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/ioctl.h>
  12 #include <linux/fs.h>
  13 #include <linux/device.h>
  14 #include <linux/err.h>
  15 #include <linux/list.h>
  16 #include <linux/errno.h>
  17 #include <linux/mod_devicetable.h>
  18 #include <linux/module.h>
  19 #include <linux/mutex.h>
  20 #include <linux/property.h>
  21 #include <linux/slab.h>
  22 #include <linux/compat.h>
  23
  24 #include <linux/spi/spi.h>
  25 #include <linux/spi/spidev.h>
  26
  27 #include <linux/uaccess.h>
  28
  29
  30 /*
  31  * This supports access to SPI devices using normal userspace I/O calls.
  32  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
  33  * and often mask message boundaries, full SPI support requires full duplex
  34  * transfers.  There are several kinds of internal message boundaries to
  35  * handle chipselect management and other protocol options.
  36  *
  37  * SPI has a character major number assigned.  We allocate minor numbers
  38  * dynamically using a bitmask.  You must use hotplug tools, such as udev
  39  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
  40  * nodes, since there is no fixed association of minor numbers with any
  41  * particular SPI bus or device.
  42  */
  43 #define SPIDEV_MAJOR                    153     /* assigned */
  44 #define N_SPI_MINORS                    32      /* ... up to 256 */
  45
  46 static DECLARE_BITMAP(minors, N_SPI_MINORS);
  47
  48 static_assert(N_SPI_MINORS > 0 && N_SPI_MINORS <= 256);
  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_MODE_X_MASK | 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                                 | SPI_RX_CPHA_FLIP | SPI_3WIRE_HIZ \
  68                                 | SPI_MOSI_IDLE_LOW)
  69
  70 struct spidev_data {
  71         dev_t                   devt;
  72         struct mutex            spi_lock;
  73         struct spi_device       *spi;
  74         struct list_head        device_entry;
  75
  76         /* TX/RX buffers are NULL unless this device is open (users > 0) */
  77         struct mutex            buf_lock;
  78         unsigned                users;
  79         u8                      *tx_buffer;
  80         u8                      *rx_buffer;
  81         u32                     speed_hz;
  82 };
  83
  84 static LIST_HEAD(device_list);
  85 static DEFINE_MUTEX(device_list_lock);
  86
  87 static unsigned bufsiz = 4096;
  88 module_param(bufsiz, uint, S_IRUGO);
  89 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  90
  91 /*-------------------------------------------------------------------------*/
  92
  93 static ssize_t
  94 spidev_sync_unlocked(struct spi_device *spi, struct spi_message *message)
  95 {
  96         ssize_t status;
  97
  98         status = spi_sync(spi, message);
  99         if (status == 0)
 100                 status = message->actual_length;
 101
 102         return status;
 103 }
 104
 105 static ssize_t
 106 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
 107 {
 108         ssize_t status;
 109         struct spi_device *spi;
 110
 111         mutex_lock(&spidev->spi_lock);
 112         spi = spidev->spi;
 113
 114         if (spi == NULL)
 115                 status = -ESHUTDOWN;
 116         else
 117                 status = spidev_sync_unlocked(spi, message);
 118
 119         mutex_unlock(&spidev->spi_lock);
 120         return status;
 121 }
 122
 123 static inline ssize_t
 124 spidev_sync_write(struct spidev_data *spidev, size_t len)
 125 {
 126         struct spi_transfer     t = {
 127                         .tx_buf         = spidev->tx_buffer,
 128                         .len            = len,
 129                         .speed_hz       = spidev->speed_hz,
 130                 };
 131         struct spi_message      m;
 132
 133         spi_message_init(&m);
 134         spi_message_add_tail(&t, &m);
 135         return spidev_sync(spidev, &m);
 136 }
 137
 138 static inline ssize_t
 139 spidev_sync_read(struct spidev_data *spidev, size_t len)
 140 {
 141         struct spi_transfer     t = {
 142                         .rx_buf         = spidev->rx_buffer,
