drivers/spi/spidev.c

   1 /*
   2  * spidev.c -- 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  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  */
  22
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/ioctl.h>
  26 #include <linux/fs.h>
  27 #include <linux/device.h>
  28 #include <linux/list.h>
  29 #include <linux/errno.h>
  30 #include <linux/mutex.h>
  31 #include <linux/slab.h>
  32
  33 #include <linux/spi/spi.h>
  34 #include <linux/spi/spidev.h>
  35
  36 #include <asm/uaccess.h>
  37
  38
  39 /*
  40  * This supports acccess 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 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 unsigned long    minors[N_SPI_MINORS / BITS_PER_LONG];
  56
  57
  58 /* Bit masks for spi_device.mode management */
  59 #define SPI_MODE_MASK                   (SPI_CPHA | SPI_CPOL)
  60
  61
  62 struct spidev_data {
  63         struct device           dev;
  64         struct spi_device       *spi;
  65         struct list_head        device_entry;
  66
  67         struct mutex            buf_lock;
  68         unsigned                users;
  69         u8                      *buffer;
  70 };
  71
  72 static LIST_HEAD(device_list);
  73 static DEFINE_MUTEX(device_list_lock);
  74
  75 static unsigned bufsiz = 4096;
  76 module_param(bufsiz, uint, S_IRUGO);
  77 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  78
  79 /*-------------------------------------------------------------------------*/
  80
  81 /* Read-only message with current device setup */
  82 static ssize_t
  83 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
  84 {
  85         struct spidev_data      *spidev;
  86         struct spi_device       *spi;
  87         ssize_t                 status = 0;
  88
  89         /* chipselect only toggles at start or end of operation */
  90         if (count > bufsiz)
  91                 return -EMSGSIZE;
  92
  93         spidev = filp->private_data;
  94         spi = spidev->spi;
  95
  96         mutex_lock(&spidev->buf_lock);
  97         status = spi_read(spi, spidev->buffer, count);
  98         if (status == 0) {
  99                 unsigned long   missing;
 100
 101                 missing = copy_to_user(buf, spidev->buffer, count);
 102                 if (count && missing == count)
 103                         status = -EFAULT;
 104                 else
 105                         status = count - missing;
 106         }
 107         mutex_unlock(&spidev->buf_lock);
 108
 109         return status;
 110 }
 111
 112 /* Write-only message with current device setup */
 113 static ssize_t
 114 spidev_write(struct file *filp, const char __user *buf,
 115                 size_t count, loff_t *f_pos)
 116 {
 117         struct spidev_data      *spidev;
 118         struct spi_device       *spi;
 119         ssize_t                 status = 0;
 120         unsigned long           missing;
 121
 122         /* chipselect only toggles at start or end of operation */
 123         if (count > bufsiz)
 124                 return -EMSGSIZE;
 125
 126         spidev = filp->private_data;
 127         spi = spidev->spi;
 128
 129         mutex_lock(&spidev->buf_lock);
 130         missing = copy_from_user(spidev->buffer, buf, count);
 131         if (missing == 0) {
 132                 status = spi_write(spi, spidev->buffer, count);
 133                 if (status == 0)
 134                         status = count;
 135         } else
 136                 status = -EFAULT;
 137         mutex_unlock(&spidev->buf_lock);
 138
 139         return status;
 140 }
 141
 142 static int spidev_message(struct spidev_data *spidev,
 143                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 144 {
 145         struct spi_message      msg;
 146         struct spi_transfer     *k_xfers;
 147         struct spi_transfer     *k_tmp;
 148         struct spi_ioc_transfer *u_tmp;
 149         struct spi_device       *spi = spidev->spi;
 150         unsigned                n, total;
 151         u8                      *buf;
 152         int                     status = -EFAULT;
 153
 154         spi_message_init(&msg);
 155         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 156         if (k_xfers == NULL)
 157                 return -ENOMEM;
 158
 159         /* Construct spi_message, copying any tx data to bounce buffer.
 160          * We walk the array of user-provided transfers, using each one
 161          * to initialize a kernel version of the same transfer.
