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 #include <linux/smp_lock.h>
  33
  34 #include <linux/spi/spi.h>
  35 #include <linux/spi/spidev.h>
  36
  37 #include <asm/uaccess.h>
  38
  39
  40 /*
  41  * This supports acccess to SPI devices using normal userspace I/O calls.
  42  * Note that while traditional UNIX/POSIX I/O semantics are half duplex,
  43  * and often mask message boundaries, full SPI support requires full duplex
  44  * transfers.  There are several kinds of of internal message boundaries to
  45  * handle chipselect management and other protocol options.
  46  *
  47  * SPI has a character major number assigned.  We allocate minor numbers
  48  * dynamically using a bitmask.  You must use hotplug tools, such as udev
  49  * (or mdev with busybox) to create and destroy the /dev/spidevB.C device
  50  * nodes, since there is no fixed association of minor numbers with any
  51  * particular SPI bus or device.
  52  */
  53 #define SPIDEV_MAJOR                    153     /* assigned */
  54 #define N_SPI_MINORS                    32      /* ... up to 256 */
  55
  56 static unsigned long    minors[N_SPI_MINORS / BITS_PER_LONG];
  57
  58
  59 /* Bit masks for spi_device.mode management.  Note that incorrect
  60  * settings for CS_HIGH and 3WIRE can cause *lots* of trouble for other
  61  * devices on a shared bus:  CS_HIGH, because this device will be
  62  * active when it shouldn't be;  3WIRE, because when active it won't
  63  * behave as it should.
  64  *
  65  * REVISIT should changing those two modes be privileged?
  66  */
  67 #define SPI_MODE_MASK           (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \
  68                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)
  69
  70 struct spidev_data {
  71         struct device           dev;
  72         struct spi_device       *spi;
  73         struct list_head        device_entry;
  74
  75         struct mutex            buf_lock;
  76         unsigned                users;
  77         u8                      *buffer;
  78 };
  79
  80 static LIST_HEAD(device_list);
  81 static DEFINE_MUTEX(device_list_lock);
  82
  83 static unsigned bufsiz = 4096;
  84 module_param(bufsiz, uint, S_IRUGO);
  85 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message");
  86
  87 /*-------------------------------------------------------------------------*/
  88
  89 /* Read-only message with current device setup */
  90 static ssize_t
  91 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
  92 {
  93         struct spidev_data      *spidev;
  94         struct spi_device       *spi;
  95         ssize_t                 status = 0;
  96
  97         /* chipselect only toggles at start or end of operation */
  98         if (count > bufsiz)
  99                 return -EMSGSIZE;
 100
 101         spidev = filp->private_data;
 102         spi = spidev->spi;
 103
 104         mutex_lock(&spidev->buf_lock);
 105         status = spi_read(spi, spidev->buffer, count);
 106         if (status == 0) {
 107                 unsigned long   missing;
 108
 109                 missing = copy_to_user(buf, spidev->buffer, count);
 110                 if (count && missing == count)
 111                         status = -EFAULT;
 112                 else
 113                         status = count - missing;
 114         }
 115         mutex_unlock(&spidev->buf_lock);
 116
 117         return status;
 118 }
 119
 120 /* Write-only message with current device setup */
 121 static ssize_t
 122 spidev_write(struct file *filp, const char __user *buf,
 123                 size_t count, loff_t *f_pos)
 124 {
 125         struct spidev_data      *spidev;
 126         struct spi_device       *spi;
 127         ssize_t                 status = 0;
 128         unsigned long           missing;
 129
 130         /* chipselect only toggles at start or end of operation */
 131         if (count > bufsiz)
 132                 return -EMSGSIZE;
 133
 134         spidev = filp->private_data;
 135         spi = spidev->spi;
 136
 137         mutex_lock(&spidev->buf_lock);
 138         missing = copy_from_user(spidev->buffer, buf, count);
 139         if (missing == 0) {
 140                 status = spi_write(spi, spidev->buffer, count);
 141                 if (status == 0)
 142                         status = count;
 143         } else
 144                 status = -EFAULT;
 145         mutex_unlock(&spidev->buf_lock);
 146
 147         return status;
 148 }
 149
 150 static int spidev_message(struct spidev_data *spidev,
 151                 struct spi_ioc_transfer *u_xfers, unsigned n_xfers)
 152 {
 153         struct spi_message      msg;
 154         struct spi_transfer     *k_xfers;
 155         struct spi_transfer     *k_tmp;
 156         struct spi_ioc_transfer *u_tmp;
 157         struct spi_device       *spi = spidev->spi;
 158         unsigned                n, total;
 159         u8                      *buf;
 160         int                     status = -EFAULT;
 161
 162         spi_message_init(&msg);
 163         k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL);
 164         if (k_xfers == NULL)
 165                 return -ENOMEM;
 166
 167         /* Construct spi_message, copying any tx data to bounce buffer.
