drivers/iio/industrialio-buffer.c

   1 /* The industrial I/O core
   2  *
   3  * Copyright (c) 2008 Jonathan Cameron
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 as published by
   7  * the Free Software Foundation.
   8  *
   9  * Handling of buffer allocation / resizing.
  10  *
  11  *
  12  * Things to look at here.
  13  * - Better memory allocation techniques?
  14  * - Alternative access techniques?
  15  */
  16 #include <linux/kernel.h>
  17 #include <linux/export.h>
  18 #include <linux/device.h>
  19 #include <linux/fs.h>
  20 #include <linux/cdev.h>
  21 #include <linux/slab.h>
  22 #include <linux/poll.h>
  23 #include <linux/sched.h>
  24
  25 #include <linux/iio/iio.h>
  26 #include "iio_core.h"
  27 #include <linux/iio/sysfs.h>
  28 #include <linux/iio/buffer.h>
  29
  30 static const char * const iio_endian_prefix[] = {
  31         [IIO_BE] = "be",
  32         [IIO_LE] = "le",
  33 };
  34
  35 static bool iio_buffer_is_active(struct iio_buffer *buf)
  36 {
  37         return !list_empty(&buf->buffer_list);
  38 }
  39
  40 static size_t iio_buffer_data_available(struct iio_buffer *buf)
  41 {
  42         return buf->access->data_available(buf);
  43 }
  44
  45 static int iio_buffer_flush_hwfifo(struct iio_dev *indio_dev,
  46                                    struct iio_buffer *buf, size_t required)
  47 {
  48         if (!indio_dev->info->hwfifo_flush_to_buffer)
  49                 return -ENODEV;
  50
  51         return indio_dev->info->hwfifo_flush_to_buffer(indio_dev, required);
  52 }
  53
  54 static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
  55                              size_t to_wait, int to_flush)
  56 {
  57         size_t avail;
  58         int flushed = 0;
  59
  60         /* wakeup if the device was unregistered */
  61         if (!indio_dev->info)
  62                 return true;
  63
  64         /* drain the buffer if it was disabled */
  65         if (!iio_buffer_is_active(buf)) {
  66                 to_wait = min_t(size_t, to_wait, 1);
  67                 to_flush = 0;
  68         }
  69
  70         avail = iio_buffer_data_available(buf);
  71
  72         if (avail >= to_wait) {
  73                 /* force a flush for non-blocking reads */
  74                 if (!to_wait && avail < to_flush)
  75                         iio_buffer_flush_hwfifo(indio_dev, buf,
  76                                                 to_flush - avail);
  77                 return true;
  78         }
  79
  80         if (to_flush)
  81                 flushed = iio_buffer_flush_hwfifo(indio_dev, buf,
  82                                                   to_wait - avail);
  83         if (flushed <= 0)
  84                 return false;
  85
  86         if (avail + flushed >= to_wait)
  87                 return true;
  88
  89         return false;
  90 }
  91
  92 /**
  93  * iio_buffer_read_first_n_outer() - chrdev read for buffer access
  94  * @filp:       File structure pointer for the char device
  95  * @buf:        Destination buffer for iio buffer read
  96  * @n:          First n bytes to read
  97  * @f_ps:       Long offset provided by the user as a seek position
  98  *
  99  * This function relies on all buffer implementations having an
 100  * iio_buffer as their first element.
 101  *
 102  * Return: negative values corresponding to error codes or ret != 0
 103  *         for ending the reading activity
 104  **/
 105 ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
 106                                       size_t n, loff_t *f_ps)
 107 {
 108         struct iio_dev *indio_dev = filp->private_data;
 109         struct iio_buffer *rb = indio_dev->buffer;
 110         DEFINE_WAIT_FUNC(wait, woken_wake_function);
 111         size_t datum_size;
 112         size_t to_wait;
 113         int ret = 0;
 114
 115         if (!indio_dev->info)
 116                 return -ENODEV;
 117
 118         if (!rb || !rb->access->read_first_n)
 119                 return -EINVAL;
 120
 121         datum_size = rb->bytes_per_datum;
 122
 123         /*
 124          * If datum_size is 0 there will never be anything to read from the
 125          * buffer, so signal end of file now.
 126          */
 127         if (!datum_size)
 128                 return 0;
 129
 130         if (filp->f_flags & O_NONBLOCK)
 131                 to_wait = 0;
 132         else
 133                 to_wait = min_t(size_t, n / datum_size, rb->watermark);
 134
 135         add_wait_queue(&rb->pollq, &wait);
 136         do {
 137                 if (!indio_dev->info) {
 138                         ret = -ENODEV;
 139                         break;
 140                 }
 141
 142                 if (!iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)) {
 143                         if (signal_pending(current)) {
 144                                 ret = -ERESTARTSYS;
 145                                 break;
 146                         }
 147
 148                         wait_woken(&wait, TASK_INTERRUPTIBLE,
 149                                    MAX_SCHEDULE_TIMEOUT);
 150                         continue;
 151                 }
 152
 153                 ret = rb->access->read_first_n(rb, n, buf);
 154                 if (ret == 0 && (filp->f_flags & O_NONBLOCK))
 155                         ret = -EAGAIN;
 156         } while (ret == 0);
 157         remove_wait_queue(&rb->pollq, &wait);
 158
 159         return ret;
 160 }
 161
 162 /**
 163  * iio_buffer_poll() - poll the buffer to find out if it has data
 164  * @filp:       File structure pointer for device access
 165  * @wait:       Poll table structure pointer for which the driver adds
 166  *              a wait queue
 167  *
 168  * Return: (POLLIN | POLLRDNORM) if data is available for reading
 169  *         or 0 for other cases
 170  */
 171 unsigned int iio_buffer_poll(struct file *filp,
 172                              struct poll_table_struct *wait)
 173 {
 174         struct iio_dev *indio_dev = filp->private_data;
 175         struct iio_buffer *rb = indio_dev->buffer;
 176
 177         if (!indio_dev->info)
 178                 return 0;
 179
 180         poll_wait(filp, &rb->pollq, wait);
 181         if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
 182                 return POLLIN | POLLRDNORM;
 183         return 0;
 184 }
 185
 186 /**
 187  * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
 188  * @indio_dev: The IIO device
 189  *
 190  * Wakes up the event waitqueue used for poll(). Should usually
 191  * be called when the device is unregistered.
