drivers/iio/industrialio-buffer.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* The industrial I/O core
   3  *
   4  * Copyright (c) 2008 Jonathan Cameron
   5  *
   6  * Handling of buffer allocation / resizing.
   7  *
   8  * Things to look at here.
   9  * - Better memory allocation techniques?
  10  * - Alternative access techniques?
  11  */
  12 #include <linux/anon_inodes.h>
  13 #include <linux/kernel.h>
  14 #include <linux/export.h>
  15 #include <linux/device.h>
  16 #include <linux/file.h>
  17 #include <linux/fs.h>
  18 #include <linux/cdev.h>
  19 #include <linux/slab.h>
  20 #include <linux/poll.h>
  21 #include <linux/sched/signal.h>
  22
  23 #include <linux/iio/iio.h>
  24 #include <linux/iio/iio-opaque.h>
  25 #include "iio_core.h"
  26 #include "iio_core_trigger.h"
  27 #include <linux/iio/sysfs.h>
  28 #include <linux/iio/buffer.h>
  29 #include <linux/iio/buffer_impl.h>
  30
  31 static const char * const iio_endian_prefix[] = {
  32         [IIO_BE] = "be",
  33         [IIO_LE] = "le",
  34 };
  35
  36 static bool iio_buffer_is_active(struct iio_buffer *buf)
  37 {
  38         return !list_empty(&buf->buffer_list);
  39 }
  40
  41 static size_t iio_buffer_data_available(struct iio_buffer *buf)
  42 {
  43         return buf->access->data_available(buf);
  44 }
  45
  46 static int iio_buffer_flush_hwfifo(struct iio_dev *indio_dev,
  47                                    struct iio_buffer *buf, size_t required)
  48 {
  49         if (!indio_dev->info->hwfifo_flush_to_buffer)
  50                 return -ENODEV;
  51
  52         return indio_dev->info->hwfifo_flush_to_buffer(indio_dev, required);
  53 }
  54
  55 static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
  56                              size_t to_wait, int to_flush)
  57 {
  58         size_t avail;
  59         int flushed = 0;
  60
  61         /* wakeup if the device was unregistered */
  62         if (!indio_dev->info)
  63                 return true;
  64
  65         /* drain the buffer if it was disabled */
  66         if (!iio_buffer_is_active(buf)) {
  67                 to_wait = min_t(size_t, to_wait, 1);
  68                 to_flush = 0;
  69         }
  70
  71         avail = iio_buffer_data_available(buf);
  72
  73         if (avail >= to_wait) {
  74                 /* force a flush for non-blocking reads */
  75                 if (!to_wait && avail < to_flush)
  76                         iio_buffer_flush_hwfifo(indio_dev, buf,
  77                                                 to_flush - avail);
  78                 return true;
  79         }
  80
  81         if (to_flush)
  82                 flushed = iio_buffer_flush_hwfifo(indio_dev, buf,
  83                                                   to_wait - avail);
  84         if (flushed <= 0)
  85                 return false;
  86
  87         if (avail + flushed >= to_wait)
  88                 return true;
  89
  90         return false;
  91 }
  92
  93 /**
  94  * iio_buffer_read() - chrdev read for buffer access
  95  * @filp:       File structure pointer for the char device
  96  * @buf:        Destination buffer for iio buffer read
  97  * @n:          First n bytes to read
  98  * @f_ps:       Long offset provided by the user as a seek position
  99  *
 100  * This function relies on all buffer implementations having an
 101  * iio_buffer as their first element.
 102  *
 103  * Return: negative values corresponding to error codes or ret != 0
 104  *         for ending the reading activity
 105  **/
 106 static ssize_t iio_buffer_read(struct file *filp, char __user *buf,
 107                                size_t n, loff_t *f_ps)
 108 {
 109         struct iio_dev_buffer_pair *ib = filp->private_data;
 110         struct iio_buffer *rb = ib->buffer;
 111         struct iio_dev *indio_dev = ib->indio_dev;
 112         DEFINE_WAIT_FUNC(wait, woken_wake_function);
 113         size_t datum_size;
 114         size_t to_wait;
 115         int ret = 0;
 116
 117         if (!indio_dev->info)
 118                 return -ENODEV;
 119
 120         if (!rb || !rb->access->read)
 121                 return -EINVAL;
 122
 123         if (rb->direction != IIO_BUFFER_DIRECTION_IN)
 124                 return -EPERM;
 125
 126         datum_size = rb->bytes_per_datum;
 127
 128         /*
 129          * If datum_size is 0 there will never be anything to read from the
 130          * buffer, so signal end of file now.
