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 || rb == NULL)
 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, largest = 0;
 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                 largest = max(largest, length);
 558         }
 559
 560         if (timestamp) {
 561                 length = iio_storage_bytes_for_timestamp(indio_dev);
 562                 bytes = ALIGN(bytes, length);
 563                 bytes += length;
 564                 largest = max(largest, length);
 565         }
 566
 567         bytes = ALIGN(bytes, largest);
 568         return bytes;
 569 }
 570
 571 static void iio_buffer_activate(struct iio_dev *indio_dev,
 572         struct iio_buffer *buffer)
 573 {
 574         iio_buffer_get(buffer);
 575         list_add(&buffer->buffer_list, &indio_dev->buffer_list);
 576 }
 577
 578 static void iio_buffer_deactivate(struct iio_buffer *buffer)
 579 {
 580         list_del_init(&buffer->buffer_list);
 581         wake_up_interruptible(&buffer->pollq);
 582         iio_buffer_put(buffer);
 583 }
 584
 585 static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
 586 {
 587         struct iio_buffer *buffer, *_buffer;
 588
 589         list_for_each_entry_safe(buffer, _buffer,
 590                         &indio_dev->buffer_list, buffer_list)
 591                 iio_buffer_deactivate(buffer);
 592 }
 593
 594 static int iio_buffer_enable(struct iio_buffer *buffer,
 595         struct iio_dev *indio_dev)
 596 {
 597         if (!buffer->access->enable)
 598                 return 0;
 599         return buffer->access->enable(buffer, indio_dev);
 600 }
 601
 602 static int iio_buffer_disable(struct iio_buffer *buffer,
 603         struct iio_dev *indio_dev)
 604 {
 605         if (!buffer->access->disable)
 606                 return 0;
 607         return buffer->access->disable(buffer, indio_dev);
 608 }
 609
 610 static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
 611         struct iio_buffer *buffer)
 612 {
 613         unsigned int bytes;
 614
 615         if (!buffer->access->set_bytes_per_datum)
 616                 return;
 617
 618         bytes = iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
 619                 buffer->scan_timestamp);
 620
 621         buffer->access->set_bytes_per_datum(buffer, bytes);
 622 }
 623
 624 static int iio_buffer_request_update(struct iio_dev *indio_dev,
 625         struct iio_buffer *buffer)
 626 {
 627         int ret;
 628
 629         iio_buffer_update_bytes_per_datum(indio_dev, buffer);
 630         if (buffer->access->request_update) {
 631                 ret = buffer->access->request_update(buffer);
 632                 if (ret) {
 633                         dev_dbg(&indio_dev->dev,
 634                                "Buffer not started: buffer parameter update failed (%d)\n",
 635                                 ret);
 636                         return ret;
 637                 }
 638         }
 639
 640         return 0;
 641 }
 642
 643 static void iio_free_scan_mask(struct iio_dev *indio_dev,
 644         const unsigned long *mask)
 645 {
 646         /* If the mask is dynamically allocated free it, otherwise do nothing */
 647         if (!indio_dev->available_scan_masks)
 648                 kfree(mask);
 649 }
 650
 651 struct iio_device_config {
 652         unsigned int mode;
 653         unsigned int watermark;
 654         const unsigned long *scan_mask;
 655         unsigned int scan_bytes;
 656         bool scan_timestamp;
 657 };
 658
 659 static int iio_verify_update(struct iio_dev *indio_dev,
 660         struct iio_buffer *insert_buffer, struct iio_buffer *remove_buffer,
 661         struct iio_device_config *config)
 662 {
 663         unsigned long *compound_mask;
 664         const unsigned long *scan_mask;
 665         bool strict_scanmask = false;
 666         struct iio_buffer *buffer;
 667         bool scan_timestamp;
 668         unsigned int modes;
 669
 670         memset(config, 0, sizeof(*config));
 671         config->watermark = ~0;
 672
 673         /*
 674          * If there is just one buffer and we are removing it there is nothing
 675          * to verify.
