drivers/staging/comedi/drivers/ni_usb6501.c

   1 /*
   2  * comedi/drivers/ni_usb6501.c
   3  * Comedi driver for National Instruments USB-6501
   4  *
   5  * COMEDI - Linux Control and Measurement Device Interface
   6  * Copyright (C) 2014 Luca Ellero <luca.ellero@brickedbrain.com>
   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  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  */
  18
  19 /*
  20  * Driver: ni_usb6501
  21  * Description: National Instruments USB-6501 module
  22  * Devices: [National Instruments] USB-6501 (ni_usb6501)
  23  * Author: Luca Ellero <luca.ellero@brickedbrain.com>
  24  * Updated: 8 Sep 2014
  25  * Status: works
  26  *
  27  *
  28  * Configuration Options:
  29  * none
  30  */
  31
  32 /*
  33  * NI-6501 - USB PROTOCOL DESCRIPTION
  34  *
  35  * Every command is composed by two USB packets:
  36  *      - request (out)
  37  *      - response (in)
  38  *
  39  * Every packet is at least 12 bytes long, here is the meaning of
  40  * every field (all values are hex):
  41  *
  42  *      byte 0 is always 00
  43  *      byte 1 is always 01
  44  *      byte 2 is always 00
  45  *      byte 3 is the total packet length
  46  *
  47  *      byte 4 is always 00
  48  *      byte 5 is is the total packet length - 4
  49  *      byte 6 is always 01
  50  *      byte 7 is the command
  51  *
  52  *      byte 8 is 02 (request) or 00 (response)
  53  *      byte 9 is 00 (response) or 10 (port request) or 20 (counter request)
  54  *      byte 10 is always 00
  55  *      byte 11 is 00 (request) or 02 (response)
  56  *
  57  * PORT PACKETS
  58  *
  59  *      CMD: 0xE READ_PORT
  60  *      REQ: 00 01 00 10 00 0C 01 0E 02 10 00 00 00 03 <PORT> 00
  61  *      RES: 00 01 00 10 00 0C 01 00 00 00 00 02 00 03 <BMAP> 00
  62  *
  63  *      CMD: 0xF WRITE_PORT
  64  *      REQ: 00 01 00 14 00 10 01 0F 02 10 00 00 00 03 <PORT> 00 03 <BMAP> 00 00
  65  *      RES: 00 01 00 0C 00 08 01 00 00 00 00 02
  66  *
  67  *      CMD: 0x12 SET_PORT_DIR (0 = input, 1 = output)
  68  *      REQ: 00 01 00 18 00 14 01 12 02 10 00 00
  69  *           00 05 <PORT 0> <PORT 1> <PORT 2> 00 05 00 00 00 00 00
  70  *      RES: 00 01 00 0C 00 08 01 00 00 00 00 02
  71  *
  72  * COUNTER PACKETS
  73  *
  74  *      CMD 0x9: START_COUNTER
  75  *      REQ: 00 01 00 0C 00 08 01 09 02 20 00 00
  76  *      RES: 00 01 00 0C 00 08 01 00 00 00 00 02
  77  *
  78  *      CMD 0xC: STOP_COUNTER
  79  *      REQ: 00 01 00 0C 00 08 01 0C 02 20 00 00
  80  *      RES: 00 01 00 0C 00 08 01 00 00 00 00 02
  81  *
  82  *      CMD 0xE: READ_COUNTER
  83  *      REQ: 00 01 00 0C 00 08 01 0E 02 20 00 00
  84  *      RES: 00 01 00 10 00 0C 01 00 00 00 00 02 <u32 counter value, Big Endian>
  85  *
  86  *      CMD 0xF: WRITE_COUNTER
  87  *      REQ: 00 01 00 10 00 0C 01 0F 02 20 00 00 <u32 counter value, Big Endian>
  88  *      RES: 00 01 00 0C 00 08 01 00 00 00 00 02
  89  *
  90  *
  91  *      Please  visit http://www.brickedbrain.com if you need
  92  *      additional information or have any questions.