 131          */
 132         if (!datum_size)
 133                 return 0;
 134
 135         if (filp->f_flags & O_NONBLOCK)
 136                 to_wait = 0;
 137         else
 138                 to_wait = min_t(size_t, n / datum_size, rb->watermark);
 139
 140         add_wait_queue(&rb->pollq, &wait);
 141         do {
 142                 if (!indio_dev->info) {
 143                         ret = -ENODEV;
 144                         break;
 145                 }
 146
 147                 if (!iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)) {
 148                         if (signal_pending(current)) {
 149                                 ret = -ERESTARTSYS;
 150                                 break;
 151                         }
 152
 153                         wait_woken(&wait, TASK_INTERRUPTIBLE,
 154                                    MAX_SCHEDULE_TIMEOUT);
 155                         continue;
 156                 }
 157
 158                 ret = rb->access->read(rb, n, buf);
 159                 if (ret == 0 && (filp->f_flags & O_NONBLOCK))
 160                         ret = -EAGAIN;
 161         } while (ret == 0);
 162         remove_wait_queue(&rb->pollq, &wait);
 163
 164         return ret;
 165 }
 166
 167 static size_t iio_buffer_space_available(struct iio_buffer *buf)
 168 {
 169         if (buf->access->space_available)
 170                 return buf->access->space_available(buf);
 171
 172         return SIZE_MAX;
 173 }
 174
 175 static ssize_t iio_buffer_write(struct file *filp, const char __user *buf,
 176                                 size_t n, loff_t *f_ps)
 177 {
 178         struct iio_dev_buffer_pair *ib = filp->private_data;
 179         struct iio_buffer *rb = ib->buffer;
 180         struct iio_dev *indio_dev = ib->indio_dev;
 181         DEFINE_WAIT_FUNC(wait, woken_wake_function);
 182         int ret = 0;
 183         size_t written;
 184
 185         if (!indio_dev->info)
 186                 return -ENODEV;
 187
 188         if (!rb || !rb->access->write)
 189                 return -EINVAL;
 190
 191         if (rb->direction != IIO_BUFFER_DIRECTION_OUT)
 192                 return -EPERM;
 193
 194         written = 0;
 195         add_wait_queue(&rb->pollq, &wait);
 196         do {
 197                 if (indio_dev->info == NULL)
 198                         return -ENODEV;
 199
 200                 if (!iio_buffer_space_available(rb)) {
 201                         if (signal_pending(current)) {
 202                                 ret = -ERESTARTSYS;
 203                                 break;
 204                         }
 205
 206                         wait_woken(&wait, TASK_INTERRUPTIBLE,
 207                                         MAX_SCHEDULE_TIMEOUT);
 208                         continue;
 209                 }
 210
 211                 ret = rb->access->write(rb, n - written, buf + written);
 212                 if (ret == 0 && (filp->f_flags & O_NONBLOCK))
 213                         ret = -EAGAIN;
 214
 215                 if (ret > 0) {
 216                         written += ret;
 217                         if (written != n && !(filp->f_flags & O_NONBLOCK))
 218                                 continue;
 219                 }
 220         } while (ret == 0);
 221         remove_wait_queue(&rb->pollq, &wait);
 222
 223         return ret < 0 ? ret : n;
 224 }
 225
 226 /**
 227  * iio_buffer_poll() - poll the buffer to find out if it has data
 228  * @filp:       File structure pointer for device access
 229  * @wait:       Poll table structure pointer for which the driver adds
 230  *              a wait queue
 231  *
 232  * Return: (EPOLLIN | EPOLLRDNORM) if data is available for reading
 233  *         or 0 for other cases
 234  */
 235 static __poll_t iio_buffer_poll(struct file *filp,
 236                                 struct poll_table_struct *wait)
 237 {
 238         struct iio_dev_buffer_pair *ib = filp->private_data;
 239         struct iio_buffer *rb = ib->buffer;
 240         struct iio_dev *indio_dev = ib->indio_dev;
 241
 242         if (!indio_dev->info || rb == NULL)
 243                 return 0;
 244
 245         poll_wait(filp, &rb->pollq, wait);
 246
 247         switch (rb->direction) {
 248         case IIO_BUFFER_DIRECTION_IN:
 249                 if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
 250                         return EPOLLIN | EPOLLRDNORM;
 251                 break;
 252         case IIO_BUFFER_DIRECTION_OUT:
 253                 if (iio_buffer_space_available(rb))
 254                         return EPOLLOUT | EPOLLWRNORM;
 255                 break;
 256         }
 257
 258         return 0;
 259 }
 260
 261 ssize_t iio_buffer_read_wrapper(struct file *filp, char __user *buf,
 262                                 size_t n, loff_t *f_ps)
 263 {
 264         struct iio_dev_buffer_pair *ib = filp->private_data;
 265         struct iio_buffer *rb = ib->buffer;
 266
 267         /* check if buffer was opened through new API */
 268         if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
 269                 return -EBUSY;
 270
 271         return iio_buffer_read(filp, buf, n, f_ps);
 272 }
 273
 274 ssize_t iio_buffer_write_wrapper(struct file *filp, const char __user *buf,
 275                                  size_t n, loff_t *f_ps)
 276 {
 277         struct iio_dev_buffer_pair *ib = filp->private_data;
 278         struct iio_buffer *rb = ib->buffer;
 279
 280         /* check if buffer was opened through new API */
 281         if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
 282                 return -EBUSY;
 283
 284         return iio_buffer_write(filp, buf, n, f_ps);
 285 }
 286
 287 __poll_t iio_buffer_poll_wrapper(struct file *filp,
 288                                  struct poll_table_struct *wait)
 289 {
 290         struct iio_dev_buffer_pair *ib = filp->private_data;
 291         struct iio_buffer *rb = ib->buffer;
 292
 293         /* check if buffer was opened through new API */
 294         if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
 295                 return 0;
 296
 297         return iio_buffer_poll(filp, wait);
 298 }
 299
 300 /**
 301  * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
 302  * @indio_dev: The IIO device
 303  *
 304  * Wakes up the event waitqueue used for poll(). Should usually
 305  * be called when the device is unregistered.
