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