drivers/spi/spidev.c

   1 /*
   2  * spidev.c -- simple synchronous userspace interface to SPI devices
   3  *
   4  * Copyright (C) 2006 SWAPP
   5  *      Andrea Paterniani <a.paterniani@swapp-eng.it>
   6  * Copyright (C) 2007 David Brownell (simplification, cleanup)
   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  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  */
  22
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/ioctl.h>
  26 #include <linux/fs.h>
  27 #include <linux/device.h>
  28 #include <linux/err.h>
  29 #include <linux/list.h>
  30 #include <linux/errno.h>
  31 #include <linux/mutex.h>
  32 #include <linux/slab.h>
  33 #include <linux/smp_lock.h>
  34
  35 #include <linux/spi/spi.h>
  36 #include <linux/spi/spidev.h>
  37
  38 #include <asm/uaccess.h>
  39
  40
  41 /*
  42  * This supports acccess to SPI devices using normal userspace I/O calls.
  43  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
  44  * and often mask message boundaries, full SPI support requires full duplex
  45  * transfers.  There are several kinds of of internal message boundaries to
  46  * handle chipselect management and other protocol options.
  47  *
  48  * SPI has a character major number assigned.  We allocate minor numbers
  49  * dynamically using a bitmask.  You must use hotplug tools, such as udev
  50  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
  51  * nodes, since there is no fixed association of minor numbers with any
  52  * particular SPI bus or device.
  53  */
  54 #define SPIDEV_MAJOR                    153     /* assigned */
  55 #define N_SPI_MINORS                    32      /* ... up to 256 */
  56
  57 static unsigned long    minors[N_SPI_MINORS / BITS_PER_LONG];
  58
  59
  60 /* Bit masks for spi_device.mode management.  Note that incorrect
  61  * settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other
  62  * devices on a shared bus:  CS_HIGH, because this device will be
  63  * active when it shouldn't be;  3WIRE, because when active it won't
  64  * behave as it should.
  65  *
  66  * REVISIT should changing those two modes be privileged?
  67  */
  68 #define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
  69                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)
  70
  71 struct spidev_data {
  72         dev_t                   devt;
  73         spinlock_t              spi_lock;
  74         struct spi_device       *spi;
  75         struct list_head        device_entry;
  76
  77         /* buffer is NULL unless this device is open (users > 0) */
  78         struct mutex            buf_lock;
  79         unsigned                users;
  80         u8                      *buffer;
  81 };
  82
  83 static LIST_HEAD(device_list);
  84 static DEFINE_MUTEX(device_list_lock);
  85
  86 static unsigned bufsiz = 4096;
  87 module_param(bufsiz, uint, S_IRUGO);
  88 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  89
  90 /*-------------------------------------------------------------------------*/
  91
  92 /*
  93  * We can't use the standard synchronous wrappers for file I/O; we
  94  * need to protect against async removal of the underlying spi_device.
  95  */
  96 static void spidev_complete(void *arg)
  97 {
  98         complete(arg);
  99 }
 100
 101 static ssize_t
 102 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
 103 {
 104         DECLARE_COMPLETION_ONSTACK(done);
 105         int status;
 106
 107         message->complete = spidev_complete;
 108         message->context = &done;
 109
 110         spin_lock_irq(&spidev->spi_lock);
 111         if (spidev->spi == NULL)
 112                 status = -ESHUTDOWN;
 113         else
 114                 status = spi_async(spidev->spi, message);
 115         spin_unlock_irq(&spidev->spi_lock);
 116
 117         if (status == 0) {
 118                 wait_for_completion(&done);
 119                 status = message->status;
 120                 if (status == 0)
 121                         status = message->actual_length;
 122         }
 123         return status;
 124 }
 125
 126 static inline ssize_t
 127 spidev_sync_write(struct spidev_data *spidev, size_t len)
 128 {
 129         struct spi_transfer     t = {
 130                         .tx_buf         = spidev->buffer,
 131                         .len            = len,
 132                 };
 133         struct spi_message      m;
 134
 135         spi_message_init(&m);
 136         spi_message_add_tail(&t, &m);
 137         return spidev_sync(spidev, &m);
 138 }
 139
 140 static inline ssize_t
 141 spidev_sync_read(struct spidev_data *spidev, size_t len)
 142 {
 143         struct spi_transfer     t = {
 144                         .rx_buf         = spidev->buffer,
 145                         .len            = len,
 146                 };
 147         struct spi_message      m;
 148
 149         spi_message_init(&m);
 150         spi_message_add_tail(&t, &m);
 151         return spidev_sync(spidev, &m);
 152 }
 153
 154 /*-------------------------------------------------------------------------*/
 155
 156 /* Read-only message with current device setup */
 157 static ssize_t
 158 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
 159 {
 160         struct spidev_data      *spidev;
 161         ssize_t                 status = 0;
 162
 163         /* chipselect only toggles at start or end of operation */
 164         if (count > bufsiz)
 165                 return -EMSGSIZE;
 166
 167         spidev = filp->private_data;
 168
 169         mutex_lock(&spidev->buf_lock);
 170         status = spidev_sync_read(spidev, count);
 171         if (status > 0) {
 172                 unsigned long   missing;
 173