 168          * We walk the array of user-provided transfers, using each one
 169          * to initialize a kernel version of the same transfer.
 170          */
 171         mutex_lock(&spidev->buf_lock);
 172         buf = spidev->buffer;
 173         total = 0;
 174         for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;
 175                         n;
 176                         n--, k_tmp++, u_tmp++) {
 177                 k_tmp->len = u_tmp->len;
 178
 179                 total += k_tmp->len;
 180                 if (total > bufsiz) {
 181                         status = -EMSGSIZE;
 182                         goto done;
 183                 }
 184
 185                 if (u_tmp->rx_buf) {
 186                         k_tmp->rx_buf = buf;
 187                         if (!access_ok(VERIFY_WRITE, (u8 __user *)
 188                                                 (uintptr_t) u_tmp->rx_buf,
 189                                                 u_tmp->len))
 190                                 goto done;
 191                 }
 192                 if (u_tmp->tx_buf) {
 193                         k_tmp->tx_buf = buf;
 194                         if (copy_from_user(buf, (const u8 __user *)
 195                                                 (uintptr_t) u_tmp->tx_buf,
 196                                         u_tmp->len))
 197                                 goto done;
 198                 }
 199                 buf += k_tmp->len;
 200
 201                 k_tmp->cs_change = !!u_tmp->cs_change;
 202                 k_tmp->bits_per_word = u_tmp->bits_per_word;
 203                 k_tmp->delay_usecs = u_tmp->delay_usecs;
 204                 k_tmp->speed_hz = u_tmp->speed_hz;
 205 #ifdef VERBOSE
 206                 dev_dbg(&spi->dev,
 207                         "  xfer len %zd %s%s%s%dbits %u usec %uHz\n",
 208                         u_tmp->len,
 209                         u_tmp->rx_buf ? "rx " : "",
 210                         u_tmp->tx_buf ? "tx " : "",
 211                         u_tmp->cs_change ? "cs " : "",
 212                         u_tmp->bits_per_word ? : spi->bits_per_word,
 213                         u_tmp->delay_usecs,
 214                         u_tmp->speed_hz ? : spi->max_speed_hz);
 215 #endif
 216                 spi_message_add_tail(k_tmp, &msg);
 217         }
 218
 219         status = spi_sync(spi, &msg);
 220         if (status < 0)
 221                 goto done;
 222
 223         /* copy any rx data out of bounce buffer */
 224         buf = spidev->buffer;
 225         for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) {
 226                 if (u_tmp->rx_buf) {
 227                         if (__copy_to_user((u8 __user *)
 228                                         (uintptr_t) u_tmp->rx_buf, buf,
 229                                         u_tmp->len)) {
 230                                 status = -EFAULT;
 231                                 goto done;
 232                         }
 233                 }
 234                 buf += u_tmp->len;
 235         }
 236         status = total;
 237
 238 done:
 239         mutex_unlock(&spidev->buf_lock);
 240         kfree(k_xfers);
 241         return status;
 242 }
 243
 244 static int
 245 spidev_ioctl(struct inode *inode, struct file *filp,
 246                 unsigned int cmd, unsigned long arg)
 247 {
 248         int                     err = 0;
 249         int                     retval = 0;
 250         struct spidev_data      *spidev;
 251         struct spi_device       *spi;
 252         u32                     tmp;
 253         unsigned                n_ioc;
 254         struct spi_ioc_transfer *ioc;
 255
 256         /* Check type and command number */
 257         if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
 258                 return -ENOTTY;
 259
 260         /* Check access direction once here; don't repeat below.
