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_TX_OCTAL | SPI_RX_DUAL \
  66                                 | SPI_RX_QUAD | SPI_RX_OCTAL)
  67
  68 struct spidev_data {
  69         dev_t                   devt;
  70         spinlock_t              spi_lock;
  71         struct spi_device       *spi;
  72         struct list_head        device_entry;
  73
  74         /* TX/RX buffers are NULL unless this device is open (users > 0) */
  75         struct mutex            buf_lock;
  76         unsigned                users;
  77         u8                      *tx_buffer;
  78         u8                      *rx_buffer;
  79         u32                     speed_hz;
  80 };
  81
  82 static LIST_HEAD(device_list);
  83 static DEFINE_MUTEX(device_list_lock);
  84
  85 static unsigned bufsiz = 4096;
  86 module_param(bufsiz, uint, S_IRUGO);
  87 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  88
  89 /*-------------------------------------------------------------------------*/
  90
  91 static ssize_t
  92 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
  93 {
  94         int status;
  95         struct spi_device *spi;
  96
  97         spin_lock_irq(&spidev->spi_lock);
  98         spi = spidev->spi;
  99         spin_unlock_irq(&spidev->spi_lock);
 100
 101         if (spi == NULL)
 102                 status = -ESHUTDOWN;
 103         else
 104                 status = spi_sync(spi, message);
 105
 106         if (status == 0)
 107                 status = message->actual_length;
 108
 109         return status;
 110 }
 111
 112 static inline ssize_t
 113 spidev_sync_write(struct spidev_data *spidev, size_t len)
 114 {
 115         struct spi_transfer     t = {
 116                         .tx_buf         = spidev->tx_buffer,
 117                         .len            = len,
 118                         .speed_hz       = spidev->speed_hz,
 119                 };
 120         struct spi_message      m;
 121
 122         spi_message_init(&m);
 123         spi_message_add_tail(&t, &m);
 124         return spidev_sync(spidev, &m);
 125 }
 126
 127 static inline ssize_t
 128 spidev_sync_read(struct spidev_data *spidev, size_t len)
 129 {
 130         struct spi_transfer     t = {
 131                         .rx_buf         = spidev->rx_buffer,
 132                         .len            = len,
 133                         .speed_hz       = spidev->speed_hz,
 134                 };
 135         struct spi_message      m;
 136
 137         spi_message_init(&m);
 138         spi_message_add_tail(&t, &m);
 139         return spidev_sync(spidev, &m);
 140 }
 141
 142 /*-------------------------------------------------------------------------*/
 143
 144 /* Read-only message with current device setup */
 145 static ssize_t
 146 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
 147 {
 148         struct spidev_data      *spidev;
 149         ssize_t                 status;
 150
 151         /* chipselect only toggles at start or end of operation */
 152         if (count > bufsiz)
 153                 return -EMSGSIZE;
 154
 155         spidev = filp->private_data;
 156
 157         mutex_lock(&spidev->buf_lock);
 158         status = spidev_sync_read(spidev, count);
 159         if (status > 0) {
 160                 unsigned long   missing;
 161
 162                 missing = copy_to_user(buf, spidev->rx_buffer, status);
 163                 if (missing == status)
 164                         status = -EFAULT;
 165                 else
 166                         status = status - missing;
 167         }
 168         mutex_unlock(&spidev->buf_lock);
 169
 170         return status;
 171 }
 172
 173 /* Write-only message with current device setup */
 174 static ssize_t
 175 spidev_write(struct file *filp, const char __user *buf,
 176                 size_t count, loff_t *f_pos)
 177 {
 178         struct spidev_data      *spidev;
 179         ssize_t                 status;
 180         unsigned long           missing;
 181
 182         /* chipselect only toggles at start or end of operation */
 183         if (count > bufsiz)
 184                 return -EMSGSIZE;
 185
 186         spidev = filp->private_data;
 187
 188         mutex_lock(&spidev->buf_lock);
 189         missing = copy_from_user(spidev->tx_buffer, buf, count);
 190         if (missing == 0)
 191                 status = spidev_sync_write(spidev, count);
 192         else
 193                 status = -EFAULT;
 194         mutex_unlock(&spidev->buf_lock);
 195
 196         return status;
 197 }
 198
 199 static int spidev_message(struct spidev_data *spidev,
 200                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 201 {
 202         struct spi_message      msg;
 203         struct spi_transfer     *k_xfers;
 204         struct spi_transfer     *k_tmp;
 205         struct spi_ioc_transfer *u_tmp;
 206         unsigned                n, total, tx_total, rx_total;
 207         u8                      *tx_buf, *rx_buf;
 208         int                     status = -EFAULT;
 209
 210         spi_message_init(&msg);
 211         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 212         if (k_xfers == NULL)
 213                 return -ENOMEM;
 214
 215         /* Construct spi_message, copying any tx data to bounce buffer.