 143                         .len            = len,
 144                         .speed_hz       = spidev->speed_hz,
 145                 };
 146         struct spi_message      m;
 147
 148         spi_message_init(&m);
 149         spi_message_add_tail(&t, &m);
 150         return spidev_sync(spidev, &m);
 151 }
 152
 153 /*-------------------------------------------------------------------------*/
 154
 155 /* Read-only message with current device setup */
 156 static ssize_t
 157 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
 158 {
 159         struct spidev_data      *spidev;
 160         ssize_t                 status;
 161
 162         /* chipselect only toggles at start or end of operation */
 163         if (count > bufsiz)
 164                 return -EMSGSIZE;
 165
 166         spidev = filp->private_data;
 167
 168         mutex_lock(&spidev->buf_lock);
 169         status = spidev_sync_read(spidev, count);
 170         if (status > 0) {
 171                 unsigned long   missing;
 172
 173                 missing = copy_to_user(buf, spidev->rx_buffer, status);
 174                 if (missing == status)
 175                         status = -EFAULT;
 176                 else
 177                         status = status - missing;
 178         }
 179         mutex_unlock(&spidev->buf_lock);
 180
 181         return status;
 182 }
 183
 184 /* Write-only message with current device setup */
 185 static ssize_t
 186 spidev_write(struct file *filp, const char __user *buf,
 187                 size_t count, loff_t *f_pos)
 188 {
 189         struct spidev_data      *spidev;
 190         ssize_t                 status;
 191         unsigned long           missing;
 192
 193         /* chipselect only toggles at start or end of operation */
 194         if (count > bufsiz)
 195                 return -EMSGSIZE;
 196
 197         spidev = filp->private_data;
 198
 199         mutex_lock(&spidev->buf_lock);
 200         missing = copy_from_user(spidev->tx_buffer, buf, count);
 201         if (missing == 0)
 202                 status = spidev_sync_write(spidev, count);
 203         else
 204                 status = -EFAULT;
 205         mutex_unlock(&spidev->buf_lock);
 206
 207         return status;
 208 }
 209
 210 static int spidev_message(struct spidev_data *spidev,
 211                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 212 {
 213         struct spi_message      msg;
 214         struct spi_transfer     *k_xfers;
 215         struct spi_transfer     *k_tmp;
 216         struct spi_ioc_transfer *u_tmp;
 217         unsigned                n, total, tx_total, rx_total;
 218         u8                      *tx_buf, *rx_buf;
 219         int                     status = -EFAULT;
 220
 221         spi_message_init(&msg);
 222         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 223         if (k_xfers == NULL)
 224                 return -ENOMEM;
 225
 226         /* Construct spi_message, copying any tx data to bounce buffer.
 227          * We walk the array of user-provided transfers, using each one
 228          * to initialize a kernel version of the same transfer.
 229          */
 230         tx_buf = spidev->tx_buffer;
 231         rx_buf = spidev->rx_buffer;
 232         total = 0;
 233         tx_total = 0;
 234         rx_total = 0;
 235         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 236                         n;
 237                         n--, k_tmp++, u_tmp++) {
 238                 /* Ensure that also following allocations from rx_buf/tx_buf will meet
 239                  * DMA alignment requirements.
 240                  */
 241                 unsigned int len_aligned = ALIGN(u_tmp->len, ARCH_DMA_MINALIGN);
 242
 243                 k_tmp->len = u_tmp->len;
 244
 245                 total += k_tmp->len;
 246                 /* Since the function returns the total length of transfers
 247                  * on success, restrict the total to positive int values to
 248                  * avoid the return value looking like an error.  Also check
 249                  * each transfer length to avoid arithmetic overflow.
