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 /*
  99  * We can't use the standard synchronous wrappers for file I/O; we
 100  * need to protect against async removal of the underlying spi_device.
 101  */
 102 static void spidev_complete(void *arg)
 103 {
 104         complete(arg);
 105 }
 106
 107 static ssize_t
 108 spidev_sync(struct spidev_data *spidev, struct spi_message *message)
 109 {
 110         DECLARE_COMPLETION_ONSTACK(done);
 111         int status;
 112
 113         message->complete = spidev_complete;
 114         message->context = &done;
 115
 116         spin_lock_irq(&spidev->spi_lock);
 117         if (spidev->spi == NULL)
 118                 status = -ESHUTDOWN;
 119         else
 120                 status = spi_async(spidev->spi, message);
 121         spin_unlock_irq(&spidev->spi_lock);
 122
 123         if (status == 0) {
 124                 wait_for_completion(&done);
 125                 status = message->status;
 126                 if (status == 0)
 127                         status = message->actual_length;
 128         }
 129         return status;
 130 }
 131
 132 static inline ssize_t
 133 spidev_sync_write(struct spidev_data *spidev, size_t len)
 134 {
 135         struct spi_transfer     t = {
 136                         .tx_buf         = spidev->tx_buffer,
 137                         .len            = len,
 138                         .speed_hz       = spidev->speed_hz,
 139                 };
 140         struct spi_message      m;
 141
 142         spi_message_init(&m);
 143         spi_message_add_tail(&t, &m);
 144         return spidev_sync(spidev, &m);
 145 }
 146
 147 static inline ssize_t
 148 spidev_sync_read(struct spidev_data *spidev, size_t len)
 149 {
 150         struct spi_transfer     t = {
 151                         .rx_buf         = spidev->rx_buffer,
 152                         .len            = len,
 153                         .speed_hz       = spidev->speed_hz,
 154                 };
 155         struct spi_message      m;
 156
 157         spi_message_init(&m);
 158         spi_message_add_tail(&t, &m);
 159         return spidev_sync(spidev, &m);
 160 }
 161
 162 /*-------------------------------------------------------------------------*/
 163
 164 /* Read-only message with current device setup */
 165 static ssize_t
 166 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
 167 {
 168         struct spidev_data      *spidev;
 169         ssize_t                 status = 0;
 170
 171         /* chipselect only toggles at start or end of operation */
 172         if (count > bufsiz)
 173                 return -EMSGSIZE;
 174
 175         spidev = filp->private_data;
 176
 177         mutex_lock(&spidev->buf_lock);
 178         status = spidev_sync_read(spidev, count);
 179         if (status > 0) {
 180                 unsigned long   missing;
 181
 182                 missing = copy_to_user(buf, spidev->rx_buffer, status);
 183                 if (missing == status)
 184                         status = -EFAULT;
 185                 else
 186                         status = status - missing;
 187         }
 188         mutex_unlock(&spidev->buf_lock);
 189
 190         return status;
 191 }
 192
 193 /* Write-only message with current device setup */
 194 static ssize_t
 195 spidev_write(struct file *filp, const char __user *buf,
 196                 size_t count, loff_t *f_pos)
 197 {
 198         struct spidev_data      *spidev;
 199         ssize_t                 status = 0;
 200         unsigned long           missing;
 201
 202         /* chipselect only toggles at start or end of operation */
 203         if (count > bufsiz)
 204                 return -EMSGSIZE;
 205
 206         spidev = filp->private_data;
 207
 208         mutex_lock(&spidev->buf_lock);
 209         missing = copy_from_user(spidev->tx_buffer, buf, count);
 210         if (missing == 0)
 211                 status = spidev_sync_write(spidev, count);
 212         else
 213                 status = -EFAULT;
 214         mutex_unlock(&spidev->buf_lock);
 215
 216         return status;
 217 }
 218
 219 static int spidev_message(struct spidev_data *spidev,
 220                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 221 {
 222         struct spi_message      msg;
 223         struct spi_transfer     *k_xfers;
 224         struct spi_transfer     *k_tmp;
 225         struct spi_ioc_transfer *u_tmp;
 226         unsigned                n, total, tx_total, rx_total;
 227         u8                      *tx_buf, *rx_buf;
 228         int                     status = -EFAULT;
 229
 230         spi_message_init(&msg);
 231         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 232         if (k_xfers == NULL)
 233                 return -ENOMEM;
 234
 235         /* Construct spi_message, copying any tx data to bounce buffer.
 236          * We walk the array of user-provided transfers, using each one
 237          * to initialize a kernel version of the same transfer.