 676          */
 677         if (remove_buffer && !insert_buffer &&
 678                 list_is_singular(&indio_dev->buffer_list))
 679                         return 0;
 680
 681         modes = indio_dev->modes;
 682
 683         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 684                 if (buffer == remove_buffer)
 685                         continue;
 686                 modes &= buffer->access->modes;
 687                 config->watermark = min(config->watermark, buffer->watermark);
 688         }
 689
 690         if (insert_buffer) {
 691                 modes &= insert_buffer->access->modes;
 692                 config->watermark = min(config->watermark,
 693                         insert_buffer->watermark);
 694         }
 695
 696         /* Definitely possible for devices to support both of these. */
 697         if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
 698                 config->mode = INDIO_BUFFER_TRIGGERED;
 699         } else if (modes & INDIO_BUFFER_HARDWARE) {
 700                 /*
 701                  * Keep things simple for now and only allow a single buffer to
 702                  * be connected in hardware mode.
 703                  */
 704                 if (insert_buffer && !list_empty(&indio_dev->buffer_list))
 705                         return -EINVAL;
 706                 config->mode = INDIO_BUFFER_HARDWARE;
 707                 strict_scanmask = true;
 708         } else if (modes & INDIO_BUFFER_SOFTWARE) {
 709                 config->mode = INDIO_BUFFER_SOFTWARE;
 710         } else {
 711                 /* Can only occur on first buffer */
 712                 if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
 713                         dev_dbg(&indio_dev->dev, "Buffer not started: no trigger\n");
 714                 return -EINVAL;
 715         }
 716
 717         /* What scan mask do we actually have? */
 718         compound_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
 719                                 sizeof(long), GFP_KERNEL);
 720         if (compound_mask == NULL)
 721                 return -ENOMEM;
 722
 723         scan_timestamp = false;
 724
 725         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 726                 if (buffer == remove_buffer)
 727                         continue;
 728                 bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
 729                           indio_dev->masklength);
 730                 scan_timestamp |= buffer->scan_timestamp;
 731         }
 732
 733         if (insert_buffer) {
 734                 bitmap_or(compound_mask, compound_mask,
 735                           insert_buffer->scan_mask, indio_dev->masklength);
 736                 scan_timestamp |= insert_buffer->scan_timestamp;
 737         }
 738
 739         if (indio_dev->available_scan_masks) {
 740                 scan_mask = iio_scan_mask_match(indio_dev->available_scan_masks,
 741                                     indio_dev->masklength,
 742                                     compound_mask,
 743                                     strict_scanmask);
 744                 kfree(compound_mask);
 745                 if (scan_mask == NULL)
 746                         return -EINVAL;
 747         } else {
 748             scan_mask = compound_mask;
 749         }
 750
 751         config->scan_bytes = iio_compute_scan_bytes(indio_dev,
 752                                     scan_mask, scan_timestamp);
 753         config->scan_mask = scan_mask;
 754         config->scan_timestamp = scan_timestamp;
 755
 756         return 0;
 757 }
 758
 759 static int iio_enable_buffers(struct iio_dev *indio_dev,
 760         struct iio_device_config *config)
 761 {
 762         struct iio_buffer *buffer;
 763         int ret;
 764
 765         indio_dev->active_scan_mask = config->scan_mask;
 766         indio_dev->scan_timestamp = config->scan_timestamp;
 767         indio_dev->scan_bytes = config->scan_bytes;
 768
 769         iio_update_demux(indio_dev);
 770
 771         /* Wind up again */
 772         if (indio_dev->setup_ops->preenable) {
 773                 ret = indio_dev->setup_ops->preenable(indio_dev);
 774                 if (ret) {
 775                         dev_dbg(&indio_dev->dev,
 776                                "Buffer not started: buffer preenable failed (%d)\n", ret);
 777                         goto err_undo_config;
 778                 }
 779         }
 780
 781         if (indio_dev->info->update_scan_mode) {
 782                 ret = indio_dev->info
 783                         ->update_scan_mode(indio_dev,
 784                                            indio_dev->active_scan_mask);
 785                 if (ret < 0) {
 786                         dev_dbg(&indio_dev->dev,
 787                                 "Buffer not started: update scan mode failed (%d)\n",