 250                  */
 251                 if (total > INT_MAX || k_tmp->len > INT_MAX) {
 252                         status = -EMSGSIZE;
 253                         goto done;
 254                 }
 255
 256                 if (u_tmp->rx_buf) {
 257                         /* this transfer needs space in RX bounce buffer */
 258                         rx_total += len_aligned;
 259                         if (rx_total > bufsiz) {
 260                                 status = -EMSGSIZE;
 261                                 goto done;
 262                         }
 263                         k_tmp->rx_buf = rx_buf;
 264                         rx_buf += len_aligned;
 265                 }
 266                 if (u_tmp->tx_buf) {
 267                         /* this transfer needs space in TX bounce buffer */
 268                         tx_total += len_aligned;
 269                         if (tx_total > bufsiz) {
 270                                 status = -EMSGSIZE;
 271                                 goto done;
 272                         }
 273                         k_tmp->tx_buf = tx_buf;
 274                         if (copy_from_user(tx_buf, (const u8 __user *)
 275                                                 (uintptr_t) u_tmp->tx_buf,
 276                                         u_tmp->len))
 277                                 goto done;
 278                         tx_buf += len_aligned;
 279                 }
 280
 281                 k_tmp->cs_change = !!u_tmp->cs_change;
 282                 k_tmp->tx_nbits = u_tmp->tx_nbits;
 283                 k_tmp->rx_nbits = u_tmp->rx_nbits;
 284                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 285                 k_tmp->delay.value = u_tmp->delay_usecs;
 286                 k_tmp->delay.unit = SPI_DELAY_UNIT_USECS;
 287                 k_tmp->speed_hz = u_tmp->speed_hz;
 288                 k_tmp->word_delay.value = u_tmp->word_delay_usecs;
 289                 k_tmp->word_delay.unit = SPI_DELAY_UNIT_USECS;
 290                 if (!k_tmp->speed_hz)
 291                         k_tmp->speed_hz = spidev->speed_hz;
 292 #ifdef VERBOSE
 293                 dev_dbg(&spidev->spi->dev,
 294                         "  xfer len %u %s%s%s%dbits %u usec %u usec %uHz\n",
 295                         k_tmp->len,
 296                         k_tmp->rx_buf ? "rx " : "",
 297                         k_tmp->tx_buf ? "tx " : "",
 298                         k_tmp->cs_change ? "cs " : "",
 299                         k_tmp->bits_per_word ? : spidev->spi->bits_per_word,
 300                         k_tmp->delay.value,
 301                         k_tmp->word_delay.value,
 302                         k_tmp->speed_hz ? : spidev->spi->max_speed_hz);
 303 #endif
 304                 spi_message_add_tail(k_tmp, &msg);
 305         }
 306
 307         status = spidev_sync_unlocked(spidev->spi, &msg);
 308         if (status < 0)
 309                 goto done;
 310
 311         /* copy any rx data out of bounce buffer */
 312         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 313                         n;
 314                         n--, k_tmp++, u_tmp++) {
 315                 if (u_tmp->rx_buf) {
 316                         if (copy_to_user((u8 __user *)
 317                                         (uintptr_t) u_tmp->rx_buf, k_tmp->rx_buf,
 318                                         u_tmp->len)) {
 319                                 status = -EFAULT;
 320                                 goto done;
 321                         }
 322                 }
 323         }
 324         status = total;
 325
 326 done:
 327         kfree(k_xfers);
 328         return status;
 329 }
 330
 331 static struct spi_ioc_transfer *
 332 spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
 333                 unsigned *n_ioc)
 334 {
 335         u32     tmp;
 336
 337         /* Check type, command number and direction */
 338         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
 339                         || _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 340                         || _IOC_DIR(cmd) != _IOC_WRITE)
 341                 return ERR_PTR(-ENOTTY);
 342
 343         tmp = _IOC_SIZE(cmd);
 344         if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
 345                 return ERR_PTR(-EINVAL);
 346         *n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 347         if (*n_ioc == 0)
 348                 return NULL;
 349
 350         /* copy into scratch area */
 351         return memdup_user(u_ioc, tmp);
 352 }
 353
 354 static long
 355 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 356 {
 357         int                     retval = 0;
 358         struct spidev_data      *spidev;
 359         struct spi_device       *spi;
 360         u32                     tmp;
 361         unsigned                n_ioc;
 362         struct spi_ioc_transfer *ioc;
 363
 364         /* Check type and command number */
 365         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 366                 return -ENOTTY;
 367
 368         /* guard against device removal before, or while,
 369          * we issue this ioctl.
