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_ON("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 int iio_compute_scan_bytes(struct iio_dev *indio_dev,
 516                                 const unsigned long *mask, bool timestamp)
 517 {
 518         const struct iio_chan_spec *ch;
 519         unsigned bytes = 0;
 520         int length, i;
 521
 522         /* How much space will the demuxed element take? */
 523         for_each_set_bit(i, mask,
 524                          indio_dev->masklength) {
 525                 ch = iio_find_channel_from_si(indio_dev, i);
 526                 if (ch->scan_type.repeat > 1)
 527                         length = ch->scan_type.storagebits / 8 *
 528                                 ch->scan_type.repeat;
 529                 else
 530                         length = ch->scan_type.storagebits / 8;
 531                 bytes = ALIGN(bytes, length);
 532                 bytes += length;
 533         }
 534         if (timestamp) {
 535                 ch = iio_find_channel_from_si(indio_dev,
 536                                               indio_dev->scan_index_timestamp);
 537                 if (ch->scan_type.repeat > 1)
 538                         length = ch->scan_type.storagebits / 8 *
 539                                 ch->scan_type.repeat;
 540                 else
 541                         length = ch->scan_type.storagebits / 8;
 542                 bytes = ALIGN(bytes, length);
 543                 bytes += length;
 544         }
 545         return bytes;
 546 }
 547
 548 static void iio_buffer_activate(struct iio_dev *indio_dev,
 549         struct iio_buffer *buffer)
 550 {
 551         iio_buffer_get(buffer);
 552         list_add(&buffer->buffer_list, &indio_dev->buffer_list);
 553 }
 554
 555 static void iio_buffer_deactivate(struct iio_buffer *buffer)
 556 {
 557         list_del_init(&buffer->buffer_list);
 558         wake_up_interruptible(&buffer->pollq);
 559         iio_buffer_put(buffer);
 560 }
 561
 562 static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
 563 {
 564         struct iio_buffer *buffer, *_buffer;
 565
 566         list_for_each_entry_safe(buffer, _buffer,
 567                         &indio_dev->buffer_list, buffer_list)
 568                 iio_buffer_deactivate(buffer);
 569 }
 570
 571 static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
 572         struct iio_buffer *buffer)
 573 {
 574         unsigned int bytes;
 575
 576         if (!buffer->access->set_bytes_per_datum)
 577                 return;
 578
 579         bytes = iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
 580                 buffer->scan_timestamp);
 581
 582         buffer->access->set_bytes_per_datum(buffer, bytes);
 583 }
 584
 585 static int iio_buffer_request_update(struct iio_dev *indio_dev,
 586         struct iio_buffer *buffer)
 587 {
 588         int ret;
 589
 590         iio_buffer_update_bytes_per_datum(indio_dev, buffer);
 591         if (buffer->access->request_update) {
 592                 ret = buffer->access->request_update(buffer);
 593                 if (ret) {
 594                         dev_dbg(&indio_dev->dev,
 595                                "Buffer not started: buffer parameter update failed (%d)\n",
 596                                 ret);
 597                         return ret;
 598                 }
 599         }
 600
 601         return 0;
 602 }
 603
 604 static void iio_free_scan_mask(struct iio_dev *indio_dev,
 605         const unsigned long *mask)
 606 {
 607         /* If the mask is dynamically allocated free it, otherwise do nothing */
 608         if (!indio_dev->available_scan_masks)
 609                 kfree(mask);
 610 }
 611
 612 struct iio_device_config {
 613         unsigned int mode;
 614         unsigned int watermark;
 615         const unsigned long *scan_mask;
 616         unsigned int scan_bytes;
 617         bool scan_timestamp;
 618 };
 619
 620 static int iio_verify_update(struct iio_dev *indio_dev,
 621         struct iio_buffer *insert_buffer, struct iio_buffer *remove_buffer,
 622         struct iio_device_config *config)
 623 {
 624         unsigned long *compound_mask;
 625         const unsigned long *scan_mask;
 626         bool strict_scanmask = false;
 627         struct iio_buffer *buffer;
 628         bool scan_timestamp;
 629         unsigned int modes;
 630
 631         memset(config, 0, sizeof(*config));
 632
 633         /*
 634          * If there is just one buffer and we are removing it there is nothing
 635          * to verify.
