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