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.  Note that incorrect
  59  * settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other
  60  * devices on a shared bus:  CS_HIGH, because this device will be
  61  * active when it shouldn't be;  3WIRE, because when active it won't
  62  * behave as it should.
  63  *
  64  * REVISIT should changing those two modes be privileged?
  65  */
  66 #define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
  67                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)
  68
  69 struct spidev_data {
  70         struct device           dev;
  71         struct spi_device       *spi;
  72         struct list_head        device_entry;
  73
  74         struct mutex            buf_lock;
  75         unsigned                users;
  76         u8                      *buffer;
  77 };
  78
  79 static LIST_HEAD(device_list);
  80 static DEFINE_MUTEX(device_list_lock);
  81
  82 static unsigned bufsiz = 4096;
  83 module_param(bufsiz, uint, S_IRUGO);
  84 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  85
  86 /*-------------------------------------------------------------------------*/
  87
  88 /* Read-only message with current device setup */
  89 static ssize_t
  90 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
  91 {
  92         struct spidev_data      *spidev;
  93         struct spi_device       *spi;
  94         ssize_t                 status = 0;
  95
  96         /* chipselect only toggles at start or end of operation */
  97         if (count > bufsiz)
  98                 return -EMSGSIZE;
  99
 100         spidev = filp->private_data;
 101         spi = spidev->spi;
 102
 103         mutex_lock(&spidev->buf_lock);
 104         status = spi_read(spi, spidev->buffer, count);
 105         if (status == 0) {
 106                 unsigned long   missing;
 107
 108                 missing = copy_to_user(buf, spidev->buffer, count);
 109                 if (count && missing == count)
 110                         status = -EFAULT;
 111                 else
 112                         status = count - missing;
 113         }
 114         mutex_unlock(&spidev->buf_lock);
 115
 116         return status;
 117 }
 118
 119 /* Write-only message with current device setup */
 120 static ssize_t
 121 spidev_write(struct file *filp, const char __user *buf,
 122                 size_t count, loff_t *f_pos)
 123 {
 124         struct spidev_data      *spidev;
 125         struct spi_device       *spi;
 126         ssize_t                 status = 0;
 127         unsigned long           missing;
 128
 129         /* chipselect only toggles at start or end of operation */
 130         if (count > bufsiz)
 131                 return -EMSGSIZE;
 132
 133         spidev = filp->private_data;
 134         spi = spidev->spi;
 135
 136         mutex_lock(&spidev->buf_lock);
 137         missing = copy_from_user(spidev->buffer, buf, count);
 138         if (missing == 0) {
 139                 status = spi_write(spi, spidev->buffer, count);
 140                 if (status == 0)
 141                         status = count;
 142         } else
 143                 status = -EFAULT;
 144         mutex_unlock(&spidev->buf_lock);
 145
 146         return status;
 147 }
 148
 149 static int spidev_message(struct spidev_data *spidev,
 150                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 151 {
 152         struct spi_message      msg;
 153         struct spi_transfer     *k_xfers;
 154         struct spi_transfer     *k_tmp;
 155         struct spi_ioc_transfer *u_tmp;
 156         struct spi_device       *spi = spidev->spi;
 157         unsigned                n, total;
 158         u8                      *buf;
 159         int                     status = -EFAULT;
 160
 161         spi_message_init(&msg);
 162         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 163         if (k_xfers == NULL)
 164                 return -ENOMEM;
 165
 166         /* Construct spi_message, copying any tx data to bounce buffer.
 167          * We walk the array of user-provided transfers, using each one
 168          * to initialize a kernel version of the same transfer.
