drivers/spi/spidev.c

   1 /*
   2  * 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/compat.h>
  34 #include <linux/of.h>
  35 #include <linux/of_device.h>
  36
  37 #include <linux/spi/spi.h>
  38 #include <linux/spi/spidev.h>
  39
  40 #include <linux/uaccess.h>
  41
  42
  43 /*
  44  * This supports access to SPI devices using normal userspace I/O calls.
  45  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
  46  * and often mask message boundaries, full SPI support requires full duplex
  47  * transfers.  There are several kinds of internal message boundaries to
  48  * handle chipselect management and other protocol options.
  49  *
  50  * SPI has a character major number assigned.  We allocate minor numbers
  51  * dynamically using a bitmask.  You must use hotplug tools, such as udev
  52  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
  53  * nodes, since there is no fixed association of minor numbers with any
  54  * particular SPI bus or device.
  55  */
  56 #define SPIDEV_MAJOR                    153     /* assigned */
  57 #define N_SPI_MINORS                    32      /* ... up to 256 */
  58
  59 static DECLARE_BITMAP(minors, N_SPI_MINORS);
  60
  61
  62 /* Bit masks for spi_device.mode management.  Note that incorrect
  63  * settings for some settings can cause *lots* of trouble for other
  64  * devices on a shared bus:
  65  *
  66  *  - CS_HIGH ... this device will be active when it shouldn't be
  67  *  - 3WIRE ... when active, it won't behave as it should
  68  *  - NO_CS ... there will be no explicit message boundaries; this
  69  *      is completely incompatible with the shared bus model
  70  *  - READY ... transfers may proceed when they shouldn't.
  71  *
  72  * REVISIT should changing those flags be privileged?
  73  */
  74 #define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
  75                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
  76                                 | SPI_NO_CS | SPI_READY)
  77
  78 struct spidev_data {
  79         dev_t                   devt;
  80         spinlock_t              spi_lock;
  81         struct spi_device       *spi;
  82         struct list_head        device_entry;
  83
  84         /* buffer is NULL unless this device is open (users > 0) */
  85         struct mutex            buf_lock;
  86         unsigned                users;
  87         u8                      *buffer;
  88 };
  89
  90 static LIST_HEAD(device_list);
  91 static DEFINE_MUTEX(device_list_lock);
  92
  93 static unsigned bufsiz = 4096;
  94 module_param(bufsiz, uint, S_IRUGO);
  95 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  96
  97 /*-------------------------------------------------------------------------*/
  98
  99 /*
 100  * We can't use the standard synchronous wrappers for file I/O; we
 101  * need to protect against async removal of the underlying spi_device.
 102  */
 103 static void spidev_complete(void *arg)
 104 {
 105         complete(arg);
 106 }
 107
 108 static ssize_t
 109 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
 110 {
 111         DECLARE_COMPLETION_ONSTACK(done);
 112         int status;
 113
 114         message->complete = spidev_complete;
 115         message->context = &done;
 116
 117         spin_lock_irq(&spidev->spi_lock);
 118         if (spidev->spi == NULL)
 119                 status = -ESHUTDOWN;
 120         else
 121                 status = spi_async(spidev->spi, message);
 122         spin_unlock_irq(&spidev->spi_lock);
 123
 124         if (status == 0) {
 125                 wait_for_completion(&done);
 126                 status = message->status;
 127                 if (status == 0)
 128                         status = message->actual_length;
 129         }
 130         return status;
 131 }
 132
 133 static inline ssize_t
 134 spidev_sync_write(struct spidev_data *spidev, size_t len)
 135 {
 136         struct spi_transfer     t = {
 137                         .tx_buf         = spidev->buffer,
 138                         .len            = len,
 139                 };
 140         struct spi_message      m;
 141
 142         spi_message_init(&m);
 143         spi_message_add_tail(&t, &m);
 144         return spidev_sync(spidev, &m);
 145 }
 146
 147 static inline ssize_t
 148 spidev_sync_read(struct spidev_data *spidev, size_t len)
 149 {
 150         struct spi_transfer     t = {
 151                         .rx_buf         = spidev->buffer,
 152                         .len            = len,
 153                 };
 154         struct spi_message      m;
 155
 156         spi_message_init(&m);
 157         spi_message_add_tail(&t, &m);
 158         return spidev_sync(spidev, &m);
 159 }
 160
 161 /*-------------------------------------------------------------------------*/
 162
 163 /* Read-only message with current device setup */
 164 static ssize_t
 165 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
 166 {
 167         struct spidev_data      *spidev;
 168         ssize_t                 status = 0;
 169
 170         /* chipselect only toggles at start or end of operation */
 171         if (count > bufsiz)
 172                 return -EMSGSIZE;
 173
 174         spidev = filp->private_data;
 175
 176         mutex_lock(&spidev->buf_lock);
 177         status = spidev_sync_read(spidev, count);
 178         if (status > 0) {
 179                 unsigned long   missing;
 180
 181                 missing = copy_to_user(buf, spidev->buffer, status);
 182                 if (missing == status)
 183                         status = -EFAULT;
