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   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                 if (u_tmp->rx_buf) {
 172                         k_tmp->rx_buf = buf;
 173                         if (!access_ok(VERIFY_WRITE, u_tmp->rx_buf, u_tmp->len))
 174                                 goto done;
 175                 }
 176                 if (u_tmp->tx_buf) {
 177                         k_tmp->tx_buf = buf;
 178                         if (copy_from_user(buf, (const u8 __user *)u_tmp->tx_buf,
 179                                         u_tmp->len))
 180                                 goto done;
 181                 }
 182
 183                 total += k_tmp->len;
 184                 if (total > bufsiz) {
 185                         status = -EMSGSIZE;
 186                         goto done;
 187                 }
 188                 buf += k_tmp->len;
 189
 190                 k_tmp->cs_change = !!u_tmp->cs_change;
 191                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 192                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 193                 k_tmp->speed_hz = u_tmp->speed_hz;
 194 #ifdef VERBOSE
 195                 dev_dbg(&spi->dev,
 196                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 197                         u_tmp->len,
 198                         u_tmp->rx_buf ? "rx " : "",
 199                         u_tmp->tx_buf ? "tx " : "",
 200                         u_tmp->cs_change ? "cs " : "",
 201                         u_tmp->bits_per_word ? : spi->bits_per_word,
 202                         u_tmp->delay_usecs,
 203                         u_tmp->speed_hz ? : spi->max_speed_hz);
 204 #endif
 205                 spi_message_add_tail(k_tmp, &msg);
 206         }
 207
 208         status = spi_sync(spi, &msg);
 209         if (status < 0)
 210                 goto done;
 211
 212         /* copy any rx data out of bounce buffer */
 213         buf = spidev->buffer;
 214         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 215                 if (u_tmp->rx_buf) {
 216                         if (__copy_to_user((u8 __user *)u_tmp->rx_buf, buf,
 217                                         u_tmp->len)) {
 218                                 status = -EFAULT;
 219                                 goto done;
 220                         }
 221                 }
 222                 buf += u_tmp->len;
 223         }
 224         status = total;
 225
 226 done:
 227         mutex_unlock(&spidev->buf_lock);
 228         kfree(k_xfers);
 229         return status;
 230 }
 231
 232 static int
 233 spidev_ioctl(struct inode *inode, struct file *filp,
 234                 unsigned int cmd, unsigned long arg)
 235 {
 236         int                     err = 0;
 237         int                     retval = 0;
 238         struct spidev_data      *spidev;
 239         struct spi_device       *spi;
 240         u32                     tmp;
 241         unsigned                n_ioc;
 242         struct spi_ioc_transfer *ioc;
 243
 244         /* Check type and command number */
 245         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 246                 return -ENOTTY;
 247
 248         /* Check access direction once here; don't repeat below.
 249          * IOC_DIR is from the user perspective, while access_ok is
 250          * from the kernel perspective; so they look reversed.
 251          */
 252         if (_IOC_DIR(cmd) & _IOC_READ)
 253                 err = !access_ok(VERIFY_WRITE,
 254                                 (void __user *)arg, _IOC_SIZE(cmd));
 255         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 256                 err = !access_ok(VERIFY_READ,
 257                                 (void __user *)arg, _IOC_SIZE(cmd));
 258         if (err)
 259                 return -EFAULT;
 260
 261         spidev = filp->private_data;
 262         spi = spidev->spi;
 263
 264         switch (cmd) {
 265         /* read requests */
 266         case SPI_IOC_RD_MODE:
 267                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 268                                         (__u8 __user *)arg);
 269                 break;
 270         case SPI_IOC_RD_LSB_FIRST:
 271                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 272                                         (__u8 __user *)arg);
 273                 break;
 274         case SPI_IOC_RD_BITS_PER_WORD:
 275                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 276                 break;
 277         case SPI_IOC_RD_MAX_SPEED_HZ:
 278                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
 279                 break;
 280
 281         /* write requests */
 282         case SPI_IOC_WR_MODE:
 283                 retval = __get_user(tmp, (u8 __user *)arg);
 284                 if (retval == 0) {
 285                         u8      save = spi->mode;
 286
 287                         if (tmp & ~SPI_MODE_MASK) {
 288                                 retval = -EINVAL;
 289                                 break;
 290                         }
 291
 292                         tmp |= spi->mode & ~SPI_MODE_MASK;
 293                         spi->mode = (u8)tmp;
 294                         retval = spi_setup(spi);
 295                         if (retval < 0)
 296                                 spi->mode = save;
 297                         else
 298                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
 299                 }
 300                 break;
 301         case SPI_IOC_WR_LSB_FIRST:
 302                 retval = __get_user(tmp, (__u8 __user *)arg);
 303                 if (retval == 0) {
