drivers/spi/spidev.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Simple synchronous userspace interface to SPI devices
   4  *
   5  * Copyright (C) 2006 SWAPP
   6  *      Andrea Paterniani <a.paterniani@swapp-eng.it>
   7  * Copyright (C) 2007 David Brownell (simplification, cleanup)
   8  */
   9
  10 #include <linux/init.h>
  11 #include <linux/module.h>
  12 #include <linux/ioctl.h>
  13 #include <linux/fs.h>
  14 #include <linux/device.h>
  15 #include <linux/err.h>
  16 #include <linux/list.h>
  17 #include <linux/errno.h>
  18 #include <linux/mutex.h>
  19 #include <linux/slab.h>
  20 #include <linux/compat.h>
  21 #include <linux/of.h>
  22 #include <linux/of_device.h>
  23 #include <linux/acpi.h>
  24
  25 #include <linux/spi/spi.h>
  26 #include <linux/spi/spidev.h>
  27
  28 #include <linux/uaccess.h>
  29
  30
  31 /*
  32  * This supports access to SPI devices using normal userspace I/O calls.
  33  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
  34  * and often mask message boundaries, full SPI support requires full duplex
  35  * transfers.  There are several kinds of internal message boundaries to
  36  * handle chipselect management and other protocol options.
  37  *
  38  * SPI has a character major number assigned.  We allocate minor numbers
  39  * dynamically using a bitmask.  You must use hotplug tools, such as udev
  40  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
  41  * nodes, since there is no fixed association of minor numbers with any
  42  * particular SPI bus or device.
  43  */
  44 #define SPIDEV_MAJOR                    153     /* assigned */
  45 #define N_SPI_MINORS                    32      /* ... up to 256 */
  46
  47 static DECLARE_BITMAP(minors, N_SPI_MINORS);
  48
  49
  50 /* Bit masks for spi_device.mode management.  Note that incorrect
  51  * settings for some settings can cause *lots* of trouble for other
  52  * devices on a shared bus:
  53  *
  54  *  - CS_HIGH ... this device will be active when it shouldn't be
  55  *  - 3WIRE ... when active, it won't behave as it should
  56  *  - NO_CS ... there will be no explicit message boundaries; this
  57  *      is completely incompatible with the shared bus model
  58  *  - READY ... transfers may proceed when they shouldn't.
  59  *
  60  * REVISIT should changing those flags be privileged?
  61  */
  62 #define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
  63                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
  64                                 | SPI_NO_CS | SPI_READY | SPI_TX_DUAL \
  65                                 | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)
  66
  67 struct spidev_data {
  68         dev_t                   devt;
  69         spinlock_t              spi_lock;
  70         struct spi_device       *spi;
  71         struct list_head        device_entry;
  72
  73         /* TX/RX buffers are NULL unless this device is open (users > 0) */
  74         struct mutex            buf_lock;
  75         unsigned                users;
  76         u8                      *tx_buffer;
  77         u8                      *rx_buffer;
  78         u32                     speed_hz;
  79 };
  80
  81 static LIST_HEAD(device_list);
  82 static DEFINE_MUTEX(device_list_lock);
  83
  84 static unsigned bufsiz = 4096;
  85 module_param(bufsiz, uint, S_IRUGO);
  86 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  87
  88 /*-------------------------------------------------------------------------*/
  89
  90 static ssize_t
  91 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
  92 {
  93         int status;
  94         struct spi_device *spi;
  95
  96         spin_lock_irq(&spidev->spi_lock);
  97         spi = spidev->spi;
  98         spin_unlock_irq(&spidev->spi_lock);
  99
 100         if (spi == NULL)
 101                 status = -ESHUTDOWN;
 102         else
 103                 status = spi_sync(spi, message);
 104
 105         if (status == 0)
 106                 status = message->actual_length;
 107
 108         return status;
 109 }
 110
 111 static inline ssize_t
 112 spidev_sync_write(struct spidev_data *spidev, size_t len)
 113 {
 114         struct spi_transfer     t = {
 115                         .tx_buf         = spidev->tx_buffer,
 116                         .len            = len,