  93  *
  94  */
  95
  96 #include <linux/kernel.h>
  97 #include <linux/module.h>
  98 #include <linux/slab.h>
  99 #include <linux/usb.h>
 100
 101 #include "../comedidev.h"
 102
 103 #define NI6501_TIMEOUT  1000
 104
 105 /* Port request packets */
 106 static const u8 READ_PORT_REQUEST[]     = {0x00, 0x01, 0x00, 0x10,
 107                                            0x00, 0x0C, 0x01, 0x0E,
 108                                            0x02, 0x10, 0x00, 0x00,
 109                                            0x00, 0x03, 0x00, 0x00};
 110
 111 static const u8 WRITE_PORT_REQUEST[]    = {0x00, 0x01, 0x00, 0x14,
 112                                            0x00, 0x10, 0x01, 0x0F,
 113                                            0x02, 0x10, 0x00, 0x00,
 114                                            0x00, 0x03, 0x00, 0x00,
 115                                            0x03, 0x00, 0x00, 0x00};
 116
 117 static const u8 SET_PORT_DIR_REQUEST[]  = {0x00, 0x01, 0x00, 0x18,
 118                                            0x00, 0x14, 0x01, 0x12,
 119                                            0x02, 0x10, 0x00, 0x00,
 120                                            0x00, 0x05, 0x00, 0x00,
 121                                            0x00, 0x00, 0x05, 0x00,
 122                                            0x00, 0x00, 0x00, 0x00};
 123
 124 /* Counter request packets */
 125 static const u8 START_COUNTER_REQUEST[] = {0x00, 0x01, 0x00, 0x0C,
 126                                            0x00, 0x08, 0x01, 0x09,
 127                                            0x02, 0x20, 0x00, 0x00};
 128
 129 static const u8 STOP_COUNTER_REQUEST[]  = {0x00, 0x01, 0x00, 0x0C,
 130                                            0x00, 0x08, 0x01, 0x0C,
 131                                            0x02, 0x20, 0x00, 0x00};
 132
 133 static const u8 READ_COUNTER_REQUEST[]  = {0x00, 0x01, 0x00, 0x0C,
 134                                            0x00, 0x08, 0x01, 0x0E,
 135                                            0x02, 0x20, 0x00, 0x00};
 136
 137 static const u8 WRITE_COUNTER_REQUEST[] = {0x00, 0x01, 0x00, 0x10,
 138                                            0x00, 0x0C, 0x01, 0x0F,
 139                                            0x02, 0x20, 0x00, 0x00,
 140                                            0x00, 0x00, 0x00, 0x00};
 141
 142 /* Response packets */
 143 static const u8 GENERIC_RESPONSE[]      = {0x00, 0x01, 0x00, 0x0C,
 144                                            0x00, 0x08, 0x01, 0x00,
 145                                            0x00, 0x00, 0x00, 0x02};
 146
 147 static const u8 READ_PORT_RESPONSE[]    = {0x00, 0x01, 0x00, 0x10,
 148                                            0x00, 0x0C, 0x01, 0x00,
 149                                            0x00, 0x00, 0x00, 0x02,
 150                                            0x00, 0x03, 0x00, 0x00};
 151
 152 static const u8 READ_COUNTER_RESPONSE[] = {0x00, 0x01, 0x00, 0x10,
 153                                            0x00, 0x0C, 0x01, 0x00,
 154                                            0x00, 0x00, 0x00, 0x02,
 155                                            0x00, 0x00, 0x00, 0x00};
 156
 157 enum commands {
 158         READ_PORT,
 159         WRITE_PORT,
 160         SET_PORT_DIR,
 161         START_COUNTER,
 162         STOP_COUNTER,
 163         READ_COUNTER,
 164         WRITE_COUNTER
 165 };
 166
 167 struct ni6501_private {
 168         struct usb_endpoint_descriptor *ep_rx;
 169         struct usb_endpoint_descriptor *ep_tx;
 170         struct semaphore sem;
 171         u8 *usb_rx_buf;
 172         u8 *usb_tx_buf;
 173 };
 174
 175 static int ni6501_port_command(struct comedi_device *dev, int command,
 176                                const u8 *port, u8 *bitmap)
 177 {
 178         struct usb_device *usb = comedi_to_usb_dev(dev);
 179         struct ni6501_private *devpriv = dev->private;
 180         int request_size, response_size;
 181         u8 *tx = devpriv->usb_tx_buf;
 182         int ret;
 183
