root/drivers/spi/spidev.c

DEFINITIONS

1. spidev_sync
2. spidev_sync_write
3. spidev_sync_read
4. spidev_read
5. spidev_write
6. spidev_message
7. spidev_get_ioc_message
8. spidev_ioctl
9. spidev_compat_ioc_message
10. spidev_compat_ioctl
11. spidev_open
12. spidev_release
13. spidev_probe_acpi
14. spidev_probe_acpi
15. spidev_probe
16. spidev_remove
17. spidev_init
18. spidev_exit

   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_usecs = u_tmp->delay_usecs;
 269                 k_tmp->speed_hz = u_tmp->speed_hz;
 270                 k_tmp->word_delay_usecs = u_tmp->word_delay_usecs;
 271                 if (!k_tmp->speed_hz)
 272                         k_tmp->speed_hz = spidev->speed_hz;
 273 #ifdef VERBOSE
 274                 dev_dbg(&spidev->spi->dev,
 275                         "  xfer len %u %s%s%s%dbits %u usec %u usec %uHz\n",
 276                         u_tmp->len,
 277                         u_tmp->rx_buf ? "rx " : "",
 278                         u_tmp->tx_buf ? "tx " : "",
 279                         u_tmp->cs_change ? "cs " : "",
 280                         u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
 281                         u_tmp->delay_usecs,
 282                         u_tmp->word_delay_usecs,
 283                         u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
 284 #endif
 285                 spi_message_add_tail(k_tmp, &msg);
 286         }
 287 
 288         status = spidev_sync(spidev, &msg);
 289         if (status < 0)
 290                 goto done;
 291 
 292         /* copy any rx data out of bounce buffer */
 293         rx_buf = spidev->rx_buffer;
 294         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 295                 if (u_tmp->rx_buf) {
 296                         if (copy_to_user((u8 __user *)
 297                                         (uintptr_t) u_tmp->rx_buf, rx_buf,
 298                                         u_tmp->len)) {
 299                                 status = -EFAULT;
 300                                 goto done;
 301                         }
 302                         rx_buf += u_tmp->len;
 303                 }
 304         }
 305         status = total;
 306 
 307 done:
 308         kfree(k_xfers);
 309         return status;
 310 }
 311 
 312 static struct spi_ioc_transfer *
 313 spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
 314                 unsigned *n_ioc)
 315 {
 316         u32     tmp;
 317 
 318         /* Check type, command number and direction */
 319         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
 320                         || _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 321                         || _IOC_DIR(cmd) != _IOC_WRITE)
 322                 return ERR_PTR(-ENOTTY);
 323 
 324         tmp = _IOC_SIZE(cmd);
 325         if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
 326                 return ERR_PTR(-EINVAL);
 327         *n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 328         if (*n_ioc == 0)
 329                 return NULL;
 330 
 331         /* copy into scratch area */
 332         return memdup_user(u_ioc, tmp);
 333 }
 334 
 335 static long
 336 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 337 {
 338         int                     retval = 0;
 339         struct spidev_data      *spidev;
 340         struct spi_device       *spi;
 341         u32                     tmp;
 342         unsigned                n_ioc;
 343         struct spi_ioc_transfer *ioc;
 344 
 345         /* Check type and command number */
 346         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 347                 return -ENOTTY;
 348 
 349         /* guard against device removal before, or while,
 350          * we issue this ioctl.