 636          */
 637         if (remove_buffer && !insert_buffer &&
 638                 list_is_singular(&indio_dev->buffer_list))
 639                         return 0;
 640
 641         modes = indio_dev->modes;
 642
 643         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 644                 if (buffer == remove_buffer)
 645                         continue;
 646                 modes &= buffer->access->modes;
 647                 config->watermark = min(config->watermark, buffer->watermark);
 648         }
 649
 650         if (insert_buffer) {
 651                 modes &= insert_buffer->access->modes;
 652                 config->watermark = min(config->watermark,
 653                         insert_buffer->watermark);
 654         }
 655
 656         /* Definitely possible for devices to support both of these. */
 657         if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
 658                 config->mode = INDIO_BUFFER_TRIGGERED;
 659         } else if (modes & INDIO_BUFFER_HARDWARE) {
 660                 /*
 661                  * Keep things simple for now and only allow a single buffer to
 662                  * be connected in hardware mode.
 663                  */
 664                 if (insert_buffer && !list_empty(&indio_dev->buffer_list))
 665                         return -EINVAL;
 666                 config->mode = INDIO_BUFFER_HARDWARE;
 667                 strict_scanmask = true;
 668         } else if (modes & INDIO_BUFFER_SOFTWARE) {
 669                 config->mode = INDIO_BUFFER_SOFTWARE;
 670         } else {
 671                 /* Can only occur on first buffer */
 672                 if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
 673                         dev_dbg(&indio_dev->dev, "Buffer not started: no trigger\n");
 674                 return -EINVAL;
 675         }
 676
 677         /* What scan mask do we actually have? */
 678         compound_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
 679                                 sizeof(long), GFP_KERNEL);
 680         if (compound_mask == NULL)
 681                 return -ENOMEM;
 682
 683         scan_timestamp = false;
 684
 685         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
 686                 if (buffer == remove_buffer)
 687                         continue;
 688                 bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
 689                           indio_dev->masklength);
 690                 scan_timestamp |= buffer->scan_timestamp;
 691         }
 692
 693         if (insert_buffer) {
 694                 bitmap_or(compound_mask, compound_mask,
 695                           insert_buffer->scan_mask, indio_dev->masklength);
 696                 scan_timestamp |= insert_buffer->scan_timestamp;
 697         }
 698
 699         if (indio_dev->available_scan_masks) {
 700                 scan_mask = iio_scan_mask_match(indio_dev->available_scan_masks,
 701                                     indio_dev->masklength,
 702                                     compound_mask,
 703                                     strict_scanmask);
 704                 kfree(compound_mask);
 705                 if (scan_mask == NULL)
 706                         return -EINVAL;
 707         } else {
 708             scan_mask = compound_mask;
 709         }
 710
 711         config->scan_bytes = iio_compute_scan_bytes(indio_dev,
 712                                     scan_mask, scan_timestamp);
 713         config->scan_mask = scan_mask;
 714         config->scan_timestamp = scan_timestamp;
 715
 716         return 0;
 717 }
 718
 719 static int iio_enable_buffers(struct iio_dev *indio_dev,
 720         struct iio_device_config *config)
 721 {
 722         int ret;
 723
 724         indio_dev->active_scan_mask = config->scan_mask;
 725         indio_dev->scan_timestamp = config->scan_timestamp;
 726         indio_dev->scan_bytes = config->scan_bytes;
 727
 728         iio_update_demux(indio_dev);
 729
 730         /* Wind up again */
 731         if (indio_dev->setup_ops->preenable) {
 732                 ret = indio_dev->setup_ops->preenable(indio_dev);
 733                 if (ret) {
 734                         dev_dbg(&indio_dev->dev,
 735                                "Buffer not started: buffer preenable failed (%d)\n", ret);
 736                         goto err_undo_config;
 737                 }
 738         }
 739
 740         if (indio_dev->info->update_scan_mode) {
 741                 ret = indio_dev->info