 192  */
 193 void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
 194 {
 195         if (!indio_dev->buffer)
 196                 return;
 197
 198         wake_up(&indio_dev->buffer->pollq);
 199 }
 200
 201 void iio_buffer_init(struct iio_buffer *buffer)
 202 {
 203         INIT_LIST_HEAD(&buffer->demux_list);
 204         INIT_LIST_HEAD(&buffer->buffer_list);
 205         init_waitqueue_head(&buffer->pollq);
 206         kref_init(&buffer->ref);
 207         if (!buffer->watermark)
 208                 buffer->watermark = 1;
 209 }
 210 EXPORT_SYMBOL(iio_buffer_init);
 211
 212 static ssize_t iio_show_scan_index(struct device *dev,
 213                                    struct device_attribute *attr,
 214                                    char *buf)
 215 {
 216         return sprintf(buf, "%u\n", to_iio_dev_attr(attr)->c->scan_index);
 217 }
 218
 219 static ssize_t iio_show_fixed_type(struct device *dev,
 220                                    struct device_attribute *attr,
 221                                    char *buf)
 222 {
 223         struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
 224         u8 type = this_attr->c->scan_type.endianness;
 225
 226         if (type == IIO_CPU) {
 227 #ifdef __LITTLE_ENDIAN
 228                 type = IIO_LE;
 229 #else
 230                 type = IIO_BE;
 231 #endif
 232         }
 233         if (this_attr->c->scan_type.repeat > 1)
 234                 return sprintf(buf, "%s:%c%d/%dX%d>>%u\n",
 235                        iio_endian_prefix[type],
 236                        this_attr->c->scan_type.sign,
 237                        this_attr->c->scan_type.realbits,
 238                        this_attr->c->scan_type.storagebits,
 239                        this_attr->c->scan_type.repeat,
 240                        this_attr->c->scan_type.shift);
 241                 else
 242                         return sprintf(buf, "%s:%c%d/%d>>%u\n",
 243                        iio_endian_prefix[type],
 244                        this_attr->c->scan_type.sign,
 245                        this_attr->c->scan_type.realbits,
 246                        this_attr->c->scan_type.storagebits,
 247                        this_attr->c->scan_type.shift);
 248 }
 249
 250 static ssize_t iio_scan_el_show(struct device *dev,
 251                                 struct device_attribute *attr,
 252                                 char *buf)
 253 {
 254         int ret;
 255         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 256
 257         /* Ensure ret is 0 or 1. */
 258         ret = !!test_bit(to_iio_dev_attr(attr)->address,
 259                        indio_dev->buffer->scan_mask);
 260
 261         return sprintf(buf, "%d\n", ret);
 262 }
 263
 264 /* Note NULL used as error indicator as it doesn't make sense. */
 265 static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
 266                                           unsigned int masklength,
 267                                           const unsigned long *mask,
 268                                           bool strict)
 269 {
 270         if (bitmap_empty(mask, masklength))
 271                 return NULL;
 272         while (*av_masks) {
 273                 if (strict) {
 274                         if (bitmap_equal(mask, av_masks, masklength))
 275                                 return av_masks;
 276                 } else {
 277                         if (bitmap_subset(mask, av_masks, masklength))
 278                                 return av_masks;
 279                 }
 280                 av_masks += BITS_TO_LONGS(masklength);
 281         }
 282         return NULL;
 283 }
 284
 285 static bool iio_validate_scan_mask(struct iio_dev *indio_dev,
 286         const unsigned long *mask)
 287 {
 288         if (!indio_dev->setup_ops->validate_scan_mask)
 289                 return true;
 290
 291         return indio_dev->setup_ops->validate_scan_mask(indio_dev, mask);
 292 }
 293
 294 /**
 295  * iio_scan_mask_set() - set particular bit in the scan mask
 296  * @indio_dev: the iio device
 297  * @buffer: the buffer whose scan mask we are interested in
 298  * @bit: the bit to be set.
 299  *
 300  * Note that at this point we have no way of knowing what other
 301  * buffers might request, hence this code only verifies that the
 302  * individual buffers request is plausible.
 303  */
 304 static int iio_scan_mask_set(struct iio_dev *indio_dev,
 305                       struct iio_buffer *buffer, int bit)
 306 {
 307         const unsigned long *mask;
 308         unsigned long *trialmask;
 309
 310         trialmask = kmalloc(sizeof(*trialmask)*
 311                             BITS_TO_LONGS(indio_dev->masklength),
 312                             GFP_KERNEL);
 313
 314         if (trialmask == NULL)
 315                 return -ENOMEM;
 316         if (!indio_dev->masklength) {
 317                 WARN(1, "Trying to set scanmask prior to registering buffer\n");
 318                 goto err_invalid_mask;
 319         }
 320         bitmap_copy(trialmask, buffer->scan_mask, indio_dev->masklength);
 321         set_bit(bit, trialmask);
 322
 323         if (!iio_validate_scan_mask(indio_dev, trialmask))
 324                 goto err_invalid_mask;
 325
 326         if (indio_dev->available_scan_masks) {
 327                 mask = iio_scan_mask_match(indio_dev->available_scan_masks,
 328                                            indio_dev->masklength,
 329                                            trialmask, false);
 330                 if (!mask)
 331                         goto err_invalid_mask;
 332         }
 333         bitmap_copy(buffer->scan_mask, trialmask, indio_dev->masklength);
 334
 335         kfree(trialmask);
 336
 337         return 0;
 338
 339 err_invalid_mask:
 340         kfree(trialmask);
 341         return -EINVAL;
 342 }
 343
 344 static int iio_scan_mask_clear(struct iio_buffer *buffer, int bit)
 345 {
 346         clear_bit(bit, buffer->scan_mask);
 347         return 0;
 348 }
 349
 350 static ssize_t iio_scan_el_store(struct device *dev,
 351                                  struct device_attribute *attr,
 352                                  const char *buf,
 353                                  size_t len)
 354 {
 355         int ret;
 356         bool state;
 357         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 358         struct iio_buffer *buffer = indio_dev->buffer;