 788                                 ret);
 789                         goto err_run_postdisable;
 790                 }
 791         }
 792
 793         if (indio_dev->info->hwfifo_set_watermark)
 794                 indio_dev->info->hwfifo_set_watermark(indio_dev,
 795                         config->watermark);
 796
 797         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 798                 ret = iio_buffer_enable(buffer, indio_dev);
 799                 if (ret)
 800                         goto err_disable_buffers;
 801         }
 802
 803         indio_dev->currentmode = config->mode;
 804
 805         if (indio_dev->setup_ops->postenable) {
 806                 ret = indio_dev->setup_ops->postenable(indio_dev);
 807                 if (ret) {
 808                         dev_dbg(&indio_dev->dev,
 809                                "Buffer not started: postenable failed (%d)\n", ret);
 810                         goto err_disable_buffers;
 811                 }
 812         }
 813
 814         return 0;
 815
 816 err_disable_buffers:
 817         list_for_each_entry_continue_reverse(buffer, &indio_dev->buffer_list,
 818                                              buffer_list)
 819                 iio_buffer_disable(buffer, indio_dev);
 820 err_run_postdisable:
 821         indio_dev->currentmode = INDIO_DIRECT_MODE;
 822         if (indio_dev->setup_ops->postdisable)
 823                 indio_dev->setup_ops->postdisable(indio_dev);
 824 err_undo_config:
 825         indio_dev->active_scan_mask = NULL;
 826
 827         return ret;
 828 }
 829
 830 static int iio_disable_buffers(struct iio_dev *indio_dev)
 831 {
 832         struct iio_buffer *buffer;
 833         int ret = 0;
 834         int ret2;
 835
 836         /* Wind down existing buffers - iff there are any */
 837         if (list_empty(&indio_dev->buffer_list))
 838                 return 0;
 839
 840         /*
 841          * If things go wrong at some step in disable we still need to continue
 842          * to perform the other steps, otherwise we leave the device in a
 843          * inconsistent state. We return the error code for the first error we
 844          * encountered.
 845          */
 846
 847         if (indio_dev->setup_ops->predisable) {
 848                 ret2 = indio_dev->setup_ops->predisable(indio_dev);
 849                 if (ret2 && !ret)
 850                         ret = ret2;
 851         }
 852
 853         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 854                 ret2 = iio_buffer_disable(buffer, indio_dev);
 855                 if (ret2 && !ret)
 856                         ret = ret2;
 857         }
 858
 859         indio_dev->currentmode = INDIO_DIRECT_MODE;
 860
 861         if (indio_dev->setup_ops->postdisable) {
 862                 ret2 = indio_dev->setup_ops->postdisable(indio_dev);
 863                 if (ret2 && !ret)
 864                         ret = ret2;
 865         }
 866
 867         iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
 868         indio_dev->active_scan_mask = NULL;
 869
 870         return ret;
 871 }
 872
 873 static int __iio_update_buffers(struct iio_dev *indio_dev,
 874                        struct iio_buffer *insert_buffer,
 875                        struct iio_buffer *remove_buffer)
 876 {
 877         struct iio_device_config new_config;
 878         int ret;
 879
 880         ret = iio_verify_update(indio_dev, insert_buffer, remove_buffer,
 881                 &new_config);
 882         if (ret)
 883                 return ret;
 884
 885         if (insert_buffer) {
 886                 ret = iio_buffer_request_update(indio_dev, insert_buffer);
 887                 if (ret)
 888                         goto err_free_config;
 889         }
 890
 891         ret = iio_disable_buffers(indio_dev);
 892         if (ret)
 893                 goto err_deactivate_all;
 894
 895         if (remove_buffer)
 896                 iio_buffer_deactivate(remove_buffer);
 897         if (insert_buffer)
 898                 iio_buffer_activate(indio_dev, insert_buffer);
 899
 900         /* If no buffers in list, we are done */
 901         if (list_empty(&indio_dev->buffer_list))
 902                 return 0;
 903
 904         ret = iio_enable_buffers(indio_dev, &new_config);
 905         if (ret)
 906                 goto err_deactivate_all;
 907
 908         return 0;
 909
 910 err_deactivate_all:
 911         /*
 912          * We've already verified that the config is valid earlier. If things go
 913          * wrong in either enable or disable the most likely reason is an IO
 914          * error from the device. In this case there is no good recovery
 915          * strategy. Just make sure to disable everything and leave the device
 916          * in a sane state.  With a bit of luck the device might come back to
 917          * life again later and userspace can try again.