 169          */
 170         mutex_lock(&spidev->buf_lock);
 171         buf = spidev->buffer;
 172         total = 0;
 173         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 174                         n;
 175                         n--, k_tmp++, u_tmp++) {
 176                 k_tmp->len = u_tmp->len;
 177
 178                 total += k_tmp->len;
 179                 if (total > bufsiz) {
 180                         status = -EMSGSIZE;
 181                         goto done;
 182                 }
 183
 184                 if (u_tmp->rx_buf) {
 185                         k_tmp->rx_buf = buf;
 186                         if (!access_ok(VERIFY_WRITE, (u8 __user *)
 187                                                 (ptrdiff_t) u_tmp->rx_buf,
 188                                                 u_tmp->len))
 189                                 goto done;
 190                 }
 191                 if (u_tmp->tx_buf) {
 192                         k_tmp->tx_buf = buf;
 193                         if (copy_from_user(buf, (const u8 __user *)
 194                                                 (ptrdiff_t) u_tmp->tx_buf,
 195                                         u_tmp->len))
 196                                 goto done;
 197                 }
 198                 buf += k_tmp->len;
 199
 200                 k_tmp->cs_change = !!u_tmp->cs_change;
 201                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 202                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 203                 k_tmp->speed_hz = u_tmp->speed_hz;
 204 #ifdef VERBOSE
 205                 dev_dbg(&spi->dev,
 206                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 207                         u_tmp->len,
 208                         u_tmp->rx_buf ? "rx " : "",
 209                         u_tmp->tx_buf ? "tx " : "",
 210                         u_tmp->cs_change ? "cs " : "",
 211                         u_tmp->bits_per_word ? : spi->bits_per_word,
 212                         u_tmp->delay_usecs,
 213                         u_tmp->speed_hz ? : spi->max_speed_hz);
 214 #endif
 215                 spi_message_add_tail(k_tmp, &msg);
 216         }
 217
 218         status = spi_sync(spi, &msg);
 219         if (status < 0)
 220                 goto done;
 221
 222         /* copy any rx data out of bounce buffer */
 223         buf = spidev->buffer;
 224         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 225                 if (u_tmp->rx_buf) {
 226                         if (__copy_to_user((u8 __user *)
 227                                         (ptrdiff_t) u_tmp->rx_buf, buf,
 228                                         u_tmp->len)) {
 229                                 status = -EFAULT;
 230                                 goto done;
 231                         }
 232                 }
 233                 buf += u_tmp->len;
 234         }
 235         status = total;
 236
 237 done:
 238         mutex_unlock(&spidev->buf_lock);
 239         kfree(k_xfers);
 240         return status;
 241 }
 242
 243 static int
 244 spidev_ioctl(struct inode *inode, struct file *filp,
 245                 unsigned int cmd, unsigned long arg)
 246 {
 247         int                     err = 0;
 248         int                     retval = 0;
 249         struct spidev_data      *spidev;
 250         struct spi_device       *spi;
 251         u32                     tmp;
 252         unsigned                n_ioc;
 253         struct spi_ioc_transfer *ioc;
 254
 255         /* Check type and command number */
 256         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 257                 return -ENOTTY;
 258
 259         /* Check access direction once here; don't repeat below.
 260          * IOC_DIR is from the user perspective, while access_ok is
 261          * from the kernel perspective; so they look reversed.
 262          */
 263         if (_IOC_DIR(cmd) & _IOC_READ)
 264                 err = !access_ok(VERIFY_WRITE,
 265                                 (void __user *)arg, _IOC_SIZE(cmd));
 266         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 267                 err = !access_ok(VERIFY_READ,
 268                                 (void __user *)arg, _IOC_SIZE(cmd));
 269         if (err)
 270                 return -EFAULT;
 271
 272         spidev = filp->private_data;
 273         spi = spidev->spi;
 274
 275         switch (cmd) {
 276         /* read requests */
 277         case SPI_IOC_RD_MODE:
 278                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 279                                         (__u8 __user *)arg);
 280                 break;
 281         case SPI_IOC_RD_LSB_FIRST:
 282                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 283                                         (__u8 __user *)arg);
 284                 break;
 285         case SPI_IOC_RD_BITS_PER_WORD:
 286                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 287                 break;
 288         case SPI_IOC_RD_MAX_SPEED_HZ:
 289                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
 290                 break;
 291
 292         /* write requests */
 293         case SPI_IOC_WR_MODE:
 294                 retval = __get_user(tmp, (u8 __user *)arg);
 295                 if (retval == 0) {
 296                         u8      save = spi->mode;
 297
 298                         if (tmp & ~SPI_MODE_MASK) {
 299                                 retval = -EINVAL;
 300                                 break;
 301                         }
 302
 303                         tmp |= spi->mode & ~SPI_MODE_MASK;
 304                         spi->mode = (u8)tmp;
 305                         retval = spi_setup(spi);
 306                         if (retval < 0)
 307                                 spi->mode = save;
 308                         else
 309                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
