drivers/usb/serial/safe_serial.c

   1 /*
   2  * Safe Encapsulated USB Serial Driver
   3  *
   4  *      Copyright (C) 2001 Lineo
   5  *      Copyright (C) 2001 Hewlett-Packard
   6  *
   7  *      This program is free software; you can redistribute it and/or modify
   8  *      it under the terms of the GNU General Public License as published by
   9  *      the Free Software Foundation; either version 2 of the License, or
  10  *      (at your option) any later version.
  11  *
  12  * By:
  13  *      Stuart Lynne <sl@lineo.com>, Tom Rushworth <tbr@lineo.com>
  14  */
  15
  16 /*
  17  * The encapsultaion is designed to overcome difficulties with some USB
  18  * hardware.
  19  *
  20  * While the USB protocol has a CRC over the data while in transit, i.e. while
  21  * being carried over the bus, there is no end to end protection. If the
  22  * hardware has any problems getting the data into or out of the USB transmit
  23  * and receive FIFO's then data can be lost.
  24  *
  25  * This protocol adds a two byte trailer to each USB packet to specify the
  26  * number of bytes of valid data and a 10 bit CRC that will allow the receiver
  27  * to verify that the entire USB packet was received without error.
  28  *
  29  * Because in this case the sender and receiver are the class and function
  30  * drivers there is now end to end protection.
  31  *
  32  * There is an additional option that can be used to force all transmitted
  33  * packets to be padded to the maximum packet size. This provides a work
  34  * around for some devices which have problems with small USB packets.
  35  *
  36  * Assuming a packetsize of N:
  37  *
  38  *      0..N-2  data and optional padding
  39  *
  40  *      N-2     bits 7-2 - number of bytes of valid data
  41  *              bits 1-0 top two bits of 10 bit CRC
  42  *      N-1     bottom 8 bits of 10 bit CRC
  43  *
  44  *
  45  *      | Data Length       | 10 bit CRC                                |
  46  *      + 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 | 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 +
  47  *
  48  * The 10 bit CRC is computed across the sent data, followed by the trailer
  49  * with the length set and the CRC set to zero. The CRC is then OR'd into
  50  * the trailer.
  51  *
  52  * When received a 10 bit CRC is computed over the entire frame including
  53  * the trailer and should be equal to zero.
  54  *
  55  * Two module parameters are used to control the encapsulation, if both are
  56  * turned of the module works as a simple serial device with NO
  57  * encapsulation.
  58  *
  59  * See linux/drivers/usbd/serial_fd for a device function driver
  60  * implementation of this.
  61  *
  62  */
  63
  64
  65 #include <linux/kernel.h>
  66 #include <linux/errno.h>
  67 #include <linux/init.h>
  68 #include <linux/slab.h>
  69 #include <linux/tty.h>
  70 #include <linux/tty_driver.h>
  71 #include <linux/tty_flip.h>
  72 #include <linux/module.h>
  73 #include <linux/spinlock.h>
  74 #include <linux/uaccess.h>
  75 #include <linux/usb.h>
  76 #include <linux/usb/serial.h>
  77
  78
  79 #ifndef CONFIG_USB_SERIAL_SAFE_PADDED
  80 #define CONFIG_USB_SERIAL_SAFE_PADDED 0
  81 #endif
  82
  83 static int debug;
  84 static int safe = 1;
  85 static int padded = CONFIG_USB_SERIAL_SAFE_PADDED;
  86
  87 #define DRIVER_VERSION "v0.0b"
  88 #define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com"
  89 #define DRIVER_DESC "USB Safe Encapsulated Serial"
  90
  91 MODULE_AUTHOR(DRIVER_AUTHOR);
  92 MODULE_DESCRIPTION(DRIVER_DESC);
  93 MODULE_LICENSE("GPL");
  94
  95 static __u16 vendor;            /* no default */
  96 static __u16 product;           /* no default */
  97 module_param(vendor, ushort, 0);
  98 MODULE_PARM_DESC(vendor, "User specified USB idVendor (required)");
  99 module_param(product, ushort, 0);
 100 MODULE_PARM_DESC(product, "User specified USB idProduct (required)");
 101
 102 module_param(debug, bool, S_IRUGO | S_IWUSR);
 103 MODULE_PARM_DESC(debug, "Debug enabled or not");
 104
 105 module_param(safe, bool, 0);