 306  */
 307 void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
 308 {
 309         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 310         struct iio_buffer *buffer;
 311         unsigned int i;
 312
 313         for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
 314                 buffer = iio_dev_opaque->attached_buffers[i];
 315                 wake_up(&buffer->pollq);
 316         }
 317 }
 318
 319 int iio_pop_from_buffer(struct iio_buffer *buffer, void *data)
 320 {
 321         if (!buffer || !buffer->access || !buffer->access->remove_from)
 322                 return -EINVAL;
 323
 324         return buffer->access->remove_from(buffer, data);
 325 }
 326 EXPORT_SYMBOL_GPL(iio_pop_from_buffer);
 327
 328 void iio_buffer_init(struct iio_buffer *buffer)
 329 {
 330         INIT_LIST_HEAD(&buffer->demux_list);
 331         INIT_LIST_HEAD(&buffer->buffer_list);
 332         init_waitqueue_head(&buffer->pollq);
 333         kref_init(&buffer->ref);
 334         if (!buffer->watermark)
 335                 buffer->watermark = 1;
 336 }
 337 EXPORT_SYMBOL(iio_buffer_init);
 338
 339 void iio_device_detach_buffers(struct iio_dev *indio_dev)
 340 {
 341         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 342         struct iio_buffer *buffer;
 343         unsigned int i;
 344
 345         for (i = 0; i < iio_dev_opaque->attached_buffers_cnt; i++) {
 346                 buffer = iio_dev_opaque->attached_buffers[i];
 347                 iio_buffer_put(buffer);
 348         }
 349
 350         kfree(iio_dev_opaque->attached_buffers);
 351 }
 352
 353 static ssize_t iio_show_scan_index(struct device *dev,
 354                                    struct device_attribute *attr,
 355                                    char *buf)
 356 {
 357         return sysfs_emit(buf, "%u\n", to_iio_dev_attr(attr)->c->scan_index);
 358 }
 359
 360 static ssize_t iio_show_fixed_type(struct device *dev,
 361                                    struct device_attribute *attr,
 362                                    char *buf)
 363 {
 364         struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
 365         u8 type = this_attr->c->scan_type.endianness;
 366
 367         if (type == IIO_CPU) {
 368 #ifdef __LITTLE_ENDIAN
 369                 type = IIO_LE;
 370 #else
 371                 type = IIO_BE;
 372 #endif
 373         }
 374         if (this_attr->c->scan_type.repeat > 1)
 375                 return sysfs_emit(buf, "%s:%c%d/%dX%d>>%u\n",
 376                        iio_endian_prefix[type],
 377                        this_attr->c->scan_type.sign,
 378                        this_attr->c->scan_type.realbits,
 379                        this_attr->c->scan_type.storagebits,
 380                        this_attr->c->scan_type.repeat,
 381                        this_attr->c->scan_type.shift);
 382         else
 383                 return sysfs_emit(buf, "%s:%c%d/%d>>%u\n",
 384                        iio_endian_prefix[type],
 385                        this_attr->c->scan_type.sign,
 386                        this_attr->c->scan_type.realbits,
 387                        this_attr->c->scan_type.storagebits,
 388                        this_attr->c->scan_type.shift);
 389 }
 390
 391 static ssize_t iio_scan_el_show(struct device *dev,
 392                                 struct device_attribute *attr,
 393                                 char *buf)
 394 {
 395         int ret;
 396         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 397
 398         /* Ensure ret is 0 or 1. */
 399         ret = !!test_bit(to_iio_dev_attr(attr)->address,
 400                        buffer->scan_mask);
 401
 402         return sysfs_emit(buf, "%d\n", ret);
 403 }
 404
 405 /* Note NULL used as error indicator as it doesn't make sense. */
 406 static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
 407                                           unsigned int masklength,
 408                                           const unsigned long *mask,
 409                                           bool strict)
 410 {
 411         if (bitmap_empty(mask, masklength))
 412                 return NULL;
 413         while (*av_masks) {
 414                 if (strict) {
 415                         if (bitmap_equal(mask, av_masks, masklength))
 416                                 return av_masks;
 417                 } else {
 418                         if (bitmap_subset(mask, av_masks, masklength))
 419                                 return av_masks;
 420                 }
 421                 av_masks += BITS_TO_LONGS(masklength);
 422         }
 423         return NULL;
 424 }
 425
 426 static bool iio_validate_scan_mask(struct iio_dev *indio_dev,
 427         const unsigned long *mask)
 428 {
 429         if (!indio_dev->setup_ops->validate_scan_mask)
 430                 return true;
 431
 432         return indio_dev->setup_ops->validate_scan_mask(indio_dev, mask);
 433 }
 434
 435 /**
 436  * iio_scan_mask_set() - set particular bit in the scan mask
 437  * @indio_dev: the iio device
 438  * @buffer: the buffer whose scan mask we are interested in
 439  * @bit: the bit to be set.
 440  *
 441  * Note that at this point we have no way of knowing what other
 442  * buffers might request, hence this code only verifies that the
 443  * individual buffers request is plausible.