 918          */
 919         iio_buffer_deactivate_all(indio_dev);
 920
 921 err_free_config:
 922         iio_free_scan_mask(indio_dev, new_config.scan_mask);
 923         return ret;
 924 }
 925
 926 int iio_update_buffers(struct iio_dev *indio_dev,
 927                        struct iio_buffer *insert_buffer,
 928                        struct iio_buffer *remove_buffer)
 929 {
 930         int ret;
 931
 932         if (insert_buffer == remove_buffer)
 933                 return 0;
 934
 935         mutex_lock(&indio_dev->info_exist_lock);
 936         mutex_lock(&indio_dev->mlock);
 937
 938         if (insert_buffer && iio_buffer_is_active(insert_buffer))
 939                 insert_buffer = NULL;
 940
 941         if (remove_buffer && !iio_buffer_is_active(remove_buffer))
 942                 remove_buffer = NULL;
 943
 944         if (!insert_buffer && !remove_buffer) {
 945                 ret = 0;
 946                 goto out_unlock;
 947         }
 948
 949         if (indio_dev->info == NULL) {
 950                 ret = -ENODEV;
 951                 goto out_unlock;
 952         }
 953
 954         ret = __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);
 955
 956 out_unlock:
 957         mutex_unlock(&indio_dev->mlock);
 958         mutex_unlock(&indio_dev->info_exist_lock);
 959
 960         return ret;
 961 }
 962 EXPORT_SYMBOL_GPL(iio_update_buffers);
 963
 964 void iio_disable_all_buffers(struct iio_dev *indio_dev)
 965 {
 966         iio_disable_buffers(indio_dev);
 967         iio_buffer_deactivate_all(indio_dev);
 968 }
 969
 970 static ssize_t iio_buffer_store_enable(struct device *dev,
 971                                        struct device_attribute *attr,
 972                                        const char *buf,
 973                                        size_t len)
 974 {
 975         int ret;
 976         bool requested_state;
 977         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 978         bool inlist;
 979
 980         ret = strtobool(buf, &requested_state);
 981         if (ret < 0)
 982                 return ret;
 983
 984         mutex_lock(&indio_dev->mlock);
 985
 986         /* Find out if it is in the list */
 987         inlist = iio_buffer_is_active(indio_dev->buffer);
 988         /* Already in desired state */
 989         if (inlist == requested_state)
 990                 goto done;
 991
 992         if (requested_state)
 993                 ret = __iio_update_buffers(indio_dev,
 994                                          indio_dev->buffer, NULL);
 995         else
 996                 ret = __iio_update_buffers(indio_dev,
 997                                          NULL, indio_dev->buffer);
 998
 999 done:
1000         mutex_unlock(&indio_dev->mlock);
1001         return (ret < 0) ? ret : len;
1002 }
1003
1004 static const char * const iio_scan_elements_group_name = "scan_elements";
1005
1006 static ssize_t iio_buffer_show_watermark(struct device *dev,
1007                                          struct device_attribute *attr,
1008                                          char *buf)
1009 {
1010         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
1011         struct iio_buffer *buffer = indio_dev->buffer;
1012
1013         return sprintf(buf, "%u\n", buffer->watermark);
1014 }
1015
1016 static ssize_t iio_buffer_store_watermark(struct device *dev,
1017                                           struct device_attribute *attr,
1018                                           const char *buf,
1019                                           size_t len)
1020 {