 117                         .speed_hz       = spidev->speed_hz,
 118                 };
 119         struct spi_message      m;
 120
 121         spi_message_init(&m);
 122         spi_message_add_tail(&t, &m);
 123         return spidev_sync(spidev, &m);
 124 }
 125
 126 static inline ssize_t
 127 spidev_sync_read(struct spidev_data *spidev, size_t len)
 128 {
 129         struct spi_transfer     t = {
 130                         .rx_buf         = spidev->rx_buffer,
 131                         .len            = len,
 132                         .speed_hz       = spidev->speed_hz,
 133                 };
 134         struct spi_message      m;
 135
 136         spi_message_init(&m);
 137         spi_message_add_tail(&t, &m);
 138         return spidev_sync(spidev, &m);
 139 }
 140
 141 /*-------------------------------------------------------------------------*/
 142
 143 /* Read-only message with current device setup */
 144 static ssize_t
 145 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
 146 {
 147         struct spidev_data      *spidev;
 148         ssize_t                 status = 0;
 149
 150         /* chipselect only toggles at start or end of operation */
 151         if (count > bufsiz)
 152                 return -EMSGSIZE;
 153
 154         spidev = filp->private_data;
 155
 156         mutex_lock(&spidev->buf_lock);
 157         status = spidev_sync_read(spidev, count);
 158         if (status > 0) {
 159                 unsigned long   missing;
 160
 161                 missing = copy_to_user(buf, spidev->rx_buffer, status);
 162                 if (missing == status)
 163                         status = -EFAULT;
 164                 else
 165                         status = status - missing;
 166         }
 167         mutex_unlock(&spidev->buf_lock);
 168
 169         return status;
 170 }
 171
 172 /* Write-only message with current device setup */
 173 static ssize_t
 174 spidev_write(struct file *filp, const char __user *buf,
 175                 size_t count, loff_t *f_pos)
 176 {
 177         struct spidev_data      *spidev;
 178         ssize_t                 status = 0;
 179         unsigned long           missing;
 180
 181         /* chipselect only toggles at start or end of operation */
 182         if (count > bufsiz)
 183                 return -EMSGSIZE;
 184
 185         spidev = filp->private_data;
 186
 187         mutex_lock(&spidev->buf_lock);
 188         missing = copy_from_user(spidev->tx_buffer, buf, count);
 189         if (missing == 0)
 190                 status = spidev_sync_write(spidev, count);
 191         else
 192                 status = -EFAULT;
 193         mutex_unlock(&spidev->buf_lock);
 194
 195         return status;
 196 }
 197
 198 static int spidev_message(struct spidev_data *spidev,
 199                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 200 {
 201         struct spi_message      msg;
 202         struct spi_transfer     *k_xfers;
 203         struct spi_transfer     *k_tmp;
 204         struct spi_ioc_transfer *u_tmp;
 205         unsigned                n, total, tx_total, rx_total;
 206         u8                      *tx_buf, *rx_buf;
 207         int                     status = -EFAULT;
 208
 209         spi_message_init(&msg);
 210         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 211         if (k_xfers == NULL)
 212                 return -ENOMEM;
 213
 214         /* Construct spi_message, copying any tx data to bounce buffer.
 215          * We walk the array of user-provided transfers, using each one
 216          * to initialize a kernel version of the same transfer.
 217          */
 218         tx_buf = spidev->tx_buffer;
 219         rx_buf = spidev->rx_buffer;
 220         total = 0;
 221         tx_total = 0;
 222         rx_total = 0;
 223         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 224                         n;
 225                         n--, k_tmp++, u_tmp++) {
 226                 k_tmp->len = u_tmp->len;
 227
 228                 total += k_tmp->len;
 229                 /* Since the function returns the total length of transfers
 230                  * on success, restrict the total to positive int values to
 231                  * avoid the return value looking like an error.  Also check
 232                  * each transfer length to avoid arithmetic overflow.