 304                         u8      save = spi->mode;
 305
 306                         if (tmp)
 307                                 spi->mode |= SPI_LSB_FIRST;
 308                         else
 309                                 spi->mode &= ~SPI_LSB_FIRST;
 310                         retval = spi_setup(spi);
 311                         if (retval < 0)
 312                                 spi->mode = save;
 313                         else
 314                                 dev_dbg(&spi->dev, "%csb first\n",
 315                                                 tmp ? 'l' : 'm');
 316                 }
 317                 break;
 318         case SPI_IOC_WR_BITS_PER_WORD:
 319                 retval = __get_user(tmp, (__u8 __user *)arg);
 320                 if (retval == 0) {
 321                         u8      save = spi->bits_per_word;
 322
 323                         spi->bits_per_word = tmp;
 324                         retval = spi_setup(spi);
 325                         if (retval < 0)
 326                                 spi->bits_per_word = save;
 327                         else
 328                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 329                 }
 330                 break;
 331         case SPI_IOC_WR_MAX_SPEED_HZ:
 332                 retval = __get_user(tmp, (__u32 __user *)arg);
 333                 if (retval == 0) {
 334                         u32     save = spi->max_speed_hz;
 335
 336                         spi->max_speed_hz = tmp;
 337                         retval = spi_setup(spi);
 338                         if (retval < 0)
 339                                 spi->max_speed_hz = save;
 340                         else
 341                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 342                 }
 343                 break;
 344
 345         default:
 346                 /* segmented and/or full-duplex I/O request */
 347                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 348                                 || _IOC_DIR(cmd) != _IOC_WRITE)
 349                         return -ENOTTY;
 350
 351                 tmp = _IOC_SIZE(cmd);
 352                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
 353                         retval = -EINVAL;
 354                         break;
 355                 }
 356                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 357                 if (n_ioc == 0)
 358                         break;
 359
 360                 /* copy into scratch area */
 361                 ioc = kmalloc(tmp, GFP_KERNEL);
 362                 if (!ioc) {
 363                         retval = -ENOMEM;
 364                         break;
 365                 }
 366                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
 367                         retval = -EFAULT;
 368                         break;
 369                 }
 370
 371                 /* translate to spi_message, execute */
 372                 retval = spidev_message(spidev, ioc, n_ioc);
 373                 kfree(ioc);
 374                 break;
 375         }
 376         return retval;
 377 }
 378
 379 static int spidev_open(struct inode *inode, struct file *filp)
 380 {
 381         struct spidev_data      *spidev;
 382         int                     status = -ENXIO;
 383
 384         mutex_lock(&device_list_lock);
 385
 386         list_for_each_entry(spidev, &device_list, device_entry) {
 387                 if (spidev->dev.devt == inode->i_rdev) {
 388                         status = 0;
 389                         break;
 390                 }
 391         }
 392         if (status == 0) {
 393                 if (!spidev->buffer) {
 394                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
 395                         if (!spidev->buffer) {
 396                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 397                                 status = -ENOMEM;
 398                         }
 399                 }
 400                 if (status == 0) {
 401                         spidev->users++;
 402                         filp->private_data = spidev;
 403                         nonseekable_open(inode, filp);
 404                 }
 405         } else
 406                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 407
 408         mutex_unlock(&device_list_lock);
 409         return status;
 410 }
 411
 412 static int spidev_release(struct inode *inode, struct file *filp)
 413 {
 414         struct spidev_data      *spidev;
 415         int                     status = 0;
 416
 417         mutex_lock(&device_list_lock);
 418         spidev = filp->private_data;
 419         filp->private_data = NULL;
 420         spidev->users--;
 421         if (!spidev->users) {
 422                 kfree(spidev->buffer);
 423                 spidev->buffer = NULL;
 424         }
 425         mutex_unlock(&device_list_lock);
 426
 427         return status;
 428 }
 429
 430 static struct file_operations spidev_fops = {
 431         .owner =        THIS_MODULE,
 432         /* REVISIT switch to aio primitives, so that userspace
 433          * gets more complete API coverage.  It'll simplify things
 434          * too, except for the locking.
 435          */
 436         .write =        spidev_write,
 437         .read =         spidev_read,
 438         .ioctl =        spidev_ioctl,
 439         .open =         spidev_open,
 440         .release =      spidev_release,
 441 };
 442
 443 /*-------------------------------------------------------------------------*/
 444
 445 /* The main reason to have this class is to make mdev/udev create the
 446  * /dev/spidevB.C character device nodes exposing our userspace API.
