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 bool debug;
  85 static bool safe = 1;
  86 static bool 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 const __u16 crc10_table[256] = {
 155         0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
 156         0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
 157         0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
 158         0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
 159         0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
 160         0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
 161         0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
 162         0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
 163         0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
 164         0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
 165         0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
 166         0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
 167         0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
 168         0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
 169         0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
 170         0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
 171         0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
 172         0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
 173         0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
 174         0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
 175         0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
 176         0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
 177         0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
 178         0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
 179         0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
 180         0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
 181         0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
 182         0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
 183         0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
 184         0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
 185         0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
 186         0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
 187 };
 188
 189 #define CRC10_INITFCS     0x000 /* Initial FCS value */
 190 #define CRC10_GOODFCS     0x000 /* Good final FCS value */
 191 #define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))
 192
 193 /**
 194  * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
 195  * @sp: pointer to buffer
 196  * @len: number of bytes
 197  * @fcs: starting FCS
 198  *
 199  * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
 200  * new 10 bit FCS.
 201  */
 202 static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
 203 {
 204         for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
 205         return fcs;
 206 }
 207
 208 static void safe_process_read_urb(struct urb *urb)
 209 {
 210         struct usb_serial_port *port = urb->context;
 211         unsigned char *data = urb->transfer_buffer;
 212         unsigned char length = urb->actual_length;
 213         int actual_length;
 214         struct tty_struct *tty;
 215         __u16 fcs;
 216
 217         if (!length)
 218                 return;
 219
 220         tty = tty_port_tty_get(&port->port);
 221         if (!tty)
 222                 return;
 223
 224         if (!safe)
 225                 goto out;
 226
 227         fcs = fcs_compute10(data, length, CRC10_INITFCS);
 228         if (fcs) {
 229                 dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
 230                 goto err;
 231         }
 232
 233         actual_length = data[length - 2] >> 2;
 234         if (actual_length > (length - 2)) {
 235                 dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
 236                                 __func__, actual_length, length);
 237                 goto err;
 238         }
 239         dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
 240         length = actual_length;
 241 out:
 242         tty_insert_flip_string(tty, data, length);
 243         tty_flip_buffer_push(tty);
 244 err:
 245         tty_kref_put(tty);
 246 }
 247
 248 static int safe_prepare_write_buffer(struct usb_serial_port *port,
 249                                                 void *dest, size_t size)
 250 {
 251         unsigned char *buf = dest;
 252         int count;
 253         int trailer_len;
 254         int pkt_len;
 255         __u16 fcs;
 256
 257         trailer_len = safe ? 2 : 0;
 258
 259         count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
 260                                                                 &port->lock);
 261         if (!safe)
 262                 return count;
 263
 264         /* pad if necessary */
 265         if (padded) {
 266                 pkt_len = size;
 267                 memset(buf + count, '0', pkt_len - count - trailer_len);
 268         } else {
 269                 pkt_len = count + trailer_len;
 270         }
 271
 272         /* set count */
 273         buf[pkt_len - 2] = count << 2;
 274         buf[pkt_len - 1] = 0;
 275
 276         /* compute fcs and insert into trailer */
 277         fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
 278         buf[pkt_len - 2] |= fcs >> 8;
 279         buf[pkt_len - 1] |= fcs & 0xff;
 280
 281         return pkt_len;
 282 }
 283
 284 static int safe_startup(struct usb_serial *serial)
 285 {
 286         switch (serial->interface->cur_altsetting->desc.bInterfaceProtocol) {
 287         case LINEO_SAFESERIAL_CRC:
 288                 break;
 289         case LINEO_SAFESERIAL_CRC_PADDED:
 290                 padded = 1;
 291                 break;
 292         default:
 293                 return -EINVAL;
 294         }
 295         return 0;
 296 }
 297
 298 static struct usb_serial_driver safe_device = {
 299         .driver = {
 300                 .owner =        THIS_MODULE,
 301                 .name =         "safe_serial",
 302         },
 303         .id_table =             id_table,
 304         .num_ports =            1,
 305         .process_read_urb =     safe_process_read_urb,
 306         .prepare_write_buffer = safe_prepare_write_buffer,
 307         .attach =               safe_startup,
 308 };
 309
 310 static struct usb_serial_driver * const serial_drivers[] = {
 311         &safe_device, NULL
 312 };
 313
 314 static int __init safe_init(void)
 315 {
 316         int i;
 317
 318         printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_VERSION ":"
 319                DRIVER_DESC "\n");
 320
 321         /* if we have vendor / product parameters patch them into id list */
 322         if (vendor || product) {
 323                 printk(KERN_INFO KBUILD_MODNAME ": vendor: %x product: %x\n",
 324                        vendor, product);
 325
 326                 for (i = 0; i < ARRAY_SIZE(id_table); i++) {
 327                         if (!id_table[i].idVendor && !id_table[i].idProduct) {
 328                                 id_table[i].idVendor = vendor;
 329                                 id_table[i].idProduct = product;
 330                                 break;
 331                         }
 332                 }
 333         }
 334
 335         return usb_serial_register_drivers(serial_drivers, KBUILD_MODNAME, id_table);
 336 }
 337
 338 static void __exit safe_exit(void)
 339 {
 340         usb_serial_deregister_drivers(serial_drivers);
 341 }
 342
 343 module_init(safe_init);
 344 module_exit(safe_exit);