 359         struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
 360
 361         ret = strtobool(buf, &state);
 362         if (ret < 0)
 363                 return ret;
 364         mutex_lock(&indio_dev->mlock);
 365         if (iio_buffer_is_active(indio_dev->buffer)) {
 366                 ret = -EBUSY;
 367                 goto error_ret;
 368         }
 369         ret = iio_scan_mask_query(indio_dev, buffer, this_attr->address);
 370         if (ret < 0)
 371                 goto error_ret;
 372         if (!state && ret) {
 373                 ret = iio_scan_mask_clear(buffer, this_attr->address);
 374                 if (ret)
 375                         goto error_ret;
 376         } else if (state && !ret) {
 377                 ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
 378                 if (ret)
 379                         goto error_ret;
 380         }
 381
 382 error_ret:
 383         mutex_unlock(&indio_dev->mlock);
 384
 385         return ret < 0 ? ret : len;
 386
 387 }
 388
 389 static ssize_t iio_scan_el_ts_show(struct device *dev,
 390                                    struct device_attribute *attr,
 391                                    char *buf)
 392 {
 393         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 394         return sprintf(buf, "%d\n", indio_dev->buffer->scan_timestamp);
 395 }
 396
 397 static ssize_t iio_scan_el_ts_store(struct device *dev,
 398                                     struct device_attribute *attr,
 399                                     const char *buf,
 400                                     size_t len)
 401 {
 402         int ret;
 403         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 404         bool state;
 405
 406         ret = strtobool(buf, &state);
 407         if (ret < 0)
 408                 return ret;
 409
 410         mutex_lock(&indio_dev->mlock);
 411         if (iio_buffer_is_active(indio_dev->buffer)) {
 412                 ret = -EBUSY;
 413                 goto error_ret;
 414         }
 415         indio_dev->buffer->scan_timestamp = state;
 416 error_ret:
 417         mutex_unlock(&indio_dev->mlock);
 418
 419         return ret ? ret : len;
 420 }
 421
 422 static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
 423                                         const struct iio_chan_spec *chan)
 424 {
 425         int ret, attrcount = 0;
 426         struct iio_buffer *buffer = indio_dev->buffer;
 427
 428         ret = __iio_add_chan_devattr("index",
 429                                      chan,
 430                                      &iio_show_scan_index,
 431                                      NULL,
 432                                      0,
 433                                      IIO_SEPARATE,
 434                                      &indio_dev->dev,
 435                                      &buffer->scan_el_dev_attr_list);
 436         if (ret)
 437                 return ret;
 438         attrcount++;
 439         ret = __iio_add_chan_devattr("type",
 440                                      chan,
 441                                      &iio_show_fixed_type,
 442                                      NULL,
 443                                      0,
 444                                      0,
 445                                      &indio_dev->dev,
 446                                      &buffer->scan_el_dev_attr_list);
 447         if (ret)
 448                 return ret;
 449         attrcount++;
 450         if (chan->type != IIO_TIMESTAMP)
 451                 ret = __iio_add_chan_devattr("en",
 452                                              chan,
 453                                              &iio_scan_el_show,
 454                                              &iio_scan_el_store,
 455                                              chan->scan_index,
 456                                              0,
 457                                              &indio_dev->dev,
 458                                              &buffer->scan_el_dev_attr_list);
 459         else
 460                 ret = __iio_add_chan_devattr("en",
 461                                              chan,
 462                                              &iio_scan_el_ts_show,
 463                                              &iio_scan_el_ts_store,
 464                                              chan->scan_index,
 465                                              0,
 466                                              &indio_dev->dev,
 467                                              &buffer->scan_el_dev_attr_list);
 468         if (ret)
 469                 return ret;
 470         attrcount++;
 471         ret = attrcount;
 472         return ret;
 473 }
 474
 475 static ssize_t iio_buffer_read_length(struct device *dev,
 476                                       struct device_attribute *attr,
 477                                       char *buf)
 478 {
 479         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 480         struct iio_buffer *buffer = indio_dev->buffer;
 481
 482         return sprintf(buf, "%d\n", buffer->length);
 483 }
 484
 485 static ssize_t iio_buffer_write_length(struct device *dev,
 486                                        struct device_attribute *attr,
 487                                        const char *buf, size_t len)
 488 {
 489         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 490         struct iio_buffer *buffer = indio_dev->buffer;
 491         unsigned int val;
 492         int ret;
 493
 494         ret = kstrtouint(buf, 10, &val);
 495         if (ret)
 496                 return ret;
 497
 498         if (val == buffer->length)
 499                 return len;
 500
 501         mutex_lock(&indio_dev->mlock);
 502         if (iio_buffer_is_active(indio_dev->buffer)) {
 503                 ret = -EBUSY;
 504         } else {
 505                 buffer->access->set_length(buffer, val);
 506                 ret = 0;
 507         }
 508         if (ret)
 509                 goto out;
 510         if (buffer->length && buffer->length < buffer->watermark)
 511                 buffer->watermark = buffer->length;
 512 out:
 513         mutex_unlock(&indio_dev->mlock);
 514
 515         return ret ? ret : len;
 516 }
 517
 518 static ssize_t iio_buffer_show_enable(struct device *dev,
 519                                       struct device_attribute *attr,
 520                                       char *buf)