 444  */
 445 static int iio_scan_mask_set(struct iio_dev *indio_dev,
 446                       struct iio_buffer *buffer, int bit)
 447 {
 448         const unsigned long *mask;
 449         unsigned long *trialmask;
 450
 451         if (!indio_dev->masklength) {
 452                 WARN(1, "Trying to set scanmask prior to registering buffer\n");
 453                 return -EINVAL;
 454         }
 455
 456         trialmask = bitmap_alloc(indio_dev->masklength, GFP_KERNEL);
 457         if (!trialmask)
 458                 return -ENOMEM;
 459         bitmap_copy(trialmask, buffer->scan_mask, indio_dev->masklength);
 460         set_bit(bit, trialmask);
 461
 462         if (!iio_validate_scan_mask(indio_dev, trialmask))
 463                 goto err_invalid_mask;
 464
 465         if (indio_dev->available_scan_masks) {
 466                 mask = iio_scan_mask_match(indio_dev->available_scan_masks,
 467                                            indio_dev->masklength,
 468                                            trialmask, false);
 469                 if (!mask)
 470                         goto err_invalid_mask;
 471         }
 472         bitmap_copy(buffer->scan_mask, trialmask, indio_dev->masklength);
 473
 474         bitmap_free(trialmask);
 475
 476         return 0;
 477
 478 err_invalid_mask:
 479         bitmap_free(trialmask);
 480         return -EINVAL;
 481 }
 482
 483 static int iio_scan_mask_clear(struct iio_buffer *buffer, int bit)
 484 {
 485         clear_bit(bit, buffer->scan_mask);
 486         return 0;
 487 }
 488
 489 static int iio_scan_mask_query(struct iio_dev *indio_dev,
 490                                struct iio_buffer *buffer, int bit)
 491 {
 492         if (bit > indio_dev->masklength)
 493                 return -EINVAL;
 494
 495         if (!buffer->scan_mask)
 496                 return 0;
 497
 498         /* Ensure return value is 0 or 1. */
 499         return !!test_bit(bit, buffer->scan_mask);
 500 };
 501
 502 static ssize_t iio_scan_el_store(struct device *dev,
 503                                  struct device_attribute *attr,
 504                                  const char *buf,
 505                                  size_t len)
 506 {
 507         int ret;
 508         bool state;
 509         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 510         struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
 511         struct iio_buffer *buffer = this_attr->buffer;
 512
 513         ret = kstrtobool(buf, &state);
 514         if (ret < 0)
 515                 return ret;
 516         mutex_lock(&indio_dev->mlock);
 517         if (iio_buffer_is_active(buffer)) {
 518                 ret = -EBUSY;
 519                 goto error_ret;
 520         }
 521         ret = iio_scan_mask_query(indio_dev, buffer, this_attr->address);
 522         if (ret < 0)
 523                 goto error_ret;
 524         if (!state && ret) {
 525                 ret = iio_scan_mask_clear(buffer, this_attr->address);
 526                 if (ret)
 527                         goto error_ret;
 528         } else if (state && !ret) {
 529                 ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
 530                 if (ret)
 531                         goto error_ret;
 532         }
 533
 534 error_ret:
 535         mutex_unlock(&indio_dev->mlock);
 536
 537         return ret < 0 ? ret : len;
 538
 539 }
 540
 541 static ssize_t iio_scan_el_ts_show(struct device *dev,
 542                                    struct device_attribute *attr,
 543                                    char *buf)
 544 {
 545         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 546
 547         return sysfs_emit(buf, "%d\n", buffer->scan_timestamp);
 548 }
 549
 550 static ssize_t iio_scan_el_ts_store(struct device *dev,
 551                                     struct device_attribute *attr,
 552                                     const char *buf,
 553                                     size_t len)
 554 {
 555         int ret;
 556         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 557         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 558         bool state;
 559
 560         ret = kstrtobool(buf, &state);
 561         if (ret < 0)
 562                 return ret;
 563
 564         mutex_lock(&indio_dev->mlock);
 565         if (iio_buffer_is_active(buffer)) {
 566                 ret = -EBUSY;
 567                 goto error_ret;
 568         }
 569         buffer->scan_timestamp = state;
 570 error_ret:
 571         mutex_unlock(&indio_dev->mlock);
 572
 573         return ret ? ret : len;
 574 }
 575
 576 static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
 577                                         struct iio_buffer *buffer,
 578                                         const struct iio_chan_spec *chan)
 579 {
 580         int ret, attrcount = 0;
 581
 582         ret = __iio_add_chan_devattr("index",
 583                                      chan,
 584                                      &iio_show_scan_index,
 585                                      NULL,
 586                                      0,
 587                                      IIO_SEPARATE,
 588                                      &indio_dev->dev,
 589                                      buffer,
 590                                      &buffer->buffer_attr_list);
 591         if (ret)
 592                 return ret;
 593         attrcount++;
 594         ret = __iio_add_chan_devattr("type",
 595                                      chan,
 596                                      &iio_show_fixed_type,
 597                                      NULL,
 598                                      0,
 599                                      0,
 600                                      &indio_dev->dev,
 601                                      buffer,
 602                                      &buffer->buffer_attr_list);
 603         if (ret)
 604                 return ret;
 605         attrcount++;
 606         if (chan->type != IIO_TIMESTAMP)
 607                 ret = __iio_add_chan_devattr("en",