 447  * It also simplifies memory management.
 448  */
 449
 450 static void spidev_classdev_release(struct device *dev)
 451 {
 452         struct spidev_data      *spidev;
 453
 454         spidev = container_of(dev, struct spidev_data, dev);
 455         kfree(spidev);
 456 }
 457
 458 static struct class spidev_class = {
 459         .name           = "spidev",
 460         .owner          = THIS_MODULE,
 461         .dev_release    = spidev_classdev_release,
 462 };
 463
 464 /*-------------------------------------------------------------------------*/
 465
 466 static int spidev_probe(struct spi_device *spi)
 467 {
 468         struct spidev_data      *spidev;
 469         int                     status;
 470         unsigned long           minor;
 471
 472         /* Allocate driver data */
 473         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 474         if (!spidev)
 475                 return -ENOMEM;
 476
 477         /* Initialize the driver data */
 478         spidev->spi = spi;
 479         mutex_init(&spidev->buf_lock);
 480
 481         INIT_LIST_HEAD(&spidev->device_entry);
 482
 483         /* If we can allocate a minor number, hook up this device.
 484          * Reusing minors is fine so long as udev or mdev is working.
 485          */
 486         mutex_lock(&device_list_lock);
 487         minor = find_first_zero_bit(minors, ARRAY_SIZE(minors));
 488         if (minor < N_SPI_MINORS) {
 489                 spidev->dev.parent = &spi->dev;
 490                 spidev->dev.class = &spidev_class;
 491                 spidev->dev.devt = MKDEV(SPIDEV_MAJOR, minor);
 492                 snprintf(spidev->dev.bus_id, sizeof spidev->dev.bus_id,
 493                                 "spidev%d.%d",
 494                                 spi->master->bus_num, spi->chip_select);
 495                 status = device_register(&spidev->dev);
 496         } else {
 497                 dev_dbg(&spi->dev, "no minor number available!\n");
 498                 status = -ENODEV;
 499         }
 500         if (status == 0) {
 501                 set_bit(minor, minors);
 502                 dev_set_drvdata(&spi->dev, spidev);
 503                 list_add(&spidev->device_entry, &device_list);
 504         }
 505         mutex_unlock(&device_list_lock);
 506
 507         if (status != 0)
 508                 kfree(spidev);
 509
 510         return status;
 511 }
 512
 513 static int spidev_remove(struct spi_device *spi)
 514 {
 515         struct spidev_data      *spidev = dev_get_drvdata(&spi->dev);
 516
 517         mutex_lock(&device_list_lock);
 518
 519         list_del(&spidev->device_entry);
 520         dev_set_drvdata(&spi->dev, NULL);
 521         clear_bit(MINOR(spidev->dev.devt), minors);
 522         device_unregister(&spidev->dev);
 523
 524         mutex_unlock(&device_list_lock);
 525
 526         return 0;
 527 }
 528
 529 static struct spi_driver spidev_spi = {
 530         .driver = {
 531                 .name =         "spidev",
 532                 .owner =        THIS_MODULE,
 533         },
 534         .probe =        spidev_probe,
 535         .remove =       __devexit_p(spidev_remove),
 536
 537         /* NOTE:  suspend/resume methods are not necessary here.
 538          * We don't do anything except pass the requests to/from
 539          * the underlying controller.  The refrigerator handles
 540          * most issues; the controller driver handles the rest.
 541          */
 542 };
 543
 544 /*-------------------------------------------------------------------------*/
 545
 546 static int __init spidev_init(void)
 547 {
 548         int status;
 549
 550         /* Claim our 256 reserved device numbers.  Then register a class
 551          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 552          * the driver which manages those device numbers.
 553          */
 554         BUILD_BUG_ON(N_SPI_MINORS > 256);
 555         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 556         if (status < 0)
 557                 return status;
 558
 559         status = class_register(&spidev_class);
 560         if (status < 0) {
 561                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 562                 return status;
 563         }
 564
 565         status = spi_register_driver(&spidev_spi);
 566         if (status < 0) {
 567                 class_unregister(&spidev_class);
 568                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 569         }
 570         return status;
 571 }
 572 module_init(spidev_init);
 573
 574 static void __exit spidev_exit(void)
 575 {
 576         spi_unregister_driver(&spidev_spi);
 577         class_unregister(&spidev_class);
 578         unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 579 }
 580 module_exit(spidev_exit);
 581
 582 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 583 MODULE_DESCRIPTION("User mode SPI device interface");
 584 MODULE_LICENSE("GPL");