1 | // SPDX-License-Identifier: GPL-2.0+ |
2 | /* |
3 | * Safe Encapsulated USB Serial Driver |
4 | * |
5 | * Copyright (C) 2010 Johan Hovold <jhovold@gmail.com> |
6 | * Copyright (C) 2001 Lineo |
7 | * Copyright (C) 2001 Hewlett-Packard |
8 | * |
9 | * By: |
10 | * Stuart Lynne <sl@lineo.com>, Tom Rushworth <tbr@lineo.com> |
11 | */ |
12 | |
13 | /* |
14 | * The encapsultaion is designed to overcome difficulties with some USB |
15 | * hardware. |
16 | * |
17 | * While the USB protocol has a CRC over the data while in transit, i.e. while |
18 | * being carried over the bus, there is no end to end protection. If the |
19 | * hardware has any problems getting the data into or out of the USB transmit |
20 | * and receive FIFO's then data can be lost. |
21 | * |
22 | * This protocol adds a two byte trailer to each USB packet to specify the |
23 | * number of bytes of valid data and a 10 bit CRC that will allow the receiver |
24 | * to verify that the entire USB packet was received without error. |
25 | * |
26 | * Because in this case the sender and receiver are the class and function |
27 | * drivers there is now end to end protection. |
28 | * |
29 | * There is an additional option that can be used to force all transmitted |
30 | * packets to be padded to the maximum packet size. This provides a work |
31 | * around for some devices which have problems with small USB packets. |
32 | * |
33 | * Assuming a packetsize of N: |
34 | * |
35 | * 0..N-2 data and optional padding |
36 | * |
37 | * N-2 bits 7-2 - number of bytes of valid data |
38 | * bits 1-0 top two bits of 10 bit CRC |
39 | * N-1 bottom 8 bits of 10 bit CRC |
40 | * |
41 | * |
42 | * | Data Length | 10 bit CRC | |
43 | * + 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 | 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 + |
44 | * |
45 | * The 10 bit CRC is computed across the sent data, followed by the trailer |
46 | * with the length set and the CRC set to zero. The CRC is then OR'd into |
47 | * the trailer. |
48 | * |
49 | * When received a 10 bit CRC is computed over the entire frame including |
50 | * the trailer and should be equal to zero. |
51 | * |
52 | * Two module parameters are used to control the encapsulation, if both are |
53 | * turned of the module works as a simple serial device with NO |
54 | * encapsulation. |
55 | * |
56 | * See linux/drivers/usbd/serial_fd for a device function driver |
57 | * implementation of this. |
58 | * |
59 | */ |
60 | |
61 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
62 | |
63 | #include <linux/kernel.h> |
64 | #include <linux/errno.h> |
65 | #include <linux/gfp.h> |
66 | #include <linux/tty.h> |
67 | #include <linux/tty_driver.h> |
68 | #include <linux/tty_flip.h> |
69 | #include <linux/module.h> |
70 | #include <linux/spinlock.h> |
71 | #include <linux/uaccess.h> |
72 | #include <linux/usb.h> |
73 | #include <linux/usb/serial.h> |
74 | |
75 | static bool safe = true; |
76 | static bool padded = IS_ENABLED(CONFIG_USB_SERIAL_SAFE_PADDED); |
77 | |
78 | #define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com, Johan Hovold <jhovold@gmail.com>" |
79 | #define DRIVER_DESC "USB Safe Encapsulated Serial" |
80 | |
81 | MODULE_AUTHOR(DRIVER_AUTHOR); |
82 | MODULE_DESCRIPTION(DRIVER_DESC); |
83 | MODULE_LICENSE("GPL" ); |
84 | |
85 | module_param(safe, bool, 0); |
86 | MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off" ); |
87 | |
88 | module_param(padded, bool, 0); |
89 | MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off" ); |
90 | |
91 | #define CDC_DEVICE_CLASS 0x02 |
92 | |
93 | #define CDC_INTERFACE_CLASS 0x02 |
94 | #define CDC_INTERFACE_SUBCLASS 0x06 |
95 | |
96 | #define LINEO_INTERFACE_CLASS 0xff |
97 | |
98 | #define LINEO_INTERFACE_SUBCLASS_SAFENET 0x01 |
99 | #define LINEO_SAFENET_CRC 0x01 |
