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, u_tmp->rx_buf, u_tmp->len))
 187                                 goto done;
 188                 }
 189                 if (u_tmp->tx_buf) {
 190                         k_tmp->tx_buf = buf;
 191                         if (copy_from_user(buf, (const u8 __user *)
 192                                                 (ptrdiff_t) u_tmp->tx_buf,
 193                                         u_tmp->len))
 194                                 goto done;
 195                 }
 196                 buf += k_tmp->len;
 197
 198                 k_tmp->cs_change = !!u_tmp->cs_change;
 199                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 200                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 201                 k_tmp->speed_hz = u_tmp->speed_hz;
 202 #ifdef VERBOSE
 203                 dev_dbg(&spi->dev,
 204                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 205                         u_tmp->len,
 206                         u_tmp->rx_buf ? "rx " : "",
 207                         u_tmp->tx_buf ? "tx " : "",
 208                         u_tmp->cs_change ? "cs " : "",
 209                         u_tmp->bits_per_word ? : spi->bits_per_word,
 210                         u_tmp->delay_usecs,
 211                         u_tmp->speed_hz ? : spi->max_speed_hz);
 212 #endif
 213                 spi_message_add_tail(k_tmp, &msg);
 214         }
 215
 216         status = spi_sync(spi, &msg);
 217         if (status < 0)
 218                 goto done;
 219
 220         /* copy any rx data out of bounce buffer */
 221         buf = spidev->buffer;
 222         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 223                 if (u_tmp->rx_buf) {
 224                         if (__copy_to_user((u8 __user *)
 225                                         (ptrdiff_t) u_tmp->rx_buf, buf,
 226                                         u_tmp->len)) {
 227                                 status = -EFAULT;
 228                                 goto done;
 229                         }
 230                 }
 231                 buf += u_tmp->len;
 232         }
 233         status = total;
 234
 235 done:
 236         mutex_unlock(&spidev->buf_lock);
 237         kfree(k_xfers);
 238         return status;
 239 }
 240
 241 static int
 242 spidev_ioctl(struct inode *inode, struct file *filp,
 243                 unsigned int cmd, unsigned long arg)
 244 {
 245         int                     err = 0;
 246         int                     retval = 0;
 247         struct spidev_data      *spidev;
 248         struct spi_device       *spi;
 249         u32                     tmp;
 250         unsigned                n_ioc;
 251         struct spi_ioc_transfer *ioc;
 252
 253         /* Check type and command number */
 254         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 255                 return -ENOTTY;
 256
 257         /* Check access direction once here; don't repeat below.
 258          * IOC_DIR is from the user perspective, while access_ok is
 259          * from the kernel perspective; so they look reversed.
 260          */
 261         if (_IOC_DIR(cmd) & _IOC_READ)
 262                 err = !access_ok(VERIFY_WRITE,
 263                                 (void __user *)arg, _IOC_SIZE(cmd));
 264         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 265                 err = !access_ok(VERIFY_READ,
 266                                 (void __user *)arg, _IOC_SIZE(cmd));
 267         if (err)
 268                 return -EFAULT;
 269
 270         spidev = filp->private_data;
 271         spi = spidev->spi;
 272
 273         switch (cmd) {
 274         /* read requests */
 275         case SPI_IOC_RD_MODE:
 276                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 277                                         (__u8 __user *)arg);
 278                 break;
 279         case SPI_IOC_RD_LSB_FIRST:
 280                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 281                                         (__u8 __user *)arg);
 282                 break;
 283         case SPI_IOC_RD_BITS_PER_WORD:
 284                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 285                 break;
 286         case SPI_IOC_RD_MAX_SPEED_HZ:
 287                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
 288                 break;
 289
 290         /* write requests */
 291         case SPI_IOC_WR_MODE:
 292                 retval = __get_user(tmp, (u8 __user *)arg);
 293                 if (retval == 0) {
 294                         u8      save = spi->mode;
 295
 296                         if (tmp & ~SPI_MODE_MASK) {
 297                                 retval = -EINVAL;
 298                                 break;
 299                         }
 300
 301                         tmp |= spi->mode & ~SPI_MODE_MASK;
 302                         spi->mode = (u8)tmp;
 303                         retval = spi_setup(spi);
 304                         if (retval < 0)
 305                                 spi->mode = save;
 306                         else
 307                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
 308                 }
 309                 break;
 310         case SPI_IOC_WR_LSB_FIRST:
 311                 retval = __get_user(tmp, (__u8 __user *)arg);
 312                 if (retval == 0) {
 313                         u8      save = spi->mode;
 314
 315                         if (tmp)
 316                                 spi->mode |= SPI_LSB_FIRST;