 162          */
 163         mutex_lock(&spidev->buf_lock);
 164         buf = spidev->buffer;
 165         total = 0;
 166         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 167                         n;
 168                         n--, k_tmp++, u_tmp++) {
 169                 k_tmp->len = u_tmp->len;
 170
 171                 total += k_tmp->len;
 172                 if (total > bufsiz) {
 173                         status = -EMSGSIZE;
 174                         goto done;
 175                 }
 176
 177                 if (u_tmp->rx_buf) {
 178                         k_tmp->rx_buf = buf;
 179                         if (!access_ok(VERIFY_WRITE, u_tmp->rx_buf, u_tmp->len))
 180                                 goto done;
 181                 }
 182                 if (u_tmp->tx_buf) {
 183                         k_tmp->tx_buf = buf;
 184                         if (copy_from_user(buf, (const u8 __user *)
 185                                                 (ptrdiff_t) u_tmp->tx_buf,
 186                                         u_tmp->len))
 187                                 goto done;
 188                 }
 189                 buf += k_tmp->len;
 190
 191                 k_tmp->cs_change = !!u_tmp->cs_change;
 192                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 193                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 194                 k_tmp->speed_hz = u_tmp->speed_hz;
 195 #ifdef VERBOSE
 196                 dev_dbg(&spi->dev,
 197                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 198                         u_tmp->len,
 199                         u_tmp->rx_buf ? "rx " : "",
 200                         u_tmp->tx_buf ? "tx " : "",
 201                         u_tmp->cs_change ? "cs " : "",
 202                         u_tmp->bits_per_word ? : spi->bits_per_word,
 203                         u_tmp->delay_usecs,
 204                         u_tmp->speed_hz ? : spi->max_speed_hz);
 205 #endif
 206                 spi_message_add_tail(k_tmp, &msg);
 207         }
 208
 209         status = spi_sync(spi, &msg);
 210         if (status < 0)
 211                 goto done;
 212
 213         /* copy any rx data out of bounce buffer */
 214         buf = spidev->buffer;
 215         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 216                 if (u_tmp->rx_buf) {
 217                         if (__copy_to_user((u8 __user *)
 218                                         (ptrdiff_t) u_tmp->rx_buf, buf,
 219                                         u_tmp->len)) {
 220                                 status = -EFAULT;
 221                                 goto done;
 222                         }
 223                 }
 224                 buf += u_tmp->len;
 225         }
 226         status = total;
 227
 228 done:
 229         mutex_unlock(&spidev->buf_lock);
 230         kfree(k_xfers);
 231         return status;
 232 }
 233
 234 static int
 235 spidev_ioctl(struct inode *inode, struct file *filp,
 236                 unsigned int cmd, unsigned long arg)
 237 {
 238         int                     err = 0;
 239         int                     retval = 0;
 240         struct spidev_data      *spidev;
 241         struct spi_device       *spi;
 242         u32                     tmp;
 243         unsigned                n_ioc;
 244         struct spi_ioc_transfer *ioc;
 245
 246         /* Check type and command number */
 247         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 248                 return -ENOTTY;
 249
 250         /* Check access direction once here; don't repeat below.
 251          * IOC_DIR is from the user perspective, while access_ok is
 252          * from the kernel perspective; so they look reversed.
 253          */
 254         if (_IOC_DIR(cmd) & _IOC_READ)
 255                 err = !access_ok(VERIFY_WRITE,
 256                                 (void __user *)arg, _IOC_SIZE(cmd));
 257         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 258                 err = !access_ok(VERIFY_READ,
 259                                 (void __user *)arg, _IOC_SIZE(cmd));
 260         if (err)
 261                 return -EFAULT;
 262
 263         spidev = filp->private_data;
 264         spi = spidev->spi;
 265
 266         switch (cmd) {
 267         /* read requests */
 268         case SPI_IOC_RD_MODE:
 269                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 270                                         (__u8 __user *)arg);
 271                 break;
 272         case SPI_IOC_RD_LSB_FIRST:
 273                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 274                                         (__u8 __user *)arg);
 275                 break;
 276         case SPI_IOC_RD_BITS_PER_WORD:
 277                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 278                 break;
 279         case SPI_IOC_RD_MAX_SPEED_HZ:
 280                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
 281                 break;
 282
 283         /* write requests */
 284         case SPI_IOC_WR_MODE:
 285                 retval = __get_user(tmp, (u8 __user *)arg);
 286                 if (retval == 0) {
 287                         u8      save = spi->mode;
 288
 289                         if (tmp & ~SPI_MODE_MASK) {
 290                                 retval = -EINVAL;
 291                                 break;
 292                         }
 293
 294                         tmp |= spi->mode & ~SPI_MODE_MASK;
 295                         spi->mode = (u8)tmp;
 296                         retval = spi_setup(spi);
 297                         if (retval < 0)
 298                                 spi->mode = save;
 299                         else
 300                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
 301                 }
 302                 break;