 174                 missing = copy_to_user(buf, spidev->buffer, status);
 175                 if (missing == status)
 176                         status = -EFAULT;
 177                 else
 178                         status = status - missing;
 179         }
 180         mutex_unlock(&spidev->buf_lock);
 181
 182         return status;
 183 }
 184
 185 /* Write-only message with current device setup */
 186 static ssize_t
 187 spidev_write(struct file *filp, const char __user *buf,
 188                 size_t count, loff_t *f_pos)
 189 {
 190         struct spidev_data      *spidev;
 191         ssize_t                 status = 0;
 192         unsigned long           missing;
 193
 194         /* chipselect only toggles at start or end of operation */
 195         if (count > bufsiz)
 196                 return -EMSGSIZE;
 197
 198         spidev = filp->private_data;
 199
 200         mutex_lock(&spidev->buf_lock);
 201         missing = copy_from_user(spidev->buffer, buf, count);
 202         if (missing == 0) {
 203                 status = spidev_sync_write(spidev, count);
 204         } else
 205                 status = -EFAULT;
 206         mutex_unlock(&spidev->buf_lock);
 207
 208         return status;
 209 }
 210
 211 static int spidev_message(struct spidev_data *spidev,
 212                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 213 {
 214         struct spi_message      msg;
 215         struct spi_transfer     *k_xfers;
 216         struct spi_transfer     *k_tmp;
 217         struct spi_ioc_transfer *u_tmp;
 218         unsigned                n, total;
 219         u8                      *buf;
 220         int                     status = -EFAULT;
 221
 222         spi_message_init(&msg);
 223         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 224         if (k_xfers == NULL)
 225                 return -ENOMEM;
 226
 227         /* Construct spi_message, copying any tx data to bounce buffer.
 228          * We walk the array of user-provided transfers, using each one
 229          * to initialize a kernel version of the same transfer.
 230          */
 231         buf = spidev->buffer;
 232         total = 0;
 233         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 234                         n;
 235                         n--, k_tmp++, u_tmp++) {
 236                 k_tmp->len = u_tmp->len;
 237
 238                 total += k_tmp->len;
 239                 if (total > bufsiz) {
 240                         status = -EMSGSIZE;
 241                         goto done;
 242                 }
 243
 244                 if (u_tmp->rx_buf) {
 245                         k_tmp->rx_buf = buf;
 246                         if (!access_ok(VERIFY_WRITE, (u8 __user *)
 247                                                 (uintptr_t) u_tmp->rx_buf,
 248                                                 u_tmp->len))
 249                                 goto done;
 250                 }
 251                 if (u_tmp->tx_buf) {
 252                         k_tmp->tx_buf = buf;
 253                         if (copy_from_user(buf, (const u8 __user *)
 254                                                 (uintptr_t) u_tmp->tx_buf,
 255                                         u_tmp->len))
 256                                 goto done;
 257                 }
 258                 buf += k_tmp->len;
 259
 260                 k_tmp->cs_change = !!u_tmp->cs_change;
 261                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 262                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 263                 k_tmp->speed_hz = u_tmp->speed_hz;
 264 #ifdef VERBOSE
 265                 dev_dbg(&spi->dev,
 266                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 267                         u_tmp->len,
 268                         u_tmp->rx_buf ? "rx " : "",
 269                         u_tmp->tx_buf ? "tx " : "",
 270                         u_tmp->cs_change ? "cs " : "",
 271                         u_tmp->bits_per_word ? : spi->bits_per_word,
 272                         u_tmp->delay_usecs,
 273                         u_tmp->speed_hz ? : spi->max_speed_hz);
 274 #endif
 275                 spi_message_add_tail(k_tmp, &msg);
 276         }
 277
 278         status = spidev_sync(spidev, &msg);
 279         if (status < 0)
 280                 goto done;
 281
 282         /* copy any rx data out of bounce buffer */
 283         buf = spidev->buffer;
 284         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 285                 if (u_tmp->rx_buf) {
 286                         if (__copy_to_user((u8 __user *)
 287                                         (uintptr_t) u_tmp->rx_buf, buf,
 288                                         u_tmp->len)) {
 289                                 status = -EFAULT;
 290                                 goto done;
 291                         }
 292                 }
 293                 buf += u_tmp->len;
 294         }
 295         status = total;
 296
 297 done:
 298         kfree(k_xfers);
 299         return status;
 300 }
 301
 302 static long
 303 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 304 {
 305         int                     err = 0;
 306         int                     retval = 0;
 307         struct spidev_data      *spidev;
 308         struct spi_device       *spi;
 309         u32                     tmp;
 310         unsigned                n_ioc;
 311         struct spi_ioc_transfer *ioc;
 312
 313         /* Check type and command number */
 314         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 315                 return -ENOTTY;
 316
 317         /* Check access direction once here; don't repeat below.