 370          */
 371         spidev = filp->private_data;
 372         mutex_lock(&spidev->spi_lock);
 373         spi = spi_dev_get(spidev->spi);
 374         if (spi == NULL) {
 375                 mutex_unlock(&spidev->spi_lock);
 376                 return -ESHUTDOWN;
 377         }
 378
 379         /* use the buffer lock here for triple duty:
 380          *  - prevent I/O (from us) so calling spi_setup() is safe;
 381          *  - prevent concurrent SPI_IOC_WR_* from morphing
 382          *    data fields while SPI_IOC_RD_* reads them;
 383          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 384          */
 385         mutex_lock(&spidev->buf_lock);
 386
 387         switch (cmd) {
 388         /* read requests */
 389         case SPI_IOC_RD_MODE:
 390         case SPI_IOC_RD_MODE32:
 391                 tmp = spi->mode;
 392
 393                 {
 394                         struct spi_controller *ctlr = spi->controller;
 395
 396                         if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
 397                             ctlr->cs_gpiods[spi_get_chipselect(spi, 0)])
 398                                 tmp &= ~SPI_CS_HIGH;
 399                 }
 400
 401                 if (cmd == SPI_IOC_RD_MODE)
 402                         retval = put_user(tmp & SPI_MODE_MASK,
 403                                           (__u8 __user *)arg);
 404                 else
 405                         retval = put_user(tmp & SPI_MODE_MASK,
 406                                           (__u32 __user *)arg);
 407                 break;
 408         case SPI_IOC_RD_LSB_FIRST:
 409                 retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 410                                         (__u8 __user *)arg);
 411                 break;
 412         case SPI_IOC_RD_BITS_PER_WORD:
 413                 retval = put_user(spi->bits_per_word, (__u8 __user *)arg);
 414                 break;
 415         case SPI_IOC_RD_MAX_SPEED_HZ:
 416                 retval = put_user(spidev->speed_hz, (__u32 __user *)arg);
 417                 break;
 418
 419         /* write requests */
 420         case SPI_IOC_WR_MODE:
 421         case SPI_IOC_WR_MODE32:
 422                 if (cmd == SPI_IOC_WR_MODE)
 423                         retval = get_user(tmp, (u8 __user *)arg);
 424                 else
 425                         retval = get_user(tmp, (u32 __user *)arg);
 426                 if (retval == 0) {
 427                         u32     save = spi->mode;
 428
 429                         if (tmp & ~SPI_MODE_MASK) {
 430                                 retval = -EINVAL;
 431                                 break;
 432                         }
 433
 434                         tmp |= spi->mode & ~SPI_MODE_MASK;
 435                         spi->mode = tmp & SPI_MODE_USER_MASK;
 436                         retval = spi_setup(spi);
 437                         if (retval < 0)
 438                                 spi->mode = save;
 439                         else
 440                                 dev_dbg(&spi->dev, "spi mode %x\n", tmp);
 441                 }
 442                 break;
 443         case SPI_IOC_WR_LSB_FIRST:
 444                 retval = get_user(tmp, (__u8 __user *)arg);
 445                 if (retval == 0) {
 446                         u32     save = spi->mode;
 447
 448                         if (tmp)
 449                                 spi->mode |= SPI_LSB_FIRST;