1021         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
1022         struct iio_buffer *buffer = indio_dev->buffer;
1023         unsigned int val;
1024         int ret;
1025
1026         ret = kstrtouint(buf, 10, &val);
1027         if (ret)
1028                 return ret;
1029         if (!val)
1030                 return -EINVAL;
1031
1032         mutex_lock(&indio_dev->mlock);
1033
1034         if (val > buffer->length) {
1035                 ret = -EINVAL;
1036                 goto out;
1037         }
1038
1039         if (iio_buffer_is_active(indio_dev->buffer)) {
1040                 ret = -EBUSY;
1041                 goto out;
1042         }
1043
1044         buffer->watermark = val;
1045 out:
1046         mutex_unlock(&indio_dev->mlock);
1047
1048         return ret ? ret : len;
1049 }
1050
1051 static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
1052                    iio_buffer_write_length);
1053 static struct device_attribute dev_attr_length_ro = __ATTR(length,
1054         S_IRUGO, iio_buffer_read_length, NULL);
1055 static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
1056                    iio_buffer_show_enable, iio_buffer_store_enable);
1057 static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
1058                    iio_buffer_show_watermark, iio_buffer_store_watermark);
1059 static struct device_attribute dev_attr_watermark_ro = __ATTR(watermark,
1060         S_IRUGO, iio_buffer_show_watermark, NULL);
1061
1062 static struct attribute *iio_buffer_attrs[] = {
1063         &dev_attr_length.attr,
1064         &dev_attr_enable.attr,
1065         &dev_attr_watermark.attr,
1066 };
1067
1068 int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
1069 {
1070         struct iio_dev_attr *p;
1071         struct attribute **attr;
1072         struct iio_buffer *buffer = indio_dev->buffer;
1073         int ret, i, attrn, attrcount, attrcount_orig = 0;
1074         const struct iio_chan_spec *channels;
1075
1076         channels = indio_dev->channels;
1077         if (channels) {
1078                 int ml = indio_dev->masklength;
1079
1080                 for (i = 0; i < indio_dev->num_channels; i++)
1081                         ml = max(ml, channels[i].scan_index + 1);
1082                 indio_dev->masklength = ml;
1083         }
1084
1085         if (!buffer)
1086                 return 0;
1087
1088         attrcount = 0;
1089         if (buffer->attrs) {
1090                 while (buffer->attrs[attrcount] != NULL)
1091                         attrcount++;
1092         }
1093
1094         attr = kcalloc(attrcount + ARRAY_SIZE(iio_buffer_attrs) + 1,
1095                        sizeof(struct attribute *), GFP_KERNEL);
1096         if (!attr)
1097                 return -ENOMEM;
1098
1099         memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
1100         if (!buffer->access->set_length)
1101                 attr[0] = &dev_attr_length_ro.attr;
1102
1103         if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
1104                 attr[2] = &dev_attr_watermark_ro.attr;
1105
1106         if (buffer->attrs)
1107                 memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
1108                        sizeof(struct attribute *) * attrcount);
1109
1110         attr[attrcount + ARRAY_SIZE(iio_buffer_attrs)] = NULL;
1111
1112         buffer->buffer_group.name = "buffer";
1113         buffer->buffer_group.attrs = attr;
1114
1115         indio_dev->groups[indio_dev->groupcounter++] = &buffer->buffer_group;
1116
1117         if (buffer->scan_el_attrs != NULL) {
1118                 attr = buffer->scan_el_attrs->attrs;