 233                  */
 234                 if (total > INT_MAX || k_tmp->len > INT_MAX) {
 235                         status = -EMSGSIZE;
 236                         goto done;
 237                 }
 238
 239                 if (u_tmp->rx_buf) {
 240                         /* this transfer needs space in RX bounce buffer */
 241                         rx_total += k_tmp->len;
 242                         if (rx_total > bufsiz) {
 243                                 status = -EMSGSIZE;
 244                                 goto done;
 245                         }
 246                         k_tmp->rx_buf = rx_buf;
 247                         rx_buf += k_tmp->len;
 248                 }
 249                 if (u_tmp->tx_buf) {
 250                         /* this transfer needs space in TX bounce buffer */
 251                         tx_total += k_tmp->len;
 252                         if (tx_total > bufsiz) {
 253                                 status = -EMSGSIZE;
 254                                 goto done;
 255                         }
 256                         k_tmp->tx_buf = tx_buf;
 257                         if (copy_from_user(tx_buf, (const u8 __user *)
 258                                                 (uintptr_t) u_tmp->tx_buf,
 259                                         u_tmp->len))
 260                                 goto done;
 261                         tx_buf += k_tmp->len;
 262                 }
 263
 264                 k_tmp->cs_change = !!u_tmp->cs_change;
 265                 k_tmp->tx_nbits = u_tmp->tx_nbits;
 266                 k_tmp->rx_nbits = u_tmp->rx_nbits;
 267                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 268                 k_tmp->delay.value = u_tmp->delay_usecs;
 269                 k_tmp->delay.unit = SPI_DELAY_UNIT_USECS;
 270                 k_tmp->speed_hz = u_tmp->speed_hz;
 271                 k_tmp->word_delay.value = u_tmp->word_delay_usecs;
 272                 k_tmp->word_delay.unit = SPI_DELAY_UNIT_USECS;
 273                 if (!k_tmp->speed_hz)
 274                         k_tmp->speed_hz = spidev->speed_hz;
 275 #ifdef VERBOSE
 276                 dev_dbg(&spidev->spi->dev,
 277                         "  xfer len %u %s%s%s%dbits %u usec %u usec %uHz\n",
 278                         u_tmp->len,
 279                         u_tmp->rx_buf ? "rx " : "",
 280                         u_tmp->tx_buf ? "tx " : "",
 281                         u_tmp->cs_change ? "cs " : "",
 282                         u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
 283                         u_tmp->delay_usecs,
 284                         u_tmp->word_delay_usecs,
 285                         u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
 286 #endif
 287                 spi_message_add_tail(k_tmp, &msg);
 288         }
 289
 290         status = spidev_sync(spidev, &msg);
 291         if (status < 0)
 292                 goto done;
 293
 294         /* copy any rx data out of bounce buffer */
 295         rx_buf = spidev->rx_buffer;
 296         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 297                 if (u_tmp->rx_buf) {
 298                         if (copy_to_user((u8 __user *)
 299                                         (uintptr_t) u_tmp->rx_buf, rx_buf,
 300                                         u_tmp->len)) {
 301                                 status = -EFAULT;
 302                                 goto done;
 303                         }
 304                         rx_buf += u_tmp->len;
 305                 }
 306         }
 307         status = total;
 308
 309 done:
 310         kfree(k_xfers);
 311         return status;
 312 }
 313
 314 static struct spi_ioc_transfer *
 315 spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
 316                 unsigned *n_ioc)
 317 {
 318         u32     tmp;
 319
 320         /* Check type, command number and direction */
 321         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
 322                         || _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 323                         || _IOC_DIR(cmd) != _IOC_WRITE)
 324                 return ERR_PTR(-ENOTTY);
 325
 326         tmp = _IOC_SIZE(cmd);
 327         if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
 328                 return ERR_PTR(-EINVAL);
 329         *n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 330         if (*n_ioc == 0)
 331                 return NULL;
 332
 333         /* copy into scratch area */
 334         return memdup_user(u_ioc, tmp);
 335 }
 336
 337 static long
 338 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 339 {
 340         int                     retval = 0;
 341         struct spidev_data      *spidev;
 342         struct spi_device       *spi;
 343         u32                     tmp;
 344         unsigned                n_ioc;
 345         struct spi_ioc_transfer *ioc;
 346
 347         /* Check type and command number */
 348         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 349                 return -ENOTTY;
 350
 351         /* guard against device removal before, or while,
 352          * we issue this ioctl.