100 | #define LINEO_SAFENET_CRC_PADDED 0x02 |
101 | |
102 | #define LINEO_INTERFACE_SUBCLASS_SAFESERIAL 0x02 |
103 | #define LINEO_SAFESERIAL_CRC 0x01 |
104 | #define LINEO_SAFESERIAL_CRC_PADDED 0x02 |
105 | |
106 | |
107 | #define MY_USB_DEVICE(vend, prod, dc, ic, isc) \ |
108 | .match_flags = USB_DEVICE_ID_MATCH_DEVICE | \ |
109 | USB_DEVICE_ID_MATCH_DEV_CLASS | \ |
110 | USB_DEVICE_ID_MATCH_INT_CLASS | \ |
111 | USB_DEVICE_ID_MATCH_INT_SUBCLASS, \ |
112 | .idVendor = (vend), \ |
113 | .idProduct = (prod),\ |
114 | .bDeviceClass = (dc),\ |
115 | .bInterfaceClass = (ic), \ |
116 | .bInterfaceSubClass = (isc), |
117 | |
118 | static const struct usb_device_id id_table[] = { |
119 | {MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Itsy */ |
120 | {MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Calypso */ |
121 | {MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Iris */ |
122 | {MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */ |
123 | {MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */ |
124 | {MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */ |
125 | {MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Sharp tmp */ |
126 | {} /* terminating entry */ |
127 | }; |
128 | |
129 | MODULE_DEVICE_TABLE(usb, id_table); |
130 | |
131 | static const __u16 crc10_table[256] = { |
132 | 0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff, |
133 | 0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe, |
134 | 0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce, |
135 | 0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf, |
136 | 0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d, |
137 | 0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c, |
138 | 0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac, |
139 | 0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad, |
140 | 0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b, |
141 | 0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a, |
142 | 0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a, |
143 | 0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b, |
144 | 0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259, |
145 | 0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158, |
146 | 0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268, |
147 | 0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169, |
148 | 0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377, |
149 | 0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076, |
150 | 0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346, |
151 | 0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047, |
152 | 0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315, |
153 | 0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014, |
154 | 0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324, |
155 | 0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025, |
156 | 0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3, |
157 | 0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2, |
158 | 0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382, |
159 | 0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083, |
160 | 0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1, |
161 | 0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0, |
162 | 0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0, |
163 | 0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1, |
164 | }; |
165 | |
166 | #define CRC10_INITFCS 0x000 /* Initial FCS value */ |
167 | #define CRC10_GOODFCS 0x000 /* Good final FCS value */ |
168 | #define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c)) |
169 | |
170 | /** |
171 | * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer |
172 | * @sp: pointer to buffer |
173 | * @len: number of bytes |
