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); 345