 310                 }
 311                 break;
 312         case SPI_IOC_WR_LSB_FIRST:
 313                 retval = __get_user(tmp, (__u8 __user *)arg);
 314                 if (retval == 0) {
 315                         u8      save = spi->mode;
 316
 317                         if (tmp)
 318                                 spi->mode |= SPI_LSB_FIRST;
 319                         else
 320                                 spi->mode &= ~SPI_LSB_FIRST;
 321                         retval = spi_setup(spi);
 322                         if (retval < 0)
 323                                 spi->mode = save;
 324                         else
 325                                 dev_dbg(&spi->dev, "%csb first\n",
 326                                                 tmp ? 'l' : 'm');
 327                 }
 328                 break;
 329         case SPI_IOC_WR_BITS_PER_WORD:
 330                 retval = __get_user(tmp, (__u8 __user *)arg);
 331                 if (retval == 0) {
 332                         u8      save = spi->bits_per_word;
 333
 334                         spi->bits_per_word = tmp;
 335                         retval = spi_setup(spi);
 336                         if (retval < 0)
 337                                 spi->bits_per_word = save;
 338                         else
 339                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 340                 }
 341                 break;
 342         case SPI_IOC_WR_MAX_SPEED_HZ:
 343                 retval = __get_user(tmp, (__u32 __user *)arg);
 344                 if (retval == 0) {
 345                         u32     save = spi->max_speed_hz;
 346
 347                         spi->max_speed_hz = tmp;
 348                         retval = spi_setup(spi);
 349                         if (retval < 0)
 350                                 spi->max_speed_hz = save;
 351                         else
 352                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 353                 }
 354                 break;
 355
 356         default:
 357                 /* segmented and/or full-duplex I/O request */
 358                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 359                                 || _IOC_DIR(cmd) != _IOC_WRITE)
 360                         return -ENOTTY;
 361
 362                 tmp = _IOC_SIZE(cmd);
 363                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
 364                         retval = -EINVAL;
 365                         break;
 366                 }
 367                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 368                 if (n_ioc == 0)
 369                         break;
 370
 371                 /* copy into scratch area */
 372                 ioc = kmalloc(tmp, GFP_KERNEL);
 373                 if (!ioc) {
 374                         retval = -ENOMEM;
 375                         break;
 376                 }
 377                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
 378                         kfree(ioc);
 379                         retval = -EFAULT;
 380                         break;
 381                 }
 382
 383                 /* translate to spi_message, execute */
 384                 retval = spidev_message(spidev, ioc, n_ioc);
 385                 kfree(ioc);
 386                 break;
 387         }
 388         return retval;
 389 }
 390
 391 static int spidev_open(struct inode *inode, struct file *filp)
 392 {
 393         struct spidev_data      *spidev;
 394         int                     status = -ENXIO;
 395
 396         mutex_lock(&device_list_lock);
 397
 398         list_for_each_entry(spidev, &device_list, device_entry) {
 399                 if (spidev->dev.devt == inode->i_rdev) {
 400                         status = 0;
 401                         break;
 402                 }
 403         }
 404         if (status == 0) {
 405                 if (!spidev->buffer) {
 406                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
 407                         if (!spidev->buffer) {
 408                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 409                                 status = -ENOMEM;
 410                         }
 411                 }
 412                 if (status == 0) {
 413                         spidev->users++;
 414                         filp->private_data = spidev;
 415                         nonseekable_open(inode, filp);
 416                 }
 417         } else
 418                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 419
 420         mutex_unlock(&device_list_lock);
 421         return status;
 422 }
 423
 424 static int spidev_release(struct inode *inode, struct file *filp)
 425 {
 426         struct spidev_data      *spidev;
 427         int                     status = 0;
 428
 429         mutex_lock(&device_list_lock);
 430         spidev = filp->private_data;
 431         filp->private_data = NULL;
 432         spidev->users--;
 433         if (!spidev->users) {
 434                 kfree(spidev->buffer);
 435                 spidev->buffer = NULL;
 436         }
 437         mutex_unlock(&device_list_lock);
 438
 439         return status;
 440 }
 441
 442 static struct file_operations spidev_fops = {
 443         .owner =        THIS_MODULE,
 444         /* REVISIT switch to aio primitives, so that userspace
 445          * gets more complete API coverage.  It'll simplify things
 446          * too, except for the locking.
 447          */
 448         .write =        spidev_write,
 449         .read =         spidev_read,
 450         .ioctl =        spidev_ioctl,
 451         .open =         spidev_open,
 452         .release =      spidev_release,
 453 };
 454
 455 /*-------------------------------------------------------------------------*/
 456
 457 /* The main reason to have this class is to make mdev/udev create the
 458  * /dev/spidevB.C character device nodes exposing our userspace API.