 521 {
 522         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 523         return sprintf(buf, "%d\n", iio_buffer_is_active(indio_dev->buffer));
 524 }
 525
 526 static unsigned int iio_storage_bytes_for_si(struct iio_dev *indio_dev,
 527                                              unsigned int scan_index)
 528 {
 529         const struct iio_chan_spec *ch;
 530         unsigned int bytes;
 531
 532         ch = iio_find_channel_from_si(indio_dev, scan_index);
 533         bytes = ch->scan_type.storagebits / 8;
 534         if (ch->scan_type.repeat > 1)
 535                 bytes *= ch->scan_type.repeat;
 536         return bytes;
 537 }
 538
 539 static unsigned int iio_storage_bytes_for_timestamp(struct iio_dev *indio_dev)
 540 {
 541         return iio_storage_bytes_for_si(indio_dev,
 542                                         indio_dev->scan_index_timestamp);
 543 }
 544
 545 static int iio_compute_scan_bytes(struct iio_dev *indio_dev,
 546                                 const unsigned long *mask, bool timestamp)
 547 {
 548         unsigned bytes = 0;
 549         int length, i;
 550
 551         /* How much space will the demuxed element take? */
 552         for_each_set_bit(i, mask,
 553                          indio_dev->masklength) {
 554                 length = iio_storage_bytes_for_si(indio_dev, i);
 555                 bytes = ALIGN(bytes, length);
 556                 bytes += length;
 557         }
 558
 559         if (timestamp) {
 560                 length = iio_storage_bytes_for_timestamp(indio_dev);
 561                 bytes = ALIGN(bytes, length);
 562                 bytes += length;
 563         }
 564         return bytes;
 565 }
 566
 567 static void iio_buffer_activate(struct iio_dev *indio_dev,
 568         struct iio_buffer *buffer)
 569 {
 570         iio_buffer_get(buffer);
 571         list_add(&buffer->buffer_list, &indio_dev->buffer_list);
 572 }
 573
 574 static void iio_buffer_deactivate(struct iio_buffer *buffer)
 575 {
 576         list_del_init(&buffer->buffer_list);
 577         wake_up_interruptible(&buffer->pollq);
 578         iio_buffer_put(buffer);
 579 }
 580
 581 static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
 582 {
 583         struct iio_buffer *buffer, *_buffer;
 584
 585         list_for_each_entry_safe(buffer, _buffer,
 586                         &indio_dev->buffer_list, buffer_list)
 587                 iio_buffer_deactivate(buffer);
 588 }
 589
 590 static int iio_buffer_enable(struct iio_buffer *buffer,
 591         struct iio_dev *indio_dev)
 592 {
 593         if (!buffer->access->enable)
 594                 return 0;
 595         return buffer->access->enable(buffer, indio_dev);
 596 }
 597
 598 static int iio_buffer_disable(struct iio_buffer *buffer,
 599         struct iio_dev *indio_dev)
 600 {
 601         if (!buffer->access->disable)
 602                 return 0;
 603         return buffer->access->disable(buffer, indio_dev);
 604 }
 605
 606 static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
 607         struct iio_buffer *buffer)
 608 {
 609         unsigned int bytes;
 610
 611         if (!buffer->access->set_bytes_per_datum)
 612                 return;
 613
 614         bytes = iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
 615                 buffer->scan_timestamp);
 616
 617         buffer->access->set_bytes_per_datum(buffer, bytes);
 618 }
 619
 620 static int iio_buffer_request_update(struct iio_dev *indio_dev,
 621         struct iio_buffer *buffer)
 622 {
 623         int ret;
 624
 625         iio_buffer_update_bytes_per_datum(indio_dev, buffer);
 626         if (buffer->access->request_update) {
 627                 ret = buffer->access->request_update(buffer);
 628                 if (ret) {
 629                         dev_dbg(&indio_dev->dev,
 630                                "Buffer not started: buffer parameter update failed (%d)\n",
 631                                 ret);
 632                         return ret;
 633                 }
 634         }
 635
 636         return 0;
 637 }
 638
 639 static void iio_free_scan_mask(struct iio_dev *indio_dev,
 640         const unsigned long *mask)
 641 {
 642         /* If the mask is dynamically allocated free it, otherwise do nothing */
 643         if (!indio_dev->available_scan_masks)
 644                 kfree(mask);
 645 }
 646
 647 struct iio_device_config {
 648         unsigned int mode;
 649         unsigned int watermark;
 650         const unsigned long *scan_mask;
 651         unsigned int scan_bytes;
 652         bool scan_timestamp;
 653 };
 654
 655 static int iio_verify_update(struct iio_dev *indio_dev,
 656         struct iio_buffer *insert_buffer, struct iio_buffer *remove_buffer,
 657         struct iio_device_config *config)
 658 {
 659         unsigned long *compound_mask;
 660         const unsigned long *scan_mask;
 661         bool strict_scanmask = false;
 662         struct iio_buffer *buffer;
 663         bool scan_timestamp;
 664         unsigned int modes;
 665
 666         memset(config, 0, sizeof(*config));
 667         config->watermark = ~0;
 668
 669         /*
 670          * If there is just one buffer and we are removing it there is nothing
 671          * to verify.
 672          */
 673         if (remove_buffer && !insert_buffer &&
 674                 list_is_singular(&indio_dev->buffer_list))
 675                         return 0;
 676
 677         modes = indio_dev->modes;
 678
 679         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 680                 if (buffer == remove_buffer)
 681                         continue;
 682                 modes &= buffer->access->modes;
 683                 config->watermark = min(config->watermark, buffer->watermark);
 684         }
 685
 686         if (insert_buffer) {
 687                 modes &= insert_buffer->access->modes;
 688                 config->watermark = min(config->watermark,
 689                         insert_buffer->watermark);
 690         }
 691
 692         /* Definitely possible for devices to support both of these. */
 693         if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
 694                 config->mode = INDIO_BUFFER_TRIGGERED;
 695         } else if (modes & INDIO_BUFFER_HARDWARE) {
 696                 /*
 697                  * Keep things simple for now and only allow a single buffer to
 698                  * be connected in hardware mode.