 608                                              chan,
 609                                              &iio_scan_el_show,
 610                                              &iio_scan_el_store,
 611                                              chan->scan_index,
 612                                              0,
 613                                              &indio_dev->dev,
 614                                              buffer,
 615                                              &buffer->buffer_attr_list);
 616         else
 617                 ret = __iio_add_chan_devattr("en",
 618                                              chan,
 619                                              &iio_scan_el_ts_show,
 620                                              &iio_scan_el_ts_store,
 621                                              chan->scan_index,
 622                                              0,
 623                                              &indio_dev->dev,
 624                                              buffer,
 625                                              &buffer->buffer_attr_list);
 626         if (ret)
 627                 return ret;
 628         attrcount++;
 629         ret = attrcount;
 630         return ret;
 631 }
 632
 633 static ssize_t iio_buffer_read_length(struct device *dev,
 634                                       struct device_attribute *attr,
 635                                       char *buf)
 636 {
 637         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 638
 639         return sysfs_emit(buf, "%d\n", buffer->length);
 640 }
 641
 642 static ssize_t iio_buffer_write_length(struct device *dev,
 643                                        struct device_attribute *attr,
 644                                        const char *buf, size_t len)
 645 {
 646         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 647         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 648         unsigned int val;
 649         int ret;
 650
 651         ret = kstrtouint(buf, 10, &val);
 652         if (ret)
 653                 return ret;
 654
 655         if (val == buffer->length)
 656                 return len;
 657
 658         mutex_lock(&indio_dev->mlock);
 659         if (iio_buffer_is_active(buffer)) {
 660                 ret = -EBUSY;
 661         } else {
 662                 buffer->access->set_length(buffer, val);
 663                 ret = 0;
 664         }
 665         if (ret)
 666                 goto out;
 667         if (buffer->length && buffer->length < buffer->watermark)
 668                 buffer->watermark = buffer->length;
 669 out:
 670         mutex_unlock(&indio_dev->mlock);
 671
 672         return ret ? ret : len;
 673 }
 674
 675 static ssize_t iio_buffer_show_enable(struct device *dev,
 676                                       struct device_attribute *attr,
 677                                       char *buf)
 678 {
 679         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
 680
 681         return sysfs_emit(buf, "%d\n", iio_buffer_is_active(buffer));
 682 }
 683
 684 static unsigned int iio_storage_bytes_for_si(struct iio_dev *indio_dev,
 685                                              unsigned int scan_index)
 686 {
 687         const struct iio_chan_spec *ch;
 688         unsigned int bytes;
 689
 690         ch = iio_find_channel_from_si(indio_dev, scan_index);
 691         bytes = ch->scan_type.storagebits / 8;
 692         if (ch->scan_type.repeat > 1)
 693                 bytes *= ch->scan_type.repeat;
 694         return bytes;
 695 }
 696
 697 static unsigned int iio_storage_bytes_for_timestamp(struct iio_dev *indio_dev)
 698 {
 699         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 700
 701         return iio_storage_bytes_for_si(indio_dev,
 702                                         iio_dev_opaque->scan_index_timestamp);
 703 }
 704
 705 static int iio_compute_scan_bytes(struct iio_dev *indio_dev,
 706                                 const unsigned long *mask, bool timestamp)
 707 {
 708         unsigned bytes = 0;
 709         int length, i, largest = 0;
 710
 711         /* How much space will the demuxed element take? */
 712         for_each_set_bit(i, mask,
 713                          indio_dev->masklength) {
 714                 length = iio_storage_bytes_for_si(indio_dev, i);
 715                 bytes = ALIGN(bytes, length);
 716                 bytes += length;
 717                 largest = max(largest, length);
 718         }
 719
 720         if (timestamp) {
 721                 length = iio_storage_bytes_for_timestamp(indio_dev);
 722                 bytes = ALIGN(bytes, length);
 723                 bytes += length;
 724                 largest = max(largest, length);
 725         }
 726
 727         bytes = ALIGN(bytes, largest);
 728         return bytes;
 729 }
 730
 731 static void iio_buffer_activate(struct iio_dev *indio_dev,
 732         struct iio_buffer *buffer)
 733 {
 734         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 735
 736         iio_buffer_get(buffer);
 737         list_add(&buffer->buffer_list, &iio_dev_opaque->buffer_list);
 738 }
 739
 740 static void iio_buffer_deactivate(struct iio_buffer *buffer)
 741 {
 742         list_del_init(&buffer->buffer_list);
 743         wake_up_interruptible(&buffer->pollq);
 744         iio_buffer_put(buffer);
 745 }
 746
 747 static void iio_buffer_deactivate_all(struct iio_dev *indio_dev)
 748 {
 749         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 750         struct iio_buffer *buffer, *_buffer;
 751
 752         list_for_each_entry_safe(buffer, _buffer,
 753                         &iio_dev_opaque->buffer_list, buffer_list)
 754                 iio_buffer_deactivate(buffer);
 755 }
 756
 757 static int iio_buffer_enable(struct iio_buffer *buffer,
 758         struct iio_dev *indio_dev)
 759 {
 760         if (!buffer->access->enable)
 761                 return 0;
 762         return buffer->access->enable(buffer, indio_dev);
 763 }
 764
 765 static int iio_buffer_disable(struct iio_buffer *buffer,
 766         struct iio_dev *indio_dev)
 767 {
