drivers/spi/spidev.c

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