 699                  */
 700                 if (insert_buffer && !list_empty(&indio_dev->buffer_list))
 701                         return -EINVAL;
 702                 config->mode = INDIO_BUFFER_HARDWARE;
 703                 strict_scanmask = true;
 704         } else if (modes & INDIO_BUFFER_SOFTWARE) {
 705                 config->mode = INDIO_BUFFER_SOFTWARE;
 706         } else {
 707                 /* Can only occur on first buffer */
 708                 if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
 709                         dev_dbg(&indio_dev->dev, "Buffer not started: no trigger\n");
 710                 return -EINVAL;
 711         }
 712
 713         /* What scan mask do we actually have? */
 714         compound_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
 715                                 sizeof(long), GFP_KERNEL);
 716         if (compound_mask == NULL)
 717                 return -ENOMEM;
 718
 719         scan_timestamp = false;
 720
 721         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 722                 if (buffer == remove_buffer)
 723                         continue;
 724                 bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
 725                           indio_dev->masklength);
 726                 scan_timestamp |= buffer->scan_timestamp;
 727         }
 728
 729         if (insert_buffer) {
 730                 bitmap_or(compound_mask, compound_mask,
 731                           insert_buffer->scan_mask, indio_dev->masklength);
 732                 scan_timestamp |= insert_buffer->scan_timestamp;
 733         }
 734
 735         if (indio_dev->available_scan_masks) {
 736                 scan_mask = iio_scan_mask_match(indio_dev->available_scan_masks,
 737                                     indio_dev->masklength,
 738                                     compound_mask,
 739                                     strict_scanmask);
 740                 kfree(compound_mask);
 741                 if (scan_mask == NULL)
 742                         return -EINVAL;
 743         } else {
 744             scan_mask = compound_mask;
 745         }
 746
 747         config->scan_bytes = iio_compute_scan_bytes(indio_dev,
 748                                     scan_mask, scan_timestamp);
 749         config->scan_mask = scan_mask;
 750         config->scan_timestamp = scan_timestamp;
 751
 752         return 0;
 753 }
 754
 755 static int iio_enable_buffers(struct iio_dev *indio_dev,
 756         struct iio_device_config *config)
 757 {
 758         struct iio_buffer *buffer;
 759         int ret;
 760
 761         indio_dev->active_scan_mask = config->scan_mask;
 762         indio_dev->scan_timestamp = config->scan_timestamp;
 763         indio_dev->scan_bytes = config->scan_bytes;
 764
 765         iio_update_demux(indio_dev);
 766
 767         /* Wind up again */
 768         if (indio_dev->setup_ops->preenable) {
 769                 ret = indio_dev->setup_ops->preenable(indio_dev);
 770                 if (ret) {
 771                         dev_dbg(&indio_dev->dev,
 772                                "Buffer not started: buffer preenable failed (%d)\n", ret);
 773                         goto err_undo_config;
 774                 }
 775         }
 776
 777         if (indio_dev->info->update_scan_mode) {
 778                 ret = indio_dev->info
 779                         ->update_scan_mode(indio_dev,
 780                                            indio_dev->active_scan_mask);
 781                 if (ret < 0) {
 782                         dev_dbg(&indio_dev->dev,
 783                                 "Buffer not started: update scan mode failed (%d)\n",
 784                                 ret);
 785                         goto err_run_postdisable;
 786                 }
 787         }
 788
 789         if (indio_dev->info->hwfifo_set_watermark)
 790                 indio_dev->info->hwfifo_set_watermark(indio_dev,
 791                         config->watermark);
 792
 793         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 794                 ret = iio_buffer_enable(buffer, indio_dev);
 795                 if (ret)
 796                         goto err_disable_buffers;
 797         }
 798
 799         indio_dev->currentmode = config->mode;
 800
 801         if (indio_dev->setup_ops->postenable) {
 802                 ret = indio_dev->setup_ops->postenable(indio_dev);
 803                 if (ret) {
 804                         dev_dbg(&indio_dev->dev,
 805                                "Buffer not started: postenable failed (%d)\n", ret);
 806                         goto err_disable_buffers;
 807                 }
 808         }
 809
 810         return 0;
 811
 812 err_disable_buffers:
 813         list_for_each_entry_continue_reverse(buffer, &indio_dev->buffer_list,
 814                                              buffer_list)
 815                 iio_buffer_disable(buffer, indio_dev);
 816 err_run_postdisable:
 817         indio_dev->currentmode = INDIO_DIRECT_MODE;
 818         if (indio_dev->setup_ops->postdisable)
 819                 indio_dev->setup_ops->postdisable(indio_dev);
 820 err_undo_config:
 821         indio_dev->active_scan_mask = NULL;
 822
 823         return ret;
 824 }
 825
 826 static int iio_disable_buffers(struct iio_dev *indio_dev)
 827 {
 828         struct iio_buffer *buffer;
 829         int ret = 0;
 830         int ret2;
 831
 832         /* Wind down existing buffers - iff there are any */
 833         if (list_empty(&indio_dev->buffer_list))
 834                 return 0;
 835
 836         /*
 837          * If things go wrong at some step in disable we still need to continue
 838          * to perform the other steps, otherwise we leave the device in a
 839          * inconsistent state. We return the error code for the first error we
 840          * encountered.
 841          */
 842
 843         if (indio_dev->setup_ops->predisable) {
 844                 ret2 = indio_dev->setup_ops->predisable(indio_dev);
 845                 if (ret2 && !ret)
 846                         ret = ret2;
 847         }
 848
 849         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 850                 ret2 = iio_buffer_disable(buffer, indio_dev);
 851                 if (ret2 && !ret)
 852                         ret = ret2;
 853         }
 854
 855         indio_dev->currentmode = INDIO_DIRECT_MODE;
 856
 857         if (indio_dev->setup_ops->postdisable) {
 858                 ret2 = indio_dev->setup_ops->postdisable(indio_dev);
 859                 if (ret2 && !ret)
 860                         ret = ret2;
 861         }
 862
 863         iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
 864         indio_dev->active_scan_mask = NULL;
 865
 866         return ret;
 867 }
 868
 869 static int __iio_update_buffers(struct iio_dev *indio_dev,
 870                        struct iio_buffer *insert_buffer,
 871                        struct iio_buffer *remove_buffer)
 872 {
 873         struct iio_device_config new_config;
 874         int ret;
 875
 876         ret = iio_verify_update(indio_dev, insert_buffer, remove_buffer,
 877                 &new_config);
 878         if (ret)
 879                 return ret;
 880
 881         if (insert_buffer) {
 882                 ret = iio_buffer_request_update(indio_dev, insert_buffer);
 883                 if (ret)
 884                         goto err_free_config;
 885         }
 886
 887         ret = iio_disable_buffers(indio_dev);
 888         if (ret)
 889                 goto err_deactivate_all;
 890
 891         if (remove_buffer)
 892                 iio_buffer_deactivate(remove_buffer);
 893         if (insert_buffer)
 894                 iio_buffer_activate(indio_dev, insert_buffer);
 895
 896         /* If no buffers in list, we are done */
 897         if (list_empty(&indio_dev->buffer_list))
 898                 return 0;
 899
 900         ret = iio_enable_buffers(indio_dev, &new_config);
 901         if (ret)
 902                 goto err_deactivate_all;
 903
 904         return 0;
 905
 906 err_deactivate_all:
 907         /*
 908          * We've already verified that the config is valid earlier. If things go
 909          * wrong in either enable or disable the most likely reason is an IO
 910          * error from the device. In this case there is no good recovery
 911          * strategy. Just make sure to disable everything and leave the device
 912          * in a sane state.  With a bit of luck the device might come back to
 913          * life again later and userspace can try again.