 450                         else
 451                                 spi->mode &= ~SPI_LSB_FIRST;
 452                         retval = spi_setup(spi);
 453                         if (retval < 0)
 454                                 spi->mode = save;
 455                         else
 456                                 dev_dbg(&spi->dev, "%csb first\n",
 457                                                 tmp ? 'l' : 'm');
 458                 }
 459                 break;
 460         case SPI_IOC_WR_BITS_PER_WORD:
 461                 retval = get_user(tmp, (__u8 __user *)arg);
 462                 if (retval == 0) {
 463                         u8      save = spi->bits_per_word;
 464
 465                         spi->bits_per_word = tmp;
 466                         retval = spi_setup(spi);
 467                         if (retval < 0)
 468                                 spi->bits_per_word = save;
 469                         else
 470                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 471                 }
 472                 break;
 473         case SPI_IOC_WR_MAX_SPEED_HZ: {
 474                 u32 save;
 475
 476                 retval = get_user(tmp, (__u32 __user *)arg);
 477                 if (retval)
 478                         break;
 479                 if (tmp == 0) {
 480                         retval = -EINVAL;
 481                         break;
 482                 }
 483
 484                 save = spi->max_speed_hz;
 485
 486                 spi->max_speed_hz = tmp;
 487                 retval = spi_setup(spi);
 488                 if (retval == 0) {
 489                         spidev->speed_hz = tmp;
 490                         dev_dbg(&spi->dev, "%d Hz (max)\n", spidev->speed_hz);
 491                 }
 492
 493                 spi->max_speed_hz = save;
 494                 break;
 495         }
 496         default:
 497                 /* segmented and/or full-duplex I/O request */
 498                 /* Check message and copy into scratch area */
 499                 ioc = spidev_get_ioc_message(cmd,
 500                                 (struct spi_ioc_transfer __user *)arg, &n_ioc);
 501                 if (IS_ERR(ioc)) {
 502                         retval = PTR_ERR(ioc);
 503                         break;
 504                 }
 505                 if (!ioc)
 506                         break;  /* n_ioc is also 0 */
 507
 508                 /* translate to spi_message, execute */
 509                 retval = spidev_message(spidev, ioc, n_ioc);
 510                 kfree(ioc);
 511                 break;
 512         }
 513
 514         mutex_unlock(&spidev->buf_lock);
 515         spi_dev_put(spi);
 516         mutex_unlock(&spidev->spi_lock);
 517         return retval;
 518 }
 519
 520 #ifdef CONFIG_COMPAT
 521 static long
 522 spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
 523                 unsigned long arg)
 524 {
 525         struct spi_ioc_transfer __user  *u_ioc;
 526         int                             retval = 0;
 527         struct spidev_data              *spidev;
 528         struct spi_device               *spi;
 529         unsigned                        n_ioc, n;
 530         struct spi_ioc_transfer         *ioc;
 531
 532         u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);
 533
 534         /* guard against device removal before, or while,
 535          * we issue this ioctl.