 303         case SPI_IOC_WR_LSB_FIRST:
 304                 retval = __get_user(tmp, (__u8 __user *)arg);
 305                 if (retval == 0) {
 306                         u8      save = spi->mode;
 307
 308                         if (tmp)
 309                                 spi->mode |= SPI_LSB_FIRST;
 310                         else
 311                                 spi->mode &= ~SPI_LSB_FIRST;
 312                         retval = spi_setup(spi);
 313                         if (retval < 0)
 314                                 spi->mode = save;
 315                         else
 316                                 dev_dbg(&spi->dev, "%csb first\n",
 317                                                 tmp ? 'l' : 'm');
 318                 }
 319                 break;
 320         case SPI_IOC_WR_BITS_PER_WORD:
 321                 retval = __get_user(tmp, (__u8 __user *)arg);
 322                 if (retval == 0) {
 323                         u8      save = spi->bits_per_word;
 324
 325                         spi->bits_per_word = tmp;
 326                         retval = spi_setup(spi);
 327                         if (retval < 0)
 328                                 spi->bits_per_word = save;
 329                         else
 330                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 331                 }
 332                 break;
 333         case SPI_IOC_WR_MAX_SPEED_HZ:
 334                 retval = __get_user(tmp, (__u32 __user *)arg);
 335                 if (retval == 0) {
 336                         u32     save = spi->max_speed_hz;
 337
 338                         spi->max_speed_hz = tmp;
 339                         retval = spi_setup(spi);
 340                         if (retval < 0)
 341                                 spi->max_speed_hz = save;
 342                         else
 343                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 344                 }
 345                 break;
 346
 347         default:
 348                 /* segmented and/or full-duplex I/O request */
 349                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 350                                 || _IOC_DIR(cmd) != _IOC_WRITE)
 351                         return -ENOTTY;
 352
 353                 tmp = _IOC_SIZE(cmd);
 354                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
 355                         retval = -EINVAL;
 356                         break;
 357                 }
 358                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 359                 if (n_ioc == 0)
 360                         break;
 361
 362                 /* copy into scratch area */
 363                 ioc = kmalloc(tmp, GFP_KERNEL);
 364                 if (!ioc) {
 365                         retval = -ENOMEM;
 366                         break;
 367                 }
 368                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
 369                         kfree(ioc);
 370                         retval = -EFAULT;
 371                         break;
 372                 }
 373
 374                 /* translate to spi_message, execute */
 375                 retval = spidev_message(spidev, ioc, n_ioc);
 376                 kfree(ioc);
 377                 break;
 378         }
 379         return retval;
 380 }
 381
 382 static int spidev_open(struct inode *inode, struct file *filp)
 383 {
 384         struct spidev_data      *spidev;
 385         int                     status = -ENXIO;
 386
 387         mutex_lock(&device_list_lock);
 388
 389         list_for_each_entry(spidev, &device_list, device_entry) {
 390                 if (spidev->dev.devt == inode->i_rdev) {
 391                         status = 0;
 392                         break;
 393                 }
 394         }
 395         if (status == 0) {
 396                 if (!spidev->buffer) {
 397                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
 398                         if (!spidev->buffer) {
 399                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 400                                 status = -ENOMEM;
 401                         }
 402                 }
 403                 if (status == 0) {
 404                         spidev->users++;
 405                         filp->private_data = spidev;
 406                         nonseekable_open(inode, filp);
 407                 }
 408         } else
 409                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 410
 411         mutex_unlock(&device_list_lock);
 412         return status;
 413 }
 414
 415 static int spidev_release(struct inode *inode, struct file *filp)
 416 {
 417         struct spidev_data      *spidev;
 418         int                     status = 0;
 419
 420         mutex_lock(&device_list_lock);
 421         spidev = filp->private_data;
 422         filp->private_data = NULL;
 423         spidev->users--;
 424         if (!spidev->users) {
 425                 kfree(spidev->buffer);
 426                 spidev->buffer = NULL;
 427         }
 428         mutex_unlock(&device_list_lock);
 429
 430         return status;
 431 }
 432
 433 static struct file_operations spidev_fops = {
 434         .owner =        THIS_MODULE,
 435         /* REVISIT switch to aio primitives, so that userspace
 436          * gets more complete API coverage.  It'll simplify things
 437          * too, except for the locking.
 438          */
 439         .write =        spidev_write,
 440         .read =         spidev_read,
 441         .ioctl =        spidev_ioctl,
 442         .open =         spidev_open,
 443         .release =      spidev_release,
 444 };
 445
 446 /*-------------------------------------------------------------------------*/
 447
 448 /* The main reason to have this class is to make mdev/udev create the
 449  * /dev/spidevB.C character device nodes exposing our userspace API.