 353          */
 354         spidev = filp->private_data;
 355         spin_lock_irq(&spidev->spi_lock);
 356         spi = spi_dev_get(spidev->spi);
 357         spin_unlock_irq(&spidev->spi_lock);
 358
 359         if (spi == NULL)
 360                 return -ESHUTDOWN;
 361
 362         /* use the buffer lock here for triple duty:
 363          *  - prevent I/O (from us) so calling spi_setup() is safe;
 364          *  - prevent concurrent SPI_IOC_WR_* from morphing
 365          *    data fields while SPI_IOC_RD_* reads them;
 366          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 367          */
 368         mutex_lock(&spidev->buf_lock);
 369
 370         switch (cmd) {
 371         /* read requests */
 372         case SPI_IOC_RD_MODE:
 373                 retval = put_user(spi->mode & SPI_MODE_MASK,
 374                                         (__u8 __user *)arg);
 375                 break;
 376         case SPI_IOC_RD_MODE32:
 377                 retval = put_user(spi->mode & SPI_MODE_MASK,
 378                                         (__u32 __user *)arg);
 379                 break;
 380         case SPI_IOC_RD_LSB_FIRST:
 381                 retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 382                                         (__u8 __user *)arg);
 383                 break;
 384         case SPI_IOC_RD_BITS_PER_WORD:
 385                 retval = put_user(spi->bits_per_word, (__u8 __user *)arg);
 386                 break;
 387         case SPI_IOC_RD_MAX_SPEED_HZ:
 388                 retval = put_user(spidev->speed_hz, (__u32 __user *)arg);
 389                 break;
 390
 391         /* write requests */
 392         case SPI_IOC_WR_MODE:
 393         case SPI_IOC_WR_MODE32:
 394                 if (cmd == SPI_IOC_WR_MODE)
 395                         retval = get_user(tmp, (u8 __user *)arg);
 396                 else
 397                         retval = get_user(tmp, (u32 __user *)arg);
 398                 if (retval == 0) {
 399                         u32     save = spi->mode;
 400
 401                         if (tmp & ~SPI_MODE_MASK) {
 402                                 retval = -EINVAL;
 403                                 break;
 404                         }
 405
 406                         tmp |= spi->mode & ~SPI_MODE_MASK;
 407                         spi->mode = (u16)tmp;
 408                         retval = spi_setup(spi);
 409                         if (retval < 0)
 410                                 spi->mode = save;
 411                         else
 412                                 dev_dbg(&spi->dev, "spi mode %x\n", tmp);
 413                 }
 414                 break;
 415         case SPI_IOC_WR_LSB_FIRST:
 416                 retval = get_user(tmp, (__u8 __user *)arg);
 417                 if (retval == 0) {
 418                         u32     save = spi->mode;
 419
 420                         if (tmp)
 421                                 spi->mode |= SPI_LSB_FIRST;
 422                         else
 423                                 spi->mode &= ~SPI_LSB_FIRST;
 424                         retval = spi_setup(spi);
 425                         if (retval < 0)
 426                                 spi->mode = save;
 427                         else
 428                                 dev_dbg(&spi->dev, "%csb first\n",
 429                                                 tmp ? 'l' : 'm');
 430                 }
 431                 break;
 432         case SPI_IOC_WR_BITS_PER_WORD:
 433                 retval = get_user(tmp, (__u8 __user *)arg);
 434                 if (retval == 0) {
 435                         u8      save = spi->bits_per_word;
 436
 437                         spi->bits_per_word = tmp;
 438                         retval = spi_setup(spi);
 439                         if (retval < 0)
 440                                 spi->bits_per_word = save;
 441                         else
 442                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 443                 }
 444                 break;
 445         case SPI_IOC_WR_MAX_SPEED_HZ:
 446                 retval = get_user(tmp, (__u32 __user *)arg);
 447                 if (retval == 0) {
 448                         u32     save = spi->max_speed_hz;
 449
 450                         spi->max_speed_hz = tmp;
 451                         retval = spi_setup(spi);
 452                         if (retval >= 0)
 453                                 spidev->speed_hz = tmp;
 454                         else
 455                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 456                         spi->max_speed_hz = save;
 457                 }
 458                 break;
 459
 460         default:
 461                 /* segmented and/or full-duplex I/O request */
 462                 /* Check message and copy into scratch area */
 463                 ioc = spidev_get_ioc_message(cmd,
 464                                 (struct spi_ioc_transfer __user *)arg, &n_ioc);
 465                 if (IS_ERR(ioc)) {
 466                         retval = PTR_ERR(ioc);
 467                         break;
 468                 }
 469                 if (!ioc)
 470                         break;  /* n_ioc is also 0 */
 471
 472                 /* translate to spi_message, execute */
 473                 retval = spidev_message(spidev, ioc, n_ioc);
 474                 kfree(ioc);
 475                 break;
 476         }
 477
 478         mutex_unlock(&spidev->buf_lock);
 479         spi_dev_put(spi);
 480         return retval;
 481 }
 482
 483 #ifdef CONFIG_COMPAT
 484 static long
 485 spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
 486                 unsigned long arg)
 487 {
 488         struct spi_ioc_transfer __user  *u_ioc;
 489         int                             retval = 0;
 490         struct spidev_data              *spidev;
 491         struct spi_device               *spi;
 492         unsigned                        n_ioc, n;
 493         struct spi_ioc_transfer         *ioc;
 494
 495         u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);
 496
 497         /* guard against device removal before, or while,
 498          * we issue this ioctl.