 106 MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");
 107
 108 module_param(padded, bool, 0);
 109 MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off");
 110
 111 #define CDC_DEVICE_CLASS                        0x02
 112
 113 #define CDC_INTERFACE_CLASS                     0x02
 114 #define CDC_INTERFACE_SUBCLASS                  0x06
 115
 116 #define LINEO_INTERFACE_CLASS                   0xff
 117
 118 #define LINEO_INTERFACE_SUBCLASS_SAFENET        0x01
 119 #define LINEO_SAFENET_CRC                       0x01
 120 #define LINEO_SAFENET_CRC_PADDED                0x02
 121
 122 #define LINEO_INTERFACE_SUBCLASS_SAFESERIAL     0x02
 123 #define LINEO_SAFESERIAL_CRC                    0x01
 124 #define LINEO_SAFESERIAL_CRC_PADDED             0x02
 125
 126
 127 #define MY_USB_DEVICE(vend, prod, dc, ic, isc) \
 128         .match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
 129                        USB_DEVICE_ID_MATCH_DEV_CLASS | \
 130                        USB_DEVICE_ID_MATCH_INT_CLASS | \
 131                        USB_DEVICE_ID_MATCH_INT_SUBCLASS, \
 132         .idVendor = (vend), \
 133         .idProduct = (prod),\
 134         .bDeviceClass = (dc),\
 135         .bInterfaceClass = (ic), \
 136         .bInterfaceSubClass = (isc),
 137
 138 static struct usb_device_id id_table[] = {
 139         {MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Itsy */
 140         {MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Calypso */
 141         {MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Iris */
 142         {MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
 143         {MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
 144         {MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
 145         {MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Sharp tmp */
 146         /* extra null entry for module vendor/produc parameters */
 147         {MY_USB_DEVICE(0, 0, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},
 148         {}                      /* terminating entry  */
 149 };
 150
 151 MODULE_DEVICE_TABLE(usb, id_table);
 152
 153 static struct usb_driver safe_driver = {
 154         .name =         "safe_serial",
 155         .probe =        usb_serial_probe,
 156         .disconnect =   usb_serial_disconnect,
 157         .id_table =     id_table,
 158         .no_dynamic_id =        1,
 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  */
 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
 215 static void safe_read_bulk_callback(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         struct tty_struct *tty;
 221         int result;
 222         int status = urb->status;
 223
 224         dbg("%s", __func__);
 225
 226         if (status) {
 227                 dbg("%s - nonzero read bulk status received: %d",
 228                     __func__, status);
 229                 return;
 230         }
 231
 232         dbg("safe_read_bulk_callback length: %d",
 233                                         port->read_urb->actual_length);
 234 #ifdef ECHO_RCV
 235         {
 236                 int i;
 237                 unsigned char *cp = port->read_urb->transfer_buffer;
 238                 for (i = 0; i < port->read_urb->actual_length; i++) {
 239                         if ((i % 32) == 0)
 240                                 printk("\nru[%02x] ", i);
 241                         printk("%02x ", *cp++);
 242                 }
 243                 printk("\n");
 244         }
 245 #endif
 246         tty = tty_port_tty_get(&port->port);
 247         if (safe) {
 248                 __u16 fcs;
 249                 fcs = fcs_compute10(data, length, CRC10_INITFCS);
 250                 if (!fcs) {
 251                         int actual_length = data[length - 2] >> 2;
 252                         if (actual_length <= (length - 2)) {
 253                                 dev_info(&urb->dev->dev, "%s - actual: %d\n",
 254                                          __func__, actual_length);
 255                                 tty_insert_flip_string(tty,