1119                 while (*attr++ != NULL)
1120                         attrcount_orig++;
1121         }
1122         attrcount = attrcount_orig;
1123         INIT_LIST_HEAD(&buffer->scan_el_dev_attr_list);
1124         channels = indio_dev->channels;
1125         if (channels) {
1126                 /* new magic */
1127                 for (i = 0; i < indio_dev->num_channels; i++) {
1128                         if (channels[i].scan_index < 0)
1129                                 continue;
1130
1131                         ret = iio_buffer_add_channel_sysfs(indio_dev,
1132                                                          &channels[i]);
1133                         if (ret < 0)
1134                                 goto error_cleanup_dynamic;
1135                         attrcount += ret;
1136                         if (channels[i].type == IIO_TIMESTAMP)
1137                                 indio_dev->scan_index_timestamp =
1138                                         channels[i].scan_index;
1139                 }
1140                 if (indio_dev->masklength && buffer->scan_mask == NULL) {
1141                         buffer->scan_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
1142                                                     sizeof(*buffer->scan_mask),
1143                                                     GFP_KERNEL);
1144                         if (buffer->scan_mask == NULL) {
1145                                 ret = -ENOMEM;
1146                                 goto error_cleanup_dynamic;
1147                         }
1148                 }
1149         }
1150
1151         buffer->scan_el_group.name = iio_scan_elements_group_name;
1152
1153         buffer->scan_el_group.attrs = kcalloc(attrcount + 1,
1154                                               sizeof(buffer->scan_el_group.attrs[0]),
1155                                               GFP_KERNEL);
1156         if (buffer->scan_el_group.attrs == NULL) {
1157                 ret = -ENOMEM;
1158                 goto error_free_scan_mask;
1159         }
1160         if (buffer->scan_el_attrs)
1161                 memcpy(buffer->scan_el_group.attrs, buffer->scan_el_attrs,
1162                        sizeof(buffer->scan_el_group.attrs[0])*attrcount_orig);
1163         attrn = attrcount_orig;
1164
1165         list_for_each_entry(p, &buffer->scan_el_dev_attr_list, l)
1166                 buffer->scan_el_group.attrs[attrn++] = &p->dev_attr.attr;
1167         indio_dev->groups[indio_dev->groupcounter++] = &buffer->scan_el_group;
1168
1169         return 0;
1170
1171 error_free_scan_mask:
1172         kfree(buffer->scan_mask);
1173 error_cleanup_dynamic:
1174         iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
1175         kfree(indio_dev->buffer->buffer_group.attrs);
1176
1177         return ret;
1178 }
1179
1180 void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
1181 {
1182         if (!indio_dev->buffer)
1183                 return;
1184
1185         kfree(indio_dev->buffer->scan_mask);
1186         kfree(indio_dev->buffer->buffer_group.attrs);
1187         kfree(indio_dev->buffer->scan_el_group.attrs);
1188         iio_free_chan_devattr_list(&indio_dev->buffer->scan_el_dev_attr_list);
1189 }
1190
1191 /**
1192  * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
1193  * @indio_dev: the iio device
1194  * @mask: scan mask to be checked
1195  *
1196  * Return true if exactly one bit is set in the scan mask, false otherwise. It
1197  * can be used for devices where only one channel can be active for sampling at
1198  * a time.