 351          */
 352         spidev = filp->private_data;
 353         spin_lock_irq(&spidev->spi_lock);
 354         spi = spi_dev_get(spidev->spi);
 355         spin_unlock_irq(&spidev->spi_lock);
 356 
 357         if (spi == NULL)
 358                 return -ESHUTDOWN;
 359 
 360         /* use the buffer lock here for triple duty:
 361          *  - prevent I/O (from us) so calling spi_setup() is safe;
 362          *  - prevent concurrent SPI_IOC_WR_* from morphing
 363          *    data fields while SPI_IOC_RD_* reads them;
 364          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 365          */
 366         mutex_lock(&spidev->buf_lock);
 367 
 368         switch (cmd) {
 369         /* read requests */
 370         case SPI_IOC_RD_MODE:
 371                 retval = put_user(spi->mode & SPI_MODE_MASK,
 372                                         (__u8 __user *)arg);
 373                 break;
 374         case SPI_IOC_RD_MODE32:
 375                 retval = put_user(spi->mode & SPI_MODE_MASK,
 376                                         (__u32 __user *)arg);
 377                 break;
 378         case SPI_IOC_RD_LSB_FIRST:
 379                 retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 380                                         (__u8 __user *)arg);
 381                 break;
 382         case SPI_IOC_RD_BITS_PER_WORD:
 383                 retval = put_user(spi->bits_per_word, (__u8 __user *)arg);
 384                 break;
 385         case SPI_IOC_RD_MAX_SPEED_HZ:
 386                 retval = put_user(spidev->speed_hz, (__u32 __user *)arg);
 387                 break;
 388 
 389         /* write requests */
 390         case SPI_IOC_WR_MODE:
 391         case SPI_IOC_WR_MODE32:
 392                 if (cmd == SPI_IOC_WR_MODE)
 393                         retval = get_user(tmp, (u8 __user *)arg);
 394                 else
 395                         retval = get_user(tmp, (u32 __user *)arg);
 396                 if (retval == 0) {
 397                         struct spi_controller *ctlr = spi->controller;
 398                         u32     save = spi->mode;
 399 
 400                         if (tmp & ~SPI_MODE_MASK) {
 401                                 retval = -EINVAL;
 402                                 break;
 403                         }
 404 
 405                         if (ctlr->use_gpio_descriptors && ctlr->cs_gpiods &&
 406                             ctlr->cs_gpiods[spi->chip_select])
 407                                 tmp |= SPI_CS_HIGH;
 408 
 409                         tmp |= spi->mode & ~SPI_MODE_MASK;
 410                         spi->mode = (u16)tmp;
 411                         retval = spi_setup(spi);
 412                         if (retval < 0)
 413                                 spi->mode = save;
 414                         else
 415                                 dev_dbg(&spi->dev, "spi mode %x\n", tmp);
 416                 }
 417                 break;
 418         case SPI_IOC_WR_LSB_FIRST:
 419                 retval = get_user(tmp, (__u8 __user *)arg);
 420                 if (retval == 0) {
 421                         u32     save = spi->mode;
 422 
 423                         if (tmp)
 424                                 spi->mode |= SPI_LSB_FIRST;
 425                         else
 426                                 spi->mode &= ~SPI_LSB_FIRST;
 427                         retval = spi_setup(spi);
 428                         if (retval < 0)
 429                                 spi->mode = save;
 430                         else
 431                                 dev_dbg(&spi->dev, "%csb first\n",
 432                                                 tmp ? 'l' : 'm');
 433                 }
 434                 break;
 435         case SPI_IOC_WR_BITS_PER_WORD:
 436                 retval = get_user(tmp, (__u8 __user *)arg);
 437                 if (retval == 0) {
 438                         u8      save = spi->bits_per_word;
 439 
 440                         spi->bits_per_word = tmp;
 441                         retval = spi_setup(spi);
 442                         if (retval < 0)
 443                                 spi->bits_per_word = save;
 444                         else
 445                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 446                 }
 447                 break;
 448         case SPI_IOC_WR_MAX_SPEED_HZ:
 449                 retval = get_user(tmp, (__u32 __user *)arg);
 450                 if (retval == 0) {
 451                         u32     save = spi->max_speed_hz;
 452 
 453                         spi->max_speed_hz = tmp;
 454                         retval = spi_setup(spi);
 455                         if (retval >= 0)
 456                                 spidev->speed_hz = tmp;
 457                         else
 458                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 459                         spi->max_speed_hz = save;
 460                 }
 461                 break;
 462 
 463         default:
 464                 /* segmented and/or full-duplex I/O request */
 465                 /* Check message and copy into scratch area */
 466                 ioc = spidev_get_ioc_message(cmd,
 467                                 (struct spi_ioc_transfer __user *)arg, &n_ioc);
 468                 if (IS_ERR(ioc)) {
 469                         retval = PTR_ERR(ioc);
 470                         break;
 471                 }
 472                 if (!ioc)
 473                         break;  /* n_ioc is also 0 */
 474 
 475                 /* translate to spi_message, execute */
 476                 retval = spidev_message(spidev, ioc, n_ioc);
 477                 kfree(ioc);
 478                 break;
 479         }
 480 
 481         mutex_unlock(&spidev->buf_lock);
 482         spi_dev_put(spi);
 483         return retval;
 484 }
 485 
 486 #ifdef CONFIG_COMPAT
 487 static long
 488 spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
 489                 unsigned long arg)
 490 {
 491         struct spi_ioc_transfer __user  *u_ioc;
 492         int                             retval = 0;
 493         struct spidev_data              *spidev;
 494         struct spi_device               *spi;
 495         unsigned                        n_ioc, n;
 496         struct spi_ioc_transfer         *ioc;
 497 
 498         u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);
 499 
 500         /* guard against device removal before, or while,
 501          * we issue this ioctl.