 256                                                         data, actual_length);
 257                                 tty_flip_buffer_push(tty);
 258                         } else {
 259                                 err("%s - inconsistent lengths %d:%d",
 260                                         __func__, actual_length, length);
 261                         }
 262                 } else {
 263                         err("%s - bad CRC %x", __func__, fcs);
 264                 }
 265         } else {
 266                 tty_insert_flip_string(tty, data, length);
 267                 tty_flip_buffer_push(tty);
 268         }
 269         tty_kref_put(tty);
 270
 271         /* Continue trying to always read  */
 272         usb_fill_bulk_urb(urb, port->serial->dev,
 273                         usb_rcvbulkpipe(port->serial->dev,
 274                                         port->bulk_in_endpointAddress),
 275                         urb->transfer_buffer, urb->transfer_buffer_length,
 276                         safe_read_bulk_callback, port);
 277
 278         result = usb_submit_urb(urb, GFP_ATOMIC);
 279         if (result)
 280                 err("%s - failed resubmitting read urb, error %d",
 281                                                         __func__, result);
 282                 /* FIXME: Need a mechanism to retry later if this happens */
 283 }
 284
 285 static int safe_write(struct tty_struct *tty, struct usb_serial_port *port,
 286                                         const unsigned char *buf, int count)
 287 {
 288         unsigned char *data;
 289         int result;
 290         int i;
 291         int packet_length;
 292
 293         dbg("safe_write port: %p %d urb: %p count: %d",
 294                                 port, port->number, port->write_urb, count);
 295
 296         if (!port->write_urb) {
 297                 dbg("%s - write urb NULL", __func__);
 298                 return 0;
 299         }
 300
 301         dbg("safe_write write_urb: %d transfer_buffer_length",
 302              port->write_urb->transfer_buffer_length);
 303
 304         if (!port->write_urb->transfer_buffer_length) {
 305                 dbg("%s - write urb transfer_buffer_length zero", __func__);
 306                 return 0;
 307         }
 308         if (count == 0) {
 309                 dbg("%s - write request of 0 bytes", __func__);
 310                 return 0;
 311         }
 312         spin_lock_bh(&port->lock);
 313         if (port->write_urb_busy) {
 314                 spin_unlock_bh(&port->lock);
 315                 dbg("%s - already writing", __func__);
 316                 return 0;
 317         }
 318         port->write_urb_busy = 1;
 319         spin_unlock_bh(&port->lock);
 320
 321         packet_length = port->bulk_out_size;    /* get max packetsize */
 322
 323         i = packet_length - (safe ? 2 : 0);     /* get bytes to send */
 324         count = (count > i) ? i : count;
 325
 326
 327         /* get the data into the transfer buffer */
 328         data = port->write_urb->transfer_buffer;
 329         memset(data, '0', packet_length);
 330
 331         memcpy(data, buf, count);
 332
 333         if (safe) {
 334                 __u16 fcs;
 335
 336                 /* pad if necessary */
 337                 if (!padded)
 338                         packet_length = count + 2;
 339                 /* set count */
 340                 data[packet_length - 2] = count << 2;
 341                 data[packet_length - 1] = 0;
 342
 343                 /* compute fcs and insert into trailer */
 344                 fcs = fcs_compute10(data, packet_length, CRC10_INITFCS);
 345                 data[packet_length - 2] |= fcs >> 8;
 346                 data[packet_length - 1] |= fcs & 0xff;
 347
 348                 /* set length to send */
 349                 port->write_urb->transfer_buffer_length = packet_length;
 350         } else {
 351                 port->write_urb->transfer_buffer_length = count;
 352         }
 353
 354         usb_serial_debug_data(debug, &port->dev, __func__, count,
 355                                         port->write_urb->transfer_buffer);