 238          */
 239         tx_buf = spidev->tx_buffer;
 240         rx_buf = spidev->rx_buffer;
 241         total = 0;
 242         tx_total = 0;
 243         rx_total = 0;
 244         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 245                         n;
 246                         n--, k_tmp++, u_tmp++) {
 247                 k_tmp->len = u_tmp->len;
 248
 249                 total += k_tmp->len;
 250                 /* Since the function returns the total length of transfers
 251                  * on success, restrict the total to positive int values to
 252                  * avoid the return value looking like an error.  Also check
 253                  * each transfer length to avoid arithmetic overflow.
 254                  */
 255                 if (total > INT_MAX || k_tmp->len > INT_MAX) {
 256                         status = -EMSGSIZE;
 257                         goto done;
 258                 }
 259
 260                 if (u_tmp->rx_buf) {
 261                         /* this transfer needs space in RX bounce buffer */
 262                         rx_total += k_tmp->len;
 263                         if (rx_total > bufsiz) {
 264                                 status = -EMSGSIZE;
 265                                 goto done;
 266                         }
 267                         k_tmp->rx_buf = rx_buf;
 268                         if (!access_ok(VERIFY_WRITE, (u8 __user *)
 269                                                 (uintptr_t) u_tmp->rx_buf,
 270                                                 u_tmp->len))
 271                                 goto done;
 272                         rx_buf += k_tmp->len;
 273                 }
 274                 if (u_tmp->tx_buf) {
 275                         /* this transfer needs space in TX bounce buffer */
 276                         tx_total += k_tmp->len;
 277                         if (tx_total > bufsiz) {
 278                                 status = -EMSGSIZE;
 279                                 goto done;
 280                         }
 281                         k_tmp->tx_buf = tx_buf;
 282                         if (copy_from_user(tx_buf, (const u8 __user *)
 283                                                 (uintptr_t) u_tmp->tx_buf,
 284                                         u_tmp->len))
 285                                 goto done;
 286                         tx_buf += k_tmp->len;
 287                 }
 288
 289                 k_tmp->cs_change = !!u_tmp->cs_change;
 290                 k_tmp->tx_nbits = u_tmp->tx_nbits;
 291                 k_tmp->rx_nbits = u_tmp->rx_nbits;
 292                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 293                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 294                 k_tmp->speed_hz = u_tmp->speed_hz;
 295                 if (!k_tmp->speed_hz)
 296                         k_tmp->speed_hz = spidev->speed_hz;
 297 #ifdef VERBOSE
 298                 dev_dbg(&spidev->spi->dev,
 299                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 300                         u_tmp->len,
 301                         u_tmp->rx_buf ? "rx " : "",
 302                         u_tmp->tx_buf ? "tx " : "",
 303                         u_tmp->cs_change ? "cs " : "",
 304                         u_tmp->bits_per_word ? : spidev->spi->bits_per_word,
 305                         u_tmp->delay_usecs,
 306                         u_tmp->speed_hz ? : spidev->spi->max_speed_hz);
 307 #endif
 308                 spi_message_add_tail(k_tmp, &msg);
 309         }
 310
 311         status = spidev_sync(spidev, &msg);
 312         if (status < 0)
 313                 goto done;
 314
 315         /* copy any rx data out of bounce buffer */
 316         rx_buf = spidev->rx_buffer;
 317         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 318                 if (u_tmp->rx_buf) {
 319                         if (__copy_to_user((u8 __user *)
 320                                         (uintptr_t) u_tmp->rx_buf, rx_buf,
 321                                         u_tmp->len)) {
 322                                 status = -EFAULT;
 323                                 goto done;
 324                         }
 325                         rx_buf += u_tmp->len;
 326                 }
 327         }
 328         status = total;
 329
 330 done:
 331         kfree(k_xfers);
 332         return status;
 333 }
 334
 335 static struct spi_ioc_transfer *
 336 spidev_get_ioc_message(unsigned int cmd, struct spi_ioc_transfer __user *u_ioc,
 337                 unsigned *n_ioc)
 338 {
 339         struct spi_ioc_transfer *ioc;
 340         u32     tmp;
 341
 342         /* Check type, command number and direction */
 343         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC
 344                         || _IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 345                         || _IOC_DIR(cmd) != _IOC_WRITE)
 346                 return ERR_PTR(-ENOTTY);
 347
 348         tmp = _IOC_SIZE(cmd);
 349         if ((tmp % sizeof(struct spi_ioc_transfer)) != 0)
 350                 return ERR_PTR(-EINVAL);
 351         *n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 352         if (*n_ioc == 0)
 353                 return NULL;
 354
 355         /* copy into scratch area */
 356         ioc = kmalloc(tmp, GFP_KERNEL);
 357         if (!ioc)
 358                 return ERR_PTR(-ENOMEM);
 359         if (__copy_from_user(ioc, u_ioc, tmp)) {
 360                 kfree(ioc);
 361                 return ERR_PTR(-EFAULT);
 362         }
 363         return ioc;
 364 }
 365
 366 static long
 367 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 368 {
 369         int                     err = 0;
 370         int                     retval = 0;
 371         struct spidev_data      *spidev;
 372         struct spi_device       *spi;
 373         u32                     tmp;
 374         unsigned                n_ioc;
 375         struct spi_ioc_transfer *ioc;
 376
 377         /* Check type and command number */
 378         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 379                 return -ENOTTY;
 380
 381         /* Check access direction once here; don't repeat below.
