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
  33 #include <linux/spi/spi.h>
  34 #include <linux/spi/spidev.h>
  35
  36 #include <linux/uaccess.h>
  37
  38
  39 /*
  40  * This supports access to SPI devices using normal userspace I/O calls.
  41  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
  42  * and often mask message boundaries, full SPI support requires full duplex
  43  * transfers.  There are several kinds of internal message boundaries to
  44  * handle chipselect management and other protocol options.
  45  *
  46  * SPI has a character major number assigned.  We allocate minor numbers
  47  * dynamically using a bitmask.  You must use hotplug tools, such as udev
  48  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
  49  * nodes, since there is no fixed association of minor numbers with any
  50  * particular SPI bus or device.
  51  */
  52 #define SPIDEV_MAJOR                    153     /* assigned */
  53 #define N_SPI_MINORS                    32      /* ... up to 256 */
  54
  55 static DECLARE_BITMAP(minors, N_SPI_MINORS);
  56
  57
  58 /* Bit masks for spi_device.mode management.  Note that incorrect
  59  * settings for some settings can cause *lots* of trouble for other
  60  * devices on a shared bus:
  61  *
  62  *  - CS_HIGH ... this device will be active when it shouldn't be
  63  *  - 3WIRE ... when active, it won't behave as it should
  64  *  - NO_CS ... there will be no explicit message boundaries; this
  65  *      is completely incompatible with the shared bus model
  66  *  - READY ... transfers may proceed when they shouldn't.
  67  *
  68  * REVISIT should changing those flags be privileged?
  69  */
  70 #define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
  71                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \
  72                                 | SPI_NO_CS | SPI_READY | SPI_TX_DUAL \
  73                                 | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)
  74
  75 struct spidev_data {
  76         dev_t                   devt;
  77         spinlock_t              spi_lock;
  78         struct spi_device       *spi;
  79         struct list_head        device_entry;
  80
  81         /* TX/RX buffers are NULL unless this device is open (users > 0) */
  82         struct mutex            buf_lock;
  83         unsigned                users;
  84         u8                      *tx_buffer;
  85         u8                      *rx_buffer;
  86         u32                     speed_hz;
  87 };
  88
  89 static LIST_HEAD(device_list);
  90 static DEFINE_MUTEX(device_list_lock);
  91
  92 static unsigned bufsiz = 4096;
  93 module_param(bufsiz, uint, S_IRUGO);
  94 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  95
  96 /*-------------------------------------------------------------------------*/
  97
  98 static ssize_t
  99 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
 100 {
 101         DECLARE_COMPLETION_ONSTACK(done);
 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                         if (!access_ok(VERIFY_WRITE, (u8 __user *)
 257                                                 (uintptr_t) u_tmp->rx_buf,
 258                                                 u_tmp->len))
 259                                 goto done;
 260                         rx_buf += k_tmp->len;
 261                 }
 262                 if (u_tmp->tx_buf) {
 263                         /* this transfer needs space in TX bounce buffer */
 264                         tx_total += k_tmp->len;
 265                         if (tx_total > bufsiz) {
 266                                 status = -EMSGSIZE;
 267                                 goto done;
 268                         }
 269                         k_tmp->tx_buf = tx_buf;
 270                         if (copy_from_user(tx_buf, (const u8 __user *)
 271                                                 (uintptr_t) u_tmp->tx_buf,
 272                                         u_tmp->len))
 273                                 goto done;
 274                         tx_buf += k_tmp->len;
 275                 }
 276
 277                 k_tmp->cs_change = !!u_tmp->cs_change;
 278                 k_tmp->tx_nbits = u_tmp->tx_nbits;
 279                 k_tmp->rx_nbits = u_tmp->rx_nbits;
 280                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 281                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 282                 k_tmp->speed_hz = u_tmp->speed_hz;
 283                 if (!k_tmp->speed_hz)
 284                         k_tmp->speed_hz = spidev->speed_hz;
 285 #ifdef VERBOSE
 286                 dev_dbg(&spidev->spi->dev,
 287                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 288                         u_tmp->len,
 289                         u_tmp->rx_buf ? "rx " : "",
 290                         u_tmp->tx_buf ? "tx " : "",
 291                         u_tmp->cs_change ? "cs " : "",