 318          * IOC_DIR is from the user perspective, while access_ok is
 319          * from the kernel perspective; so they look reversed.
 320          */
 321         if (_IOC_DIR(cmd) & _IOC_READ)
 322                 err = !access_ok(VERIFY_WRITE,
 323                                 (void __user *)arg, _IOC_SIZE(cmd));
 324         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 325                 err = !access_ok(VERIFY_READ,
 326                                 (void __user *)arg, _IOC_SIZE(cmd));
 327         if (err)
 328                 return -EFAULT;
 329
 330         /* guard against device removal before, or while,
 331          * we issue this ioctl.
 332          */
 333         spidev = filp->private_data;
 334         spin_lock_irq(&spidev->spi_lock);
 335         spi = spi_dev_get(spidev->spi);
 336         spin_unlock_irq(&spidev->spi_lock);
 337
 338         if (spi == NULL)
 339                 return -ESHUTDOWN;
 340
 341         /* use the buffer lock here for triple duty:
 342          *  - prevent I/O (from us) so calling spi_setup() is safe;
 343          *  - prevent concurrent SPI_IOC_WR_* from morphing
 344          *    data fields while SPI_IOC_RD_* reads them;
 345          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 346          */
 347         mutex_lock(&spidev->buf_lock);
 348
 349         switch (cmd) {
 350         /* read requests */
 351         case SPI_IOC_RD_MODE:
 352                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 353                                         (__u8 __user *)arg);
 354                 break;
 355         case SPI_IOC_RD_LSB_FIRST:
 356                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 357                                         (__u8 __user *)arg);
 358                 break;
 359         case SPI_IOC_RD_BITS_PER_WORD:
 360                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 361                 break;
 362         case SPI_IOC_RD_MAX_SPEED_HZ:
 363                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
 364                 break;
 365
 366         /* write requests */
 367         case SPI_IOC_WR_MODE:
 368                 retval = __get_user(tmp, (u8 __user *)arg);
 369                 if (retval == 0) {
 370                         u8      save = spi->mode;
 371
 372                         if (tmp & ~SPI_MODE_MASK) {
 373                                 retval = -EINVAL;
 374                                 break;
 375                         }
 376
 377                         tmp |= spi->mode & ~SPI_MODE_MASK;
 378                         spi->mode = (u8)tmp;
 379                         retval = spi_setup(spi);
 380                         if (retval < 0)
 381                                 spi->mode = save;
 382                         else
 383                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
 384                 }
 385                 break;
 386         case SPI_IOC_WR_LSB_FIRST:
 387                 retval = __get_user(tmp, (__u8 __user *)arg);
 388                 if (retval == 0) {
 389                         u8      save = spi->mode;
 390
 391                         if (tmp)
 392                                 spi->mode |= SPI_LSB_FIRST;
 393                         else
 394                                 spi->mode &= ~SPI_LSB_FIRST;
 395                         retval = spi_setup(spi);
 396                         if (retval < 0)
 397                                 spi->mode = save;
 398                         else
 399                                 dev_dbg(&spi->dev, "%csb first\n",
 400                                                 tmp ? 'l' : 'm');
 401                 }
 402                 break;
 403         case SPI_IOC_WR_BITS_PER_WORD:
 404                 retval = __get_user(tmp, (__u8 __user *)arg);
 405                 if (retval == 0) {
 406                         u8      save = spi->bits_per_word;
 407
 408                         spi->bits_per_word = tmp;
 409                         retval = spi_setup(spi);
 410                         if (retval < 0)
 411                                 spi->bits_per_word = save;
 412                         else
 413                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 414                 }
 415                 break;
 416         case SPI_IOC_WR_MAX_SPEED_HZ:
 417                 retval = __get_user(tmp, (__u32 __user *)arg);
 418                 if (retval == 0) {
 419                         u32     save = spi->max_speed_hz;
 420
 421                         spi->max_speed_hz = tmp;
 422                         retval = spi_setup(spi);
 423                         if (retval < 0)
 424                                 spi->max_speed_hz = save;