 499          */
 500         spidev = filp->private_data;
 501         spin_lock_irq(&spidev->spi_lock);
 502         spi = spi_dev_get(spidev->spi);
 503         spin_unlock_irq(&spidev->spi_lock);
 504
 505         if (spi == NULL)
 506                 return -ESHUTDOWN;
 507
 508         /* SPI_IOC_MESSAGE needs the buffer locked "normally" */
 509         mutex_lock(&spidev->buf_lock);
 510
 511         /* Check message and copy into scratch area */
 512         ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
 513         if (IS_ERR(ioc)) {
 514                 retval = PTR_ERR(ioc);
 515                 goto done;
 516         }
 517         if (!ioc)
 518                 goto done;      /* n_ioc is also 0 */
 519
 520         /* Convert buffer pointers */
 521         for (n = 0; n < n_ioc; n++) {
 522                 ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
 523                 ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
 524         }
 525
 526         /* translate to spi_message, execute */
 527         retval = spidev_message(spidev, ioc, n_ioc);
 528         kfree(ioc);
 529
 530 done:
 531         mutex_unlock(&spidev->buf_lock);
 532         spi_dev_put(spi);
 533         return retval;
 534 }
 535
 536 static long
 537 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 538 {
 539         if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
 540                         && _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
 541                         && _IOC_DIR(cmd) == _IOC_WRITE)
 542                 return spidev_compat_ioc_message(filp, cmd, arg);
 543
 544         return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 545 }
 546 #else
 547 #define spidev_compat_ioctl NULL
 548 #endif /* CONFIG_COMPAT */
 549
 550 static int spidev_open(struct inode *inode, struct file *filp)
 551 {
 552         struct spidev_data      *spidev;
 553         int                     status = -ENXIO;
 554
 555         mutex_lock(&device_list_lock);
 556
 557         list_for_each_entry(spidev, &device_list, device_entry) {
 558                 if (spidev->devt == inode->i_rdev) {
 559                         status = 0;
 560                         break;
 561                 }
 562         }
 563
 564         if (status) {
 565                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 566                 goto err_find_dev;
 567         }
 568
 569         if (!spidev->tx_buffer) {
 570                 spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 571                 if (!spidev->tx_buffer) {
 572                         dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 573                         status = -ENOMEM;
 574                         goto err_find_dev;
 575                 }
 576         }
 577
 578         if (!spidev->rx_buffer) {
 579                 spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 580                 if (!spidev->rx_buffer) {
 581                         dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 582                         status = -ENOMEM;
 583                         goto err_alloc_rx_buf;
 584                 }
 585         }
 586
 587         spidev->users++;
 588         filp->private_data = spidev;
 589         stream_open(inode, filp);
 590
 591         mutex_unlock(&device_list_lock);
 592         return 0;
 593
 594 err_alloc_rx_buf:
 595         kfree(spidev->tx_buffer);
 596         spidev->tx_buffer = NULL;
 597 err_find_dev:
 598         mutex_unlock(&device_list_lock);
 599         return status;
 600 }
 601
 602 static int spidev_release(struct inode *inode, struct file *filp)
 603 {
 604         struct spidev_data      *spidev;
 605
 606         mutex_lock(&device_list_lock);
 607         spidev = filp->private_data;
 608         filp->private_data = NULL;
 609
 610         /* last close? */
 611         spidev->users--;
 612         if (!spidev->users) {
 613                 int             dofree;
 614
 615                 kfree(spidev->tx_buffer);
 616                 spidev->tx_buffer = NULL;
 617
 618                 kfree(spidev->rx_buffer);
 619                 spidev->rx_buffer = NULL;
 620
 621                 spin_lock_irq(&spidev->spi_lock);
 622                 if (spidev->spi)
 623                         spidev->speed_hz = spidev->spi->max_speed_hz;
 624
 625                 /* ... after we unbound from the underlying device? */
 626                 dofree = (spidev->spi == NULL);
 627                 spin_unlock_irq(&spidev->spi_lock);
 628
 629                 if (dofree)
 630                         kfree(spidev);
 631         }
 632 #ifdef CONFIG_SPI_SLAVE
 633         spi_slave_abort(spidev->spi);
 634 #endif
 635         mutex_unlock(&device_list_lock);
 636
 637         return 0;
 638 }
 639
 640 static const struct file_operations spidev_fops = {
 641         .owner =        THIS_MODULE,
 642         /* REVISIT switch to aio primitives, so that userspace
 643          * gets more complete API coverage.  It'll simplify things
 644          * too, except for the locking.