 216          * We walk the array of user-provided transfers, using each one
 217          * to initialize a kernel version of the same transfer.
 218          */
 219         tx_buf = spidev->tx_buffer;
 220         rx_buf = spidev->rx_buffer;
 221         total = 0;
 222         tx_total = 0;
 223         rx_total = 0;
 224         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 225                         n;
 226                         n--, k_tmp++, u_tmp++) {
 227                 /* Ensure that also following allocations from rx_buf/tx_buf will meet
 228                  * DMA alignment requirements.
 229                  */
 230                 unsigned int len_aligned = ALIGN(u_tmp->len, ARCH_KMALLOC_MINALIGN);
 231
 232                 k_tmp->len = u_tmp->len;
 233
 234                 total += k_tmp->len;
 235                 /* Since the function returns the total length of transfers
 236                  * on success, restrict the total to positive int values to
 237                  * avoid the return value looking like an error.  Also check
 238                  * each transfer length to avoid arithmetic overflow.
 239                  */
 240                 if (total > INT_MAX || k_tmp->len > INT_MAX) {
 241                         status = -EMSGSIZE;
 242                         goto done;
 243                 }
 244
 245                 if (u_tmp->rx_buf) {
 246                         /* this transfer needs space in RX bounce buffer */
 247                         rx_total += len_aligned;
 248                         if (rx_total > bufsiz) {
 249                                 status = -EMSGSIZE;
 250                                 goto done;
 251                         }
 252                         k_tmp->rx_buf = rx_buf;
 253                         rx_buf += len_aligned;
 254                 }
 255                 if (u_tmp->tx_buf) {
 256                         /* this transfer needs space in TX bounce buffer */
 257                         tx_total += len_aligned;
 258                         if (tx_total > bufsiz) {
 259                                 status = -EMSGSIZE;
 260                                 goto done;
 261                         }
 262                         k_tmp->tx_buf = tx_buf;
 263                         if (copy_from_user(tx_buf, (const u8 __user *)
 264                                                 (uintptr_t) u_tmp->tx_buf,
 265                                         u_tmp->len))
 266                                 goto done;
 267                         tx_buf += len_aligned;
 268                 }
 269
 270                 k_tmp->cs_change = !!u_tmp->cs_change;
 271                 k_tmp->tx_nbits = u_tmp->tx_nbits;
 272                 k_tmp->rx_nbits = u_tmp->rx_nbits;
 273                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 274                 k_tmp->delay.value = u_tmp->delay_usecs;
 275                 k_tmp->delay.unit = SPI_DELAY_UNIT_USECS;
 276                 k_tmp->speed_hz = u_tmp->speed_hz;
 277                 k_tmp->word_delay.value = u_tmp->word_delay_usecs;
 278                 k_tmp->word_delay.unit = SPI_DELAY_UNIT_USECS;
 279                 if (!k_tmp->speed_hz)
 280                         k_tmp->speed_hz = spidev->speed_hz;
 281 #ifdef VERBOSE
 282                 dev_dbg(&spidev->spi->dev,
 283                         "  xfer len %u %s%s%s%dbits %u usec %u usec %uHz\n",
 284                         k_tmp->len,
 285                         k_tmp->rx_buf ? "rx " : "",
 286                         k_tmp->tx_buf ? "tx " : "",
 287                         k_tmp->cs_change ? "cs " : "",
 288                         k_tmp->bits_per_word ? : spidev->spi->bits_per_word,
 289                         k_tmp->delay.value,
 290                         k_tmp->word_delay.value,
 291                         k_tmp->speed_hz ? : spidev->spi->max_speed_hz);
 292 #endif
 293                 spi_message_add_tail(k_tmp, &msg);
 294         }
 295
 296         status = spidev_sync(spidev, &msg);
 297         if (status < 0)
 298                 goto done;
 299
 300         /* copy any rx data out of bounce buffer */
 301         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 302                         n;
 303                         n--, k_tmp++, u_tmp++) {
 304                 if (u_tmp->rx_buf) {
 305                         if (copy_to_user((u8 __user *)