 536          */
 537         spidev = filp->private_data;
 538         mutex_lock(&spidev->spi_lock);
 539         spi = spi_dev_get(spidev->spi);
 540         if (spi == NULL) {
 541                 mutex_unlock(&spidev->spi_lock);
 542                 return -ESHUTDOWN;
 543         }
 544
 545         /* SPI_IOC_MESSAGE needs the buffer locked "normally" */
 546         mutex_lock(&spidev->buf_lock);
 547
 548         /* Check message and copy into scratch area */
 549         ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
 550         if (IS_ERR(ioc)) {
 551                 retval = PTR_ERR(ioc);
 552                 goto done;
 553         }
 554         if (!ioc)
 555                 goto done;      /* n_ioc is also 0 */
 556
 557         /* Convert buffer pointers */
 558         for (n = 0; n < n_ioc; n++) {
 559                 ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
 560                 ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
 561         }
 562
 563         /* translate to spi_message, execute */
 564         retval = spidev_message(spidev, ioc, n_ioc);
 565         kfree(ioc);
 566
 567 done:
 568         mutex_unlock(&spidev->buf_lock);
 569         spi_dev_put(spi);
 570         mutex_unlock(&spidev->spi_lock);
 571         return retval;
 572 }
 573
 574 static long
 575 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 576 {
 577         if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
 578                         && _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
 579                         && _IOC_DIR(cmd) == _IOC_WRITE)
 580                 return spidev_compat_ioc_message(filp, cmd, arg);
 581
 582         return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 583 }
 584 #else
 585 #define spidev_compat_ioctl NULL
 586 #endif /* CONFIG_COMPAT */
 587
 588 static int spidev_open(struct inode *inode, struct file *filp)
 589 {
 590         struct spidev_data      *spidev = NULL, *iter;
 591         int                     status = -ENXIO;
 592
 593         mutex_lock(&device_list_lock);
 594
 595         list_for_each_entry(iter, &device_list, device_entry) {
 596                 if (iter->devt == inode->i_rdev) {
 597                         status = 0;
 598                         spidev = iter;
 599                         break;
 600                 }
 601         }
 602
 603         if (!spidev) {
 604                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 605                 goto err_find_dev;
 606         }
 607
 608         if (!spidev->tx_buffer) {
 609                 spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 610                 if (!spidev->tx_buffer) {
 611                         status = -ENOMEM;
 612                         goto err_find_dev;
 613                 }
 614         }
 615
 616         if (!spidev->rx_buffer) {
 617                 spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 618                 if (!spidev->rx_buffer) {
 619                         status = -ENOMEM;
 620                         goto err_alloc_rx_buf;
 621                 }
 622         }
 623
 624         spidev->users++;
 625         filp->private_data = spidev;
 626         stream_open(inode, filp);
 627
 628         mutex_unlock(&device_list_lock);
 629         return 0;
 630
 631 err_alloc_rx_buf:
 632         kfree(spidev->tx_buffer);
 633         spidev->tx_buffer = NULL;
 634 err_find_dev:
 635         mutex_unlock(&device_list_lock);
 636         return status;
 637 }
 638
 639 static int spidev_release(struct inode *inode, struct file *filp)
 640 {
 641         struct spidev_data      *spidev;
 642         int                     dofree;
 643
 644         mutex_lock(&device_list_lock);
 645         spidev = filp->private_data;
 646         filp->private_data = NULL;
 647
 648         mutex_lock(&spidev->spi_lock);
 649         /* ... after we unbound from the underlying device? */
 650         dofree = (spidev->spi == NULL);
 651         mutex_unlock(&spidev->spi_lock);
 652
 653         /* last close? */
 654         spidev->users--;
 655         if (!spidev->users) {
 656
 657                 kfree(spidev->tx_buffer);
 658                 spidev->tx_buffer = NULL;
 659
 660                 kfree(spidev->rx_buffer);
 661                 spidev->rx_buffer = NULL;
 662
 663                 if (dofree)
 664                         kfree(spidev);
 665                 else
 666                         spidev->speed_hz = spidev->spi->max_speed_hz;
 667         }
 668 #ifdef CONFIG_SPI_SLAVE
 669         if (!dofree)
 670                 spi_slave_abort(spidev->spi);
 671 #endif
 672         mutex_unlock(&device_list_lock);
 673
 674         return 0;
 675 }
 676
 677 static const struct file_operations spidev_fops = {
 678         .owner =        THIS_MODULE,
 679         /* REVISIT switch to aio primitives, so that userspace
 680          * gets more complete API coverage.  It'll simplify things
 681          * too, except for the locking.
 682          */
 683         .write =        spidev_write,
 684         .read =         spidev_read,
 685         .unlocked_ioctl = spidev_ioctl,
 686         .compat_ioctl = spidev_compat_ioctl,
 687         .open =         spidev_open,
 688         .release =      spidev_release,
 689         .llseek =       no_llseek,
 690 };
 691
 692 /*-------------------------------------------------------------------------*/
 693
 694 /* The main reason to have this class is to make mdev/udev create the
 695  * /dev/spidevB.C character device nodes exposing our userspace API.