 261          * IOC_DIR is from the user perspective, while access_ok is
 262          * from the kernel perspective; so they look reversed.
 263          */
 264         if (_IOC_DIR(cmd) & _IOC_READ)
 265                 err = !access_ok(VERIFY_WRITE,
 266                                 (void __user *)arg, _IOC_SIZE(cmd));
 267         if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE)
 268                 err = !access_ok(VERIFY_READ,
 269                                 (void __user *)arg, _IOC_SIZE(cmd));
 270         if (err)
 271                 return -EFAULT;
 272
 273         spidev = filp->private_data;
 274         spi = spidev->spi;
 275
 276         switch (cmd) {
 277         /* read requests */
 278         case SPI_IOC_RD_MODE:
 279                 retval = __put_user(spi->mode & SPI_MODE_MASK,
 280                                         (__u8 __user *)arg);
 281                 break;
 282         case SPI_IOC_RD_LSB_FIRST:
 283                 retval = __put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
 284                                         (__u8 __user *)arg);
 285                 break;
 286         case SPI_IOC_RD_BITS_PER_WORD:
 287                 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg);
 288                 break;
 289         case SPI_IOC_RD_MAX_SPEED_HZ:
 290                 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg);
 291                 break;
 292
 293         /* write requests */
 294         case SPI_IOC_WR_MODE:
 295                 retval = __get_user(tmp, (u8 __user *)arg);
 296                 if (retval == 0) {
 297                         u8      save = spi->mode;
 298
 299                         if (tmp & ~SPI_MODE_MASK) {
 300                                 retval = -EINVAL;
 301                                 break;
 302                         }
 303
 304                         tmp |= spi->mode & ~SPI_MODE_MASK;
 305                         spi->mode = (u8)tmp;
 306                         retval = spi_setup(spi);
 307                         if (retval < 0)
 308                                 spi->mode = save;
 309                         else
 310                                 dev_dbg(&spi->dev, "spi mode %02x\n", tmp);
 311                 }
 312                 break;
 313         case SPI_IOC_WR_LSB_FIRST:
 314                 retval = __get_user(tmp, (__u8 __user *)arg);
 315                 if (retval == 0) {
 316                         u8      save = spi->mode;
 317
 318                         if (tmp)
 319                                 spi->mode |= SPI_LSB_FIRST;
 320                         else
 321                                 spi->mode &= ~SPI_LSB_FIRST;
 322                         retval = spi_setup(spi);
 323                         if (retval < 0)
 324                                 spi->mode = save;
 325                         else
 326                                 dev_dbg(&spi->dev, "%csb first\n",
 327                                                 tmp ? 'l' : 'm');
 328                 }
 329                 break;
 330         case SPI_IOC_WR_BITS_PER_WORD:
 331                 retval = __get_user(tmp, (__u8 __user *)arg);
 332                 if (retval == 0) {
 333                         u8      save = spi->bits_per_word;
 334
 335                         spi->bits_per_word = tmp;
 336                         retval = spi_setup(spi);
 337                         if (retval < 0)
 338                                 spi->bits_per_word = save;
 339                         else
 340                                 dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 341                 }
 342                 break;
 343         case SPI_IOC_WR_MAX_SPEED_HZ:
 344                 retval = __get_user(tmp, (__u32 __user *)arg);
 345                 if (retval == 0) {
 346                         u32     save = spi->max_speed_hz;
 347
 348                         spi->max_speed_hz = tmp;
 349                         retval = spi_setup(spi);
 350                         if (retval < 0)
 351                                 spi->max_speed_hz = save;
 352                         else