 450  * It also simplifies memory management.
 451  */
 452
 453 static void spidev_classdev_release(struct device *dev)
 454 {
 455         struct spidev_data      *spidev;
 456
 457         spidev = container_of(dev, struct spidev_data, dev);
 458         kfree(spidev);
 459 }
 460
 461 static struct class spidev_class = {
 462         .name           = "spidev",
 463         .owner          = THIS_MODULE,
 464         .dev_release    = spidev_classdev_release,
 465 };
 466
 467 /*-------------------------------------------------------------------------*/
 468
 469 static int spidev_probe(struct spi_device *spi)
 470 {
 471         struct spidev_data      *spidev;
 472         int                     status;
 473         unsigned long           minor;
 474
 475         /* Allocate driver data */
 476         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 477         if (!spidev)
 478                 return -ENOMEM;
 479
 480         /* Initialize the driver data */
 481         spidev->spi = spi;
 482         mutex_init(&spidev->buf_lock);
 483
 484         INIT_LIST_HEAD(&spidev->device_entry);
 485
 486         /* If we can allocate a minor number, hook up this device.
 487          * Reusing minors is fine so long as udev or mdev is working.
 488          */
 489         mutex_lock(&device_list_lock);
 490         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 491         if (minor < N_SPI_MINORS) {
 492                 spidev->dev.parent = &spi->dev;
 493                 spidev->dev.class = &spidev_class;
 494                 spidev->dev.devt = MKDEV(SPIDEV_MAJOR, minor);
 495                 snprintf(spidev->dev.bus_id, sizeof spidev->dev.bus_id,
 496                                 "spidev%d.%d",
 497                                 spi->master->bus_num, spi->chip_select);
 498                 status = device_register(&spidev->dev);
 499         } else {
 500                 dev_dbg(&spi->dev, "no minor number available!\n");
 501                 status = -ENODEV;
 502         }
 503         if (status == 0) {
 504                 set_bit(minor, minors);
 505                 dev_set_drvdata(&spi->dev, spidev);
 506                 list_add(&spidev->device_entry, &device_list);
 507         }
 508         mutex_unlock(&device_list_lock);
 509
 510         if (status != 0)
 511                 kfree(spidev);
 512
 513         return status;
 514 }
 515
 516 static int spidev_remove(struct spi_device *spi)
 517 {
 518         struct spidev_data      *spidev = dev_get_drvdata(&spi->dev);
 519
 520         mutex_lock(&device_list_lock);
 521
 522         list_del(&spidev->device_entry);
 523         dev_set_drvdata(&spi->dev, NULL);
 524         clear_bit(MINOR(spidev->dev.devt), minors);
 525         device_unregister(&spidev->dev);
 526
 527         mutex_unlock(&device_list_lock);
 528
 529         return 0;
 530 }
 531
 532 static struct spi_driver spidev_spi = {
 533         .driver = {
 534                 .name =         "spidev",
 535                 .owner =        THIS_MODULE,
 536         },
 537         .probe =        spidev_probe,
 538         .remove =       __devexit_p(spidev_remove),
 539
 540         /* NOTE:  suspend/resume methods are not necessary here.
 541          * We don't do anything except pass the requests to/from
 542          * the underlying controller.  The refrigerator handles
 543          * most issues; the controller driver handles the rest.
 544          */
 545 };
 546
 547 /*-------------------------------------------------------------------------*/
 548
 549 static int __init spidev_init(void)
 550 {
 551         int status;
 552
 553         /* Claim our 256 reserved device numbers.  Then register a class
 554          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 555          * the driver which manages those device numbers.
 556          */
 557         BUILD_BUG_ON(N_SPI_MINORS > 256);
 558         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 559         if (status < 0)
 560                 return status;
 561
 562         status = class_register(&spidev_class);
 563         if (status < 0) {
 564                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 565                 return status;
 566         }
 567
 568         status = spi_register_driver(&spidev_spi);
 569         if (status < 0) {
 570                 class_unregister(&spidev_class);
 571                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 572         }
 573         return status;
 574 }
 575 module_init(spidev_init);
 576
 577 static void __exit spidev_exit(void)
 578 {
 579         spi_unregister_driver(&spidev_spi);
 580         class_unregister(&spidev_class);
 581         unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 582 }
 583 module_exit(spidev_exit);
 584
 585 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 586 MODULE_DESCRIPTION("User mode SPI device interface");
 587 MODULE_LICENSE("GPL");