 292                         u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
 293                         u_tmp->delay_usecs,
 294                         u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
 295 #endif
 296                 spi_message_add_tail(k_tmp, &msg);
 297         }
 298
 299         status = spidev_sync(spidev, &msg);
 300         if (status < 0)
 301                 goto done;
 302
 303         /* copy any rx data out of bounce buffer */
 304         rx_buf = spidev->rx_buffer;
 305         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 306                 if (u_tmp->rx_buf) {
 307                         if (__copy_to_user((u8 __user *)
 308                                         (uintptr_t) u_tmp->rx_buf, rx_buf,
 309                                         u_tmp->len)) {
 310                                 status = -EFAULT;
 311                                 goto done;
 312                         }
 313                         rx_buf += u_tmp->len;
 314                 }
 315         }
 316         status = total;
 317
 318 done:
 319         kfree(k_xfers);
 320         return status;
 321 }
 322
 323 static struct spi_ioc_transfer *
 324 spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
 325                 unsigned *n_ioc)
 326 {
 327         struct spi_ioc_transfer *ioc;
 328         u32     tmp;
 329
 330         /* Check type, command number and direction */
 331         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
 332                         || _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 333                         || _IOC_DIR(cmd) != _IOC_WRITE)
 334                 return ERR_PTR(-ENOTTY);
 335
 336         tmp = _IOC_SIZE(cmd);
 337         if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
 338                 return ERR_PTR(-EINVAL);
 339         *n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 340         if (*n_ioc == 0)
 341                 return NULL;
 342
 343         /* copy into scratch area */
 344         ioc = kmalloc(tmp, GFP_KERNEL);
 345         if (!ioc)
 346                 return ERR_PTR(-ENOMEM);
 347         if (__copy_from_user(ioc, u_ioc, tmp)) {
 348                 kfree(ioc);
 349                 return ERR_PTR(-EFAULT);
 350         }
 351         return ioc;
 352 }
 353
 354 static long
 355 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 356 {
 357         int                     err = 0;
 358         int                     retval = 0;
 359         struct spidev_data      *spidev;
 360         struct spi_device       *spi;
 361         u32                     tmp;
 362         unsigned                n_ioc;
 363         struct spi_ioc_transfer *ioc;
 364
 365         /* Check type and command number */
 366         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 367                 return -ENOTTY;
 368
 369         /* Check access direction once here; don't repeat below.
 370          * IOC_DIR is from the user perspective, while access_ok is
 371          * from the kernel perspective; so they look reversed.
 372          */
 373         if (_IOC_DIR(cmd) & _IOC_READ)
 374                 err = !access_ok(VERIFY_WRITE,
 375                                 (void __user *)arg, _IOC_SIZE(cmd));
 376         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 377                 err = !access_ok(VERIFY_READ,
 378                                 (void __user *)arg, _IOC_SIZE(cmd));
 379         if (err)
 380                 return -EFAULT;
 381
 382         /* guard against device removal before, or while,
 383          * we issue this ioctl.
 384          */
 385         spidev = filp->private_data;
 386         spin_lock_irq(&spidev->spi_lock);
 387         spi = spi_dev_get(spidev->spi);
 388         spin_unlock_irq(&spidev->spi_lock);
 389
 390         if (spi == NULL)
 391                 return -ESHUTDOWN;
 392
 393         /* use the buffer lock here for triple duty:
 394          *  - prevent I/O (from us) so calling spi_setup() is safe;
 395          *  - prevent concurrent SPI_IOC_WR_* from morphing
 396          *    data fields while SPI_IOC_RD_* reads them;
 397          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 398          */
 399         mutex_lock(&spidev->buf_lock);
 400
 401         switch (cmd) {
 402         /* read requests */
 403         case SPI_IOC_RD_MODE:
 404                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 405                                         (__u8 __user *)arg);
 406                 break;
 407         case SPI_IOC_RD_MODE32:
 408                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 409                                         (__u32 __user *)arg);
 410                 break;
 411         case SPI_IOC_RD_LSB_FIRST:
 412                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 413                                         (__u8 __user *)arg);
 414                 break;