 306                                         (uintptr_t) u_tmp->rx_buf, k_tmp->rx_buf,
 307                                         u_tmp->len)) {
 308                                 status = -EFAULT;
 309                                 goto done;
 310                         }
 311                 }
 312         }
 313         status = total;
 314
 315 done:
 316         kfree(k_xfers);
 317         return status;
 318 }
 319
 320 static struct spi_ioc_transfer *
 321 spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
 322                 unsigned *n_ioc)
 323 {
 324         u32     tmp;
 325
 326         /* Check type, command number and direction */
 327         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
 328                         || _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 329                         || _IOC_DIR(cmd) != _IOC_WRITE)
 330                 return ERR_PTR(-ENOTTY);
 331
 332         tmp = _IOC_SIZE(cmd);
 333         if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
 334                 return ERR_PTR(-EINVAL);
 335         *n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 336         if (*n_ioc == 0)
 337                 return NULL;
 338
 339         /* copy into scratch area */
 340         return memdup_user(u_ioc, tmp);
 341 }
 342
 343 static long
 344 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 345 {
 346         int                     retval = 0;
 347         struct spidev_data      *spidev;
 348         struct spi_device       *spi;
 349         u32                     tmp;
 350         unsigned                n_ioc;
 351         struct spi_ioc_transfer *ioc;
 352
 353         /* Check type and command number */
 354         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 355                 return -ENOTTY;
 356
 357         /* guard against device removal before, or while,
 358          * we issue this ioctl.
 359          */
 360         spidev = filp->private_data;
 361         spin_lock_irq(&spidev->spi_lock);
 362         spi = spi_dev_get(spidev->spi);
 363         spin_unlock_irq(&spidev->spi_lock);
 364
 365         if (spi == NULL)
 366                 return -ESHUTDOWN;
 367
 368         /* use the buffer lock here for triple duty:
 369          *  - prevent I/O (from us) so calling spi_setup() is safe;
 370          *  - prevent concurrent SPI_IOC_WR_* from morphing
 371          *    data fields while SPI_IOC_RD_* reads them;
 372          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 373          */
 374         mutex_lock(&spidev->buf_lock);
 375
 376         switch (cmd) {
 377         /* read requests */
 378         case SPI_IOC_RD_MODE:
 379         case SPI_IOC_RD_MODE32:
 380                 tmp = spi->mode;
 381
 382                 {
 383                         struct spi_controller *ctlr = spi->controller;
 384
 385                         if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
 386                             ctlr->cs_gpiods[spi->chip_select])
 387                                 tmp &= ~SPI_CS_HIGH;
 388                 }
 389
 390                 if (cmd == SPI_IOC_RD_MODE)
 391                         retval = put_user(tmp & SPI_MODE_MASK,
 392                                           (__u8 __user *)arg);
 393                 else
 394                         retval = put_user(tmp & SPI_MODE_MASK,
 395                                           (__u32 __user *)arg);
 396                 break;
 397         case SPI_IOC_RD_LSB_FIRST:
 398                 retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 399                                         (__u8 __user *)arg);
 400                 break;
 401         case SPI_IOC_RD_BITS_PER_WORD:
 402                 retval = put_user(spi->bits_per_word, (__u8 __user *)arg);
 403                 break;
 404         case SPI_IOC_RD_MAX_SPEED_HZ:
 405                 retval = put_user(spidev->speed_hz, (__u32 __user *)arg);
 406                 break;
 407
 408         /* write requests */
 409         case SPI_IOC_WR_MODE:
 410         case SPI_IOC_WR_MODE32:
 411                 if (cmd == SPI_IOC_WR_MODE)
 412                         retval = get_user(tmp, (u8 __user *)arg);
 413                 else
 414                         retval = get_user(tmp, (u32 __user *)arg);
 415                 if (retval == 0) {
 416                         struct spi_controller *ctlr = spi->controller;
 417                         u32     save = spi->mode;