 184                 else
 185                         status = status - missing;
 186         }
 187         mutex_unlock(&spidev->buf_lock);
 188
 189         return status;
 190 }
 191
 192 /* Write-only message with current device setup */
 193 static ssize_t
 194 spidev_write(struct file *filp, const char __user *buf,
 195                 size_t count, loff_t *f_pos)
 196 {
 197         struct spidev_data      *spidev;
 198         ssize_t                 status = 0;
 199         unsigned long           missing;
 200
 201         /* chipselect only toggles at start or end of operation */
 202         if (count > bufsiz)
 203                 return -EMSGSIZE;
 204
 205         spidev = filp->private_data;
 206
 207         mutex_lock(&spidev->buf_lock);
 208         missing = copy_from_user(spidev->buffer, buf, count);
 209         if (missing == 0)
 210                 status = spidev_sync_write(spidev, count);
 211         else
 212                 status = -EFAULT;
 213         mutex_unlock(&spidev->buf_lock);
 214
 215         return status;
 216 }
 217
 218 static int spidev_message(struct spidev_data *spidev,
 219                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 220 {
 221         struct spi_message      msg;
 222         struct spi_transfer     *k_xfers;
 223         struct spi_transfer     *k_tmp;
 224         struct spi_ioc_transfer *u_tmp;
 225         unsigned                n, total;
 226         u8                      *buf;
 227         int                     status = -EFAULT;
 228
 229         spi_message_init(&msg);
 230         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 231         if (k_xfers == NULL)
 232                 return -ENOMEM;
 233
 234         /* Construct spi_message, copying any tx data to bounce buffer.
 235          * We walk the array of user-provided transfers, using each one
 236          * to initialize a kernel version of the same transfer.
 237          */
 238         buf = spidev->buffer;
 239         total = 0;
 240         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 241                         n;
 242                         n--, k_tmp++, u_tmp++) {
 243                 k_tmp->len = u_tmp->len;
 244
 245                 total += k_tmp->len;
 246                 if (total > bufsiz) {
 247                         status = -EMSGSIZE;
 248                         goto done;
 249                 }
 250
 251                 if (u_tmp->rx_buf) {
 252                         k_tmp->rx_buf = buf;
 253                         if (!access_ok(VERIFY_WRITE, (u8 __user *)
 254                                                 (uintptr_t) u_tmp->rx_buf,
 255                                                 u_tmp->len))
 256                                 goto done;
 257                 }
 258                 if (u_tmp->tx_buf) {
 259                         k_tmp->tx_buf = buf;
 260                         if (copy_from_user(buf, (const u8 __user *)
 261                                                 (uintptr_t) u_tmp->tx_buf,
 262                                         u_tmp->len))
 263                                 goto done;
 264                 }
 265                 buf += k_tmp->len;
 266
 267                 k_tmp->cs_change = !!u_tmp->cs_change;
 268                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 269                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 270                 k_tmp->speed_hz = u_tmp->speed_hz;
 271 #ifdef VERBOSE
 272                 dev_dbg(&spidev->spi->dev,
 273                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 274                         u_tmp->len,
 275                         u_tmp->rx_buf ? "rx " : "",
 276                         u_tmp->tx_buf ? "tx " : "",
 277                         u_tmp->cs_change ? "cs " : "",
 278                         u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
 279                         u_tmp->delay_usecs,
 280                         u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
 281 #endif
 282                 spi_message_add_tail(k_tmp, &msg);
 283         }
 284
 285         status = spidev_sync(spidev, &msg);
 286         if (status < 0)
 287                 goto done;
 288
 289         /* copy any rx data out of bounce buffer */
 290         buf = spidev->buffer;
 291         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 292                 if (u_tmp->rx_buf) {
 293                         if (__copy_to_user((u8 __user *)
 294                                         (uintptr_t) u_tmp->rx_buf, buf,
 295                                         u_tmp->len)) {
 296                                 status = -EFAULT;
 297                                 goto done;
 298                         }
 299                 }
 300                 buf += u_tmp->len;
 301         }
 302         status = total;
 303
 304 done:
 305         kfree(k_xfers);
 306         return status;
 307 }
 308
 309 static long
 310 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 311 {
 312         int                     err = 0;
 313         int                     retval = 0;
 314         struct spidev_data      *spidev;
 315         struct spi_device       *spi;
 316         u32                     tmp;
 317         unsigned                n_ioc;
 318         struct spi_ioc_transfer *ioc;
 319
 320         /* Check type and command number */
 321         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 322                 return -ENOTTY;
 323
 324         /* Check access direction once here; don't repeat below.