 768         if (!buffer->access->disable)
 769                 return 0;
 770         return buffer->access->disable(buffer, indio_dev);
 771 }
 772
 773 static void iio_buffer_update_bytes_per_datum(struct iio_dev *indio_dev,
 774         struct iio_buffer *buffer)
 775 {
 776         unsigned int bytes;
 777
 778         if (!buffer->access->set_bytes_per_datum)
 779                 return;
 780
 781         bytes = iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
 782                 buffer->scan_timestamp);
 783
 784         buffer->access->set_bytes_per_datum(buffer, bytes);
 785 }
 786
 787 static int iio_buffer_request_update(struct iio_dev *indio_dev,
 788         struct iio_buffer *buffer)
 789 {
 790         int ret;
 791
 792         iio_buffer_update_bytes_per_datum(indio_dev, buffer);
 793         if (buffer->access->request_update) {
 794                 ret = buffer->access->request_update(buffer);
 795                 if (ret) {
 796                         dev_dbg(&indio_dev->dev,
 797                                "Buffer not started: buffer parameter update failed (%d)\n",
 798                                 ret);
 799                         return ret;
 800                 }
 801         }
 802
 803         return 0;
 804 }
 805
 806 static void iio_free_scan_mask(struct iio_dev *indio_dev,
 807         const unsigned long *mask)
 808 {
 809         /* If the mask is dynamically allocated free it, otherwise do nothing */
 810         if (!indio_dev->available_scan_masks)
 811                 bitmap_free(mask);
 812 }
 813
 814 struct iio_device_config {
 815         unsigned int mode;
 816         unsigned int watermark;
 817         const unsigned long *scan_mask;
 818         unsigned int scan_bytes;
 819         bool scan_timestamp;
 820 };
 821
 822 static int iio_verify_update(struct iio_dev *indio_dev,
 823         struct iio_buffer *insert_buffer, struct iio_buffer *remove_buffer,
 824         struct iio_device_config *config)
 825 {
 826         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
 827         unsigned long *compound_mask;
 828         const unsigned long *scan_mask;
 829         bool strict_scanmask = false;
 830         struct iio_buffer *buffer;
 831         bool scan_timestamp;
 832         unsigned int modes;
 833
 834         if (insert_buffer &&
 835             bitmap_empty(insert_buffer->scan_mask, indio_dev->masklength)) {
 836                 dev_dbg(&indio_dev->dev,
 837                         "At least one scan element must be enabled first\n");
 838                 return -EINVAL;
 839         }
 840
 841         memset(config, 0, sizeof(*config));
 842         config->watermark = ~0;
 843
 844         /*
 845          * If there is just one buffer and we are removing it there is nothing
 846          * to verify.
 847          */
 848         if (remove_buffer && !insert_buffer &&
 849                 list_is_singular(&iio_dev_opaque->buffer_list))
 850                         return 0;
 851
 852         modes = indio_dev->modes;
 853
 854         list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
 855                 if (buffer == remove_buffer)
 856                         continue;
 857                 modes &= buffer->access->modes;
 858                 config->watermark = min(config->watermark, buffer->watermark);
 859         }
 860
 861         if (insert_buffer) {
 862                 modes &= insert_buffer->access->modes;
 863                 config->watermark = min(config->watermark,
 864                         insert_buffer->watermark);
 865         }
 866
 867         /* Definitely possible for devices to support both of these. */
 868         if ((modes & INDIO_BUFFER_TRIGGERED) && indio_dev->trig) {
 869                 config->mode = INDIO_BUFFER_TRIGGERED;
 870         } else if (modes & INDIO_BUFFER_HARDWARE) {
 871                 /*
 872                  * Keep things simple for now and only allow a single buffer to
 873                  * be connected in hardware mode.
 874                  */
 875                 if (insert_buffer && !list_empty(&iio_dev_opaque->buffer_list))
 876                         return -EINVAL;
 877                 config->mode = INDIO_BUFFER_HARDWARE;
 878                 strict_scanmask = true;
 879         } else if (modes & INDIO_BUFFER_SOFTWARE) {
 880                 config->mode = INDIO_BUFFER_SOFTWARE;
 881         } else {
 882                 /* Can only occur on first buffer */
 883                 if (indio_dev->modes & INDIO_BUFFER_TRIGGERED)
 884                         dev_dbg(&indio_dev->dev, "Buffer not started: no trigger\n");
 885                 return -EINVAL;
 886         }
 887
 888         /* What scan mask do we actually have? */
 889         compound_mask = bitmap_zalloc(indio_dev->masklength, GFP_KERNEL);
 890         if (compound_mask == NULL)
 891                 return -ENOMEM;
 892
 893         scan_timestamp = false;
 894
 895         list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
 896                 if (buffer == remove_buffer)
 897                         continue;
 898                 bitmap_or(compound_mask, compound_mask, buffer->scan_mask,
 899                           indio_dev->masklength);
 900                 scan_timestamp |= buffer->scan_timestamp;
 901         }
 902
 903         if (insert_buffer) {
 904                 bitmap_or(compound_mask, compound_mask,
 905                           insert_buffer->scan_mask, indio_dev->masklength);
 906                 scan_timestamp |= insert_buffer->scan_timestamp;
 907         }
 908
 909         if (indio_dev->available_scan_masks) {
 910                 scan_mask = iio_scan_mask_match(indio_dev->available_scan_masks,
 911                                     indio_dev->masklength,
 912                                     compound_mask,
 913                                     strict_scanmask);
 914                 bitmap_free(compound_mask);
 915                 if (scan_mask == NULL)
 916                         return -EINVAL;
 917         } else {
 918                 scan_mask = compound_mask;
 919         }
 920