 418
 419                         if (tmp & ~SPI_MODE_MASK) {
 420                                 retval = -EINVAL;
 421                                 break;
 422                         }
 423
 424                         if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
 425                             ctlr->cs_gpiods[spi->chip_select])
 426                                 tmp |= SPI_CS_HIGH;
 427
 428                         tmp |= spi->mode & ~SPI_MODE_MASK;
 429                         spi->mode = (u16)tmp;
 430                         retval = spi_setup(spi);
 431                         if (retval < 0)
 432                                 spi->mode = save;
 433                         else
 434                                 dev_dbg(&spi->dev, "spi mode %x\n", tmp);
 435                 }
 436                 break;
 437         case SPI_IOC_WR_LSB_FIRST:
 438                 retval = get_user(tmp, (__u8 __user *)arg);
 439                 if (retval == 0) {
 440                         u32     save = spi->mode;
 441
 442                         if (tmp)
 443                                 spi->mode |= SPI_LSB_FIRST;
 444                         else
 445                                 spi->mode &= ~SPI_LSB_FIRST;
 446                         retval = spi_setup(spi);
 447                         if (retval < 0)
 448                                 spi->mode = save;
 449                         else
 450                                 dev_dbg(&spi->dev, "%csb first\n",
 451                                                 tmp ? 'l' : 'm');
 452                 }
 453                 break;
 454         case SPI_IOC_WR_BITS_PER_WORD:
 455                 retval = get_user(tmp, (__u8 __user *)arg);
 456                 if (retval == 0) {
 457                         u8      save = spi->bits_per_word;
 458
 459                         spi->bits_per_word = tmp;
 460                         retval = spi_setup(spi);
 461                         if (retval < 0)
 462                                 spi->bits_per_word = save;
 463                         else
 464                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 465                 }
 466                 break;
 467         case SPI_IOC_WR_MAX_SPEED_HZ:
 468                 retval = get_user(tmp, (__u32 __user *)arg);
 469                 if (retval == 0) {
 470                         u32     save = spi->max_speed_hz;
 471
 472                         spi->max_speed_hz = tmp;
 473                         retval = spi_setup(spi);
 474                         if (retval == 0) {
 475                                 spidev->speed_hz = tmp;
 476                                 dev_dbg(&spi->dev, "%d Hz (max)\n",
 477                                         spidev->speed_hz);
 478                         }
 479                         spi->max_speed_hz = save;
 480                 }
 481                 break;
 482
 483         default:
 484                 /* segmented and/or full-duplex I/O request */
 485                 /* Check message and copy into scratch area */
 486                 ioc = spidev_get_ioc_message(cmd,
 487                                 (struct spi_ioc_transfer __user *)arg, &n_ioc);
 488                 if (IS_ERR(ioc)) {
 489                         retval = PTR_ERR(ioc);
 490                         break;
 491                 }
 492                 if (!ioc)
 493                         break;  /* n_ioc is also 0 */
 494
 495                 /* translate to spi_message, execute */
 496                 retval = spidev_message(spidev, ioc, n_ioc);
 497                 kfree(ioc);
 498                 break;
 499         }
 500
 501         mutex_unlock(&spidev->buf_lock);
 502         spi_dev_put(spi);
 503         return retval;
 504 }
 505
 506 #ifdef CONFIG_COMPAT
 507 static long
 508 spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
 509                 unsigned long arg)
 510 {
 511         struct spi_ioc_transfer __user  *u_ioc;
 512         int                             retval = 0;
 513         struct spidev_data              *spidev;
 514         struct spi_device               *spi;
 515         unsigned                        n_ioc, n;
 516         struct spi_ioc_transfer         *ioc;
 517
 518         u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);
 519
 520         /* guard against device removal before, or while,
 521          * we issue this ioctl.