 425                         else
 426                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 427                 }
 428                 break;
 429
 430         default:
 431                 /* segmented and/or full-duplex I/O request */
 432                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 433                                 || _IOC_DIR(cmd) != _IOC_WRITE) {
 434                         retval = -ENOTTY;
 435                         break;
 436                 }
 437
 438                 tmp = _IOC_SIZE(cmd);
 439                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
 440                         retval = -EINVAL;
 441                         break;
 442                 }
 443                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 444                 if (n_ioc == 0)
 445                         break;
 446
 447                 /* copy into scratch area */
 448                 ioc = kmalloc(tmp, GFP_KERNEL);
 449                 if (!ioc) {
 450                         retval = -ENOMEM;
 451                         break;
 452                 }
 453                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
 454                         kfree(ioc);
 455                         retval = -EFAULT;
 456                         break;
 457                 }
 458
 459                 /* translate to spi_message, execute */
 460                 retval = spidev_message(spidev, ioc, n_ioc);
 461                 kfree(ioc);
 462                 break;
 463         }
 464
 465         mutex_unlock(&spidev->buf_lock);
 466         spi_dev_put(spi);
 467         return retval;
 468 }
 469
 470 static int spidev_open(struct inode *inode, struct file *filp)
 471 {
 472         struct spidev_data      *spidev;
 473         int                     status = -ENXIO;
 474
 475         lock_kernel();
 476         mutex_lock(&device_list_lock);
 477
 478         list_for_each_entry(spidev, &device_list, device_entry) {
 479                 if (spidev->devt == inode->i_rdev) {
 480                         status = 0;
 481                         break;
 482                 }
 483         }
 484         if (status == 0) {
 485                 if (!spidev->buffer) {
 486                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
 487                         if (!spidev->buffer) {
 488                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 489                                 status = -ENOMEM;
 490                         }
 491                 }
 492                 if (status == 0) {
 493                         spidev->users++;
 494                         filp->private_data = spidev;
 495                         nonseekable_open(inode, filp);
 496                 }
 497         } else
 498                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 499
 500         mutex_unlock(&device_list_lock);
 501         unlock_kernel();
 502         return status;
 503 }
 504
 505 static int spidev_release(struct inode *inode, struct file *filp)
 506 {
 507         struct spidev_data      *spidev;
 508         int                     status = 0;
 509
 510         mutex_lock(&device_list_lock);
 511         spidev = filp->private_data;
 512         filp->private_data = NULL;
 513
 514         /* last close? */
 515         spidev->users--;
 516         if (!spidev->users) {
 517                 int             dofree;
 518
 519                 kfree(spidev->buffer);
 520                 spidev->buffer = NULL;
 521
 522                 /* ... after we unbound from the underlying device? */
 523                 spin_lock_irq(&spidev->spi_lock);
 524                 dofree = (spidev->spi == NULL);
 525                 spin_unlock_irq(&spidev->spi_lock);
 526
 527                 if (dofree)
 528                         kfree(spidev);
 529         }
 530         mutex_unlock(&device_list_lock);
 531
 532         return status;
 533 }
 534
 535 static struct file_operations spidev_fops = {
 536         .owner =        THIS_MODULE,
 537         /* REVISIT switch to aio primitives, so that userspace
 538          * gets more complete API coverage.  It'll simplify things
 539          * too, except for the locking.
 540          */
 541         .write =        spidev_write,
 542         .read =         spidev_read,
 543         .unlocked_ioctl = spidev_ioctl,
 544         .open =         spidev_open,
 545         .release =      spidev_release,
 546 };
 547
 548 /*-------------------------------------------------------------------------*/
 549
 550 /* The main reason to have this class is to make mdev/udev create the
 551  * /dev/spidevB.C character device nodes exposing our userspace API.