 325          * IOC_DIR is from the user perspective, while access_ok is
 326          * from the kernel perspective; so they look reversed.
 327          */
 328         if (_IOC_DIR(cmd) & _IOC_READ)
 329                 err = !access_ok(VERIFY_WRITE,
 330                                 (void __user *)arg, _IOC_SIZE(cmd));
 331         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 332                 err = !access_ok(VERIFY_READ,
 333                                 (void __user *)arg, _IOC_SIZE(cmd));
 334         if (err)
 335                 return -EFAULT;
 336
 337         /* guard against device removal before, or while,
 338          * we issue this ioctl.
 339          */
 340         spidev = filp->private_data;
 341         spin_lock_irq(&spidev->spi_lock);
 342         spi = spi_dev_get(spidev->spi);
 343         spin_unlock_irq(&spidev->spi_lock);
 344
 345         if (spi == NULL)
 346                 return -ESHUTDOWN;
 347
 348         /* use the buffer lock here for triple duty:
 349          *  - prevent I/O (from us) so calling spi_setup() is safe;
 350          *  - prevent concurrent SPI_IOC_WR_* from morphing
 351          *    data fields while SPI_IOC_RD_* reads them;
 352          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 353          */
 354         mutex_lock(&spidev->buf_lock);
 355
 356         switch (cmd) {
 357         /* read requests */
 358         case SPI_IOC_RD_MODE:
 359                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 360                                         (__u8 __user *)arg);
 361                 break;
 362         case SPI_IOC_RD_LSB_FIRST:
 363                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 364                                         (__u8 __user *)arg);
 365                 break;
 366         case SPI_IOC_RD_BITS_PER_WORD:
 367                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 368                 break;
 369         case SPI_IOC_RD_MAX_SPEED_HZ:
 370                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
 371                 break;
 372
 373         /* write requests */
 374         case SPI_IOC_WR_MODE:
 375                 retval = __get_user(tmp, (u8 __user *)arg);
 376                 if (retval == 0) {
 377                         u8      save = spi->mode;
 378
 379                         if (tmp & ~SPI_MODE_MASK) {
 380                                 retval = -EINVAL;
 381                                 break;
 382                         }
 383
 384                         tmp |= spi->mode & ~SPI_MODE_MASK;
 385                         spi->mode = (u8)tmp;
 386                         retval = spi_setup(spi);
 387                         if (retval < 0)
 388                                 spi->mode = save;
 389                         else
 390                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
 391                 }
 392                 break;
 393         case SPI_IOC_WR_LSB_FIRST:
 394                 retval = __get_user(tmp, (__u8 __user *)arg);
 395                 if (retval == 0) {
 396                         u8      save = spi->mode;
 397
 398                         if (tmp)
 399                                 spi->mode |= SPI_LSB_FIRST;
 400                         else
 401                                 spi->mode &= ~SPI_LSB_FIRST;
 402                         retval = spi_setup(spi);
 403                         if (retval < 0)
 404                                 spi->mode = save;
 405                         else
 406                                 dev_dbg(&spi->dev, "%csb first\n",
 407                                                 tmp ? 'l' : 'm');
 408                 }
 409                 break;
 410         case SPI_IOC_WR_BITS_PER_WORD:
 411                 retval = __get_user(tmp, (__u8 __user *)arg);
 412                 if (retval == 0) {
 413                         u8      save = spi->bits_per_word;
 414
 415                         spi->bits_per_word = tmp;
 416                         retval = spi_setup(spi);
 417                         if (retval < 0)
 418                                 spi->bits_per_word = save;
 419                         else
 420                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 421                 }
 422                 break;
 423         case SPI_IOC_WR_MAX_SPEED_HZ:
 424                 retval = __get_user(tmp, (__u32 __user *)arg);
 425                 if (retval == 0) {
 426                         u32     save = spi->max_speed_hz;
 427
 428                         spi->max_speed_hz = tmp;
 429                         retval = spi_setup(spi);
 430                         if (retval < 0)
 431                                 spi->max_speed_hz = save;
 432                         else
 433                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 434                 }
 435                 break;