 522          */
 523         spidev = filp->private_data;
 524         spin_lock_irq(&spidev->spi_lock);
 525         spi = spi_dev_get(spidev->spi);
 526         spin_unlock_irq(&spidev->spi_lock);
 527
 528         if (spi == NULL)
 529                 return -ESHUTDOWN;
 530
 531         /* SPI_IOC_MESSAGE needs the buffer locked "normally" */
 532         mutex_lock(&spidev->buf_lock);
 533
 534         /* Check message and copy into scratch area */
 535         ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
 536         if (IS_ERR(ioc)) {
 537                 retval = PTR_ERR(ioc);
 538                 goto done;
 539         }
 540         if (!ioc)
 541                 goto done;      /* n_ioc is also 0 */
 542
 543         /* Convert buffer pointers */
 544         for (n = 0; n < n_ioc; n++) {
 545                 ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
 546                 ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
 547         }
 548
 549         /* translate to spi_message, execute */
 550         retval = spidev_message(spidev, ioc, n_ioc);
 551         kfree(ioc);
 552
 553 done:
 554         mutex_unlock(&spidev->buf_lock);
 555         spi_dev_put(spi);
 556         return retval;
 557 }
 558
 559 static long
 560 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 561 {
 562         if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
 563                         && _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
 564                         && _IOC_DIR(cmd) == _IOC_WRITE)
 565                 return spidev_compat_ioc_message(filp, cmd, arg);
 566
 567         return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 568 }
 569 #else
 570 #define spidev_compat_ioctl NULL
 571 #endif /* CONFIG_COMPAT */
 572
 573 static int spidev_open(struct inode *inode, struct file *filp)
 574 {
 575         struct spidev_data      *spidev;
 576         int                     status = -ENXIO;
 577
 578         mutex_lock(&device_list_lock);
 579
 580         list_for_each_entry(spidev, &device_list, device_entry) {
 581                 if (spidev->devt == inode->i_rdev) {
 582                         status = 0;
 583                         break;
 584                 }
 585         }
 586
 587         if (status) {
 588                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 589                 goto err_find_dev;
 590         }
 591
 592         if (!spidev->tx_buffer) {
 593                 spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 594                 if (!spidev->tx_buffer) {
 595                         status = -ENOMEM;
 596                         goto err_find_dev;
 597                 }
 598         }
 599
 600         if (!spidev->rx_buffer) {
 601                 spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 602                 if (!spidev->rx_buffer) {
 603                         status = -ENOMEM;
 604                         goto err_alloc_rx_buf;
 605                 }
 606         }
 607
 608         spidev->users++;
 609         filp->private_data = spidev;
 610         stream_open(inode, filp);
 611
 612         mutex_unlock(&device_list_lock);
 613         return 0;
 614
 615 err_alloc_rx_buf:
 616         kfree(spidev->tx_buffer);
 617         spidev->tx_buffer = NULL;
 618 err_find_dev:
 619         mutex_unlock(&device_list_lock);
 620         return status;
 621 }
 622
 623 static int spidev_release(struct inode *inode, struct file *filp)
 624 {
 625         struct spidev_data      *spidev;
 626         int                     dofree;
 627
 628         mutex_lock(&device_list_lock);
 629         spidev = filp->private_data;
 630         filp->private_data = NULL;
 631
 632         spin_lock_irq(&spidev->spi_lock);
 633         /* ... after we unbound from the underlying device? */
 634         dofree = (spidev->spi == NULL);
 635         spin_unlock_irq(&spidev->spi_lock);
 636
 637         /* last close? */
 638         spidev->users--;
 639         if (!spidev->users) {
 640
 641                 kfree(spidev->tx_buffer);
 642                 spidev->tx_buffer = NULL;
 643
 644                 kfree(spidev->rx_buffer);
 645                 spidev->rx_buffer = NULL;
 646
 647                 if (dofree)
 648                         kfree(spidev);
 649                 else
 650                         spidev->speed_hz = spidev->spi->max_speed_hz;
 651         }
 652 #ifdef CONFIG_SPI_SLAVE
 653         if (!dofree)
 654                 spi_slave_abort(spidev->spi);
 655 #endif
 656         mutex_unlock(&device_list_lock);
 657
 658         return 0;
 659 }
 660
 661 static const struct file_operations spidev_fops = {
 662         .owner =        THIS_MODULE,
 663         /* REVISIT switch to aio primitives, so that userspace
 664          * gets more complete API coverage.  It'll simplify things
 665          * too, except for the locking.