 317                         else
 318                                 spi->mode &= ~SPI_LSB_FIRST;
 319                         retval = spi_setup(spi);
 320                         if (retval < 0)
 321                                 spi->mode = save;
 322                         else
 323                                 dev_dbg(&spi->dev, "%csb first\n",
 324                                                 tmp ? 'l' : 'm');
 325                 }
 326                 break;
 327         case SPI_IOC_WR_BITS_PER_WORD:
 328                 retval = __get_user(tmp, (__u8 __user *)arg);
 329                 if (retval == 0) {
 330                         u8      save = spi->bits_per_word;
 331
 332                         spi->bits_per_word = tmp;
 333                         retval = spi_setup(spi);
 334                         if (retval < 0)
 335                                 spi->bits_per_word = save;
 336                         else
 337                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 338                 }
 339                 break;
 340         case SPI_IOC_WR_MAX_SPEED_HZ:
 341                 retval = __get_user(tmp, (__u32 __user *)arg);
 342                 if (retval == 0) {
 343                         u32     save = spi->max_speed_hz;
 344
 345                         spi->max_speed_hz = tmp;
 346                         retval = spi_setup(spi);
 347                         if (retval < 0)
 348                                 spi->max_speed_hz = save;
 349                         else
 350                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 351                 }
 352                 break;
 353
 354         default:
 355                 /* segmented and/or full-duplex I/O request */
 356                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 357                                 || _IOC_DIR(cmd) != _IOC_WRITE)
 358                         return -ENOTTY;
 359
 360                 tmp = _IOC_SIZE(cmd);
 361                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
 362                         retval = -EINVAL;
 363                         break;
 364                 }
 365                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 366                 if (n_ioc == 0)
 367                         break;
 368
 369                 /* copy into scratch area */
 370                 ioc = kmalloc(tmp, GFP_KERNEL);
 371                 if (!ioc) {
 372                         retval = -ENOMEM;
 373                         break;
 374                 }
 375                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
 376                         kfree(ioc);
 377                         retval = -EFAULT;
 378                         break;
 379                 }
 380
 381                 /* translate to spi_message, execute */
 382                 retval = spidev_message(spidev, ioc, n_ioc);
 383                 kfree(ioc);
 384                 break;
 385         }
 386         return retval;
 387 }
 388
 389 static int spidev_open(struct inode *inode, struct file *filp)
 390 {
 391         struct spidev_data      *spidev;
 392         int                     status = -ENXIO;
 393
 394         mutex_lock(&device_list_lock);
 395
 396         list_for_each_entry(spidev, &device_list, device_entry) {
 397                 if (spidev->dev.devt == inode->i_rdev) {
 398                         status = 0;
 399                         break;
 400                 }
 401         }
 402         if (status == 0) {
 403                 if (!spidev->buffer) {
 404                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
 405                         if (!spidev->buffer) {
 406                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 407                                 status = -ENOMEM;
 408                         }
 409                 }
 410                 if (status == 0) {
 411                         spidev->users++;
 412                         filp->private_data = spidev;
 413                         nonseekable_open(inode, filp);
 414                 }
 415         } else
 416                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 417
 418         mutex_unlock(&device_list_lock);
 419         return status;
 420 }
 421
 422 static int spidev_release(struct inode *inode, struct file *filp)
 423 {
 424         struct spidev_data      *spidev;
 425         int                     status = 0;
 426
 427         mutex_lock(&device_list_lock);
 428         spidev = filp->private_data;
 429         filp->private_data = NULL;
 430         spidev->users--;
 431         if (!spidev->users) {
 432                 kfree(spidev->buffer);
 433                 spidev->buffer = NULL;
 434         }
 435         mutex_unlock(&device_list_lock);
 436
 437         return status;
 438 }
 439
 440 static struct file_operations spidev_fops = {
 441         .owner =        THIS_MODULE,
 442         /* REVISIT switch to aio primitives, so that userspace
 443          * gets more complete API coverage.  It'll simplify things
 444          * too, except for the locking.
 445          */
 446         .write =        spidev_write,
 447         .read =         spidev_read,
 448         .ioctl =        spidev_ioctl,
 449         .open =         spidev_open,
 450         .release =      spidev_release,
 451 };
 452
 453 /*-------------------------------------------------------------------------*/
 454
 455 /* The main reason to have this class is to make mdev/udev create the
 456  * /dev/spidevB.C character device nodes exposing our userspace API.