 382          * IOC_DIR is from the user perspective, while access_ok is
 383          * from the kernel perspective; so they look reversed.
 384          */
 385         if (_IOC_DIR(cmd) & _IOC_READ)
 386                 err = !access_ok(VERIFY_WRITE,
 387                                 (void __user *)arg, _IOC_SIZE(cmd));
 388         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 389                 err = !access_ok(VERIFY_READ,
 390                                 (void __user *)arg, _IOC_SIZE(cmd));
 391         if (err)
 392                 return -EFAULT;
 393
 394         /* guard against device removal before, or while,
 395          * we issue this ioctl.
 396          */
 397         spidev = filp->private_data;
 398         spin_lock_irq(&spidev->spi_lock);
 399         spi = spi_dev_get(spidev->spi);
 400         spin_unlock_irq(&spidev->spi_lock);
 401
 402         if (spi == NULL)
 403                 return -ESHUTDOWN;
 404
 405         /* use the buffer lock here for triple duty:
 406          *  - prevent I/O (from us) so calling spi_setup() is safe;
 407          *  - prevent concurrent SPI_IOC_WR_* from morphing
 408          *    data fields while SPI_IOC_RD_* reads them;
 409          *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
 410          */
 411         mutex_lock(&spidev->buf_lock);
 412
 413         switch (cmd) {
 414         /* read requests */
 415         case SPI_IOC_RD_MODE:
 416                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 417                                         (__u8 __user *)arg);
 418                 break;
 419         case SPI_IOC_RD_MODE32:
 420                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 421                                         (__u32 __user *)arg);
 422                 break;
 423         case SPI_IOC_RD_LSB_FIRST:
 424                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 425                                         (__u8 __user *)arg);
 426                 break;
 427         case SPI_IOC_RD_BITS_PER_WORD:
 428                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 429                 break;
 430         case SPI_IOC_RD_MAX_SPEED_HZ:
 431                 retval = __put_user(spidev->speed_hz, (__u32 __user *)arg);
 432                 break;
 433
 434         /* write requests */
 435         case SPI_IOC_WR_MODE:
 436         case SPI_IOC_WR_MODE32:
 437                 if (cmd == SPI_IOC_WR_MODE)
 438                         retval = __get_user(tmp, (u8 __user *)arg);
 439                 else
 440                         retval = __get_user(tmp, (u32 __user *)arg);
 441                 if (retval == 0) {
 442                         u32     save = spi->mode;
 443
 444                         if (tmp & ~SPI_MODE_MASK) {
 445                                 retval = -EINVAL;
 446                                 break;
 447                         }
 448
 449                         tmp |= spi->mode & ~SPI_MODE_MASK;
 450                         spi->mode = (u16)tmp;
 451                         retval = spi_setup(spi);
 452                         if (retval < 0)
 453                                 spi->mode = save;
 454                         else
 455                                 dev_dbg(&spi->dev, "spi mode %x\n", tmp);
 456                 }
 457                 break;
 458         case SPI_IOC_WR_LSB_FIRST:
 459                 retval = __get_user(tmp, (__u8 __user *)arg);
 460                 if (retval == 0) {
 461                         u32     save = spi->mode;
 462
 463                         if (tmp)
 464                                 spi->mode |= SPI_LSB_FIRST;
 465                         else
 466                                 spi->mode &= ~SPI_LSB_FIRST;
 467                         retval = spi_setup(spi);
 468                         if (retval < 0)
 469                                 spi->mode = save;
 470                         else
 471                                 dev_dbg(&spi->dev, "%csb first\n",
 472                                                 tmp ? 'l' : 'm');
 473                 }
 474                 break;
 475         case SPI_IOC_WR_BITS_PER_WORD:
 476                 retval = __get_user(tmp, (__u8 __user *)arg);
 477                 if (retval == 0) {
 478                         u8      save = spi->bits_per_word;
 479
 480                         spi->bits_per_word = tmp;
 481                         retval = spi_setup(spi);
 482                         if (retval < 0)