 184         if (command != SET_PORT_DIR && !bitmap)
 185                 return -EINVAL;
 186
 187         down(&devpriv->sem);
 188
 189         switch (command) {
 190         case READ_PORT:
 191                 request_size = sizeof(READ_PORT_REQUEST);
 192                 response_size = sizeof(READ_PORT_RESPONSE);
 193                 memcpy(tx, READ_PORT_REQUEST, request_size);
 194                 tx[14] = port[0];
 195                 break;
 196         case WRITE_PORT:
 197                 request_size = sizeof(WRITE_PORT_REQUEST);
 198                 response_size = sizeof(GENERIC_RESPONSE);
 199                 memcpy(tx, WRITE_PORT_REQUEST, request_size);
 200                 tx[14] = port[0];
 201                 tx[17] = bitmap[0];
 202                 break;
 203         case SET_PORT_DIR:
 204                 request_size = sizeof(SET_PORT_DIR_REQUEST);
 205                 response_size = sizeof(GENERIC_RESPONSE);
 206                 memcpy(tx, SET_PORT_DIR_REQUEST, request_size);
 207                 tx[14] = port[0];
 208                 tx[15] = port[1];
 209                 tx[16] = port[2];
 210                 break;
 211         default:
 212                 ret = -EINVAL;
 213                 goto end;
 214         }
 215
 216         ret = usb_bulk_msg(usb,
 217                            usb_sndbulkpipe(usb,
 218                                            devpriv->ep_tx->bEndpointAddress),
 219                            devpriv->usb_tx_buf,
 220                            request_size,
 221                            NULL,
 222                            NI6501_TIMEOUT);
 223         if (ret)
 224                 goto end;
 225
 226         ret = usb_bulk_msg(usb,
 227                            usb_rcvbulkpipe(usb,
 228                                            devpriv->ep_rx->bEndpointAddress),
 229                            devpriv->usb_rx_buf,
 230                            response_size,
 231                            NULL,
 232                            NI6501_TIMEOUT);
 233         if (ret)
 234                 goto end;
 235
 236         /* Check if results are valid */
 237
 238         if (command == READ_PORT) {
 239                 bitmap[0] = devpriv->usb_rx_buf[14];
 240                 /* mask bitmap for comparing */
 241                 devpriv->usb_rx_buf[14] = 0x00;
 242
 243                 if (memcmp(devpriv->usb_rx_buf, READ_PORT_RESPONSE,
 244                            sizeof(READ_PORT_RESPONSE))) {
 245                         ret = -EINVAL;
 246                 }
 247         } else if (memcmp(devpriv->usb_rx_buf, GENERIC_RESPONSE,
 248                           sizeof(GENERIC_RESPONSE))) {
 249                 ret = -EINVAL;
 250         }
 251 end:
 252         up(&devpriv->sem);
 253
 254         return ret;
 255 }
 256
 257 static int ni6501_counter_command(struct comedi_device *dev, int command,
 258                                   u32 *val)
 259 {
 260         struct usb_device *usb = comedi_to_usb_dev(dev);
 261         struct ni6501_private *devpriv = dev->private;
 262         int request_size, response_size;
 263         u8 *tx = devpriv->usb_tx_buf;
 264         int ret;
 265
 266         if ((command == READ_COUNTER || command ==  WRITE_COUNTER) && !val)
 267                 return -EINVAL;
 268
 269         down(&devpriv->sem);
 270
 271         switch (command) {
 272         case START_COUNTER:
 273                 request_size = sizeof(START_COUNTER_REQUEST);
 274                 response_size = sizeof(GENERIC_RESPONSE);
 275                 memcpy(tx, START_COUNTER_REQUEST, request_size);
 276                 break;
 277         case STOP_COUNTER:
 278                 request_size = sizeof(STOP_COUNTER_REQUEST);
 279                 response_size = sizeof(GENERIC_RESPONSE);
 280                 memcpy(tx, STOP_COUNTER_REQUEST, request_size);
 281                 break;
 282         case READ_COUNTER:
 283                 request_size = sizeof(READ_COUNTER_REQUEST);
 284                 response_size = sizeof(READ_COUNTER_RESPONSE);