 502          */
 503         spidev = filp->private_data;
 504         spin_lock_irq(&spidev->spi_lock);
 505         spi = spi_dev_get(spidev->spi);
 506         spin_unlock_irq(&spidev->spi_lock);
 507 
 508         if (spi == NULL)
 509                 return -ESHUTDOWN;
 510 
 511         /* SPI_IOC_MESSAGE needs the buffer locked "normally" */
 512         mutex_lock(&spidev->buf_lock);
 513 
 514         /* Check message and copy into scratch area */
 515         ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
 516         if (IS_ERR(ioc)) {
 517                 retval = PTR_ERR(ioc);
 518                 goto done;
 519         }
 520         if (!ioc)
 521                 goto done;      /* n_ioc is also 0 */
 522 
 523         /* Convert buffer pointers */
 524         for (n = 0; n < n_ioc; n++) {
 525                 ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
 526                 ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
 527         }
 528 
 529         /* translate to spi_message, execute */
 530         retval = spidev_message(spidev, ioc, n_ioc);
 531         kfree(ioc);
 532 
 533 done:
 534         mutex_unlock(&spidev->buf_lock);
 535         spi_dev_put(spi);
 536         return retval;
 537 }
 538 
 539 static long
 540 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 541 {
 542         if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
 543                         && _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
 544                         && _IOC_DIR(cmd) == _IOC_WRITE)
 545                 return spidev_compat_ioc_message(filp, cmd, arg);
 546 
 547         return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 548 }
 549 #else
 550 #define spidev_compat_ioctl NULL
 551 #endif /* CONFIG_COMPAT */
 552 
 553 static int spidev_open(struct inode *inode, struct file *filp)
 554 {
 555         struct spidev_data      *spidev;
 556         int                     status = -ENXIO;
 557 
 558         mutex_lock(&device_list_lock);
 559 
 560         list_for_each_entry(spidev, &device_list, device_entry) {
 561                 if (spidev->devt == inode->i_rdev) {
 562                         status = 0;
 563                         break;
 564                 }
 565         }
 566 
 567         if (status) {
 568                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 569                 goto err_find_dev;
 570         }
 571 
 572         if (!spidev->tx_buffer) {
 573                 spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 574                 if (!spidev->tx_buffer) {
 575                         dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 576                         status = -ENOMEM;
 577                         goto err_find_dev;
 578                 }
 579         }
 580 
 581         if (!spidev->rx_buffer) {
 582                 spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 583                 if (!spidev->rx_buffer) {
 584                         dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 585                         status = -ENOMEM;
 586                         goto err_alloc_rx_buf;
 587                 }
 588         }
 589 
 590         spidev->users++;
 591         filp->private_data = spidev;
 592         stream_open(inode, filp);
 593 
 594         mutex_unlock(&device_list_lock);
 595         return 0;
 596 
 597 err_alloc_rx_buf:
 598         kfree(spidev->tx_buffer);
 599         spidev->tx_buffer = NULL;
 600 err_find_dev:
 601         mutex_unlock(&device_list_lock);
 602         return status;
 603 }
 604 
 605 static int spidev_release(struct inode *inode, struct file *filp)
 606 {
 607         struct spidev_data      *spidev;
 608 
 609         mutex_lock(&device_list_lock);
 610         spidev = filp->private_data;
 611         filp->private_data = NULL;
 612 
 613         /* last close? */
 614         spidev->users--;
 615         if (!spidev->users) {
 616                 int             dofree;
 617 
 618                 kfree(spidev->tx_buffer);
 619                 spidev->tx_buffer = NULL;
 620 
 621                 kfree(spidev->rx_buffer);
 622                 spidev->rx_buffer = NULL;
 623 
 624                 spin_lock_irq(&spidev->spi_lock);
 625                 if (spidev->spi)
 626                         spidev->speed_hz = spidev->spi->max_speed_hz;
 627 
 628                 /* ... after we unbound from the underlying device? */
 629                 dofree = (spidev->spi == NULL);
 630                 spin_unlock_irq(&spidev->spi_lock);
 631 
 632                 if (dofree)
 633                         kfree(spidev);
 634         }
 635 #ifdef CONFIG_SPI_SLAVE
 636         spi_slave_abort(spidev->spi);
 637 #endif
 638         mutex_unlock(&device_list_lock);
 639 
 640         return 0;
 641 }
 642 
 643 static const struct file_operations spidev_fops = {
 644         .owner =        THIS_MODULE,
 645         /* REVISIT switch to aio primitives, so that userspace
 646          * gets more complete API coverage.  It'll simplify things
 647          * too, except for the locking.