 742                         ->update_scan_mode(indio_dev,
 743                                            indio_dev->active_scan_mask);
 744                 if (ret < 0) {
 745                         dev_dbg(&indio_dev->dev,
 746                                 "Buffer not started: update scan mode failed (%d)\n",
 747                                 ret);
 748                         goto err_run_postdisable;
 749                 }
 750         }
 751
 752         if (indio_dev->info->hwfifo_set_watermark)
 753                 indio_dev->info->hwfifo_set_watermark(indio_dev,
 754                         config->watermark);
 755
 756         indio_dev->currentmode = config->mode;
 757
 758         if (indio_dev->setup_ops->postenable) {
 759                 ret = indio_dev->setup_ops->postenable(indio_dev);
 760                 if (ret) {
 761                         dev_dbg(&indio_dev->dev,
 762                                "Buffer not started: postenable failed (%d)\n", ret);
 763                         goto err_run_postdisable;
 764                 }
 765         }
 766
 767         return 0;
 768
 769 err_run_postdisable:
 770         indio_dev->currentmode = INDIO_DIRECT_MODE;
 771         if (indio_dev->setup_ops->postdisable)
 772                 indio_dev->setup_ops->postdisable(indio_dev);
 773 err_undo_config:
 774         indio_dev->active_scan_mask = NULL;
 775
 776         return ret;
 777 }
 778
 779 static int iio_disable_buffers(struct iio_dev *indio_dev)
 780 {
 781         int ret = 0;
 782         int ret2;
 783
 784         /* Wind down existing buffers - iff there are any */
 785         if (list_empty(&indio_dev->buffer_list))
 786                 return 0;
 787
 788         /*
 789          * If things go wrong at some step in disable we still need to continue
 790          * to perform the other steps, otherwise we leave the device in a
 791          * inconsistent state. We return the error code for the first error we
 792          * encountered.
 793          */
 794
 795         if (indio_dev->setup_ops->predisable) {
 796                 ret2 = indio_dev->setup_ops->predisable(indio_dev);
 797                 if (ret2 && !ret)
 798                         ret = ret2;
 799         }
 800
 801         indio_dev->currentmode = INDIO_DIRECT_MODE;
 802
 803         if (indio_dev->setup_ops->postdisable) {
 804                 ret2 = indio_dev->setup_ops->postdisable(indio_dev);
 805                 if (ret2 && !ret)
 806                         ret = ret2;
 807         }
 808
 809         iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
 810         indio_dev->active_scan_mask = NULL;
 811
 812         return ret;
 813 }
 814
 815 static int __iio_update_buffers(struct iio_dev *indio_dev,
 816                        struct iio_buffer *insert_buffer,
 817                        struct iio_buffer *remove_buffer)
 818 {
 819         struct iio_device_config new_config;
 820         int ret;
 821
 822         ret = iio_verify_update(indio_dev, insert_buffer, remove_buffer,
 823                 &new_config);
 824         if (ret)
 825                 return ret;
 826
 827         if (insert_buffer) {
 828                 ret = iio_buffer_request_update(indio_dev, insert_buffer);
 829                 if (ret)
 830                         goto err_free_config;
 831         }
 832
 833         ret = iio_disable_buffers(indio_dev);
 834         if (ret)
 835                 goto err_deactivate_all;
 836
 837         if (remove_buffer)
 838                 iio_buffer_deactivate(remove_buffer);
 839         if (insert_buffer)
 840                 iio_buffer_activate(indio_dev, insert_buffer);
 841
 842         /* If no buffers in list, we are done */
 843         if (list_empty(&indio_dev->buffer_list))
 844                 return 0;
 845
 846         ret = iio_enable_buffers(indio_dev, &new_config);
 847         if (ret)
 848                 goto err_deactivate_all;
 849
 850         return 0;
 851
 852 err_deactivate_all:
 853         /*
 854          * We've already verified that the config is valid earlier. If things go
 855          * wrong in either enable or disable the most likely reason is an IO
 856          * error from the device. In this case there is no good recovery
 857          * strategy. Just make sure to disable everything and leave the device
 858          * in a sane state.  With a bit of luck the device might come back to
 859          * life again later and userspace can try again.