 415         case SPI_IOC_RD_BITS_PER_WORD:
 416                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 417                 break;
 418         case SPI_IOC_RD_MAX_SPEED_HZ:
 419                 retval = __put_user(spidev->speed_hz, (__u32 __user *)arg);
 420                 break;
 421
 422         /* write requests */
 423         case SPI_IOC_WR_MODE:
 424         case SPI_IOC_WR_MODE32:
 425                 if (cmd == SPI_IOC_WR_MODE)
 426                         retval = __get_user(tmp, (u8 __user *)arg);
 427                 else
 428                         retval = __get_user(tmp, (u32 __user *)arg);
 429                 if (retval == 0) {
 430                         u32     save = spi->mode;
 431
 432                         if (tmp & ~SPI_MODE_MASK) {
 433                                 retval = -EINVAL;
 434                                 break;
 435                         }
 436
 437                         tmp |= spi->mode & ~SPI_MODE_MASK;
 438                         spi->mode = (u16)tmp;
 439                         retval = spi_setup(spi);
 440                         if (retval < 0)
 441                                 spi->mode = save;
 442                         else
 443                                 dev_dbg(&spi->dev, "spi mode %x\n", tmp);
 444                 }
 445                 break;
 446         case SPI_IOC_WR_LSB_FIRST:
 447                 retval = __get_user(tmp, (__u8 __user *)arg);
 448                 if (retval == 0) {
 449                         u32     save = spi->mode;
 450
 451                         if (tmp)
 452                                 spi->mode |= SPI_LSB_FIRST;
 453                         else
 454                                 spi->mode &= ~SPI_LSB_FIRST;
 455                         retval = spi_setup(spi);
 456                         if (retval < 0)
 457                                 spi->mode = save;
 458                         else
 459                                 dev_dbg(&spi->dev, "%csb first\n",
 460                                                 tmp ? 'l' : 'm');
 461                 }
 462                 break;
 463         case SPI_IOC_WR_BITS_PER_WORD:
 464                 retval = __get_user(tmp, (__u8 __user *)arg);
 465                 if (retval == 0) {
 466                         u8      save = spi->bits_per_word;
 467
 468                         spi->bits_per_word = tmp;
 469                         retval = spi_setup(spi);
 470                         if (retval < 0)
 471                                 spi->bits_per_word = save;
 472                         else
 473                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 474                 }
 475                 break;
 476         case SPI_IOC_WR_MAX_SPEED_HZ:
 477                 retval = __get_user(tmp, (__u32 __user *)arg);
 478                 if (retval == 0) {
 479                         u32     save = spi->max_speed_hz;
 480
 481                         spi->max_speed_hz = tmp;
 482                         retval = spi_setup(spi);
 483                         if (retval >= 0)
 484                                 spidev->speed_hz = tmp;
 485                         else
 486                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 487                         spi->max_speed_hz = save;
 488                 }
 489                 break;
 490
 491         default:
 492                 /* segmented and/or full-duplex I/O request */
 493                 /* Check message and copy into scratch area */
 494                 ioc = spidev_get_ioc_message(cmd,
 495                                 (struct spi_ioc_transfer __user *)arg, &n_ioc);
 496                 if (IS_ERR(ioc)) {
 497                         retval = PTR_ERR(ioc);
 498                         break;
 499                 }
 500                 if (!ioc)
 501                         break;  /* n_ioc is also 0 */
 502
 503                 /* translate to spi_message, execute */
 504                 retval = spidev_message(spidev, ioc, n_ioc);
 505                 kfree(ioc);
 506                 break;
 507         }
 508
 509         mutex_unlock(&spidev->buf_lock);
 510         spi_dev_put(spi);
 511         return retval;
 512 }
 513
 514 #ifdef CONFIG_COMPAT
 515 static long
 516 spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
 517                 unsigned long arg)
 518 {
 519         struct spi_ioc_transfer __user  *u_ioc;
 520         int                             retval = 0;
 521         struct spidev_data              *spidev;
 522         struct spi_device               *spi;
 523         unsigned                        n_ioc, n;
 524         struct spi_ioc_transfer         *ioc;
 525
 526         u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);
 527         if (!access_ok(VERIFY_READ, u_ioc, _IOC_SIZE(cmd)))
 528                 return -EFAULT;
 529
 530         /* guard against device removal before, or while,
 531          * we issue this ioctl.