 285                 memcpy(tx, READ_COUNTER_REQUEST, request_size);
 286                 break;
 287         case WRITE_COUNTER:
 288                 request_size = sizeof(WRITE_COUNTER_REQUEST);
 289                 response_size = sizeof(GENERIC_RESPONSE);
 290                 memcpy(tx, WRITE_COUNTER_REQUEST, request_size);
 291                 /* Setup tx packet: bytes 12,13,14,15 hold the */
 292                 /* u32 counter value (Big Endian)              */
 293                 *((__be32 *)&tx[12]) = cpu_to_be32(*val);
 294                 break;
 295         default:
 296                 ret = -EINVAL;
 297                 goto end;
 298         }
 299
 300         ret = usb_bulk_msg(usb,
 301                            usb_sndbulkpipe(usb,
 302                                            devpriv->ep_tx->bEndpointAddress),
 303                            devpriv->usb_tx_buf,
 304                            request_size,
 305                            NULL,
 306                            NI6501_TIMEOUT);
 307         if (ret)
 308                 goto end;
 309
 310         ret = usb_bulk_msg(usb,
 311                            usb_rcvbulkpipe(usb,
 312                                            devpriv->ep_rx->bEndpointAddress),
 313                            devpriv->usb_rx_buf,
 314                            response_size,
 315                            NULL,
 316                            NI6501_TIMEOUT);
 317         if (ret)
 318                 goto end;
 319
 320         /* Check if results are valid */
 321
 322         if (command == READ_COUNTER) {
 323                 int i;
 324
 325                 /* Read counter value: bytes 12,13,14,15 of rx packet */
 326                 /* hold the u32 counter value (Big Endian)            */
 327                 *val = be32_to_cpu(*((__be32 *)&devpriv->usb_rx_buf[12]));
 328
 329                 /* mask counter value for comparing */
 330                 for (i = 12; i < sizeof(READ_COUNTER_RESPONSE); ++i)
 331                         devpriv->usb_rx_buf[i] = 0x00;
 332
 333                 if (memcmp(devpriv->usb_rx_buf, READ_COUNTER_RESPONSE,
 334                            sizeof(READ_COUNTER_RESPONSE))) {
 335                         ret = -EINVAL;
 336                 }
 337         } else if (memcmp(devpriv->usb_rx_buf, GENERIC_RESPONSE,
 338                           sizeof(GENERIC_RESPONSE))) {
 339                 ret = -EINVAL;
 340         }
 341 end:
 342         up(&devpriv->sem);
 343
 344         return ret;
 345 }
 346
 347 static int ni6501_dio_insn_config(struct comedi_device *dev,
 348                                   struct comedi_subdevice *s,
 349                                   struct comedi_insn *insn,
 350                                   unsigned int *data)
 351 {
 352         int ret;
 353         u8 port[3];
 354
 355         ret = comedi_dio_insn_config(dev, s, insn, data, 0);
 356         if (ret)
 357                 return ret;
 358
 359         port[0] = (s->io_bits) & 0xff;
 360         port[1] = (s->io_bits >> 8) & 0xff;
 361         port[2] = (s->io_bits >> 16) & 0xff;
 362
 363         ret = ni6501_port_command(dev, SET_PORT_DIR, port, NULL);
 364         if (ret)
 365                 return ret;
 366
 367         return insn->n;
 368 }
 369
 370 static int ni6501_dio_insn_bits(struct comedi_device *dev,
 371                                 struct comedi_subdevice *s,
 372                                 struct comedi_insn *insn,
 373                                 unsigned int *data)
 374 {
 375         unsigned int mask;
 376         int ret;
 377         u8 port;
 378         u8 bitmap;
 379
 380         mask = comedi_dio_update_state(s, data);
 381
 382         for (port = 0; port < 3; port++) {
 383                 if (mask & (0xFF << port * 8)) {
 384                         bitmap = (s->state >> port * 8) & 0xFF;
 385                         ret = ni6501_port_command(dev, WRITE_PORT,
 386                                                   &port, &bitmap);