 645          */
 646         .write =        spidev_write,
 647         .read =         spidev_read,
 648         .unlocked_ioctl = spidev_ioctl,
 649         .compat_ioctl = spidev_compat_ioctl,
 650         .open =         spidev_open,
 651         .release =      spidev_release,
 652         .llseek =       no_llseek,
 653 };
 654
 655 /*-------------------------------------------------------------------------*/
 656
 657 /* The main reason to have this class is to make mdev/udev create the
 658  * /dev/spidevB.C character device nodes exposing our userspace API.
 659  * It also simplifies memory management.
 660  */
 661
 662 static struct class *spidev_class;
 663
 664 #ifdef CONFIG_OF
 665 static const struct of_device_id spidev_dt_ids[] = {
 666         { .compatible = "rohm,dh2228fv" },
 667         { .compatible = "lineartechnology,ltc2488" },
 668         { .compatible = "ge,achc" },
 669         { .compatible = "semtech,sx1301" },
 670         { .compatible = "lwn,bk4" },
 671         { .compatible = "dh,dhcom-board" },
 672         { .compatible = "menlo,m53cpld" },
 673         {},
 674 };
 675 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 676 #endif
 677
 678 #ifdef CONFIG_ACPI
 679
 680 /* Dummy SPI devices not to be used in production systems */
 681 #define SPIDEV_ACPI_DUMMY       1
 682
 683 static const struct acpi_device_id spidev_acpi_ids[] = {
 684         /*
 685          * The ACPI SPT000* devices are only meant for development and
 686          * testing. Systems used in production should have a proper ACPI
 687          * description of the connected peripheral and they should also use
 688          * a proper driver instead of poking directly to the SPI bus.
 689          */
 690         { "SPT0001", SPIDEV_ACPI_DUMMY },
 691         { "SPT0002", SPIDEV_ACPI_DUMMY },
 692         { "SPT0003", SPIDEV_ACPI_DUMMY },
 693         {},
 694 };
 695 MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);
 696
 697 static void spidev_probe_acpi(struct spi_device *spi)
 698 {
 699         const struct acpi_device_id *id;
 700
 701         if (!has_acpi_companion(&spi->dev))
 702                 return;
 703
 704         id = acpi_match_device(spidev_acpi_ids, &spi->dev);
 705         if (WARN_ON(!id))
 706                 return;
 707
 708         if (id->driver_data == SPIDEV_ACPI_DUMMY)
 709                 dev_warn(&spi->dev, "do not use this driver in production systems!\n");
 710 }
 711 #else
 712 static inline void spidev_probe_acpi(struct spi_device *spi) {}
 713 #endif
 714
 715 /*-------------------------------------------------------------------------*/
 716
 717 static int spidev_probe(struct spi_device *spi)
 718 {
 719         struct spidev_data      *spidev;
 720         int                     status;
 721         unsigned long           minor;
 722
 723         /*
 724          * spidev should never be referenced in DT without a specific
 725          * compatible string, it is a Linux implementation thing
 726          * rather than a description of the hardware.