 532          */
 533         spidev = filp->private_data;
 534         spin_lock_irq(&spidev->spi_lock);
 535         spi = spi_dev_get(spidev->spi);
 536         spin_unlock_irq(&spidev->spi_lock);
 537
 538         if (spi == NULL)
 539                 return -ESHUTDOWN;
 540
 541         /* SPI_IOC_MESSAGE needs the buffer locked "normally" */
 542         mutex_lock(&spidev->buf_lock);
 543
 544         /* Check message and copy into scratch area */
 545         ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
 546         if (IS_ERR(ioc)) {
 547                 retval = PTR_ERR(ioc);
 548                 goto done;
 549         }
 550         if (!ioc)
 551                 goto done;      /* n_ioc is also 0 */
 552
 553         /* Convert buffer pointers */
 554         for (n = 0; n < n_ioc; n++) {
 555                 ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
 556                 ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
 557         }
 558
 559         /* translate to spi_message, execute */
 560         retval = spidev_message(spidev, ioc, n_ioc);
 561         kfree(ioc);
 562
 563 done:
 564         mutex_unlock(&spidev->buf_lock);
 565         spi_dev_put(spi);
 566         return retval;
 567 }
 568
 569 static long
 570 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 571 {
 572         if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
 573                         && _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
 574                         && _IOC_DIR(cmd) == _IOC_WRITE)
 575                 return spidev_compat_ioc_message(filp, cmd, arg);
 576
 577         return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 578 }
 579 #else
 580 #define spidev_compat_ioctl NULL
 581 #endif /* CONFIG_COMPAT */
 582
 583 static int spidev_open(struct inode *inode, struct file *filp)
 584 {
 585         struct spidev_data      *spidev;
 586         int                     status = -ENXIO;
 587
 588         mutex_lock(&device_list_lock);
 589
 590         list_for_each_entry(spidev, &device_list, device_entry) {
 591                 if (spidev->devt == inode->i_rdev) {
 592                         status = 0;
 593                         break;
 594                 }
 595         }
 596
 597         if (status) {
 598                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 599                 goto err_find_dev;
 600         }
 601
 602         if (!spidev->tx_buffer) {
 603                 spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 604                 if (!spidev->tx_buffer) {
 605                         dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 606                         status = -ENOMEM;
 607                         goto err_find_dev;
 608                 }
 609         }
 610
 611         if (!spidev->rx_buffer) {
 612                 spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 613                 if (!spidev->rx_buffer) {
 614                         dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 615                         status = -ENOMEM;
 616                         goto err_alloc_rx_buf;
 617                 }
 618         }
 619
 620         spidev->users++;
 621         filp->private_data = spidev;
 622         nonseekable_open(inode, filp);
 623
 624         mutex_unlock(&device_list_lock);
 625         return 0;
 626
 627 err_alloc_rx_buf:
 628         kfree(spidev->tx_buffer);
 629         spidev->tx_buffer = NULL;
 630 err_find_dev:
 631         mutex_unlock(&device_list_lock);
 632         return status;
 633 }
 634
 635 static int spidev_release(struct inode *inode, struct file *filp)
 636 {
 637         struct spidev_data      *spidev;
 638
 639         mutex_lock(&device_list_lock);
 640         spidev = filp->private_data;
 641         filp->private_data = NULL;
 642
 643         /* last close? */
 644         spidev->users--;
 645         if (!spidev->users) {
 646                 int             dofree;
 647
 648                 kfree(spidev->tx_buffer);
 649                 spidev->tx_buffer = NULL;
 650
 651                 kfree(spidev->rx_buffer);
 652                 spidev->rx_buffer = NULL;
 653
 654                 if (spidev->spi)
 655                         spidev->speed_hz = spidev->spi->max_speed_hz;
 656
 657                 /* ... after we unbound from the underlying device? */
 658                 spin_lock_irq(&spidev->spi_lock);
 659                 dofree = (spidev->spi == NULL);
 660                 spin_unlock_irq(&spidev->spi_lock);
 661
 662                 if (dofree)
 663                         kfree(spidev);
 664         }
 665         mutex_unlock(&device_list_lock);
 666
 667         return 0;
 668 }
 669
 670 static const struct file_operations spidev_fops = {
 671         .owner =        THIS_MODULE,
 672         /* REVISIT switch to aio primitives, so that userspace
 673          * gets more complete API coverage.  It'll simplify things
 674          * too, except for the locking.
 675          */
 676         .write =        spidev_write,
 677         .read =         spidev_read,
 678         .unlocked_ioctl = spidev_ioctl,
 679         .compat_ioctl = spidev_compat_ioctl,
 680         .open =         spidev_open,
 681         .release =      spidev_release,
 682         .llseek =       no_llseek,
 683 };
 684
 685 /*-------------------------------------------------------------------------*/
 686
 687 /* The main reason to have this class is to make mdev/udev create the
 688  * /dev/spidevB.C character device nodes exposing our userspace API.
 689  * It also simplifies memory management.
 690  */
 691
 692 static struct class *spidev_class;
 693
 694 #ifdef CONFIG_OF
 695 static const struct of_device_id spidev_dt_ids[] = {
 696         { .compatible = "rohm,dh2228fv" },
 697         { .compatible = "lineartechnology,ltc2488" },
 698         {},
 699 };
 700 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 701 #endif
 702
 703 /*-------------------------------------------------------------------------*/
 704
 705 static int spidev_probe(struct spi_device *spi)
 706 {
 707         struct spidev_data      *spidev;
 708         int                     status;
 709         unsigned long           minor;
 710
 711         /*
 712          * spidev should never be referenced in DT without a specific
 713          * compatible string, it is a Linux implementation thing
 714          * rather than a description of the hardware.