 914          */
 915         iio_buffer_deactivate_all(indio_dev);
 916
 917 err_free_config:
 918         iio_free_scan_mask(indio_dev, new_config.scan_mask);
 919         return ret;
 920 }
 921
 922 int iio_update_buffers(struct iio_dev *indio_dev,
 923                        struct iio_buffer *insert_buffer,
 924                        struct iio_buffer *remove_buffer)
 925 {
 926         int ret;
 927
 928         if (insert_buffer == remove_buffer)
 929                 return 0;
 930
 931         mutex_lock(&indio_dev->info_exist_lock);
 932         mutex_lock(&indio_dev->mlock);
 933
 934         if (insert_buffer && iio_buffer_is_active(insert_buffer))
 935                 insert_buffer = NULL;
 936
 937         if (remove_buffer && !iio_buffer_is_active(remove_buffer))
 938                 remove_buffer = NULL;
 939
 940         if (!insert_buffer && !remove_buffer) {
 941                 ret = 0;
 942                 goto out_unlock;
 943         }
 944
 945         if (indio_dev->info == NULL) {
 946                 ret = -ENODEV;
 947                 goto out_unlock;
 948         }
 949
 950         ret = __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);
 951
 952 out_unlock:
 953         mutex_unlock(&indio_dev->mlock);
 954         mutex_unlock(&indio_dev->info_exist_lock);
 955
 956         return ret;
 957 }
 958 EXPORT_SYMBOL_GPL(iio_update_buffers);
 959
 960 void iio_disable_all_buffers(struct iio_dev *indio_dev)
 961 {
 962         iio_disable_buffers(indio_dev);
 963         iio_buffer_deactivate_all(indio_dev);
 964 }
 965
 966 static ssize_t iio_buffer_store_enable(struct device *dev,
 967                                        struct device_attribute *attr,
 968                                        const char *buf,
 969                                        size_t len)
 970 {
 971         int ret;
 972         bool requested_state;
 973         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 974         bool inlist;
 975
 976         ret = strtobool(buf, &requested_state);
 977         if (ret < 0)
 978                 return ret;
 979
 980         mutex_lock(&indio_dev->mlock);
 981
 982         /* Find out if it is in the list */
 983         inlist = iio_buffer_is_active(indio_dev->buffer);
 984         /* Already in desired state */
 985         if (inlist == requested_state)
 986                 goto done;
 987
 988         if (requested_state)
 989                 ret = __iio_update_buffers(indio_dev,
 990                                          indio_dev->buffer, NULL);
 991         else
 992                 ret = __iio_update_buffers(indio_dev,
 993                                          NULL, indio_dev->buffer);
 994
 995 done:
 996         mutex_unlock(&indio_dev->mlock);
 997         return (ret < 0) ? ret : len;
 998 }
 999
1000 static const char * const iio_scan_elements_group_name = "scan_elements";
1001
1002 static ssize_t iio_buffer_show_watermark(struct device *dev,
1003                                          struct device_attribute *attr,
1004                                          char *buf)
1005 {
1006         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
1007         struct iio_buffer *buffer = indio_dev->buffer;
1008
1009         return sprintf(buf, "%u\n", buffer->watermark);
1010 }
1011
1012 static ssize_t iio_buffer_store_watermark(struct device *dev,
1013                                           struct device_attribute *attr,
1014                                           const char *buf,
1015                                           size_t len)
1016 {
1017         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
1018         struct iio_buffer *buffer = indio_dev->buffer;
1019         unsigned int val;
1020         int ret;
1021
1022         ret = kstrtouint(buf, 10, &val);
1023         if (ret)
1024                 return ret;
1025         if (!val)
1026                 return -EINVAL;
1027
1028         mutex_lock(&indio_dev->mlock);
1029
1030         if (val > buffer->length) {
1031                 ret = -EINVAL;
1032                 goto out;
1033         }
1034
1035         if (iio_buffer_is_active(indio_dev->buffer)) {
1036                 ret = -EBUSY;
1037                 goto out;
1038         }
1039
1040         buffer->watermark = val;
1041 out:
1042         mutex_unlock(&indio_dev->mlock);
1043
1044         return ret ? ret : len;
1045 }
1046
1047 static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
1048                    iio_buffer_write_length);
1049 static struct device_attribute dev_attr_length_ro = __ATTR(length,
1050         S_IRUGO, iio_buffer_read_length, NULL);
1051 static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
1052                    iio_buffer_show_enable, iio_buffer_store_enable);
1053 static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
1054                    iio_buffer_show_watermark, iio_buffer_store_watermark);
1055 static struct device_attribute dev_attr_watermark_ro = __ATTR(watermark,
1056         S_IRUGO, iio_buffer_show_watermark, NULL);
1057
1058 static struct attribute *iio_buffer_attrs[] = {
1059         &dev_attr_length.attr,
1060         &dev_attr_enable.attr,
1061         &dev_attr_watermark.attr,
1062 };
1063
1064 int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
1065 {
1066         struct iio_dev_attr *p;
1067         struct attribute **attr;
1068         struct iio_buffer *buffer = indio_dev->buffer;
1069         int ret, i, attrn, attrcount, attrcount_orig = 0;
1070         const struct iio_chan_spec *channels;
1071
1072         channels = indio_dev->channels;
1073         if (channels) {
1074                 int ml = indio_dev->masklength;
1075
1076                 for (i = 0; i < indio_dev->num_channels; i++)
1077                         ml = max(ml, channels[i].scan_index + 1);
1078                 indio_dev->masklength = ml;
1079         }
1080
1081         if (!buffer)
1082                 return 0;
1083
1084         attrcount = 0;
1085         if (buffer->attrs) {
1086                 while (buffer->attrs[attrcount] != NULL)
1087                         attrcount++;
1088         }
1089
1090         attr = kcalloc(attrcount + ARRAY_SIZE(iio_buffer_attrs) + 1,
1091                        sizeof(struct attribute *), GFP_KERNEL);
1092         if (!attr)
1093                 return -ENOMEM;
1094
1095         memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