 860          */
 861         iio_buffer_deactivate_all(indio_dev);
 862
 863 err_free_config:
 864         iio_free_scan_mask(indio_dev, new_config.scan_mask);
 865         return ret;
 866 }
 867
 868 int iio_update_buffers(struct iio_dev *indio_dev,
 869                        struct iio_buffer *insert_buffer,
 870                        struct iio_buffer *remove_buffer)
 871 {
 872         int ret;
 873
 874         if (insert_buffer == remove_buffer)
 875                 return 0;
 876
 877         mutex_lock(&indio_dev->info_exist_lock);
 878         mutex_lock(&indio_dev->mlock);
 879
 880         if (insert_buffer && iio_buffer_is_active(insert_buffer))
 881                 insert_buffer = NULL;
 882
 883         if (remove_buffer && !iio_buffer_is_active(remove_buffer))
 884                 remove_buffer = NULL;
 885
 886         if (!insert_buffer && !remove_buffer) {
 887                 ret = 0;
 888                 goto out_unlock;
 889         }
 890
 891         if (indio_dev->info == NULL) {
 892                 ret = -ENODEV;
 893                 goto out_unlock;
 894         }
 895
 896         ret = __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);
 897
 898 out_unlock:
 899         mutex_unlock(&indio_dev->mlock);
 900         mutex_unlock(&indio_dev->info_exist_lock);
 901
 902         return ret;
 903 }
 904 EXPORT_SYMBOL_GPL(iio_update_buffers);
 905
 906 void iio_disable_all_buffers(struct iio_dev *indio_dev)
 907 {
 908         iio_disable_buffers(indio_dev);
 909         iio_buffer_deactivate_all(indio_dev);
 910 }
 911
 912 static ssize_t iio_buffer_store_enable(struct device *dev,
 913                                        struct device_attribute *attr,
 914                                        const char *buf,
 915                                        size_t len)
 916 {
 917         int ret;
 918         bool requested_state;
 919         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 920         bool inlist;
 921
 922         ret = strtobool(buf, &requested_state);
 923         if (ret < 0)
 924                 return ret;
 925
 926         mutex_lock(&indio_dev->mlock);
 927
 928         /* Find out if it is in the list */
 929         inlist = iio_buffer_is_active(indio_dev->buffer);
 930         /* Already in desired state */
 931         if (inlist == requested_state)
 932                 goto done;
 933
 934         if (requested_state)
 935                 ret = __iio_update_buffers(indio_dev,
 936                                          indio_dev->buffer, NULL);
 937         else
 938                 ret = __iio_update_buffers(indio_dev,
 939                                          NULL, indio_dev->buffer);
 940
 941 done:
 942         mutex_unlock(&indio_dev->mlock);
 943         return (ret < 0) ? ret : len;
 944 }
 945
 946 static const char * const iio_scan_elements_group_name = "scan_elements";
 947
 948 static ssize_t iio_buffer_show_watermark(struct device *dev,
 949                                          struct device_attribute *attr,
 950                                          char *buf)
 951 {
 952         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 953         struct iio_buffer *buffer = indio_dev->buffer;
 954
 955         return sprintf(buf, "%u\n", buffer->watermark);
 956 }
 957
 958 static ssize_t iio_buffer_store_watermark(struct device *dev,
 959                                           struct device_attribute *attr,
 960                                           const char *buf,
 961                                           size_t len)
 962 {
 963         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 964         struct iio_buffer *buffer = indio_dev->buffer;
 965         unsigned int val;
 966         int ret;
 967
 968         ret = kstrtouint(buf, 10, &val);
 969         if (ret)
 970                 return ret;
 971         if (!val)
 972                 return -EINVAL;
 973
 974         mutex_lock(&indio_dev->mlock);
 975
 976         if (val > buffer->length) {
 977                 ret = -EINVAL;
 978                 goto out;
 979         }
 980
 981         if (iio_buffer_is_active(indio_dev->buffer)) {
 982                 ret = -EBUSY;