 921         config->scan_bytes = iio_compute_scan_bytes(indio_dev,
 922                                     scan_mask, scan_timestamp);
 923         config->scan_mask = scan_mask;
 924         config->scan_timestamp = scan_timestamp;
 925
 926         return 0;
 927 }
 928
 929 /**
 930  * struct iio_demux_table - table describing demux memcpy ops
 931  * @from:       index to copy from
 932  * @to:         index to copy to
 933  * @length:     how many bytes to copy
 934  * @l:          list head used for management
 935  */
 936 struct iio_demux_table {
 937         unsigned from;
 938         unsigned to;
 939         unsigned length;
 940         struct list_head l;
 941 };
 942
 943 static void iio_buffer_demux_free(struct iio_buffer *buffer)
 944 {
 945         struct iio_demux_table *p, *q;
 946         list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
 947                 list_del(&p->l);
 948                 kfree(p);
 949         }
 950 }
 951
 952 static int iio_buffer_add_demux(struct iio_buffer *buffer,
 953         struct iio_demux_table **p, unsigned int in_loc, unsigned int out_loc,
 954         unsigned int length)
 955 {
 956
 957         if (*p && (*p)->from + (*p)->length == in_loc &&
 958                 (*p)->to + (*p)->length == out_loc) {
 959                 (*p)->length += length;
 960         } else {
 961                 *p = kmalloc(sizeof(**p), GFP_KERNEL);
 962                 if (*p == NULL)
 963                         return -ENOMEM;
 964                 (*p)->from = in_loc;
 965                 (*p)->to = out_loc;
 966                 (*p)->length = length;
 967                 list_add_tail(&(*p)->l, &buffer->demux_list);
 968         }
 969
 970         return 0;
 971 }
 972
 973 static int iio_buffer_update_demux(struct iio_dev *indio_dev,
 974                                    struct iio_buffer *buffer)
 975 {
 976         int ret, in_ind = -1, out_ind, length;
 977         unsigned in_loc = 0, out_loc = 0;
 978         struct iio_demux_table *p = NULL;
 979
 980         /* Clear out any old demux */
 981         iio_buffer_demux_free(buffer);
 982         kfree(buffer->demux_bounce);
 983         buffer->demux_bounce = NULL;
 984
 985         /* First work out which scan mode we will actually have */
 986         if (bitmap_equal(indio_dev->active_scan_mask,
 987                          buffer->scan_mask,
 988                          indio_dev->masklength))
 989                 return 0;
 990
 991         /* Now we have the two masks, work from least sig and build up sizes */
 992         for_each_set_bit(out_ind,
 993                          buffer->scan_mask,
 994                          indio_dev->masklength) {
 995                 in_ind = find_next_bit(indio_dev->active_scan_mask,
 996                                        indio_dev->masklength,
 997                                        in_ind + 1);
 998                 while (in_ind != out_ind) {
 999                         length = iio_storage_bytes_for_si(indio_dev, in_ind);
1000                         /* Make sure we are aligned */
1001                         in_loc = roundup(in_loc, length) + length;
1002                         in_ind = find_next_bit(indio_dev->active_scan_mask,
1003                                                indio_dev->masklength,
1004                                                in_ind + 1);
1005                 }
1006                 length = iio_storage_bytes_for_si(indio_dev, in_ind);
1007                 out_loc = roundup(out_loc, length);
1008                 in_loc = roundup(in_loc, length);
1009                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1010                 if (ret)
1011                         goto error_clear_mux_table;
1012                 out_loc += length;
1013                 in_loc += length;
1014         }
1015         /* Relies on scan_timestamp being last */
1016         if (buffer->scan_timestamp) {
1017                 length = iio_storage_bytes_for_timestamp(indio_dev);
1018                 out_loc = roundup(out_loc, length);
1019                 in_loc = roundup(in_loc, length);
1020                 ret = iio_buffer_add_demux(buffer, &p, in_loc, out_loc, length);
1021                 if (ret)
1022                         goto error_clear_mux_table;
1023                 out_loc += length;
1024         }
1025         buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
1026         if (buffer->demux_bounce == NULL) {
1027                 ret = -ENOMEM;
1028                 goto error_clear_mux_table;
1029         }
1030         return 0;
1031
1032 error_clear_mux_table:
1033         iio_buffer_demux_free(buffer);
1034
1035         return ret;
1036 }
1037
1038 static int iio_update_demux(struct iio_dev *indio_dev)
1039 {
1040         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1041         struct iio_buffer *buffer;
1042         int ret;
1043
1044         list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
1045                 ret = iio_buffer_update_demux(indio_dev, buffer);
1046                 if (ret < 0)
1047                         goto error_clear_mux_table;
1048         }
1049         return 0;
1050
1051 error_clear_mux_table:
1052         list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list)
1053                 iio_buffer_demux_free(buffer);
1054
1055         return ret;
1056 }
1057
1058 static int iio_enable_buffers(struct iio_dev *indio_dev,
1059         struct iio_device_config *config)
1060 {
1061         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1062         struct iio_buffer *buffer, *tmp = NULL;
1063         int ret;
1064
1065         indio_dev->active_scan_mask = config->scan_mask;
1066         indio_dev->scan_timestamp = config->scan_timestamp;
1067         indio_dev->scan_bytes = config->scan_bytes;
1068         iio_dev_opaque->currentmode = config->mode;
1069
1070         iio_update_demux(indio_dev);
1071
1072         /* Wind up again */
1073         if (indio_dev->setup_ops->preenable) {
1074                 ret = indio_dev->setup_ops->preenable(indio_dev);
1075                 if (ret) {