1199  */
1200 bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
1201         const unsigned long *mask)
1202 {
1203         return bitmap_weight(mask, indio_dev->masklength) == 1;
1204 }
1205 EXPORT_SYMBOL_GPL(iio_validate_scan_mask_onehot);
1206
1207 int iio_scan_mask_query(struct iio_dev *indio_dev,
1208                         struct iio_buffer *buffer, int bit)
1209 {
1210         if (bit > indio_dev->masklength)
1211                 return -EINVAL;
1212
1213         if (!buffer->scan_mask)
1214                 return 0;
1215
1216         /* Ensure return value is 0 or 1. */
1217         return !!test_bit(bit, buffer->scan_mask);
1218 };
1219 EXPORT_SYMBOL_GPL(iio_scan_mask_query);
1220
1221 /**
1222  * struct iio_demux_table - table describing demux memcpy ops
1223  * @from:       index to copy from
1224  * @to:         index to copy to
1225  * @length:     how many bytes to copy
1226  * @l:          list head used for management
1227  */
1228 struct iio_demux_table {
1229         unsigned from;
1230         unsigned to;
1231         unsigned length;
1232         struct list_head l;
1233 };
1234
1235 static const void *iio_demux(struct iio_buffer *buffer,
1236                                  const void *datain)
1237 {
1238         struct iio_demux_table *t;
1239
1240         if (list_empty(&buffer->demux_list))
1241                 return datain;
1242         list_for_each_entry(t, &buffer->demux_list, l)
1243                 memcpy(buffer->demux_bounce + t->to,
1244                        datain + t->from, t->length);
1245
1246         return buffer->demux_bounce;
1247 }
1248
1249 static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
1250 {
1251         const void *dataout = iio_demux(buffer, data);
1252         int ret;
1253
1254         ret = buffer->access->store_to(buffer, dataout);
1255         if (ret)
1256                 return ret;
1257
1258         /*
1259          * We can't just test for watermark to decide if we wake the poll queue
1260          * because read may request less samples than the watermark.
1261          */
1262         wake_up_interruptible_poll(&buffer->pollq, POLLIN | POLLRDNORM);
1263         return 0;
1264 }
1265
1266 static void iio_buffer_demux_free(struct iio_buffer *buffer)
1267 {
1268         struct iio_demux_table *p, *q;
1269         list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
1270                 list_del(&p->l);
1271                 kfree(p);
1272         }
1273 }
1274
1275
1276 int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
1277 {
1278         int ret;
1279         struct iio_buffer *buf;
1280
1281         list_for_each_entry(buf, &indio_dev->buffer_list, buffer_list) {
1282                 ret = iio_push_to_buffer(buf, data);
1283                 if (ret < 0)
1284                         return ret;
1285         }
1286
1287         return 0;
1288 }
1289 EXPORT_SYMBOL_GPL(iio_push_to_buffers);
1290
1291 static int iio_buffer_add_demux(struct iio_buffer *buffer,
1292         struct iio_demux_table **p, unsigned int in_loc, unsigned int out_loc,
1293         unsigned int length)
1294 {
1295
1296         if (*p && (*p)->from + (*p)->length == in_loc &&
1297                 (*p)->to + (*p)->length == out_loc) {
1298                 (*p)->length += length;
1299         } else {
1300                 *p = kmalloc(sizeof(**p), GFP_KERNEL);
1301                 if (*p == NULL)
1302                         return -ENOMEM;
1303                 (*p)->from = in_loc;
1304                 (*p)->to = out_loc;
1305                 (*p)->length = length;
1306                 list_add_tail(&(*p)->l, &buffer->demux_list);
1307         }
1308
1309         return 0;
1310 }
1311
1312 static int iio_buffer_update_demux(struct iio_dev *indio_dev,
1313                                    struct iio_buffer *buffer)
1314 {
1315         int ret, in_ind = -1, out_ind, length;
1316         unsigned in_loc = 0, out_loc = 0;
1317         struct iio_demux_table *p = NULL;
1318
1319         /* Clear out any old demux */
1320         iio_buffer_demux_free(buffer);
1321         kfree(buffer->demux_bounce);
1322         buffer->demux_bounce = NULL;
1323
1324         /* First work out which scan mode we will actually have */
1325         if (bitmap_equal(indio_dev->active_scan_mask,
1326                          buffer->scan_mask,