 436
 437         default:
 438                 /* segmented and/or full-duplex I/O request */
 439                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 440                                 || _IOC_DIR(cmd) != _IOC_WRITE) {
 441                         retval = -ENOTTY;
 442                         break;
 443                 }
 444
 445                 tmp = _IOC_SIZE(cmd);
 446                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
 447                         retval = -EINVAL;
 448                         break;
 449                 }
 450                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 451                 if (n_ioc == 0)
 452                         break;
 453
 454                 /* copy into scratch area */
 455                 ioc = kmalloc(tmp, GFP_KERNEL);
 456                 if (!ioc) {
 457                         retval = -ENOMEM;
 458                         break;
 459                 }
 460                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
 461                         kfree(ioc);
 462                         retval = -EFAULT;
 463                         break;
 464                 }
 465
 466                 /* translate to spi_message, execute */
 467                 retval = spidev_message(spidev, ioc, n_ioc);
 468                 kfree(ioc);
 469                 break;
 470         }
 471
 472         mutex_unlock(&spidev->buf_lock);
 473         spi_dev_put(spi);
 474         return retval;
 475 }
 476
 477 #ifdef CONFIG_COMPAT
 478 static long
 479 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 480 {
 481         return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 482 }
 483 #else
 484 #define spidev_compat_ioctl NULL
 485 #endif /* CONFIG_COMPAT */
 486
 487 static int spidev_open(struct inode *inode, struct file *filp)
 488 {
 489         struct spidev_data      *spidev;
 490         int                     status = -ENXIO;
 491
 492         mutex_lock(&device_list_lock);
 493
 494         list_for_each_entry(spidev, &device_list, device_entry) {
 495                 if (spidev->devt == inode->i_rdev) {
 496                         status = 0;
 497                         break;
 498                 }
 499         }
 500         if (status == 0) {
 501                 if (!spidev->buffer) {
 502                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
 503                         if (!spidev->buffer) {
 504                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 505                                 status = -ENOMEM;
 506                         }
 507                 }
 508                 if (status == 0) {
 509                         spidev->users++;
 510                         filp->private_data = spidev;
 511                         nonseekable_open(inode, filp);
 512                 }
 513         } else
 514                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 515
 516         mutex_unlock(&device_list_lock);
 517         return status;
 518 }
 519
 520 static int spidev_release(struct inode *inode, struct file *filp)
 521 {
 522         struct spidev_data      *spidev;
 523         int                     status = 0;
 524
 525         mutex_lock(&device_list_lock);
 526         spidev = filp->private_data;
 527         filp->private_data = NULL;
 528
 529         /* last close? */
 530         spidev->users--;
 531         if (!spidev->users) {
 532                 int             dofree;
 533
 534                 kfree(spidev->buffer);
 535                 spidev->buffer = NULL;
 536
 537                 /* ... after we unbound from the underlying device? */
 538                 spin_lock_irq(&spidev->spi_lock);
 539                 dofree = (spidev->spi == NULL);
 540                 spin_unlock_irq(&spidev->spi_lock);
 541
 542                 if (dofree)
 543                         kfree(spidev);
 544         }
 545         mutex_unlock(&device_list_lock);
 546
 547         return status;
 548 }
 549
 550 static const struct file_operations spidev_fops = {
 551         .owner =        THIS_MODULE,
 552         /* REVISIT switch to aio primitives, so that userspace
 553          * gets more complete API coverage.  It'll simplify things
 554          * too, except for the locking.
 555          */
 556         .write =        spidev_write,
 557         .read =         spidev_read,
 558         .unlocked_ioctl = spidev_ioctl,
 559         .compat_ioctl = spidev_compat_ioctl,
 560         .open =         spidev_open,
 561         .release =      spidev_release,
 562         .llseek =       no_llseek,
 563 };
 564
 565 /*-------------------------------------------------------------------------*/
 566
 567 /* The main reason to have this class is to make mdev/udev create the
 568  * /dev/spidevB.C character device nodes exposing our userspace API.
 569  * It also simplifies memory management.