 666          */
 667         .write =        spidev_write,
 668         .read =         spidev_read,
 669         .unlocked_ioctl = spidev_ioctl,
 670         .compat_ioctl = spidev_compat_ioctl,
 671         .open =         spidev_open,
 672         .release =      spidev_release,
 673         .llseek =       no_llseek,
 674 };
 675
 676 /*-------------------------------------------------------------------------*/
 677
 678 /* The main reason to have this class is to make mdev/udev create the
 679  * /dev/spidevB.C character device nodes exposing our userspace API.
 680  * It also simplifies memory management.
 681  */
 682
 683 static struct class *spidev_class;
 684
 685 #ifdef CONFIG_OF
 686 static const struct of_device_id spidev_dt_ids[] = {
 687         { .compatible = "rohm,dh2228fv" },
 688         { .compatible = "lineartechnology,ltc2488" },
 689         { .compatible = "ge,achc" },
 690         { .compatible = "semtech,sx1301" },
 691         { .compatible = "lwn,bk4" },
 692         { .compatible = "dh,dhcom-board" },
 693         { .compatible = "menlo,m53cpld" },
 694         {},
 695 };
 696 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 697 #endif
 698
 699 #ifdef CONFIG_ACPI
 700
 701 /* Dummy SPI devices not to be used in production systems */
 702 #define SPIDEV_ACPI_DUMMY       1
 703
 704 static const struct acpi_device_id spidev_acpi_ids[] = {
 705         /*
 706          * The ACPI SPT000* devices are only meant for development and
 707          * testing. Systems used in production should have a proper ACPI
 708          * description of the connected peripheral and they should also use
 709          * a proper driver instead of poking directly to the SPI bus.
 710          */
 711         { "SPT0001", SPIDEV_ACPI_DUMMY },
 712         { "SPT0002", SPIDEV_ACPI_DUMMY },
 713         { "SPT0003", SPIDEV_ACPI_DUMMY },
 714         {},
 715 };
 716 MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);
 717
 718 static void spidev_probe_acpi(struct spi_device *spi)
 719 {
 720         const struct acpi_device_id *id;
 721
 722         if (!has_acpi_companion(&spi->dev))
 723                 return;
 724
 725         id = acpi_match_device(spidev_acpi_ids, &spi->dev);
 726         if (WARN_ON(!id))
 727                 return;
 728
 729         if (id->driver_data == SPIDEV_ACPI_DUMMY)
 730                 dev_warn(&spi->dev, "do not use this driver in production systems!\n");
 731 }
 732 #else
 733 static inline void spidev_probe_acpi(struct spi_device *spi) {}
 734 #endif
 735
 736 /*-------------------------------------------------------------------------*/
 737
 738 static int spidev_probe(struct spi_device *spi)
 739 {
 740         struct spidev_data      *spidev;
 741         int                     status;
 742         unsigned long           minor;
 743
 744         /*
 745          * spidev should never be referenced in DT without a specific
 746          * compatible string, it is a Linux implementation thing
 747          * rather than a description of the hardware.
 748          */
 749         WARN(spi->dev.of_node &&
 750              of_device_is_compatible(spi->dev.of_node, "spidev"),
 751              "%pOF: buggy DT: spidev listed directly in DT\n", spi->dev.of_node);
 752
 753         spidev_probe_acpi(spi);
 754
 755         /* Allocate driver data */
 756         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 757         if (!spidev)
 758                 return -ENOMEM;
 759
 760         /* Initialize the driver data */
 761         spidev->spi = spi;
 762         spin_lock_init(&spidev->spi_lock);
 763         mutex_init(&spidev->buf_lock);
 764
 765         INIT_LIST_HEAD(&spidev->device_entry);
 766
 767         /* If we can allocate a minor number, hook up this device.