 727          */
 728         WARN(spi->dev.of_node &&
 729              of_device_is_compatible(spi->dev.of_node, "spidev"),
 730              "%pOF: buggy DT: spidev listed directly in DT\n", spi->dev.of_node);
 731
 732         spidev_probe_acpi(spi);
 733
 734         /* Allocate driver data */
 735         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 736         if (!spidev)
 737                 return -ENOMEM;
 738
 739         /* Initialize the driver data */
 740         spidev->spi = spi;
 741         spin_lock_init(&spidev->spi_lock);
 742         mutex_init(&spidev->buf_lock);
 743
 744         INIT_LIST_HEAD(&spidev->device_entry);
 745
 746         /* If we can allocate a minor number, hook up this device.
 747          * Reusing minors is fine so long as udev or mdev is working.
 748          */
 749         mutex_lock(&device_list_lock);
 750         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 751         if (minor < N_SPI_MINORS) {
 752                 struct device *dev;
 753
 754                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
 755                 dev = device_create(spidev_class, &spi->dev, spidev->devt,
 756                                     spidev, "spidev%d.%d",
 757                                     spi->master->bus_num, spi->chip_select);
 758                 status = PTR_ERR_OR_ZERO(dev);
 759         } else {
 760                 dev_dbg(&spi->dev, "no minor number available!\n");
 761                 status = -ENODEV;
 762         }
 763         if (status == 0) {
 764                 set_bit(minor, minors);
 765                 list_add(&spidev->device_entry, &device_list);
 766         }
 767         mutex_unlock(&device_list_lock);
 768
 769         spidev->speed_hz = spi->max_speed_hz;
 770
 771         if (status == 0)
 772                 spi_set_drvdata(spi, spidev);
 773         else
 774                 kfree(spidev);
 775
 776         return status;
 777 }
 778
 779 static int spidev_remove(struct spi_device *spi)
 780 {
 781         struct spidev_data      *spidev = spi_get_drvdata(spi);
 782
 783         /* make sure ops on existing fds can abort cleanly */
 784         spin_lock_irq(&spidev->spi_lock);
 785         spidev->spi = NULL;
 786         spin_unlock_irq(&spidev->spi_lock);
 787
 788         /* prevent new opens */
 789         mutex_lock(&device_list_lock);
 790         list_del(&spidev->device_entry);
 791         device_destroy(spidev_class, spidev->devt);
 792         clear_bit(MINOR(spidev->devt), minors);
 793         if (spidev->users == 0)
 794                 kfree(spidev);
 795         mutex_unlock(&device_list_lock);
 796
 797         return 0;
 798 }
 799
 800 static struct spi_driver spidev_spi_driver = {
 801         .driver = {
 802                 .name =         "spidev",
 803                 .of_match_table = of_match_ptr(spidev_dt_ids),
 804                 .acpi_match_table = ACPI_PTR(spidev_acpi_ids),
 805         },
 806         .probe =        spidev_probe,
 807         .remove =       spidev_remove,
 808
 809         /* NOTE:  suspend/resume methods are not necessary here.
 810          * We don't do anything except pass the requests to/from
 811          * the underlying controller.  The refrigerator handles
 812          * most issues; the controller driver handles the rest.
 813          */
 814 };
 815
 816 /*-------------------------------------------------------------------------*/
 817
 818 static int __init spidev_init(void)
 819 {
 820         int status;
 821
 822         /* Claim our 256 reserved device numbers.  Then register a class
 823          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 824          * the driver which manages those device numbers.
 825          */
 826         BUILD_BUG_ON(N_SPI_MINORS > 256);
 827         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 828         if (status < 0)
 829                 return status;
 830
 831         spidev_class = class_create(THIS_MODULE, "spidev");
 832         if (IS_ERR(spidev_class)) {
 833                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 834                 return PTR_ERR(spidev_class);
 835         }
 836
 837         status = spi_register_driver(&spidev_spi_driver);
 838         if (status < 0) {
 839                 class_destroy(spidev_class);
 840                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 841         }
 842         return status;
 843 }
 844 module_init(spidev_init);
 845
 846 static void __exit spidev_exit(void)
 847 {
 848         spi_unregister_driver(&spidev_spi_driver);
 849         class_destroy(spidev_class);
 850         unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 851 }
 852 module_exit(spidev_exit);
 853
 854 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 855 MODULE_DESCRIPTION("User mode SPI device interface");
 856 MODULE_LICENSE("GPL");
 857 MODULE_ALIAS("spi:spidev");