 353                                 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
 354                 }
 355                 break;
 356
 357         default:
 358                 /* segmented and/or full-duplex I/O request */
 359                 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))
 360                                 || _IOC_DIR(cmd) != _IOC_WRITE)
 361                         return -ENOTTY;
 362
 363                 tmp = _IOC_SIZE(cmd);
 364                 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) {
 365                         retval = -EINVAL;
 366                         break;
 367                 }
 368                 n_ioc = tmp / sizeof(struct spi_ioc_transfer);
 369                 if (n_ioc == 0)
 370                         break;
 371
 372                 /* copy into scratch area */
 373                 ioc = kmalloc(tmp, GFP_KERNEL);
 374                 if (!ioc) {
 375                         retval = -ENOMEM;
 376                         break;
 377                 }
 378                 if (__copy_from_user(ioc, (void __user *)arg, tmp)) {
 379                         kfree(ioc);
 380                         retval = -EFAULT;
 381                         break;
 382                 }
 383
 384                 /* translate to spi_message, execute */
 385                 retval = spidev_message(spidev, ioc, n_ioc);
 386                 kfree(ioc);
 387                 break;
 388         }
 389         return retval;
 390 }
 391
 392 static int spidev_open(struct inode *inode, struct file *filp)
 393 {
 394         struct spidev_data      *spidev;
 395         int                     status = -ENXIO;
 396
 397         lock_kernel();
 398         mutex_lock(&device_list_lock);
 399
 400         list_for_each_entry(spidev, &device_list, device_entry) {
 401                 if (spidev->dev.devt == inode->i_rdev) {
 402                         status = 0;
 403                         break;
 404                 }
 405         }
 406         if (status == 0) {
 407                 if (!spidev->buffer) {
 408                         spidev->buffer = kmalloc(bufsiz, GFP_KERNEL);
 409                         if (!spidev->buffer) {
 410                                 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n");
 411                                 status = -ENOMEM;
 412                         }
 413                 }
 414                 if (status == 0) {
 415                         spidev->users++;
 416                         filp->private_data = spidev;
 417                         nonseekable_open(inode, filp);
 418                 }
 419         } else
 420                 pr_debug("spidev: nothing for minor %d\n", iminor(inode));
 421
 422         mutex_unlock(&device_list_lock);
 423         unlock_kernel();
 424         return status;
 425 }
 426
 427 static int spidev_release(struct inode *inode, struct file *filp)
 428 {
 429         struct spidev_data      *spidev;
 430         int                     status = 0;
 431
 432         mutex_lock(&device_list_lock);
 433         spidev = filp->private_data;
 434         filp->private_data = NULL;
 435         spidev->users--;
 436         if (!spidev->users) {
 437                 kfree(spidev->buffer);
 438                 spidev->buffer = NULL;
 439         }
 440         mutex_unlock(&device_list_lock);
 441
 442         return status;
 443 }
 444
 445 static struct file_operations spidev_fops = {
 446         .owner =        THIS_MODULE,
 447         /* REVISIT switch to aio primitives, so that userspace
 448          * gets more complete API coverage.  It'll simplify things
 449          * too, except for the locking.
 450          */
 451         .write =        spidev_write,
 452         .read =         spidev_read,
 453         .ioctl =        spidev_ioctl,
 454         .open =         spidev_open,
 455         .release =      spidev_release,
 456 };
 457
 458 /*-------------------------------------------------------------------------*/
 459
 460 /* The main reason to have this class is to make mdev/udev create the
 461  * /dev/spidevB.C character device nodes exposing our userspace API.
 462  * It also simplifies memory management.