1096         if (!buffer->access->set_length)
1097                 attr[0] = &dev_attr_length_ro.attr;
1098
1099         if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
1100                 attr[2] = &dev_attr_watermark_ro.attr;
1101
1102         if (buffer->attrs)
1103                 memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
1104                        sizeof(struct attribute *) * attrcount);
1105
1106         attr[attrcount + ARRAY_SIZE(iio_buffer_attrs)] = NULL;
1107
1108         buffer->buffer_group.name = "buffer";
1109         buffer->buffer_group.attrs = attr;
1110
1111         indio_dev->groups[indio_dev->groupcounter++] = &buffer->buffer_group;
1112
1113         if (buffer->scan_el_attrs != NULL) {
1114                 attr = buffer->scan_el_attrs->attrs;
1115                 while (*attr++ != NULL)
1116                         attrcount_orig++;
1117         }
1118         attrcount = attrcount_orig;
1119         INIT_LIST_HEAD(&buffer->scan_el_dev_attr_list);
1120         channels = indio_dev->channels;
1121         if (channels) {
1122                 /* new magic */
1123                 for (i = 0; i < indio_dev->num_channels; i++) {
1124                         if (channels[i].scan_index < 0)
1125                                 continue;
1126
1127                         ret = iio_buffer_add_channel_sysfs(indio_dev,
1128                                                          &channels[i]);
1129                         if (ret < 0)
1130                                 goto error_cleanup_dynamic;
1131                         attrcount += ret;
1132                         if (channels[i].type == IIO_TIMESTAMP)
1133                                 indio_dev->scan_index_timestamp =
1134                                         channels[i].scan_index;
1135                 }
1136                 if (indio_dev->masklength && buffer->scan_mask == NULL) {
1137                         buffer->scan_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
1138                                                     sizeof(*buffer->scan_mask),
1139                                                     GFP_KERNEL);
1140                         if (buffer->scan_mask == NULL) {
1141                                 ret = -ENOMEM;
1142                                 goto error_cleanup_dynamic;
1143                         }
1144                 }
1145         }
1146
1147         buffer->scan_el_group.name = iio_scan_elements_group_name;
1148
1149         buffer->scan_el_group.attrs = kcalloc(attrcount + 1,
1150                                               sizeof(buffer->scan_el_group.attrs[0]),
1151                                               GFP_KERNEL);
1152         if (buffer->scan_el_group.attrs == NULL) {
1153                 ret = -ENOMEM;
1154                 goto error_free_scan_mask;
1155         }
1156         if (buffer->scan_el_attrs)
1157                 memcpy(buffer->scan_el_group.attrs, buffer->scan_el_attrs,
1158                        sizeof(buffer->scan_el_group.attrs[0])*attrcount_orig);
1159         attrn = attrcount_orig;
1160
1161         list_for_each_entry(p, &buffer->scan_el_dev_attr_list, l)
1162                 buffer->scan_el_group.attrs[attrn++] = &p->dev_attr.attr;
1163         indio_dev->groups[indio_dev->groupcounter++] = &buffer->scan_el_group;
1164
1165         return 0;
1166
1167 error_free_scan_mask:
1168         kfree(buffer->scan_mask);
1169 error_cleanup_dynamic:
1170         iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
1171         kfree(indio_dev->buffer->buffer_group.attrs);
1172
1173         return ret;
1174 }
1175
1176 void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
1177 {
1178         if (!indio_dev->buffer)
1179                 return;
1180
1181         kfree(indio_dev->buffer->scan_mask);
1182         kfree(indio_dev->buffer->buffer_group.attrs);
1183         kfree(indio_dev->buffer->scan_el_group.attrs);
1184         iio_free_chan_devattr_list(&indio_dev->buffer->scan_el_dev_attr_list);
1185 }
1186
1187 /**
1188  * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
1189  * @indio_dev: the iio device
1190  * @mask: scan mask to be checked
1191  *
1192  * Return true if exactly one bit is set in the scan mask, false otherwise. It
1193  * can be used for devices where only one channel can be active for sampling at
1194  * a time.
1195  */
1196 bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
1197         const unsigned long *mask)
1198 {
1199         return bitmap_weight(mask, indio_dev->masklength) == 1;
1200 }
1201 EXPORT_SYMBOL_GPL(iio_validate_scan_mask_onehot);
1202
1203 int iio_scan_mask_query(struct iio_dev *indio_dev,
1204                         struct iio_buffer *buffer, int bit)
1205 {
1206         if (bit > indio_dev->masklength)
1207                 return -EINVAL;
1208
1209         if (!buffer->scan_mask)
1210                 return 0;
1211
1212         /* Ensure return value is 0 or 1. */
1213         return !!test_bit(bit, buffer->scan_mask);
1214 };
1215 EXPORT_SYMBOL_GPL(iio_scan_mask_query);
1216
1217 /**
1218  * struct iio_demux_table - table describing demux memcpy ops
1219  * @from:       index to copy from
1220  * @to:         index to copy to
1221  * @length:     how many bytes to copy
1222  * @l:          list head used for management
1223  */
1224 struct iio_demux_table {
1225         unsigned from;
1226         unsigned to;
1227         unsigned length;
1228         struct list_head l;
1229 };
1230
1231 static const void *iio_demux(struct iio_buffer *buffer,
1232                                  const void *datain)
1233 {
1234         struct iio_demux_table *t;
1235
1236         if (list_empty(&buffer->demux_list))
1237                 return datain;
1238         list_for_each_entry(t, &buffer->demux_list, l)
1239                 memcpy(buffer->demux_bounce + t->to,
1240                        datain + t->from, t->length);
1241
1242         return buffer->demux_bounce;
1243 }
1244
1245 static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
1246 {
1247         const void *dataout = iio_demux(buffer, data);
1248         int ret;
1249
1250         ret = buffer->access->store_to(buffer, dataout);
1251         if (ret)
1252                 return ret;
1253
1254         /*
1255          * We can't just test for watermark to decide if we wake the poll queue
1256          * because read may request less samples than the watermark.