 983                 goto out;
 984         }
 985
 986         buffer->watermark = val;
 987 out:
 988         mutex_unlock(&indio_dev->mlock);
 989
 990         return ret ? ret : len;
 991 }
 992
 993 static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
 994                    iio_buffer_write_length);
 995 static struct device_attribute dev_attr_length_ro = __ATTR(length,
 996         S_IRUGO, iio_buffer_read_length, NULL);
 997 static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
 998                    iio_buffer_show_enable, iio_buffer_store_enable);
 999 static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
1000                    iio_buffer_show_watermark, iio_buffer_store_watermark);
1001
1002 static struct attribute *iio_buffer_attrs[] = {
1003         &dev_attr_length.attr,
1004         &dev_attr_enable.attr,
1005         &dev_attr_watermark.attr,
1006 };
1007
1008 int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
1009 {
1010         struct iio_dev_attr *p;
1011         struct attribute **attr;
1012         struct iio_buffer *buffer = indio_dev->buffer;
1013         int ret, i, attrn, attrcount, attrcount_orig = 0;
1014         const struct iio_chan_spec *channels;
1015
1016         channels = indio_dev->channels;
1017         if (channels) {
1018                 int ml = indio_dev->masklength;
1019
1020                 for (i = 0; i < indio_dev->num_channels; i++)
1021                         ml = max(ml, channels[i].scan_index + 1);
1022                 indio_dev->masklength = ml;
1023         }
1024
1025         if (!buffer)
1026                 return 0;
1027
1028         attrcount = 0;
1029         if (buffer->attrs) {
1030                 while (buffer->attrs[attrcount] != NULL)
1031                         attrcount++;
1032         }
1033
1034         attr = kcalloc(attrcount + ARRAY_SIZE(iio_buffer_attrs) + 1,
1035                        sizeof(struct attribute *), GFP_KERNEL);
1036         if (!attr)
1037                 return -ENOMEM;
1038
1039         memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
1040         if (!buffer->access->set_length)
1041                 attr[0] = &dev_attr_length_ro.attr;
1042
1043         if (buffer->attrs)
1044                 memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
1045                        sizeof(struct attribute *) * attrcount);
1046
1047         attr[attrcount + ARRAY_SIZE(iio_buffer_attrs)] = NULL;
1048
1049         buffer->buffer_group.name = "buffer";
1050         buffer->buffer_group.attrs = attr;
1051
1052         indio_dev->groups[indio_dev->groupcounter++] = &buffer->buffer_group;
1053
1054         if (buffer->scan_el_attrs != NULL) {
1055                 attr = buffer->scan_el_attrs->attrs;
1056                 while (*attr++ != NULL)
1057                         attrcount_orig++;
1058         }
1059         attrcount = attrcount_orig;
1060         INIT_LIST_HEAD(&buffer->scan_el_dev_attr_list);
1061         channels = indio_dev->channels;
1062         if (channels) {
1063                 /* new magic */
1064                 for (i = 0; i < indio_dev->num_channels; i++) {
1065                         if (channels[i].scan_index < 0)
1066                                 continue;
1067
1068                         ret = iio_buffer_add_channel_sysfs(indio_dev,
1069                                                          &channels[i]);
1070                         if (ret < 0)
1071                                 goto error_cleanup_dynamic;
1072                         attrcount += ret;
1073                         if (channels[i].type == IIO_TIMESTAMP)
1074                                 indio_dev->scan_index_timestamp =
1075                                         channels[i].scan_index;
1076                 }
1077                 if (indio_dev->masklength && buffer->scan_mask == NULL) {
1078                         buffer->scan_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
1079                                                     sizeof(*buffer->scan_mask),
1080                                                     GFP_KERNEL);
1081                         if (buffer->scan_mask == NULL) {