 457  * It also simplifies memory management.
 458  */
 459
 460 static void spidev_classdev_release(struct device *dev)
 461 {
 462         struct spidev_data      *spidev;
 463
 464         spidev = container_of(dev, struct spidev_data, dev);
 465         kfree(spidev);
 466 }
 467
 468 static struct class spidev_class = {
 469         .name           = "spidev",
 470         .owner          = THIS_MODULE,
 471         .dev_release    = spidev_classdev_release,
 472 };
 473
 474 /*-------------------------------------------------------------------------*/
 475
 476 static int spidev_probe(struct spi_device *spi)
 477 {
 478         struct spidev_data      *spidev;
 479         int                     status;
 480         unsigned long           minor;
 481
 482         /* Allocate driver data */
 483         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 484         if (!spidev)
 485                 return -ENOMEM;
 486
 487         /* Initialize the driver data */
 488         spidev->spi = spi;
 489         mutex_init(&spidev->buf_lock);
 490
 491         INIT_LIST_HEAD(&spidev->device_entry);
 492
 493         /* If we can allocate a minor number, hook up this device.
 494          * Reusing minors is fine so long as udev or mdev is working.
 495          */
 496         mutex_lock(&device_list_lock);
 497         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 498         if (minor < N_SPI_MINORS) {
 499                 spidev->dev.parent = &spi->dev;
 500                 spidev->dev.class = &spidev_class;
 501                 spidev->dev.devt = MKDEV(SPIDEV_MAJOR, minor);
 502                 snprintf(spidev->dev.bus_id, sizeof spidev->dev.bus_id,
 503                                 "spidev%d.%d",
 504                                 spi->master->bus_num, spi->chip_select);
 505                 status = device_register(&spidev->dev);
 506         } else {
 507                 dev_dbg(&spi->dev, "no minor number available!\n");
 508                 status = -ENODEV;
 509         }
 510         if (status == 0) {
 511                 set_bit(minor, minors);
 512                 dev_set_drvdata(&spi->dev, spidev);
 513                 list_add(&spidev->device_entry, &device_list);
 514         }
 515         mutex_unlock(&device_list_lock);
 516
 517         if (status != 0)
 518                 kfree(spidev);
 519
 520         return status;
 521 }
 522
 523 static int spidev_remove(struct spi_device *spi)
 524 {
 525         struct spidev_data      *spidev = dev_get_drvdata(&spi->dev);
 526
 527         mutex_lock(&device_list_lock);
 528
 529         list_del(&spidev->device_entry);
 530         dev_set_drvdata(&spi->dev, NULL);
 531         clear_bit(MINOR(spidev->dev.devt), minors);
 532         device_unregister(&spidev->dev);
 533
 534         mutex_unlock(&device_list_lock);
 535
 536         return 0;
 537 }
 538
 539 static struct spi_driver spidev_spi = {
 540         .driver = {
 541                 .name =         "spidev",
 542                 .owner =        THIS_MODULE,
 543         },
 544         .probe =        spidev_probe,
 545         .remove =       __devexit_p(spidev_remove),
 546
 547         /* NOTE:  suspend/resume methods are not necessary here.
 548          * We don't do anything except pass the requests to/from
 549          * the underlying controller.  The refrigerator handles
 550          * most issues; the controller driver handles the rest.
 551          */
 552 };
 553
 554 /*-------------------------------------------------------------------------*/
 555
 556 static int __init spidev_init(void)
 557 {
 558         int status;
 559
 560         /* Claim our 256 reserved device numbers.  Then register a class
 561          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 562          * the driver which manages those device numbers.
 563          */
 564         BUILD_BUG_ON(N_SPI_MINORS > 256);
 565         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 566         if (status < 0)
 567                 return status;
 568
 569         status = class_register(&spidev_class);
 570         if (status < 0) {
 571                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 572                 return status;
 573         }
 574
 575         status = spi_register_driver(&spidev_spi);
 576         if (status < 0) {
 577                 class_unregister(&spidev_class);
 578                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 579         }
 580         return status;
 581 }
 582 module_init(spidev_init);
 583
 584 static void __exit spidev_exit(void)
 585 {
 586         spi_unregister_driver(&spidev_spi);
 587         class_unregister(&spidev_class);
 588         unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 589 }
 590 module_exit(spidev_exit);
 591
 592 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 593 MODULE_DESCRIPTION("User mode SPI device interface");
 594 MODULE_LICENSE("GPL");