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); 330