 648          */
 649         .write =        spidev_write,
 650         .read =         spidev_read,
 651         .unlocked_ioctl = spidev_ioctl,
 652         .compat_ioctl = spidev_compat_ioctl,
 653         .open =         spidev_open,
 654         .release =      spidev_release,
 655         .llseek =       no_llseek,
 656 };
 657 
 658 /*-------------------------------------------------------------------------*/
 659 
 660 /* The main reason to have this class is to make mdev/udev create the
 661  * /dev/spidevB.C character device nodes exposing our userspace API.
 662  * It also simplifies memory management.
 663  */
 664 
 665 static struct class *spidev_class;
 666 
 667 #ifdef CONFIG_OF
 668 static const struct of_device_id spidev_dt_ids[] = {
 669         { .compatible = "rohm,dh2228fv" },
 670         { .compatible = "lineartechnology,ltc2488" },
 671         { .compatible = "ge,achc" },
 672         { .compatible = "semtech,sx1301" },
 673         { .compatible = "lwn,bk4" },
 674         { .compatible = "dh,dhcom-board" },
 675         { .compatible = "menlo,m53cpld" },
 676         {},
 677 };
 678 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 679 #endif
 680 
 681 #ifdef CONFIG_ACPI
 682 
 683 /* Dummy SPI devices not to be used in production systems */
 684 #define SPIDEV_ACPI_DUMMY       1
 685 
 686 static const struct acpi_device_id spidev_acpi_ids[] = {
 687         /*
 688          * The ACPI SPT000* devices are only meant for development and
 689          * testing. Systems used in production should have a proper ACPI
 690          * description of the connected peripheral and they should also use
 691          * a proper driver instead of poking directly to the SPI bus.
 692          */
 693         { "SPT0001", SPIDEV_ACPI_DUMMY },
 694         { "SPT0002", SPIDEV_ACPI_DUMMY },
 695         { "SPT0003", SPIDEV_ACPI_DUMMY },
 696         {},
 697 };
 698 MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);
 699 
 700 static void spidev_probe_acpi(struct spi_device *spi)
 701 {
 702         const struct acpi_device_id *id;
 703 
 704         if (!has_acpi_companion(&spi->dev))
 705                 return;
 706 
 707         id = acpi_match_device(spidev_acpi_ids, &spi->dev);
 708         if (WARN_ON(!id))
 709                 return;
 710 
 711         if (id->driver_data == SPIDEV_ACPI_DUMMY)
 712                 dev_warn(&spi->dev, "do not use this driver in production systems!\n");
 713 }
 714 #else
 715 static inline void spidev_probe_acpi(struct spi_device *spi) {}
 716 #endif
 717 
 718 /*-------------------------------------------------------------------------*/
 719 
 720 static int spidev_probe(struct spi_device *spi)
 721 {
 722         struct spidev_data      *spidev;
 723         int                     status;
 724         unsigned long           minor;
 725 
 726         /*
 727          * spidev should never be referenced in DT without a specific
 728          * compatible string, it is a Linux implementation thing
 729          * rather than a description of the hardware.
