define LINEO_INTERFACE_SUBCLASS_SAFESERIAL     0x02
112#define LINEO_SAFESERIAL_CRC                    0x01
113#define LINEO_SAFESERIAL_CRC_PADDED             0x02
114
115
116#define MY_USB_DEVICE(vend, prod, dc, ic, isc) \
117        .match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
118                       USB_DEVICE_ID_MATCH_DEV_CLASS | \
119                       USB_DEVICE_ID_MATCH_INT_CLASS | \
120                       USB_DEVICE_ID_MATCH_INT_SUBCLASS, \
121        .idVendor = (vend), \
122        .idProduct = (prod),\
123        .bDeviceClass = (dc),\
124        .bInterfaceClass = (ic), \
125        .bInterfaceSubClass = (isc),
126
127static const struct usb_device_id id_table[] = {
128        {MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Itsy */
129        {MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Calypso */
130        {MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Iris */
131        {MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
132        {MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
133        {MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
134        {MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Sharp tmp */
135        {}                      /* terminating entry  */
136};
137
138MODULE_DEVICE_TABLE(usb, id_table);
139
140static const __u16 crc10_table[256] = {
141        0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
142        0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
143        0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
144        0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
145        0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
146        0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
147        0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
148        0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
149        0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
150        0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
151        0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
152        0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
153        0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
154        0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
155        0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
156        0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
157        0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
158        0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
159        0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
160        0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
161        0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
162        0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
163        0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
164        0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
165        0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
166        0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
167        0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
168        0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
169        0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
170        0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
171        0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
172        0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
173};
174
175#define CRC10_INITFCS     0x000 /* Initial FCS value */
176#define CRC10_GOODFCS     0x000 /* Good final FCS value */
177#define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))
178
179/**
180 * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
181 * @sp: pointer to buffer
182 * @len: number of bytes
183 * @fcs: starting FCS
184 *
185 * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
186 * new 10 bit FCS.
187 */
188static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
189{
190        for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
191        return fcs;
192}
193
194static void safe_process_read_urb(struct urb *urb)
195{
196        struct usb_serial_port *port = urb->context;
197        unsigned char *data = urb->transfer_buffer;
198        unsigned char length = urb->actual_length;
199        int actual_length;
200        __u16 fcs;
201
202        if (!length)
203                return;
204
205        if (!safe)
206                goto out;
207
208        if (length < 2) {
209                dev_err(&port->dev, "malformed packet\n");
210                return;
211        }
212
213        fcs = fcs_compute10(data, length, CRC10_INITFCS);
214        if (fcs) {
215                dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
216                return;
217        }
218
219        actual_length = data[length - 2] >> 2;
220        if (actual_length > (length - 2)) {
221                dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
222                                __func__, actual_length, length);
223                return;
224        }
225        dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
226        length = actual_length;
227out:
228        tty_insert_flip_string(&port->port, data, length);
229        tty_flip_buffer_push(&port->port);
230}
231
232static int safe_prepare_write_buffer(struct usb_serial_port *port,
233                                                void *dest, size_t size)
234{
235        unsigned char *buf = dest;
236        int count;
237        int trailer_len;
238        int pkt_len;
239        __u16 fcs;
240
241        trailer_len = safe ? 2 : 0;
242
243        count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
244                                                                &port->lock);
245        if (!safe)
246                return count;
247
248        /* pad if necessary */
249        if (padded) {
250                pkt_len = size;
251                memset(buf + count, '0', pkt_len - count - trailer_len);
252        } else {
253                pkt_len = count + trailer_len;
254        }
255
256        /* set count */
257        buf[pkt_len - 2] = count << 2;
258        buf[pkt_len - 1] = 0;
259
260        /* compute fcs and insert into trailer */
261        fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
262        buf[pkt_len - 2] |= fcs >> 8;
263        buf[pkt_len - 1] |= fcs & 0xff;
264
265        return pkt_len;
266}
267
268static int safe_startup(struct usb_serial *serial)
269{
270        struct usb_interface_descriptor *desc;
271
272        if (serial->dev->descriptor.bDeviceClass != CDC_DEVICE_CLASS)
273                return -ENODEV;
274
275        desc = &serial->interface->cur_altsetting->desc;
276
277        if (desc->bInterfaceClass != LINEO_INTERFACE_CLASS)
278                return -ENODEV;
279        if (desc->bInterfaceSubClass != LINEO_INTERFACE_SUBCLASS_SAFESERIAL)
280                return -ENODEV;
281
282        switch (desc->bInterfaceProtocol) {
283        case LINEO_SAFESERIAL_CRC:
284                break;
285        case LINEO_SAFESERIAL_CRC_PADDED:
286                padded = 1;
287                break;
288        default:
289                return -EINVAL;
290        }
291        return 0;
292}
293
294static struct usb_serial_driver safe_device = {
295        .driver = {
296                .owner =        THIS_MODULE,
297                .name =         "safe_serial",
298        },
299        .id_table =             id_table,
300        .num_ports =            1,
301        .process_read_urb =     safe_process_read_urb,
302        .prepare_write_buffer = safe_prepare_write_buffer,
303        .attach =               safe_startup,
304};
305
306static struct usb_serial_driver * const serial_drivers[] = {
307        &safe_device, NULL
308};
309
310module_usb_serial_driver(serial_drivers, id_table);
Note: See TracBrowser for help on using the repository browser.