 483                                 spi->bits_per_word = save;
 484                         else
 485                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 486                 }
 487                 break;
 488         case SPI_IOC_WR_MAX_SPEED_HZ:
 489                 retval = __get_user(tmp, (__u32 __user *)arg);
 490                 if (retval == 0) {
 491                         u32     save = spi->max_speed_hz;
 492
 493                         spi->max_speed_hz = tmp;
 494                         retval = spi_setup(spi);
 495                         if (retval >= 0)
 496                                 spidev->speed_hz = tmp;
 497                         else
 498                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 499                         spi->max_speed_hz = save;
 500                 }
 501                 break;
 502
 503         default:
 504                 /* segmented and/or full-duplex I/O request */
 505                 /* Check message and copy into scratch area */
 506                 ioc = spidev_get_ioc_message(cmd,
 507                                 (struct spi_ioc_transfer __user *)arg, &n_ioc);
 508                 if (IS_ERR(ioc)) {
 509                         retval = PTR_ERR(ioc);
 510                         break;
 511                 }
 512                 if (!ioc)
 513                         break;  /* n_ioc is also 0 */
 514
 515                 /* translate to spi_message, execute */
 516                 retval = spidev_message(spidev, ioc, n_ioc);
 517                 kfree(ioc);
 518                 break;
 519         }
 520
 521         mutex_unlock(&spidev->buf_lock);
 522         spi_dev_put(spi);
 523         return retval;
 524 }
 525
 526 #ifdef CONFIG_COMPAT
 527 static long
 528 spidev_compat_ioc_message(struct file *filp, unsigned int cmd,
 529                 unsigned long arg)
 530 {
 531         struct spi_ioc_transfer __user  *u_ioc;
 532         int                             retval = 0;
 533         struct spidev_data              *spidev;
 534         struct spi_device               *spi;
 535         unsigned                        n_ioc, n;
 536         struct spi_ioc_transfer         *ioc;
 537
 538         u_ioc = (struct spi_ioc_transfer __user *) compat_ptr(arg);
 539         if (!access_ok(VERIFY_READ, u_ioc, _IOC_SIZE(cmd)))
 540                 return -EFAULT;
 541
 542         /* guard against device removal before, or while,
 543          * we issue this ioctl.
 544          */
 545         spidev = filp->private_data;
 546         spin_lock_irq(&spidev->spi_lock);
 547         spi = spi_dev_get(spidev->spi);
 548         spin_unlock_irq(&spidev->spi_lock);
 549
 550         if (spi == NULL)
 551                 return -ESHUTDOWN;
 552
 553         /* SPI_IOC_MESSAGE needs the buffer locked "normally" */
 554         mutex_lock(&spidev->buf_lock);
 555
 556         /* Check message and copy into scratch area */
 557         ioc = spidev_get_ioc_message(cmd, u_ioc, &n_ioc);
 558         if (IS_ERR(ioc)) {
 559                 retval = PTR_ERR(ioc);
 560                 goto done;
 561         }
 562         if (!ioc)
 563                 goto done;      /* n_ioc is also 0 */
 564
 565         /* Convert buffer pointers */
 566         for (n = 0; n < n_ioc; n++) {
 567                 ioc[n].rx_buf = (uintptr_t) compat_ptr(ioc[n].rx_buf);
 568                 ioc[n].tx_buf = (uintptr_t) compat_ptr(ioc[n].tx_buf);
 569         }
 570
 571         /* translate to spi_message, execute */
 572         retval = spidev_message(spidev, ioc, n_ioc);
 573         kfree(ioc);
 574
 575 done:
 576         mutex_unlock(&spidev->buf_lock);
 577         spi_dev_put(spi);
 578         return retval;
 579 }
 580
 581 static long
 582 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 583 {
 584         if (_IOC_TYPE(cmd) == SPI_IOC_MAGIC
 585                         && _IOC_NR(cmd) == _IOC_NR(SPI_IOC_MESSAGE(0))
 586                         && _IOC_DIR(cmd) == _IOC_WRITE)
 587                 return spidev_compat_ioc_message(filp, cmd, arg);
 588
 589         return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
 590 }
 591 #else
 592 #define spidev_compat_ioctl NULL
 593 #endif /* CONFIG_COMPAT */
 594
 595 static int spidev_open(struct inode *inode, struct file *filp)
 596 {
 597         struct spidev_data      *spidev;
 598         int                     status = -ENXIO;
 599
 600         mutex_lock(&device_list_lock);
 601
 602         list_for_each_entry(spidev, &device_list, device_entry) {
 603                 if (spidev->devt == inode->i_rdev) {