 356 #ifdef ECHO_TX
 357         {
 358                 int i;
 359                 unsigned char *cp = port->write_urb->transfer_buffer;
 360                 for (i = 0; i < port->write_urb->transfer_buffer_length; i++) {
 361                         if ((i % 32) == 0)
 362                                 printk("\nsu[%02x] ", i);
 363                         printk("%02x ", *cp++);
 364                 }
 365                 printk("\n");
 366         }
 367 #endif
 368         port->write_urb->dev = port->serial->dev;
 369         result = usb_submit_urb(port->write_urb, GFP_KERNEL);
 370         if (result) {
 371                 port->write_urb_busy = 0;
 372                 err("%s - failed submitting write urb, error %d",
 373                                                         __func__, result);
 374                 return 0;
 375         }
 376         dbg("%s urb: %p submitted", __func__, port->write_urb);
 377
 378         return count;
 379 }
 380
 381 static int safe_write_room(struct tty_struct *tty)
 382 {
 383         struct usb_serial_port *port = tty->driver_data;
 384         int room = 0;           /* Default: no room */
 385         unsigned long flags;
 386
 387         dbg("%s", __func__);
 388
 389         spin_lock_irqsave(&port->lock, flags);
 390         if (port->write_urb_busy)
 391                 room = port->bulk_out_size - (safe ? 2 : 0);
 392         spin_unlock_irqrestore(&port->lock, flags);
 393
 394         if (room)
 395                 dbg("safe_write_room returns %d", room);
 396         return room;
 397 }
 398
 399 static int safe_startup(struct usb_serial *serial)
 400 {
 401         switch (serial->interface->cur_altsetting->desc.bInterfaceProtocol) {
 402         case LINEO_SAFESERIAL_CRC:
 403                 break;
 404         case LINEO_SAFESERIAL_CRC_PADDED:
 405                 padded = 1;
 406                 break;
 407         default:
 408                 return -EINVAL;
 409         }
 410         return 0;
 411 }
 412
 413 static struct usb_serial_driver safe_device = {
 414         .driver = {
 415                 .owner =        THIS_MODULE,
 416                 .name =         "safe_serial",
 417         },
 418         .id_table =             id_table,
 419         .usb_driver =           &safe_driver,
 420         .num_ports =            1,
 421         .write =                safe_write,
 422         .write_room =           safe_write_room,
 423         .read_bulk_callback =   safe_read_bulk_callback,
 424         .attach =               safe_startup,
 425 };
 426
 427 static int __init safe_init(void)
 428 {
 429         int i, retval;
 430
 431         printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_VERSION ":"
 432                DRIVER_DESC "\n");
 433
 434         /* if we have vendor / product parameters patch them into id list */
 435         if (vendor || product) {
 436                 printk(KERN_INFO KBUILD_MODNAME ": vendor: %x product: %x\n",
 437                        vendor, product);
 438
 439                 for (i = 0; i < ARRAY_SIZE(id_table); i++) {
 440                         if (!id_table[i].idVendor && !id_table[i].idProduct) {
 441                                 id_table[i].idVendor = vendor;
 442                                 id_table[i].idProduct = product;
 443                                 break;
 444                         }
 445                 }
 446         }
 447
 448         retval = usb_serial_register(&safe_device);
 449         if (retval)
 450                 goto failed_usb_serial_register;
 451         retval = usb_register(&safe_driver);
 452         if (retval)
 453                 goto failed_usb_register;
 454
 455         return 0;
 456 failed_usb_register:
 457         usb_serial_deregister(&safe_device);
 458 failed_usb_serial_register:
 459         return retval;
 460 }
 461
 462 static void __exit safe_exit(void)
 463 {
 464         usb_deregister(&safe_driver);
 465         usb_serial_deregister(&safe_device);
 466 }
 467
 468 module_init(safe_init);
 469 module_exit(safe_exit);