 463  */
 464
 465 static void spidev_classdev_release(struct device *dev)
 466 {
 467         struct spidev_data      *spidev;
 468
 469         spidev = container_of(dev, struct spidev_data, dev);
 470         kfree(spidev);
 471 }
 472
 473 static struct class spidev_class = {
 474         .name           = "spidev",
 475         .owner          = THIS_MODULE,
 476         .dev_release    = spidev_classdev_release,
 477 };
 478
 479 /*-------------------------------------------------------------------------*/
 480
 481 static int spidev_probe(struct spi_device *spi)
 482 {
 483         struct spidev_data      *spidev;
 484         int                     status;
 485         unsigned long           minor;
 486
 487         /* Allocate driver data */
 488         spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 489         if (!spidev)
 490                 return -ENOMEM;
 491
 492         /* Initialize the driver data */
 493         spidev->spi = spi;
 494         mutex_init(&spidev->buf_lock);
 495
 496         INIT_LIST_HEAD(&spidev->device_entry);
 497
 498         /* If we can allocate a minor number, hook up this device.
 499          * Reusing minors is fine so long as udev or mdev is working.
 500          */
 501         mutex_lock(&device_list_lock);
 502         minor = find_first_zero_bit(minors, N_SPI_MINORS);
 503         if (minor < N_SPI_MINORS) {
 504                 spidev->dev.parent = &spi->dev;
 505                 spidev->dev.class = &spidev_class;
 506                 spidev->dev.devt = MKDEV(SPIDEV_MAJOR, minor);
 507                 snprintf(spidev->dev.bus_id, sizeof spidev->dev.bus_id,
 508                                 "spidev%d.%d",
 509                                 spi->master->bus_num, spi->chip_select);
 510                 status = device_register(&spidev->dev);
 511         } else {
 512                 dev_dbg(&spi->dev, "no minor number available!\n");
 513                 status = -ENODEV;
 514         }
 515         if (status == 0) {
 516                 set_bit(minor, minors);
 517                 dev_set_drvdata(&spi->dev, spidev);
 518                 list_add(&spidev->device_entry, &device_list);
 519         }
 520         mutex_unlock(&device_list_lock);
 521
 522         if (status != 0)
 523                 kfree(spidev);
 524
 525         return status;
 526 }
 527
 528 static int spidev_remove(struct spi_device *spi)
 529 {
 530         struct spidev_data      *spidev = dev_get_drvdata(&spi->dev);
 531
 532         mutex_lock(&device_list_lock);
 533
 534         list_del(&spidev->device_entry);
 535         dev_set_drvdata(&spi->dev, NULL);
 536         clear_bit(MINOR(spidev->dev.devt), minors);
 537         device_unregister(&spidev->dev);
 538
 539         mutex_unlock(&device_list_lock);
 540
 541         return 0;
 542 }
 543
 544 static struct spi_driver spidev_spi = {
 545         .driver = {
 546                 .name =         "spidev",
 547                 .owner =        THIS_MODULE,
 548         },
 549         .probe =        spidev_probe,
 550         .remove =       __devexit_p(spidev_remove),
 551
 552         /* NOTE:  suspend/resume methods are not necessary here.
 553          * We don't do anything except pass the requests to/from
 554          * the underlying controller.  The refrigerator handles
 555          * most issues; the controller driver handles the rest.
 556          */
 557 };
 558
 559 /*-------------------------------------------------------------------------*/
 560
 561 static int __init spidev_init(void)
 562 {
 563         int status;
 564
 565         /* Claim our 256 reserved device numbers.  Then register a class
 566          * that will key udev/mdev to add/remove /dev nodes.  Last, register
 567          * the driver which manages those device numbers.
 568          */
 569         BUILD_BUG_ON(N_SPI_MINORS > 256);
 570         status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
 571         if (status < 0)
 572                 return status;
 573
 574         status = class_register(&spidev_class);
 575         if (status < 0) {
 576                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 577                 return status;
 578         }
 579
 580         status = spi_register_driver(&spidev_spi);
 581         if (status < 0) {
 582                 class_unregister(&spidev_class);
 583                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 584         }
 585         return status;
 586 }
 587 module_init(spidev_init);
 588
 589 static void __exit spidev_exit(void)
 590 {
 591         spi_unregister_driver(&spidev_spi);
 592         class_unregister(&spidev_class);
 593         unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 594 }
 595 module_exit(spidev_exit);
 596
 597 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
 598 MODULE_DESCRIPTION("User mode SPI device interface");
 599 MODULE_LICENSE("GPL");