 570  */
 571
 572 static struct class *spidev_class;
 573
 574 /*-------------------------------------------------------------------------*/
 575
 576 static int spidev_probe(struct spi_device *spi)
 577 {
 578         struct spidev_data      *spidev;
 579         int                     status;
 580         unsigned long           minor;
 581
 582         /* Allocate driver data */
 583         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 584         if (!spidev)
 585                 return -ENOMEM;
 586
 587         /* Initialize the driver data */
 588         spidev->spi = spi;
 589         spin_lock_init(&spidev->spi_lock);
 590         mutex_init(&spidev->buf_lock);
 591
 592         INIT_LIST_HEAD(&spidev->device_entry);
 593
 594         /* If we can allocate a minor number, hook up this device.
 595          * Reusing minors is fine so long as udev or mdev is working.
 596          */
 597         mutex_lock(&device_list_lock);
 598         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 599         if (minor < N_SPI_MINORS) {
 600                 struct device *dev;
 601
 602                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
 603                 dev = device_create(spidev_class, &spi->dev, spidev->devt,
 604                                     spidev, "spidev%d.%d",
 605                                     spi->master->bus_num, spi->chip_select);
 606                 status = PTR_ERR_OR_ZERO(dev);
 607         } else {
 608                 dev_dbg(&spi->dev, "no minor number available!\n");
 609                 status = -ENODEV;
 610         }
 611         if (status == 0) {
 612                 set_bit(minor, minors);
 613                 list_add(&spidev->device_entry, &device_list);
 614         }
 615         mutex_unlock(&device_list_lock);
 616
 617         if (status == 0)
 618                 spi_set_drvdata(spi, spidev);
 619         else
 620                 kfree(spidev);
 621
 622         return status;
 623 }
 624
 625 static int spidev_remove(struct spi_device *spi)
 626 {
 627         struct spidev_data      *spidev = spi_get_drvdata(spi);
 628
 629         /* make sure ops on existing fds can abort cleanly */
 630         spin_lock_irq(&spidev->spi_lock);
 631         spidev->spi = NULL;
 632         spin_unlock_irq(&spidev->spi_lock);
 633
 634         /* prevent new opens */
 635         mutex_lock(&device_list_lock);
 636         list_del(&spidev->device_entry);
 637         device_destroy(spidev_class, spidev->devt);
 638         clear_bit(MINOR(spidev->devt), minors);
 639         if (spidev->users == 0)
 640                 kfree(spidev);
 641         mutex_unlock(&device_list_lock);
 642
 643         return 0;
 644 }
 645
 646 static const struct of_device_id spidev_dt_ids[] = {
 647         { .compatible = "rohm,dh2228fv" },
 648         {},
 649 };
 650
 651 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 652
 653 static struct spi_driver spidev_spi_driver = {
 654         .driver = {
 655                 .name =         "spidev",
 656                 .owner =        THIS_MODULE,
 657                 .of_match_table = of_match_ptr(spidev_dt_ids),
 658         },
 659         .probe =        spidev_probe,
 660         .remove =       spidev_remove,
 661
 662         /* NOTE:  suspend/resume methods are not necessary here.
 663          * We don't do anything except pass the requests to/from
 664          * the underlying controller.  The refrigerator handles
 665          * most issues; the controller driver handles the rest.
 666          */
 667 };
 668
 669 /*-------------------------------------------------------------------------*/
 670
 671 static int __init spidev_init(void)
 672 {
 673         int status;
 674
 675         /* Claim our 256 reserved device numbers.  Then register a class
 676          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 677          * the driver which manages those device numbers.
 678          */
 679         BUILD_BUG_ON(N_SPI_MINORS > 256);
 680         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 681         if (status < 0)
 682                 return status;
 683
 684         spidev_class = class_create(THIS_MODULE, "spidev");
 685         if (IS_ERR(spidev_class)) {
 686                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 687                 return PTR_ERR(spidev_class);
 688         }
 689
 690         status = spi_register_driver(&spidev_spi_driver);
 691         if (status < 0) {
 692                 class_destroy(spidev_class);
 693                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 694         }
 695         return status;
 696 }
 697 module_init(spidev_init);
 698
 699 static void __exit spidev_exit(void)
 700 {
 701         spi_unregister_driver(&spidev_spi_driver);
 702         class_destroy(spidev_class);
 703         unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 704 }
 705 module_exit(spidev_exit);
 706
 707 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 708 MODULE_DESCRIPTION("User mode SPI device interface");
 709 MODULE_LICENSE("GPL");
 710 MODULE_ALIAS("spi:spidev");