Version:  2.0.40 2.2.26 2.4.37 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17

Linux/drivers/usb/serial/safe_serial.c

  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 
 84 static bool safe = 1;
 85 static 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 
 90 MODULE_AUTHOR(DRIVER_AUTHOR);
 91 MODULE_DESCRIPTION(DRIVER_DESC);
 92 MODULE_LICENSE("GPL");
 93 
 94 module_param(safe, bool, 0);
 95 MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");
 96 
 97 module_param(padded, bool, 0);
 98 MODULE_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 
127 static 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 
138 MODULE_DEVICE_TABLE(usb, id_table);
139 
140 static 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  */
188 static __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 
194 static 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         fcs = fcs_compute10(data, length, CRC10_INITFCS);
209         if (fcs) {
210                 dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
211                 return;
212         }
213 
214         actual_length = data[length - 2] >> 2;
215         if (actual_length > (length - 2)) {
216                 dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
217                                 __func__, actual_length, length);
218                 return;
219         }
220         dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
221         length = actual_length;
222 out:
223         tty_insert_flip_string(&port->port, data, length);
224         tty_flip_buffer_push(&port->port);
225 }
226 
227 static int safe_prepare_write_buffer(struct usb_serial_port *port,
228                                                 void *dest, size_t size)
229 {
230         unsigned char *buf = dest;
231         int count;
232         int trailer_len;
233         int pkt_len;
234         __u16 fcs;
235 
236         trailer_len = safe ? 2 : 0;
237 
238         count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
239                                                                 &port->lock);
240         if (!safe)
241                 return count;
242 
243         /* pad if necessary */
244         if (padded) {
245                 pkt_len = size;
246                 memset(buf + count, '', pkt_len - count - trailer_len);
247         } else {
248                 pkt_len = count + trailer_len;
249         }
250 
251         /* set count */
252         buf[pkt_len - 2] = count << 2;
253         buf[pkt_len - 1] = 0;
254 
255         /* compute fcs and insert into trailer */
256         fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
257         buf[pkt_len - 2] |= fcs >> 8;
258         buf[pkt_len - 1] |= fcs & 0xff;
259 
260         return pkt_len;
261 }
262 
263 static int safe_startup(struct usb_serial *serial)
264 {
265         struct usb_interface_descriptor *desc;
266 
267         if (serial->dev->descriptor.bDeviceClass != CDC_DEVICE_CLASS)
268                 return -ENODEV;
269 
270         desc = &serial->interface->cur_altsetting->desc;
271 
272         if (desc->bInterfaceClass != LINEO_INTERFACE_CLASS)
273                 return -ENODEV;
274         if (desc->bInterfaceSubClass != LINEO_INTERFACE_SUBCLASS_SAFESERIAL)
275                 return -ENODEV;
276 
277         switch (desc->bInterfaceProtocol) {
278         case LINEO_SAFESERIAL_CRC:
279                 break;
280         case LINEO_SAFESERIAL_CRC_PADDED:
281                 padded = 1;
282                 break;
283         default:
284                 return -EINVAL;
285         }
286         return 0;
287 }
288 
289 static struct usb_serial_driver safe_device = {
290         .driver = {
291                 .owner =        THIS_MODULE,
292                 .name =         "safe_serial",
293         },
294         .id_table =             id_table,
295         .num_ports =            1,
296         .process_read_urb =     safe_process_read_urb,
297         .prepare_write_buffer = safe_prepare_write_buffer,
298         .attach =               safe_startup,
299 };
300 
301 static struct usb_serial_driver * const serial_drivers[] = {
302         &safe_device, NULL
303 };
304 
305 module_usb_serial_driver(serial_drivers, id_table);
306 

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us