 387                         if (ret)
 388                                 return ret;
 389                 }
 390         }
 391
 392         data[1] = 0;
 393
 394         for (port = 0; port < 3; port++) {
 395                 ret = ni6501_port_command(dev, READ_PORT, &port, &bitmap);
 396                 if (ret)
 397                         return ret;
 398                 data[1] |= bitmap << port * 8;
 399         }
 400
 401         return insn->n;
 402 }
 403
 404 static int ni6501_cnt_insn_config(struct comedi_device *dev,
 405                                   struct comedi_subdevice *s,
 406                                   struct comedi_insn *insn,
 407                                   unsigned int *data)
 408 {
 409         int ret;
 410         u32 val = 0;
 411
 412         switch (data[0]) {
 413         case INSN_CONFIG_ARM:
 414                 ret = ni6501_counter_command(dev, START_COUNTER, NULL);
 415                 break;
 416         case INSN_CONFIG_DISARM:
 417                 ret = ni6501_counter_command(dev, STOP_COUNTER, NULL);
 418                 break;
 419         case INSN_CONFIG_RESET:
 420                 ret = ni6501_counter_command(dev, STOP_COUNTER, NULL);
 421                 if (ret)
 422                         break;
 423                 ret = ni6501_counter_command(dev, WRITE_COUNTER, &val);
 424                 break;
 425         default:
 426                 return -EINVAL;
 427         }
 428
 429         return ret ? ret : insn->n;
 430 }
 431
 432 static int ni6501_cnt_insn_read(struct comedi_device *dev,
 433                                 struct comedi_subdevice *s,
 434                                 struct comedi_insn *insn,
 435                                 unsigned int *data)
 436 {
 437         int ret;
 438         u32 val;
 439         unsigned int i;
 440
 441         for (i = 0; i < insn->n; i++) {
 442                 ret = ni6501_counter_command(dev, READ_COUNTER, &val);
 443                 if (ret)
 444                         return ret;
 445                 data[i] = val;
 446         }
 447
 448         return insn->n;
 449 }
 450
 451 static int ni6501_cnt_insn_write(struct comedi_device *dev,
 452                                  struct comedi_subdevice *s,
 453                                  struct comedi_insn *insn,
 454                                  unsigned int *data)
 455 {
 456         int ret;
 457
 458         if (insn->n) {
 459                 u32 val = data[insn->n - 1];
 460
 461                 ret = ni6501_counter_command(dev, WRITE_COUNTER, &val);
 462                 if (ret)
 463                         return ret;
 464         }
 465
 466         return insn->n;
 467 }
 468
 469 static int ni6501_alloc_usb_buffers(struct comedi_device *dev)
 470 {
 471         struct ni6501_private *devpriv = dev->private;
 472         size_t size;
 473
 474         size = le16_to_cpu(devpriv->ep_rx->wMaxPacketSize);
 475         devpriv->usb_rx_buf = kzalloc(size, GFP_KERNEL);
 476         if (!devpriv->usb_rx_buf)
 477                 return -ENOMEM;
 478
 479         size = le16_to_cpu(devpriv->ep_tx->wMaxPacketSize);
 480         devpriv->usb_tx_buf = kzalloc(size, GFP_KERNEL);
 481         if (!devpriv->usb_tx_buf) {
 482                 kfree(devpriv->usb_rx_buf);
 483                 return -ENOMEM;
 484         }
 485
 486         return 0;
 487 }
 488
 489 static int ni6501_find_endpoints(struct comedi_device *dev)
 490 {
 491         struct usb_interface *intf = comedi_to_usb_interface(dev);
 492         struct ni6501_private *devpriv = dev->private;
 493         struct usb_host_interface *iface_desc = intf->cur_altsetting;
 494         struct usb_endpoint_descriptor *ep_desc;
 495         int i;
 496
 497         if (iface_desc->desc.bNumEndpoints != 2) {
 498                 dev_err(dev->class_dev, "Wrong number of endpoints\n");
 499                 return -ENODEV;
 500         }
 501
 502         for (i = 0; i < iface_desc->desc.bNumEndpoints; i++) {
