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); 362