 552  * It also simplifies memory management.
 553  */
 554
 555 static struct class *spidev_class;
 556
 557 /*-------------------------------------------------------------------------*/
 558
 559 static int spidev_probe(struct spi_device *spi)
 560 {
 561         struct spidev_data      *spidev;
 562         int                     status;
 563         unsigned long           minor;
 564
 565         /* Allocate driver data */
 566         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 567         if (!spidev)
 568                 return -ENOMEM;
 569
 570         /* Initialize the driver data */
 571         spidev->spi = spi;
 572         spin_lock_init(&spidev->spi_lock);
 573         mutex_init(&spidev->buf_lock);
 574
 575         INIT_LIST_HEAD(&spidev->device_entry);
 576
 577         /* If we can allocate a minor number, hook up this device.
 578          * Reusing minors is fine so long as udev or mdev is working.
 579          */
 580         mutex_lock(&device_list_lock);
 581         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 582         if (minor < N_SPI_MINORS) {
 583                 struct device *dev;
 584
 585                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
 586                 dev = device_create_drvdata(spidev_class, &spi->dev,
 587                                 spidev->devt, spidev,
 588                                 "spidev%d.%d",
 589                                 spi->master->bus_num, spi->chip_select);
 590                 status = IS_ERR(dev) ? PTR_ERR(dev) : 0;
 591         } else {
 592                 dev_dbg(&spi->dev, "no minor number available!\n");
 593                 status = -ENODEV;
 594         }
 595         if (status == 0) {
 596                 set_bit(minor, minors);
 597                 list_add(&spidev->device_entry, &device_list);
 598         }
 599         mutex_unlock(&device_list_lock);
 600
 601         if (status != 0)
 602                 kfree(spidev);
 603
 604         return status;
 605 }
 606
 607 static int spidev_remove(struct spi_device *spi)
 608 {
 609         struct spidev_data      *spidev = spi_get_drvdata(spi);
 610
 611         /* make sure ops on existing fds can abort cleanly */
 612         spin_lock_irq(&spidev->spi_lock);
 613         spidev->spi = NULL;
 614         spi_set_drvdata(spi, NULL);
 615         spin_unlock_irq(&spidev->spi_lock);
 616
 617         /* prevent new opens */
 618         mutex_lock(&device_list_lock);
 619         list_del(&spidev->device_entry);
 620         device_destroy(spidev_class, spidev->devt);
 621         clear_bit(MINOR(spidev->devt), minors);
 622         if (spidev->users == 0)
 623                 kfree(spidev);
 624         mutex_unlock(&device_list_lock);
 625
 626         return 0;
 627 }
 628
 629 static struct spi_driver spidev_spi = {
 630         .driver = {
 631                 .name =         "spidev",
 632                 .owner =        THIS_MODULE,
 633         },
 634         .probe =        spidev_probe,
 635         .remove =       __devexit_p(spidev_remove),
 636
 637         /* NOTE:  suspend/resume methods are not necessary here.
 638          * We don't do anything except pass the requests to/from
 639          * the underlying controller.  The refrigerator handles
 640          * most issues; the controller driver handles the rest.
 641          */
 642 };
 643
 644 /*-------------------------------------------------------------------------*/
 645
 646 static int __init spidev_init(void)
 647 {
 648         int status;
 649
 650         /* Claim our 256 reserved device numbers.  Then register a class
 651          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 652          * the driver which manages those device numbers.
 653          */
 654         BUILD_BUG_ON(N_SPI_MINORS > 256);
 655         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 656         if (status < 0)
 657                 return status;
 658
 659         spidev_class = class_create(THIS_MODULE, "spidev");
 660         if (IS_ERR(spidev_class)) {
 661                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 662                 return PTR_ERR(spidev_class);
 663         }
 664
 665         status = spi_register_driver(&spidev_spi);
 666         if (status < 0) {
 667                 class_destroy(spidev_class);
 668                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 669         }
 670         return status;
 671 }
 672 module_init(spidev_init);
 673
 674 static void __exit spidev_exit(void)
 675 {
 676         spi_unregister_driver(&spidev_spi);
 677         class_destroy(spidev_class);
 678         unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 679 }
 680 module_exit(spidev_exit);
 681
 682 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 683 MODULE_DESCRIPTION("User mode SPI device interface");
 684 MODULE_LICENSE("GPL");