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/init.h>
  71 #include <linux/tty.h>
  72 #include <linux/tty_driver.h>
  73 #include <linux/tty_flip.h>
  74 #include <linux/module.h>
  75 #include <linux/spinlock.h>
  76 #include <linux/uaccess.h>
  77 #include <linux/usb.h>
  78 #include <linux/usb/serial.h>
  79
  80
  81 #ifndef CONFIG_USB_SERIAL_SAFE_PADDED
  82 #define CONFIG_USB_SERIAL_SAFE_PADDED 0
  83 #endif
  84
  85 static bool safe = 1;
  86 static bool padded = CONFIG_USB_SERIAL_SAFE_PADDED;
  87
  88 #define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com, Johan Hovold <jhovold@gmail.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(safe, bool, 0);
 103 MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");
 104
 105 module_param(padded, bool, 0);
 106 MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off");
 107
 108 #define CDC_DEVICE_CLASS                        0x02
 109
 110 #define CDC_INTERFACE_CLASS                     0x02
 111 #define CDC_INTERFACE_SUBCLASS                  0x06
 112
 113 #define LINEO_INTERFACE_CLASS                   0xff
 114
 115 #define LINEO_INTERFACE_SUBCLASS_SAFENET        0x01
 116 #define LINEO_SAFENET_CRC                       0x01
 117 #define LINEO_SAFENET_CRC_PADDED                0x02
 118
 119 #define LINEO_INTERFACE_SUBCLASS_SAFESERIAL     0x02
 120 #define LINEO_SAFESERIAL_CRC                    0x01
 121 #define LINEO_SAFESERIAL_CRC_PADDED             0x02
 122
 123
 124 #define MY_USB_DEVICE(vend, prod, dc, ic, isc) \
 125         .match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
 126                        USB_DEVICE_ID_MATCH_DEV_CLASS | \
 127                        USB_DEVICE_ID_MATCH_INT_CLASS | \
 128                        USB_DEVICE_ID_MATCH_INT_SUBCLASS, \
 129         .idVendor = (vend), \
 130         .idProduct = (prod),\
 131         .bDeviceClass = (dc),\
 132         .bInterfaceClass = (ic), \
 133         .bInterfaceSubClass = (isc),
 134
 135 static struct usb_device_id id_table[] = {
 136         {MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Itsy */
 137         {MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Calypso */
 138         {MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Iris */
 139         {MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
 140         {MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
 141         {MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
 142         {MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Sharp tmp */
 143         /* extra null entry for module vendor/produc parameters */
 144         {MY_USB_DEVICE(0, 0, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},
 145         {}                      /* terminating entry  */
 146 };
 147
 148 MODULE_DEVICE_TABLE(usb, id_table);
 149
 150 static const __u16 crc10_table[256] = {
 151         0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
 152         0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
 153         0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
 154         0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
 155         0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
 156         0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
 157         0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
 158         0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
 159         0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
 160         0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
 161         0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
 162         0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
 163         0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
 164         0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
 165         0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
 166         0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
 167         0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
 168         0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
 169         0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
 170         0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
 171         0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
 172         0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
 173         0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
 174         0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
 175         0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
 176         0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
 177         0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
 178         0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
 179         0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
 180         0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
 181         0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
 182         0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
 183 };
 184
 185 #define CRC10_INITFCS     0x000 /* Initial FCS value */
 186 #define CRC10_GOODFCS     0x000 /* Good final FCS value */
 187 #define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))
 188
 189 /**
 190  * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
 191  * @sp: pointer to buffer
 192  * @len: number of bytes
 193  * @fcs: starting FCS
 194  *
 195  * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
 196  * new 10 bit FCS.
 197  */
 198 static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
 199 {
 200         for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
 201         return fcs;
 202 }
 203
 204 static void safe_process_read_urb(struct urb *urb)
 205 {
 206         struct usb_serial_port *port = urb->context;
 207         unsigned char *data = urb->transfer_buffer;
 208         unsigned char length = urb->actual_length;
 209         int actual_length;
 210         __u16 fcs;
 211
 212         if (!length)
 213                 return;
 214
 215         if (!safe)
 216                 goto out;
 217
 218         fcs = fcs_compute10(data, length, CRC10_INITFCS);
 219         if (fcs) {
 220                 dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
 221                 return;
 222         }
 223
 224         actual_length = data[length - 2] >> 2;
 225         if (actual_length > (length - 2)) {
 226                 dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
 227                                 __func__, actual_length, length);
 228                 return;
 229         }
 230         dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
 231         length = actual_length;
 232 out:
 233         tty_insert_flip_string(&port->port, data, length);
 234         tty_flip_buffer_push(&port->port);
 235 }
 236
 237 static int safe_prepare_write_buffer(struct usb_serial_port *port,
 238                                                 void *dest, size_t size)
 239 {
 240         unsigned char *buf = dest;
 241         int count;
 242         int trailer_len;
 243         int pkt_len;
 244         __u16 fcs;
 245
 246         trailer_len = safe ? 2 : 0;
 247
 248         count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
 249                                                                 &port->lock);
 250         if (!safe)
 251                 return count;
 252
 253         /* pad if necessary */
 254         if (padded) {
 255                 pkt_len = size;
 256                 memset(buf + count, '0', pkt_len - count - trailer_len);
 257         } else {
 258                 pkt_len = count + trailer_len;
 259         }
 260
 261         /* set count */
 262         buf[pkt_len - 2] = count << 2;
 263         buf[pkt_len - 1] = 0;
 264
 265         /* compute fcs and insert into trailer */
 266         fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
 267         buf[pkt_len - 2] |= fcs >> 8;
 268         buf[pkt_len - 1] |= fcs & 0xff;
 269
 270         return pkt_len;
 271 }
 272
 273 static int safe_startup(struct usb_serial *serial)
 274 {
 275         switch (serial->interface->cur_altsetting->desc.bInterfaceProtocol) {
 276         case LINEO_SAFESERIAL_CRC:
 277                 break;
 278         case LINEO_SAFESERIAL_CRC_PADDED:
 279                 padded = 1;
 280                 break;
 281         default:
 282                 return -EINVAL;
 283         }
 284         return 0;
 285 }
 286
 287 static struct usb_serial_driver safe_device = {
 288         .driver = {
 289                 .owner =        THIS_MODULE,
 290                 .name =         "safe_serial",
 291         },
 292         .id_table =             id_table,
 293         .num_ports =            1,
 294         .process_read_urb =     safe_process_read_urb,
 295         .prepare_write_buffer = safe_prepare_write_buffer,
 296         .attach =               safe_startup,
 297 };
 298
 299 static struct usb_serial_driver * const serial_drivers[] = {
 300         &safe_device, NULL
 301 };
 302
 303 static int __init safe_init(void)
 304 {
 305         int i;
 306
 307         /* if we have vendor / product parameters patch them into id list */
 308         if (vendor || product) {
 309                 pr_info("vendor: %x product: %x\n", vendor, product);
 310
 311                 for (i = 0; i < ARRAY_SIZE(id_table); i++) {
 312                         if (!id_table[i].idVendor && !id_table[i].idProduct) {
 313                                 id_table[i].idVendor = vendor;
 314                                 id_table[i].idProduct = product;
 315                                 break;
 316                         }
 317                 }
 318         }
 319
 320         return usb_serial_register_drivers(serial_drivers, KBUILD_MODNAME, id_table);
 321 }
 322
 323 static void __exit safe_exit(void)
 324 {
 325         usb_serial_deregister_drivers(serial_drivers);
 326 }
 327
 328 module_init(safe_init);
 329 module_exit(safe_exit);