 696  * It also simplifies memory management.
 697  */
 698
 699 static struct class *spidev_class;
 700
 701 static const struct spi_device_id spidev_spi_ids[] = {
 702         { .name = "spidev" },
 703         { .name = "dh2228fv" },
 704         { .name = "ltc2488" },
 705         { .name = "sx1301" },
 706         { .name = "bk4" },
 707         { .name = "dhcom-board" },
 708         { .name = "m53cpld" },
 709         { .name = "spi-petra" },
 710         { .name = "spi-authenta" },
 711         { .name = "em3581" },
 712         { .name = "si3210" },
 713         {},
 714 };
 715 MODULE_DEVICE_TABLE(spi, spidev_spi_ids);
 716
 717 /*
 718  * spidev should never be referenced in DT without a specific compatible string,
 719  * it is a Linux implementation thing rather than a description of the hardware.
 720  */
 721 static int spidev_of_check(struct device *dev)
 722 {
 723         if (1 || device_property_match_string(dev, "compatible", "spidev") < 0)
 724                 return 0;
 725
 726         dev_err(dev, "spidev listed directly in DT is not supported\n");
 727         return -EINVAL;
 728 }
 729
 730 static const struct of_device_id spidev_dt_ids[] = {
 731         { .compatible = "cisco,spi-petra", .data = &spidev_of_check },
 732         { .compatible = "dh,dhcom-board", .data = &spidev_of_check },
 733         { .compatible = "lineartechnology,ltc2488", .data = &spidev_of_check },
 734         { .compatible = "lwn,bk4", .data = &spidev_of_check },
 735         { .compatible = "menlo,m53cpld", .data = &spidev_of_check },
 736         { .compatible = "micron,spi-authenta", .data = &spidev_of_check },
 737         { .compatible = "rohm,dh2228fv", .data = &spidev_of_check },
 738         { .compatible = "semtech,sx1301", .data = &spidev_of_check },
 739         { .compatible = "silabs,em3581", .data = &spidev_of_check },
 740         { .compatible = "silabs,si3210", .data = &spidev_of_check },
 741         {},
 742 };
 743 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 744
 745 /* Dummy SPI devices not to be used in production systems */
 746 static int spidev_acpi_check(struct device *dev)
 747 {
 748         dev_warn(dev, "do not use this driver in production systems!\n");
 749         return 0;
 750 }
 751
 752 static const struct acpi_device_id spidev_acpi_ids[] = {
 753         /*
 754          * The ACPI SPT000* devices are only meant for development and
 755          * testing. Systems used in production should have a proper ACPI
 756          * description of the connected peripheral and they should also use
 757          * a proper driver instead of poking directly to the SPI bus.
 758          */
 759         { "SPT0001", (kernel_ulong_t)&spidev_acpi_check },
 760         { "SPT0002", (kernel_ulong_t)&spidev_acpi_check },
 761         { "SPT0003", (kernel_ulong_t)&spidev_acpi_check },
 762         {},
 763 };
 764 MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);
 765
 766 /*-------------------------------------------------------------------------*/
 767
 768 static int spidev_probe(struct spi_device *spi)
 769 {
 770         int (*match)(struct device *dev);
 771         struct spidev_data      *spidev;
 772         int                     status;
 773         unsigned long           minor;
 774
 775         match = device_get_match_data(&spi->dev);
 776         if (match) {
 777                 status = match(&spi->dev);
 778                 if (status)
 779                         return status;
 780         }
 781
 782         /* Allocate driver data */
 783         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 784         if (!spidev)
 785                 return -ENOMEM;
 786
 787         /* Initialize the driver data */
 788         spidev->spi = spi;
 789         mutex_init(&spidev->spi_lock);
 790         mutex_init(&spidev->buf_lock);
 791
 792         INIT_LIST_HEAD(&spidev->device_entry);
 793
 794         /* If we can allocate a minor number, hook up this device.