1257          */
1258         wake_up_interruptible_poll(&buffer->pollq, POLLIN | POLLRDNORM);
1259         return 0;
1260 }
1261
1262 static void iio_buffer_demux_free(struct iio_buffer *buffer)
1263 {
1264         struct iio_demux_table *p, *q;
1265         list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
1266                 list_del(&p->l);
1267                 kfree(p);
1268         }
1269 }
1270
1271
1272 int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
1273 {
1274         int ret;
1275         struct iio_buffer *buf;
1276
1277         list_for_each_entry(buf, &indio_dev->buffer_list, buffer_list) {
1278                 ret = iio_push_to_buffer(buf, data);
1279                 if (ret < 0)
1280                         return ret;
1281         }
1282
1283         return 0;
1284 }
1285 EXPORT_SYMBOL_GPL(iio_push_to_buffers);
1286
1287 static int iio_buffer_add_demux(struct iio_buffer *buffer,
1288         struct iio_demux_table **p, unsigned int in_loc, unsigned int out_loc,
1289         unsigned int length)
1290 {
1291
1292         if (*p && (*p)->from + (*p)->length == in_loc &&
1293                 (*p)->to + (*p)->length == out_loc) {
1294                 (*p)->length += length;
1295         } else {
1296                 *p = kmalloc(sizeof(**p), GFP_KERNEL);
1297                 if (*p == NULL)
1298                         return -ENOMEM;
1299                 (*p)->from = in_loc;
1300                 (*p)->to = out_loc;
1301                 (*p)->length = length;
1302                 list_add_tail(&(*p)->l, &buffer->demux_list);
1303         }
1304
1305         return 0;
1306 }
1307
1308 static int iio_buffer_update_demux(struct iio_dev *indio_dev,
1309                                    struct iio_buffer *buffer)
1310 {
1311         int ret, in_ind = -1, out_ind, length;
1312         unsigned in_loc = 0, out_loc = 0;
1313         struct iio_demux_table *p = NULL;
1314
1315         /* Clear out any old demux */
1316         iio_buffer_demux_free(buffer);
1317         kfree(buffer->demux_bounce);
1318         buffer->demux_bounce = NULL;
1319
1320         /* First work out which scan mode we will actually have */
1321         if (bitmap_equal(indio_dev->active_scan_mask,
1322                          buffer->scan_mask,
1323                          indio_dev->masklength))
1324                 return 0;
1325
1326         /* Now we have the two masks, work from least sig and build up sizes */
1327         for_each_set_bit(out_ind,
1328                          buffer->scan_mask,
1329                          indio_dev->masklength) {
1330                 in_ind = find_next_bit(indio_dev->active_scan_mask,
1331                                        indio_dev->masklength,
1332                                        in_ind + 1);
1333                 while (in_ind != out_ind) {
1334                         in_ind = find_next_bit(indio_dev->active_scan_mask,
1335                                                indio_dev->masklength,
1336                                                in_ind + 1);
1337                         length = iio_storage_bytes_for_si(indio_dev, in_ind);
1338                         /* Make sure we are aligned */
1339                         in_loc = roundup(in_loc, length) + length;
1340                 }
1341                 length = iio_storage_bytes_for_si(indio_dev, in_ind);
1342                 out_loc = roundup(out_loc, length);
1343                 in_loc = roundup(in_loc, length);
1344                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1345                 if (ret)
1346                         goto error_clear_mux_table;
1347                 out_loc += length;
1348                 in_loc += length;
1349         }
1350         /* Relies on scan_timestamp being last */
1351         if (buffer->scan_timestamp) {
1352                 length = iio_storage_bytes_for_timestamp(indio_dev);
1353                 out_loc = roundup(out_loc, length);
1354                 in_loc = roundup(in_loc, length);
1355                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1356                 if (ret)
1357                         goto error_clear_mux_table;
1358                 out_loc += length;
1359                 in_loc += length;
1360         }
1361         buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
1362         if (buffer->demux_bounce == NULL) {
1363                 ret = -ENOMEM;
1364                 goto error_clear_mux_table;
1365         }
1366         return 0;
1367
1368 error_clear_mux_table:
1369         iio_buffer_demux_free(buffer);
1370
1371         return ret;
1372 }
1373
1374 int iio_update_demux(struct iio_dev *indio_dev)
1375 {
1376         struct iio_buffer *buffer;
1377         int ret;
1378
1379         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
1380                 ret = iio_buffer_update_demux(indio_dev, buffer);
1381                 if (ret < 0)
1382                         goto error_clear_mux_table;
1383         }
1384         return 0;
1385
1386 error_clear_mux_table:
1387         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list)
1388                 iio_buffer_demux_free(buffer);
1389
1390         return ret;
1391 }
1392 EXPORT_SYMBOL_GPL(iio_update_demux);
1393
1394 /**
1395  * iio_buffer_release() - Free a buffer's resources
1396  * @ref: Pointer to the kref embedded in the iio_buffer struct
1397  *
1398  * This function is called when the last reference to the buffer has been
1399  * dropped. It will typically free all resources allocated by the buffer. Do not
1400  * call this function manually, always use iio_buffer_put() when done using a
1401  * buffer.
1402  */
1403 static void iio_buffer_release(struct kref *ref)
1404 {
1405         struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);
1406
1407         buffer->access->release(buffer);
1408 }
1409
1410 /**
1411  * iio_buffer_get() - Grab a reference to the buffer
1412  * @buffer: The buffer to grab a reference for, may be NULL
1413  *
1414  * Returns the pointer to the buffer that was passed into the function.
1415  */
1416 struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer)
1417 {
1418         if (buffer)
1419                 kref_get(&buffer->ref);
1420
1421         return buffer;
1422 }
1423 EXPORT_SYMBOL_GPL(iio_buffer_get);
1424
1425 /**
1426  * iio_buffer_put() - Release the reference to the buffer
1427  * @buffer: The buffer to release the reference for, may be NULL
1428  */
1429 void iio_buffer_put(struct iio_buffer *buffer)
1430 {
1431         if (buffer)
1432                 kref_put(&buffer->ref, iio_buffer_release);
1433 }
1434 EXPORT_SYMBOL_GPL(iio_buffer_put);