174 | * @fcs: starting FCS |
175 | * |
176 | * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return |
177 | * new 10 bit FCS. |
178 | */ |
179 | static inline __u16 fcs_compute10(unsigned char *sp, int len, __u16 fcs) |
180 | { |
181 | for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++)); |
182 | return fcs; |
183 | } |
184 | |
185 | static void safe_process_read_urb(struct urb *urb) |
186 | { |
187 | struct usb_serial_port *port = urb->context; |
188 | unsigned char *data = urb->transfer_buffer; |
189 | unsigned char length = urb->actual_length; |
190 | int actual_length; |
191 | __u16 fcs; |
192 | |
193 | if (!length) |
194 | return; |
195 | |
196 | if (!safe) |
197 | goto out; |
198 | |
199 | if (length < 2) { |
200 | dev_err(&port->dev, "malformed packet\n" ); |
201 | return; |
202 | } |
203 | |
204 | fcs = fcs_compute10(sp: data, len: length, CRC10_INITFCS); |
205 | if (fcs) { |
206 | dev_err(&port->dev, "%s - bad CRC %x\n" , __func__, fcs); |
207 | return; |
208 | } |
209 | |
210 | actual_length = data[length - 2] >> 2; |
211 | if (actual_length > (length - 2)) { |
212 | dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n" , |
213 | __func__, actual_length, length); |
214 | return; |
215 | } |
216 | dev_info(&urb->dev->dev, "%s - actual: %d\n" , __func__, actual_length); |
217 | length = actual_length; |
218 | out: |
219 | tty_insert_flip_string(port: &port->port, chars: data, size: length); |
220 | tty_flip_buffer_push(port: &port->port); |
221 | } |
222 | |
223 | static int safe_prepare_write_buffer(struct usb_serial_port *port, |
224 | void *dest, size_t size) |
225 | { |
226 | unsigned char *buf = dest; |
227 | int count; |
228 | int trailer_len; |
229 | int pkt_len; |
230 | __u16 fcs; |
231 | |
232 | trailer_len = safe ? 2 : 0; |
233 | |
234 | count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len, |
235 | &port->lock); |
236 | if (!safe) |
237 | return count; |
238 | |
239 | /* pad if necessary */ |
240 | if (padded) { |
241 | pkt_len = size; |
242 | memset(buf + count, '0', pkt_len - count - trailer_len); |
243 | } else { |
244 | pkt_len = count + trailer_len; |
245 | } |
246 | |
247 | /* set count */ |
248 | buf[pkt_len - 2] = count << 2; |
249 | buf[pkt_len - 1] = 0; |
250 | |
251 | /* compute fcs and insert into trailer */ |
252 | fcs = fcs_compute10(sp: buf, len: pkt_len, CRC10_INITFCS); |
253 | buf[pkt_len - 2] |= fcs >> 8; |
254 | buf[pkt_len - 1] |= fcs & 0xff; |
255 | |
256 | return pkt_len; |
257 | } |
258 | |
259 | static int safe_startup(struct usb_serial *serial) |
260 | { |
261 | struct usb_interface_descriptor *desc; |
262 | |
263 | if (serial->dev->descriptor.bDeviceClass != CDC_DEVICE_CLASS) |
264 | return -ENODEV; |
265 | |
266 | desc = &serial->interface->cur_altsetting->desc; |
267 | |
268 | if (desc->bInterfaceClass != LINEO_INTERFACE_CLASS) |
269 | return -ENODEV; |
270 | if (desc->bInterfaceSubClass != LINEO_INTERFACE_SUBCLASS_SAFESERIAL) |
271 | return -ENODEV; |
272 | |
273 | switch (desc->bInterfaceProtocol) { |
274 | case LINEO_SAFESERIAL_CRC: |
275 | break; |
276 | case LINEO_SAFESERIAL_CRC_PADDED: |
277 | padded = true; |
278 | break; |
279 | default: |
280 | return -EINVAL; |
281 | } |
282 | return 0; |
283 | } |
284 | |
285 | static struct usb_serial_driver safe_device = { |
286 | .driver = { |
287 | .owner = THIS_MODULE, |
288 | .name = "safe_serial" , |
289 | }, |
290 | .id_table = id_table, |
291 | .num_ports = 1, |
292 | .process_read_urb = safe_process_read_urb, |
293 | .prepare_write_buffer = safe_prepare_write_buffer, |
294 | .attach = safe_startup, |
295 | }; |
296 | |
297 | static struct usb_serial_driver * const serial_drivers[] = { |
298 | &safe_device, NULL |
299 | }; |
300 | |
301 | module_usb_serial_driver(serial_drivers, id_table); |
302 | |