 730          */
 731         WARN(spi->dev.of_node &&
 732              of_device_is_compatible(spi->dev.of_node, "spidev"),
 733              "%pOF: buggy DT: spidev listed directly in DT\n", spi->dev.of_node);
 734 
 735         spidev_probe_acpi(spi);
 736 
 737         /* Allocate driver data */
 738         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 739         if (!spidev)
 740                 return -ENOMEM;
 741 
 742         /* Initialize the driver data */
 743         spidev->spi = spi;
 744         spin_lock_init(&spidev->spi_lock);
 745         mutex_init(&spidev->buf_lock);
 746 
 747         INIT_LIST_HEAD(&spidev->device_entry);
 748 
 749         /* If we can allocate a minor number, hook up this device.
 750          * Reusing minors is fine so long as udev or mdev is working.
 751          */
 752         mutex_lock(&device_list_lock);
 753         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 754         if (minor < N_SPI_MINORS) {
 755                 struct device *dev;
 756 
 757                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
 758                 dev = device_create(spidev_class, &spi->dev, spidev->devt,
 759                                     spidev, "spidev%d.%d",
 760                                     spi->master->bus_num, spi->chip_select);
 761                 status = PTR_ERR_OR_ZERO(dev);
 762         } else {
 763                 dev_dbg(&spi->dev, "no minor number available!\n");
 764                 status = -ENODEV;
 765         }
 766         if (status == 0) {
 767                 set_bit(minor, minors);
 768                 list_add(&spidev->device_entry, &device_list);
 769         }
 770         mutex_unlock(&device_list_lock);
 771 
 772         spidev->speed_hz = spi->max_speed_hz;
 773 
 774         if (status == 0)
 775                 spi_set_drvdata(spi, spidev);
 776         else
 777                 kfree(spidev);
 778 
 779         return status;
 780 }
 781 
 782 static int spidev_remove(struct spi_device *spi)
 783 {
 784         struct spidev_data      *spidev = spi_get_drvdata(spi);
 785 
 786         /* make sure ops on existing fds can abort cleanly */
 787         spin_lock_irq(&spidev->spi_lock);
 788         spidev->spi = NULL;
 789         spin_unlock_irq(&spidev->spi_lock);
 790 
 791         /* prevent new opens */
 792         mutex_lock(&device_list_lock);
 793         list_del(&spidev->device_entry);
 794         device_destroy(spidev_class, spidev->devt);
 795         clear_bit(MINOR(spidev->devt), minors);
 796         if (spidev->users == 0)
 797                 kfree(spidev);
 798         mutex_unlock(&device_list_lock);
 799 
 800         return 0;
 801 }
 802 
 803 static struct spi_driver spidev_spi_driver = {
 804         .driver = {
 805                 .name =         "spidev",
 806                 .of_match_table = of_match_ptr(spidev_dt_ids),
 807                 .acpi_match_table = ACPI_PTR(spidev_acpi_ids),
 808         },
 809         .probe =        spidev_probe,
 810         .remove =       spidev_remove,
 811 
 812         /* NOTE:  suspend/resume methods are not necessary here.
 813          * We don't do anything except pass the requests to/from
 814          * the underlying controller.  The refrigerator handles
 815          * most issues; the controller driver handles the rest.
 816          */
 817 };
 818 
 819 /*-------------------------------------------------------------------------*/
 820 
 821 static int __init spidev_init(void)
 822 {
 823         int status;
 824 
 825         /* Claim our 256 reserved device numbers.  Then register a class
 826          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 827          * the driver which manages those device numbers.
 828          */
 829         BUILD_BUG_ON(N_SPI_MINORS > 256);
 830         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 831         if (status < 0)
 832                 return status;
 833 
 834         spidev_class = class_create(THIS_MODULE, "spidev");
 835         if (IS_ERR(spidev_class)) {
 836                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 837                 return PTR_ERR(spidev_class);
 838         }
 839 
 840         status = spi_register_driver(&spidev_spi_driver);
 841         if (status < 0) {
 842                 class_destroy(spidev_class);
 843                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 844         }
 845         return status;
 846 }
 847 module_init(spidev_init);
 848 
 849 static void __exit spidev_exit(void)
 850 {
 851         spi_unregister_driver(&spidev_spi_driver);
 852         class_destroy(spidev_class);
 853         unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 854 }
 855 module_exit(spidev_exit);
 856 
 857 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 858 MODULE_DESCRIPTION("User mode SPI device interface");
 859 MODULE_LICENSE("GPL");
 860 MODULE_ALIAS("spi:spidev");