 715          */
 716         if (spi->dev.of_node && !of_match_device(spidev_dt_ids, &spi->dev)) {
 717                 dev_err(&spi->dev, "buggy DT: spidev listed directly in DT\n");
 718                 WARN_ON(spi->dev.of_node &&
 719                         !of_match_device(spidev_dt_ids, &spi->dev));
 720         }
 721
 722         /* Allocate driver data */
 723         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 724         if (!spidev)
 725                 return -ENOMEM;
 726
 727         /* Initialize the driver data */
 728         spidev->spi = spi;
 729         spin_lock_init(&spidev->spi_lock);
 730         mutex_init(&spidev->buf_lock);
 731
 732         INIT_LIST_HEAD(&spidev->device_entry);
 733
 734         /* If we can allocate a minor number, hook up this device.
 735          * Reusing minors is fine so long as udev or mdev is working.
 736          */
 737         mutex_lock(&device_list_lock);
 738         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 739         if (minor < N_SPI_MINORS) {
 740                 struct device *dev;
 741
 742                 spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
 743                 dev = device_create(spidev_class, &spi->dev, spidev->devt,
 744                                     spidev, "spidev%d.%d",
 745                                     spi->master->bus_num, spi->chip_select);
 746                 status = PTR_ERR_OR_ZERO(dev);
 747         } else {
 748                 dev_dbg(&spi->dev, "no minor number available!\n");
 749                 status = -ENODEV;
 750         }
 751         if (status == 0) {
 752                 set_bit(minor, minors);
 753                 list_add(&spidev->device_entry, &device_list);
 754         }
 755         mutex_unlock(&device_list_lock);
 756
 757         spidev->speed_hz = spi->max_speed_hz;
 758
 759         if (status == 0)
 760                 spi_set_drvdata(spi, spidev);
 761         else
 762                 kfree(spidev);
 763
 764         return status;
 765 }
 766
 767 static int spidev_remove(struct spi_device *spi)
 768 {
 769         struct spidev_data      *spidev = spi_get_drvdata(spi);
 770
 771         /* make sure ops on existing fds can abort cleanly */
 772         spin_lock_irq(&spidev->spi_lock);
 773         spidev->spi = NULL;
 774         spin_unlock_irq(&spidev->spi_lock);
 775
 776         /* prevent new opens */
 777         mutex_lock(&device_list_lock);
 778         list_del(&spidev->device_entry);
 779         device_destroy(spidev_class, spidev->devt);
 780         clear_bit(MINOR(spidev->devt), minors);
 781         if (spidev->users == 0)
 782                 kfree(spidev);
 783         mutex_unlock(&device_list_lock);
 784
 785         return 0;
 786 }
 787
 788 static struct spi_driver spidev_spi_driver = {
 789         .driver = {
 790                 .name =         "spidev",
 791                 .of_match_table = of_match_ptr(spidev_dt_ids),
 792         },
 793         .probe =        spidev_probe,
 794         .remove =       spidev_remove,
 795
 796         /* NOTE:  suspend/resume methods are not necessary here.
 797          * We don't do anything except pass the requests to/from
 798          * the underlying controller.  The refrigerator handles
 799          * most issues; the controller driver handles the rest.
 800          */
 801 };
 802
 803 /*-------------------------------------------------------------------------*/
 804
 805 static int __init spidev_init(void)
 806 {
 807         int status;
 808
 809         /* Claim our 256 reserved device numbers.  Then register a class
 810          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 811          * the driver which manages those device numbers.
 812          */
 813         BUILD_BUG_ON(N_SPI_MINORS > 256);
 814         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 815         if (status < 0)
 816                 return status;
 817
 818         spidev_class = class_create(THIS_MODULE, "spidev");
 819         if (IS_ERR(spidev_class)) {
 820                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 821                 return PTR_ERR(spidev_class);
 822         }
 823
 824         status = spi_register_driver(&spidev_spi_driver);
 825         if (status < 0) {
 826                 class_destroy(spidev_class);
 827                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 828         }
 829         return status;
 830 }
 831 module_init(spidev_init);
 832
 833 static void __exit spidev_exit(void)
 834 {
 835         spi_unregister_driver(&spidev_spi_driver);
 836         class_destroy(spidev_class);
 837         unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
 838 }
 839 module_exit(spidev_exit);
 840
 841 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 842 MODULE_DESCRIPTION("User mode SPI device interface");
 843 MODULE_LICENSE("GPL");
 844 MODULE_ALIAS("spi:spidev");