 795          * Reusing minors is fine so long as udev or mdev is working.
 796          */
 797         mutex_lock(&device_list_lock);
 798         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 799         if (minor < N_SPI_MINORS) {
 800                 struct device *dev;
 801
 802                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
 803                 dev = device_create(spidev_class, &spi->dev, spidev->devt,
 804                                     spidev, "spidev%d.%d",
 805                                     spi->master->bus_num, spi_get_chipselect(spi, 0));
 806                 status = PTR_ERR_OR_ZERO(dev);
 807         } else {
 808                 dev_dbg(&spi->dev, "no minor number available!\n");
 809                 status = -ENODEV;
 810         }
 811         if (status == 0) {
 812                 set_bit(minor, minors);
 813                 list_add(&spidev->device_entry, &device_list);
 814         }
 815         mutex_unlock(&device_list_lock);
 816
 817         spidev->speed_hz = spi->max_speed_hz;
 818
 819         if (status == 0)
 820                 spi_set_drvdata(spi, spidev);
 821         else
 822                 kfree(spidev);
 823
 824         return status;
 825 }
 826
 827 static void spidev_remove(struct spi_device *spi)
 828 {
 829         struct spidev_data      *spidev = spi_get_drvdata(spi);
 830
 831         /* prevent new opens */
 832         mutex_lock(&device_list_lock);
 833         /* make sure ops on existing fds can abort cleanly */
 834         mutex_lock(&spidev->spi_lock);
 835         spidev->spi = NULL;
 836         mutex_unlock(&spidev->spi_lock);
 837
 838         list_del(&spidev->device_entry);
 839         device_destroy(spidev_class, spidev->devt);
 840         clear_bit(MINOR(spidev->devt), minors);
 841         if (spidev->users == 0)
 842                 kfree(spidev);
 843         mutex_unlock(&device_list_lock);
 844 }
 845
 846 static struct spi_driver spidev_spi_driver = {
 847         .driver = {
 848                 .name =         "spidev",
 849                 .of_match_table = spidev_dt_ids,
 850                 .acpi_match_table = spidev_acpi_ids,
 851         },
 852         .probe =        spidev_probe,
 853         .remove =       spidev_remove,
 854         .id_table =     spidev_spi_ids,
 855
 856         /* NOTE:  suspend/resume methods are not necessary here.
 857          * We don't do anything except pass the requests to/from
 858          * the underlying controller.  The refrigerator handles
 859          * most issues; the controller driver handles the rest.
 860          */
 861 };
 862
 863 /*-------------------------------------------------------------------------*/
 864
 865 static int __init spidev_init(void)
 866 {
 867         int status;
 868
 869         /* Claim our 256 reserved device numbers.  Then register a class
 870          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 871          * the driver which manages those device numbers.
 872          */
 873         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 874         if (status < 0)
 875                 return status;
 876
 877         spidev_class = class_create("spidev");
 878         if (IS_ERR(spidev_class)) {
 879                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 880                 return PTR_ERR(spidev_class);
 881         }
 882
 883         status = spi_register_driver(&spidev_spi_driver);
 884         if (status < 0) {
 885                 class_destroy(spidev_class);
 886                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 887         }
 888         return status;
 889 }
 890 module_init(spidev_init);
 891
 892 static void __exit spidev_exit(void)
 893 {
 894         spi_unregister_driver(&spidev_spi_driver);
 895         class_destroy(spidev_class);
 896         unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 897 }
 898 module_exit(spidev_exit);
 899
 900 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 901 MODULE_DESCRIPTION("User mode SPI device interface");
 902 MODULE_LICENSE("GPL");
 903 MODULE_ALIAS("spi:spidev");