1082                                 ret = -ENOMEM;
1083                                 goto error_cleanup_dynamic;
1084                         }
1085                 }
1086         }
1087
1088         buffer->scan_el_group.name = iio_scan_elements_group_name;
1089
1090         buffer->scan_el_group.attrs = kcalloc(attrcount + 1,
1091                                               sizeof(buffer->scan_el_group.attrs[0]),
1092                                               GFP_KERNEL);
1093         if (buffer->scan_el_group.attrs == NULL) {
1094                 ret = -ENOMEM;
1095                 goto error_free_scan_mask;
1096         }
1097         if (buffer->scan_el_attrs)
1098                 memcpy(buffer->scan_el_group.attrs, buffer->scan_el_attrs,
1099                        sizeof(buffer->scan_el_group.attrs[0])*attrcount_orig);
1100         attrn = attrcount_orig;
1101
1102         list_for_each_entry(p, &buffer->scan_el_dev_attr_list, l)
1103                 buffer->scan_el_group.attrs[attrn++] = &p->dev_attr.attr;
1104         indio_dev->groups[indio_dev->groupcounter++] = &buffer->scan_el_group;
1105
1106         return 0;
1107
1108 error_free_scan_mask:
1109         kfree(buffer->scan_mask);
1110 error_cleanup_dynamic:
1111         iio_free_chan_devattr_list(&buffer->scan_el_dev_attr_list);
1112         kfree(indio_dev->buffer->buffer_group.attrs);
1113
1114         return ret;
1115 }
1116
1117 void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
1118 {
1119         if (!indio_dev->buffer)
1120                 return;
1121
1122         kfree(indio_dev->buffer->scan_mask);
1123         kfree(indio_dev->buffer->buffer_group.attrs);
1124         kfree(indio_dev->buffer->scan_el_group.attrs);
1125         iio_free_chan_devattr_list(&indio_dev->buffer->scan_el_dev_attr_list);
1126 }
1127
1128 /**
1129  * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
1130  * @indio_dev: the iio device
1131  * @mask: scan mask to be checked
1132  *
1133  * Return true if exactly one bit is set in the scan mask, false otherwise. It
1134  * can be used for devices where only one channel can be active for sampling at
1135  * a time.
1136  */
1137 bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
1138         const unsigned long *mask)
1139 {
1140         return bitmap_weight(mask, indio_dev->masklength) == 1;
1141 }
1142 EXPORT_SYMBOL_GPL(iio_validate_scan_mask_onehot);
1143
1144 int iio_scan_mask_query(struct iio_dev *indio_dev,
1145                         struct iio_buffer *buffer, int bit)
1146 {
1147         if (bit > indio_dev->masklength)
1148                 return -EINVAL;
1149
1150         if (!buffer->scan_mask)
1151                 return 0;
1152
1153         /* Ensure return value is 0 or 1. */
1154         return !!test_bit(bit, buffer->scan_mask);
1155 };
1156 EXPORT_SYMBOL_GPL(iio_scan_mask_query);
1157
1158 /**
1159  * struct iio_demux_table - table describing demux memcpy ops
1160  * @from:       index to copy from
1161  * @to:         index to copy to
1162  * @length:     how many bytes to copy
1163  * @l:          list head used for management
1164  */
1165 struct iio_demux_table {
1166         unsigned from;
1167         unsigned to;
1168         unsigned length;
1169         struct list_head l;
1170 };
1171
1172 static const void *iio_demux(struct iio_buffer *buffer,
1173                                  const void *datain)
1174 {
1175         struct iio_demux_table *t;
1176
1177         if (list_empty(&buffer->demux_list))
1178                 return datain;
1179         list_for_each_entry(t, &buffer->demux_list, l)
1180                 memcpy(buffer->demux_bounce + t->to,
1181                        datain + t->from, t->length);
1182
1183         return buffer->demux_bounce;
1184 }
1185
1186 static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
1187 {
1188         const void *dataout = iio_demux(buffer, data);
1189         int ret;
1190
1191         ret = buffer->access->store_to(buffer, dataout);
1192         if (ret)
1193                 return ret;
1194
1195         /*
1196          * We can't just test for watermark to decide if we wake the poll queue
1197          * because read may request less samples than the watermark.