 604                         status = 0;
 605                         break;
 606                 }
 607         }
 608
 609         if (status) {
 610                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 611                 goto err_find_dev;
 612         }
 613
 614         if (!spidev->tx_buffer) {
 615                 spidev->tx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 616                 if (!spidev->tx_buffer) {
 617                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 618                                 status = -ENOMEM;
 619                         goto err_find_dev;
 620                         }
 621                 }
 622
 623         if (!spidev->rx_buffer) {
 624                 spidev->rx_buffer = kmalloc(bufsiz, GFP_KERNEL);
 625                 if (!spidev->rx_buffer) {
 626                         dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 627                         status = -ENOMEM;
 628                         goto err_alloc_rx_buf;
 629                 }
 630         }
 631
 632         spidev->users++;
 633         filp->private_data = spidev;
 634         nonseekable_open(inode, filp);
 635
 636         mutex_unlock(&device_list_lock);
 637         return 0;
 638
 639 err_alloc_rx_buf:
 640         kfree(spidev->tx_buffer);
 641         spidev->tx_buffer = NULL;
 642 err_find_dev:
 643         mutex_unlock(&device_list_lock);
 644         return status;
 645 }
 646
 647 static int spidev_release(struct inode *inode, struct file *filp)
 648 {
 649         struct spidev_data      *spidev;
 650         int                     status = 0;
 651
 652         mutex_lock(&device_list_lock);
 653         spidev = filp->private_data;
 654         filp->private_data = NULL;
 655
 656         /* last close? */
 657         spidev->users--;
 658         if (!spidev->users) {
 659                 int             dofree;
 660
 661                 kfree(spidev->tx_buffer);
 662                 spidev->tx_buffer = NULL;
 663
 664                 kfree(spidev->rx_buffer);
 665                 spidev->rx_buffer = NULL;
 666
 667                 if (spidev->spi)
 668                         spidev->speed_hz = spidev->spi->max_speed_hz;
 669
 670                 /* ... after we unbound from the underlying device? */
 671                 spin_lock_irq(&spidev->spi_lock);
 672                 dofree = (spidev->spi == NULL);
 673                 spin_unlock_irq(&spidev->spi_lock);
 674
 675                 if (dofree)
 676                         kfree(spidev);
 677         }
 678         mutex_unlock(&device_list_lock);
 679
 680         return status;
 681 }
 682
 683 static const struct file_operations spidev_fops = {
 684         .owner =        THIS_MODULE,
 685         /* REVISIT switch to aio primitives, so that userspace
 686          * gets more complete API coverage.  It'll simplify things
 687          * too, except for the locking.
 688          */
 689         .write =        spidev_write,
 690         .read =         spidev_read,
 691         .unlocked_ioctl = spidev_ioctl,
 692         .compat_ioctl = spidev_compat_ioctl,
 693         .open =         spidev_open,
 694         .release =      spidev_release,
 695         .llseek =       no_llseek,
 696 };
 697
 698 /*-------------------------------------------------------------------------*/
 699
 700 /* The main reason to have this class is to make mdev/udev create the
 701  * /dev/spidevB.C character device nodes exposing our userspace API.
 702  * It also simplifies memory management.
 703  */
 704
 705 static struct class *spidev_class;
 706
 707 #ifdef CONFIG_OF
 708 static const struct of_device_id spidev_dt_ids[] = {
 709         { .compatible = "rohm,dh2228fv" },
 710         {},
 711 };
 712 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 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          * compatbile string, it is a Linux implementation thing
 726          * rather than a description of the hardware.
 727          */
 728         if (spi->dev.of_node && !of_match_device(spidev_dt_ids, &spi->dev)) {
 729                 dev_err(&spi->dev, "buggy DT: spidev listed directly in DT\n");
 730                 WARN_ON(spi->dev.of_node &&
 731                         !of_match_device(spidev_dt_ids, &spi->dev));
 732         }
 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                 .owner =        THIS_MODULE,
 804                 .of_match_table = of_match_ptr(spidev_dt_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");