 503                 ep_desc = &iface_desc->endpoint[i].desc;
 504
 505                 if (usb_endpoint_is_bulk_in(ep_desc)) {
 506                         if (!devpriv->ep_rx)
 507                                 devpriv->ep_rx = ep_desc;
 508                         continue;
 509                 }
 510
 511                 if (usb_endpoint_is_bulk_out(ep_desc)) {
 512                         if (!devpriv->ep_tx)
 513                                 devpriv->ep_tx = ep_desc;
 514                         continue;
 515                 }
 516         }
 517
 518         if (!devpriv->ep_rx || !devpriv->ep_tx)
 519                 return -ENODEV;
 520
 521         return 0;
 522 }
 523
 524 static int ni6501_auto_attach(struct comedi_device *dev,
 525                               unsigned long context)
 526 {
 527         struct usb_interface *intf = comedi_to_usb_interface(dev);
 528         struct ni6501_private *devpriv;
 529         struct comedi_subdevice *s;
 530         int ret;
 531
 532         devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
 533         if (!devpriv)
 534                 return -ENOMEM;
 535
 536         ret = ni6501_find_endpoints(dev);
 537         if (ret)
 538                 return ret;
 539
 540         ret = ni6501_alloc_usb_buffers(dev);
 541         if (ret)
 542                 return ret;
 543
 544         sema_init(&devpriv->sem, 1);
 545         usb_set_intfdata(intf, devpriv);
 546
 547         ret = comedi_alloc_subdevices(dev, 2);
 548         if (ret)
 549                 return ret;
 550
 551         /* Digital Input/Output subdevice */
 552         s = &dev->subdevices[0];
 553         s->type         = COMEDI_SUBD_DIO;
 554         s->subdev_flags = SDF_READABLE | SDF_WRITABLE;
 555         s->n_chan       = 24;
 556         s->maxdata      = 1;
 557         s->range_table  = &range_digital;
 558         s->insn_bits    = ni6501_dio_insn_bits;
 559         s->insn_config  = ni6501_dio_insn_config;
 560
 561         /* Counter subdevice */
 562         s = &dev->subdevices[1];
 563         s->type         = COMEDI_SUBD_COUNTER;
 564         s->subdev_flags = SDF_READABLE | SDF_WRITEABLE | SDF_LSAMPL;
 565         s->n_chan       = 1;
 566         s->maxdata      = 0xffffffff;
 567         s->insn_read    = ni6501_cnt_insn_read;
 568         s->insn_write   = ni6501_cnt_insn_write;
 569         s->insn_config  = ni6501_cnt_insn_config;
 570
 571         return 0;
 572 }
 573
 574 static void ni6501_detach(struct comedi_device *dev)
 575 {
 576         struct usb_interface *intf = comedi_to_usb_interface(dev);
 577         struct ni6501_private *devpriv = dev->private;
 578
 579         if (!devpriv)
 580                 return;
 581
 582         down(&devpriv->sem);
 583
 584         usb_set_intfdata(intf, NULL);
 585
 586         kfree(devpriv->usb_rx_buf);
 587         kfree(devpriv->usb_tx_buf);
 588
 589         up(&devpriv->sem);
 590 }
 591
 592 static struct comedi_driver ni6501_driver = {
 593         .module         = THIS_MODULE,
 594         .driver_name    = "ni6501",
 595         .auto_attach    = ni6501_auto_attach,
 596         .detach         = ni6501_detach,
 597 };
 598
 599 static int ni6501_usb_probe(struct usb_interface *intf,
 600                             const struct usb_device_id *id)
 601 {
 602         return comedi_usb_auto_config(intf, &ni6501_driver, id->driver_info);
 603 }
 604
 605 static const struct usb_device_id ni6501_usb_table[] = {
 606         { USB_DEVICE(0x3923, 0x718a) },
 607         { }
 608 };
 609 MODULE_DEVICE_TABLE(usb, ni6501_usb_table);
 610
 611 static struct usb_driver ni6501_usb_driver = {
 612         .name           = "ni6501",
 613         .id_table       = ni6501_usb_table,
 614         .probe          = ni6501_usb_probe,
 615         .disconnect     = comedi_usb_auto_unconfig,
 616 };
 617 module_comedi_usb_driver(ni6501_driver, ni6501_usb_driver);
 618
 619 MODULE_AUTHOR("Luca Ellero");
 620 MODULE_DESCRIPTION("Comedi driver for National Instruments USB-6501");
 621 MODULE_LICENSE("GPL");