 459  * It also simplifies memory management.
 460  */
 461
 462 static void spidev_classdev_release(struct device *dev)
 463 {
 464         struct spidev_data      *spidev;
 465
 466         spidev = container_of(dev, struct spidev_data, dev);
 467         kfree(spidev);
 468 }
 469
 470 static struct class spidev_class = {
 471         .name           = "spidev",
 472         .owner          = THIS_MODULE,
 473         .dev_release    = spidev_classdev_release,
 474 };
 475
 476 /*-------------------------------------------------------------------------*/
 477
 478 static int spidev_probe(struct spi_device *spi)
 479 {
 480         struct spidev_data      *spidev;
 481         int                     status;
 482         unsigned long           minor;
 483
 484         /* Allocate driver data */
 485         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 486         if (!spidev)
 487                 return -ENOMEM;
 488
 489         /* Initialize the driver data */
 490         spidev->spi = spi;
 491         mutex_init(&spidev->buf_lock);
 492
 493         INIT_LIST_HEAD(&spidev->device_entry);
 494
 495         /* If we can allocate a minor number, hook up this device.
 496          * Reusing minors is fine so long as udev or mdev is working.
 497          */
 498         mutex_lock(&device_list_lock);
 499         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 500         if (minor < N_SPI_MINORS) {
 501                 spidev->dev.parent = &spi->dev;
 502                 spidev->dev.class = &spidev_class;
 503                 spidev->dev.devt = MKDEV(SPIDEV_MAJOR, minor);
 504                 snprintf(spidev->dev.bus_id, sizeof spidev->dev.bus_id,
 505                                 "spidev%d.%d",
 506                                 spi->master->bus_num, spi->chip_select);
 507                 status = device_register(&spidev->dev);
 508         } else {
 509                 dev_dbg(&spi->dev, "no minor number available!\n");
 510                 status = -ENODEV;
 511         }
 512         if (status == 0) {
 513                 set_bit(minor, minors);
 514                 dev_set_drvdata(&spi->dev, spidev);
 515                 list_add(&spidev->device_entry, &device_list);
 516         }
 517         mutex_unlock(&device_list_lock);
 518
 519         if (status != 0)
 520                 kfree(spidev);
 521
 522         return status;
 523 }
 524
 525 static int spidev_remove(struct spi_device *spi)
 526 {
 527         struct spidev_data      *spidev = dev_get_drvdata(&spi->dev);
 528
 529         mutex_lock(&device_list_lock);
 530
 531         list_del(&spidev->device_entry);
 532         dev_set_drvdata(&spi->dev, NULL);
 533         clear_bit(MINOR(spidev->dev.devt), minors);
 534         device_unregister(&spidev->dev);
 535
 536         mutex_unlock(&device_list_lock);
 537
 538         return 0;
 539 }
 540
 541 static struct spi_driver spidev_spi = {
 542         .driver = {
 543                 .name =         "spidev",
 544                 .owner =        THIS_MODULE,
 545         },
 546         .probe =        spidev_probe,
 547         .remove =       __devexit_p(spidev_remove),
 548
 549         /* NOTE:  suspend/resume methods are not necessary here.
 550          * We don't do anything except pass the requests to/from
 551          * the underlying controller.  The refrigerator handles
 552          * most issues; the controller driver handles the rest.
 553          */
 554 };
 555
 556 /*-------------------------------------------------------------------------*/
 557
 558 static int __init spidev_init(void)
 559 {
 560         int status;
 561
 562         /* Claim our 256 reserved device numbers.  Then register a class
 563          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 564          * the driver which manages those device numbers.
 565          */
 566         BUILD_BUG_ON(N_SPI_MINORS > 256);
 567         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 568         if (status < 0)
 569                 return status;
 570
 571         status = class_register(&spidev_class);
 572         if (status < 0) {
 573                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 574                 return status;
 575         }
 576
 577         status = spi_register_driver(&spidev_spi);
 578         if (status < 0) {
 579                 class_unregister(&spidev_class);
 580                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 581         }
 582         return status;
 583 }
 584 module_init(spidev_init);
 585
 586 static void __exit spidev_exit(void)
 587 {
 588         spi_unregister_driver(&spidev_spi);
 589         class_unregister(&spidev_class);
 590         unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 591 }
 592 module_exit(spidev_exit);
 593
 594 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 595 MODULE_DESCRIPTION("User mode SPI device interface");
 596 MODULE_LICENSE("GPL");