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
  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 int debug;
  85 static int safe = 1;
  86 static int 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         .no_dynamic_id =        1,
 160 };
 161
 162 static const __u16 crc10_table[256] = {
 163         0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
 164         0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
 165         0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
 166         0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
 167         0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
 168         0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
 169         0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
 170         0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
 171         0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
 172         0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
 173         0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
 174         0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
 175         0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
 176         0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
 177         0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
 178         0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
 179         0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
 180         0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
 181         0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
 182         0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
 183         0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
 184         0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
 185         0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
 186         0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
 187         0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
 188         0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
 189         0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
 190         0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
 191         0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
 192         0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
 193         0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
 194         0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
 195 };
 196
 197 #define CRC10_INITFCS     0x000 /* Initial FCS value */
 198 #define CRC10_GOODFCS     0x000 /* Good final FCS value */
 199 #define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))
 200
 201 /**
 202  * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
 203  * @sp: pointer to buffer
 204  * @len: number of bytes
 205  * @fcs: starting FCS
 206  *
 207  * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
 208  * new 10 bit FCS.
 209  */
 210 static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
 211 {
 212         for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
 213         return fcs;
 214 }
 215
 216 static void safe_process_read_urb(struct urb *urb)
 217 {
 218         struct usb_serial_port *port = urb->context;
 219         unsigned char *data = urb->transfer_buffer;
 220         unsigned char length = urb->actual_length;
 221         int actual_length;
 222         struct tty_struct *tty;
 223         __u16 fcs;
 224
 225         if (!length)
 226                 return;
 227
 228         tty = tty_port_tty_get(&port->port);
 229         if (!tty)
 230                 return;
 231
 232         if (!safe)
 233                 goto out;
 234
 235         fcs = fcs_compute10(data, length, CRC10_INITFCS);
 236         if (fcs) {
 237                 dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
 238                 goto err;
 239         }
 240
 241         actual_length = data[length - 2] >> 2;
 242         if (actual_length > (length - 2)) {
 243                 dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
 244                                 __func__, actual_length, length);
 245                 goto err;
 246         }
 247         dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
 248         length = actual_length;
 249 out:
 250         tty_insert_flip_string(tty, data, length);
 251         tty_flip_buffer_push(tty);
 252 err:
 253         tty_kref_put(tty);
 254 }
 255
 256 static int safe_prepare_write_buffer(struct usb_serial_port *port,
 257                                                 void *dest, size_t size)
 258 {
 259         unsigned char *buf = dest;
 260         int count;
 261         int trailer_len;
 262         int pkt_len;
 263         __u16 fcs;
 264
 265         trailer_len = safe ? 2 : 0;
 266
 267         count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
 268                                                                 &port->lock);
 269         if (!safe)
 270                 return count;
 271
 272         /* pad if necessary */
 273         if (padded) {
 274                 pkt_len = size;
 275                 memset(buf + count, '0', pkt_len - count - trailer_len);
 276         } else {
 277                 pkt_len = count + trailer_len;
 278         }
 279
 280         /* set count */
 281         buf[pkt_len - 2] = count << 2;
 282         buf[pkt_len - 1] = 0;
 283
 284         /* compute fcs and insert into trailer */
 285         fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
 286         buf[pkt_len - 2] |= fcs >> 8;
 287         buf[pkt_len - 1] |= fcs & 0xff;
 288
 289         return pkt_len;
 290 }
 291
 292 static int safe_startup(struct usb_serial *serial)
 293 {
 294         switch (serial->interface->cur_altsetting->desc.bInterfaceProtocol) {
 295         case LINEO_SAFESERIAL_CRC:
 296                 break;
 297         case LINEO_SAFESERIAL_CRC_PADDED:
 298                 padded = 1;
 299                 break;
 300         default:
 301                 return -EINVAL;
 302         }
 303         return 0;
 304 }
 305
 306 static struct usb_serial_driver safe_device = {
 307         .driver = {
 308                 .owner =        THIS_MODULE,
 309                 .name =         "safe_serial",
 310         },
 311         .id_table =             id_table,
 312         .usb_driver =           &safe_driver,
 313         .num_ports =            1,
 314         .process_read_urb =     safe_process_read_urb,
 315         .prepare_write_buffer = safe_prepare_write_buffer,
 316         .attach =               safe_startup,
 317 };
 318
 319 static int __init safe_init(void)
 320 {
 321         int i, retval;
 322
 323         printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_VERSION ":"
 324                DRIVER_DESC "\n");
 325
 326         /* if we have vendor / product parameters patch them into id list */
 327         if (vendor || product) {
 328                 printk(KERN_INFO KBUILD_MODNAME ": vendor: %x product: %x\n",
 329                        vendor, product);
 330
 331                 for (i = 0; i < ARRAY_SIZE(id_table); i++) {
 332                         if (!id_table[i].idVendor && !id_table[i].idProduct) {
 333                                 id_table[i].idVendor = vendor;
 334                                 id_table[i].idProduct = product;
 335                                 break;
 336                         }
 337                 }
 338         }
 339
 340         retval = usb_serial_register(&safe_device);
 341         if (retval)
 342                 goto failed_usb_serial_register;
 343         retval = usb_register(&safe_driver);
 344         if (retval)
 345                 goto failed_usb_register;
 346
 347         return 0;
 348 failed_usb_register:
 349         usb_serial_deregister(&safe_device);
 350 failed_usb_serial_register:
 351         return retval;
 352 }
 353
 354 static void __exit safe_exit(void)
 355 {
 356         usb_deregister(&safe_driver);
 357         usb_serial_deregister(&safe_device);
 358 }
 359
 360 module_init(safe_init);
 361 module_exit(safe_exit);