1198          */
1199         wake_up_interruptible_poll(&buffer->pollq, POLLIN | POLLRDNORM);
1200         return 0;
1201 }
1202
1203 static void iio_buffer_demux_free(struct iio_buffer *buffer)
1204 {
1205         struct iio_demux_table *p, *q;
1206         list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
1207                 list_del(&p->l);
1208                 kfree(p);
1209         }
1210 }
1211
1212
1213 int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
1214 {
1215         int ret;
1216         struct iio_buffer *buf;
1217
1218         list_for_each_entry(buf, &indio_dev->buffer_list, buffer_list) {
1219                 ret = iio_push_to_buffer(buf, data);
1220                 if (ret < 0)
1221                         return ret;
1222         }
1223
1224         return 0;
1225 }
1226 EXPORT_SYMBOL_GPL(iio_push_to_buffers);
1227
1228 static int iio_buffer_add_demux(struct iio_buffer *buffer,
1229         struct iio_demux_table **p, unsigned int in_loc, unsigned int out_loc,
1230         unsigned int length)
1231 {
1232
1233         if (*p && (*p)->from + (*p)->length == in_loc &&
1234                 (*p)->to + (*p)->length == out_loc) {
1235                 (*p)->length += length;
1236         } else {
1237                 *p = kmalloc(sizeof(**p), GFP_KERNEL);
1238                 if (*p == NULL)
1239                         return -ENOMEM;
1240                 (*p)->from = in_loc;
1241                 (*p)->to = out_loc;
1242                 (*p)->length = length;
1243                 list_add_tail(&(*p)->l, &buffer->demux_list);
1244         }
1245
1246         return 0;
1247 }
1248
1249 static int iio_buffer_update_demux(struct iio_dev *indio_dev,
1250                                    struct iio_buffer *buffer)
1251 {
1252         const struct iio_chan_spec *ch;
1253         int ret, in_ind = -1, out_ind, length;
1254         unsigned in_loc = 0, out_loc = 0;
1255         struct iio_demux_table *p = NULL;
1256
1257         /* Clear out any old demux */
1258         iio_buffer_demux_free(buffer);
1259         kfree(buffer->demux_bounce);
1260         buffer->demux_bounce = NULL;
1261
1262         /* First work out which scan mode we will actually have */
1263         if (bitmap_equal(indio_dev->active_scan_mask,
1264                          buffer->scan_mask,
1265                          indio_dev->masklength))
1266                 return 0;
1267
1268         /* Now we have the two masks, work from least sig and build up sizes */
1269         for_each_set_bit(out_ind,
1270                          buffer->scan_mask,
1271                          indio_dev->masklength) {
1272                 in_ind = find_next_bit(indio_dev->active_scan_mask,
1273                                        indio_dev->masklength,
1274                                        in_ind + 1);
1275                 while (in_ind != out_ind) {
1276                         in_ind = find_next_bit(indio_dev->active_scan_mask,
1277                                                indio_dev->masklength,
1278                                                in_ind + 1);
1279                         ch = iio_find_channel_from_si(indio_dev, in_ind);
1280                         if (ch->scan_type.repeat > 1)
1281                                 length = ch->scan_type.storagebits / 8 *
1282                                         ch->scan_type.repeat;
1283                         else
1284                                 length = ch->scan_type.storagebits / 8;
1285                         /* Make sure we are aligned */
1286                         in_loc = roundup(in_loc, length) + length;
1287                 }
1288                 ch = iio_find_channel_from_si(indio_dev, in_ind);
1289                 if (ch->scan_type.repeat > 1)
1290                         length = ch->scan_type.storagebits / 8 *