 768          * Reusing minors is fine so long as udev or mdev is working.
 769          */
 770         mutex_lock(&device_list_lock);
 771         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 772         if (minor < N_SPI_MINORS) {
 773                 struct device *dev;
 774
 775                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
 776                 dev = device_create(spidev_class, &spi->dev, spidev->devt,
 777                                     spidev, "spidev%d.%d",
 778                                     spi->master->bus_num, spi->chip_select);
 779                 status = PTR_ERR_OR_ZERO(dev);
 780         } else {
 781                 dev_dbg(&spi->dev, "no minor number available!\n");
 782                 status = -ENODEV;
 783         }
 784         if (status == 0) {
 785                 set_bit(minor, minors);
 786                 list_add(&spidev->device_entry, &device_list);
 787         }
 788         mutex_unlock(&device_list_lock);
 789
 790         spidev->speed_hz = spi->max_speed_hz;
 791
 792         if (status == 0)
 793                 spi_set_drvdata(spi, spidev);
 794         else
 795                 kfree(spidev);
 796
 797         return status;
 798 }
 799
 800 static int spidev_remove(struct spi_device *spi)
 801 {
 802         struct spidev_data      *spidev = spi_get_drvdata(spi);
 803
 804         /* prevent new opens */
 805         mutex_lock(&device_list_lock);
 806         /* make sure ops on existing fds can abort cleanly */
 807         spin_lock_irq(&spidev->spi_lock);
 808         spidev->spi = NULL;
 809         spin_unlock_irq(&spidev->spi_lock);
 810
 811         list_del(&spidev->device_entry);
 812         device_destroy(spidev_class, spidev->devt);
 813         clear_bit(MINOR(spidev->devt), minors);
 814         if (spidev->users == 0)
 815                 kfree(spidev);
 816         mutex_unlock(&device_list_lock);
 817
 818         return 0;
 819 }
 820
 821 static struct spi_driver spidev_spi_driver = {
 822         .driver = {
 823                 .name =         "spidev",
 824                 .of_match_table = of_match_ptr(spidev_dt_ids),
 825                 .acpi_match_table = ACPI_PTR(spidev_acpi_ids),
 826         },
 827         .probe =        spidev_probe,
 828         .remove =       spidev_remove,
 829
 830         /* NOTE:  suspend/resume methods are not necessary here.
 831          * We don't do anything except pass the requests to/from
 832          * the underlying controller.  The refrigerator handles
 833          * most issues; the controller driver handles the rest.
 834          */
 835 };
 836
 837 /*-------------------------------------------------------------------------*/
 838
 839 static int __init spidev_init(void)
 840 {
 841         int status;
 842
 843         /* Claim our 256 reserved device numbers.  Then register a class
 844          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 845          * the driver which manages those device numbers.
 846          */
 847         BUILD_BUG_ON(N_SPI_MINORS > 256);
 848         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 849         if (status < 0)
 850                 return status;
 851
 852         spidev_class = class_create(THIS_MODULE, "spidev");
 853         if (IS_ERR(spidev_class)) {
 854                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 855                 return PTR_ERR(spidev_class);
 856         }
 857
 858         status = spi_register_driver(&spidev_spi_driver);
 859         if (status < 0) {
 860                 class_destroy(spidev_class);
 861                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 862         }
 863         return status;
 864 }
 865 module_init(spidev_init);
 866
 867 static void __exit spidev_exit(void)
 868 {
 869         spi_unregister_driver(&spidev_spi_driver);
 870         class_destroy(spidev_class);
 871         unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 872 }
 873 module_exit(spidev_exit);
 874
 875 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 876 MODULE_DESCRIPTION("User mode SPI device interface");
 877 MODULE_LICENSE("GPL");
 878 MODULE_ALIAS("spi:spidev");