1327                          indio_dev->masklength))
1328                 return 0;
1329
1330         /* Now we have the two masks, work from least sig and build up sizes */
1331         for_each_set_bit(out_ind,
1332                          buffer->scan_mask,
1333                          indio_dev->masklength) {
1334                 in_ind = find_next_bit(indio_dev->active_scan_mask,
1335                                        indio_dev->masklength,
1336                                        in_ind + 1);
1337                 while (in_ind != out_ind) {
1338                         length = iio_storage_bytes_for_si(indio_dev, in_ind);
1339                         /* Make sure we are aligned */
1340                         in_loc = roundup(in_loc, length) + length;
1341                         in_ind = find_next_bit(indio_dev->active_scan_mask,
1342                                                indio_dev->masklength,
1343                                                in_ind + 1);
1344                 }
1345                 length = iio_storage_bytes_for_si(indio_dev, in_ind);
1346                 out_loc = roundup(out_loc, length);
1347                 in_loc = roundup(in_loc, length);
1348                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1349                 if (ret)
1350                         goto error_clear_mux_table;
1351                 out_loc += length;
1352                 in_loc += length;
1353         }
1354         /* Relies on scan_timestamp being last */
1355         if (buffer->scan_timestamp) {
1356                 length = iio_storage_bytes_for_timestamp(indio_dev);
1357                 out_loc = roundup(out_loc, length);
1358                 in_loc = roundup(in_loc, length);
1359                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1360                 if (ret)
1361                         goto error_clear_mux_table;
1362                 out_loc += length;
1363                 in_loc += length;
1364         }
1365         buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
1366         if (buffer->demux_bounce == NULL) {
1367                 ret = -ENOMEM;
1368                 goto error_clear_mux_table;
1369         }
1370         return 0;
1371
1372 error_clear_mux_table:
1373         iio_buffer_demux_free(buffer);
1374
1375         return ret;
1376 }
1377
1378 int iio_update_demux(struct iio_dev *indio_dev)
1379 {
1380         struct iio_buffer *buffer;
1381         int ret;
1382
1383         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
1384                 ret = iio_buffer_update_demux(indio_dev, buffer);
1385                 if (ret < 0)
1386                         goto error_clear_mux_table;
1387         }
1388         return 0;
1389
1390 error_clear_mux_table:
1391         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list)
1392                 iio_buffer_demux_free(buffer);
1393
1394         return ret;
1395 }
1396 EXPORT_SYMBOL_GPL(iio_update_demux);
1397
1398 /**
1399  * iio_buffer_release() - Free a buffer's resources
1400  * @ref: Pointer to the kref embedded in the iio_buffer struct
1401  *
1402  * This function is called when the last reference to the buffer has been
1403  * dropped. It will typically free all resources allocated by the buffer. Do not
1404  * call this function manually, always use iio_buffer_put() when done using a
1405  * buffer.
1406  */
1407 static void iio_buffer_release(struct kref *ref)
1408 {
1409         struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);
1410
1411         buffer->access->release(buffer);
1412 }
1413
1414 /**
1415  * iio_buffer_get() - Grab a reference to the buffer
1416  * @buffer: The buffer to grab a reference for, may be NULL
1417  *
1418  * Returns the pointer to the buffer that was passed into the function.
1419  */
1420 struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer)
1421 {
1422         if (buffer)
1423                 kref_get(&buffer->ref);
1424
1425         return buffer;
1426 }
1427 EXPORT_SYMBOL_GPL(iio_buffer_get);
1428
1429 /**
1430  * iio_buffer_put() - Release the reference to the buffer
1431  * @buffer: The buffer to release the reference for, may be NULL
1432  */
1433 void iio_buffer_put(struct iio_buffer *buffer)
1434 {
1435         if (buffer)
1436                 kref_put(&buffer->ref, iio_buffer_release);
1437 }
1438 EXPORT_SYMBOL_GPL(iio_buffer_put);