1291                                 ch->scan_type.repeat;
1292                 else
1293                         length = ch->scan_type.storagebits / 8;
1294                 out_loc = roundup(out_loc, length);
1295                 in_loc = roundup(in_loc, length);
1296                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1297                 if (ret)
1298                         goto error_clear_mux_table;
1299                 out_loc += length;
1300                 in_loc += length;
1301         }
1302         /* Relies on scan_timestamp being last */
1303         if (buffer->scan_timestamp) {
1304                 ch = iio_find_channel_from_si(indio_dev,
1305                         indio_dev->scan_index_timestamp);
1306                 if (ch->scan_type.repeat > 1)
1307                         length = ch->scan_type.storagebits / 8 *
1308                                 ch->scan_type.repeat;
1309                 else
1310                         length = ch->scan_type.storagebits / 8;
1311                 out_loc = roundup(out_loc, length);
1312                 in_loc = roundup(in_loc, length);
1313                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1314                 if (ret)
1315                         goto error_clear_mux_table;
1316                 out_loc += length;
1317                 in_loc += length;
1318         }
1319         buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
1320         if (buffer->demux_bounce == NULL) {
1321                 ret = -ENOMEM;
1322                 goto error_clear_mux_table;
1323         }
1324         return 0;
1325
1326 error_clear_mux_table:
1327         iio_buffer_demux_free(buffer);
1328
1329         return ret;
1330 }
1331
1332 int iio_update_demux(struct iio_dev *indio_dev)
1333 {
1334         struct iio_buffer *buffer;
1335         int ret;
1336
1337         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list) {
1338                 ret = iio_buffer_update_demux(indio_dev, buffer);
1339                 if (ret < 0)
1340                         goto error_clear_mux_table;
1341         }
1342         return 0;
1343
1344 error_clear_mux_table:
1345         list_for_each_entry(buffer, &indio_dev->buffer_list, buffer_list)
1346                 iio_buffer_demux_free(buffer);
1347
1348         return ret;
1349 }
1350 EXPORT_SYMBOL_GPL(iio_update_demux);
1351
1352 /**
1353  * iio_buffer_release() - Free a buffer's resources
1354  * @ref: Pointer to the kref embedded in the iio_buffer struct
1355  *
1356  * This function is called when the last reference to the buffer has been
1357  * dropped. It will typically free all resources allocated by the buffer. Do not
1358  * call this function manually, always use iio_buffer_put() when done using a
1359  * buffer.
1360  */
1361 static void iio_buffer_release(struct kref *ref)
1362 {
1363         struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);
1364
1365         buffer->access->release(buffer);
1366 }
1367
1368 /**
1369  * iio_buffer_get() - Grab a reference to the buffer
1370  * @buffer: The buffer to grab a reference for, may be NULL
1371  *
1372  * Returns the pointer to the buffer that was passed into the function.
1373  */
1374 struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer)
1375 {
1376         if (buffer)
1377                 kref_get(&buffer->ref);
1378
1379         return buffer;
1380 }
1381 EXPORT_SYMBOL_GPL(iio_buffer_get);
1382
1383 /**
1384  * iio_buffer_put() - Release the reference to the buffer
1385  * @buffer: The buffer to release the reference for, may be NULL
1386  */
1387 void iio_buffer_put(struct iio_buffer *buffer)
1388 {
1389         if (buffer)
1390                 kref_put(&buffer->ref, iio_buffer_release);
1391 }
1392 EXPORT_SYMBOL_GPL(iio_buffer_put);