1076                         dev_dbg(&indio_dev->dev,
1077                                "Buffer not started: buffer preenable failed (%d)\n", ret);
1078                         goto err_undo_config;
1079                 }
1080         }
1081
1082         if (indio_dev->info->update_scan_mode) {
1083                 ret = indio_dev->info
1084                         ->update_scan_mode(indio_dev,
1085                                            indio_dev->active_scan_mask);
1086                 if (ret < 0) {
1087                         dev_dbg(&indio_dev->dev,
1088                                 "Buffer not started: update scan mode failed (%d)\n",
1089                                 ret);
1090                         goto err_run_postdisable;
1091                 }
1092         }
1093
1094         if (indio_dev->info->hwfifo_set_watermark)
1095                 indio_dev->info->hwfifo_set_watermark(indio_dev,
1096                         config->watermark);
1097
1098         list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
1099                 ret = iio_buffer_enable(buffer, indio_dev);
1100                 if (ret) {
1101                         tmp = buffer;
1102                         goto err_disable_buffers;
1103                 }
1104         }
1105
1106         if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
1107                 ret = iio_trigger_attach_poll_func(indio_dev->trig,
1108                                                    indio_dev->pollfunc);
1109                 if (ret)
1110                         goto err_disable_buffers;
1111         }
1112
1113         if (indio_dev->setup_ops->postenable) {
1114                 ret = indio_dev->setup_ops->postenable(indio_dev);
1115                 if (ret) {
1116                         dev_dbg(&indio_dev->dev,
1117                                "Buffer not started: postenable failed (%d)\n", ret);
1118                         goto err_detach_pollfunc;
1119                 }
1120         }
1121
1122         return 0;
1123
1124 err_detach_pollfunc:
1125         if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
1126                 iio_trigger_detach_poll_func(indio_dev->trig,
1127                                              indio_dev->pollfunc);
1128         }
1129 err_disable_buffers:
1130         buffer = list_prepare_entry(tmp, &iio_dev_opaque->buffer_list, buffer_list);
1131         list_for_each_entry_continue_reverse(buffer, &iio_dev_opaque->buffer_list,
1132                                              buffer_list)
1133                 iio_buffer_disable(buffer, indio_dev);
1134 err_run_postdisable:
1135         if (indio_dev->setup_ops->postdisable)
1136                 indio_dev->setup_ops->postdisable(indio_dev);
1137 err_undo_config:
1138         iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;
1139         indio_dev->active_scan_mask = NULL;
1140
1141         return ret;
1142 }
1143
1144 static int iio_disable_buffers(struct iio_dev *indio_dev)
1145 {
1146         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1147         struct iio_buffer *buffer;
1148         int ret = 0;
1149         int ret2;
1150
1151         /* Wind down existing buffers - iff there are any */
1152         if (list_empty(&iio_dev_opaque->buffer_list))
1153                 return 0;
1154
1155         /*
1156          * If things go wrong at some step in disable we still need to continue
1157          * to perform the other steps, otherwise we leave the device in a
1158          * inconsistent state. We return the error code for the first error we
1159          * encountered.
1160          */
1161
1162         if (indio_dev->setup_ops->predisable) {
1163                 ret2 = indio_dev->setup_ops->predisable(indio_dev);
1164                 if (ret2 && !ret)
1165                         ret = ret2;
1166         }
1167
1168         if (iio_dev_opaque->currentmode == INDIO_BUFFER_TRIGGERED) {
1169                 iio_trigger_detach_poll_func(indio_dev->trig,
1170                                              indio_dev->pollfunc);
1171         }
1172
1173         list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
1174                 ret2 = iio_buffer_disable(buffer, indio_dev);
1175                 if (ret2 && !ret)
1176                         ret = ret2;
1177         }
1178
1179         if (indio_dev->setup_ops->postdisable) {
1180                 ret2 = indio_dev->setup_ops->postdisable(indio_dev);
1181                 if (ret2 && !ret)
1182                         ret = ret2;
1183         }
1184
1185         iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
1186         indio_dev->active_scan_mask = NULL;
1187         iio_dev_opaque->currentmode = INDIO_DIRECT_MODE;
1188
1189         return ret;
1190 }
1191
1192 static int __iio_update_buffers(struct iio_dev *indio_dev,
1193                        struct iio_buffer *insert_buffer,
1194                        struct iio_buffer *remove_buffer)
1195 {
1196         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1197         struct iio_device_config new_config;
1198         int ret;
1199
1200         ret = iio_verify_update(indio_dev, insert_buffer, remove_buffer,
1201                 &new_config);
1202         if (ret)
1203                 return ret;
1204
1205         if (insert_buffer) {
1206                 ret = iio_buffer_request_update(indio_dev, insert_buffer);
1207                 if (ret)
1208                         goto err_free_config;
1209         }
1210
1211         ret = iio_disable_buffers(indio_dev);
1212         if (ret)
1213                 goto err_deactivate_all;
1214
1215         if (remove_buffer)
1216                 iio_buffer_deactivate(remove_buffer);
1217         if (insert_buffer)
1218                 iio_buffer_activate(indio_dev, insert_buffer);
1219
1220         /* If no buffers in list, we are done */
1221         if (list_empty(&iio_dev_opaque->buffer_list))
1222                 return 0;
1223
1224         ret = iio_enable_buffers(indio_dev, &new_config);
1225         if (ret)
1226                 goto err_deactivate_all;
1227
1228         return 0;
1229
1230 err_deactivate_all:
1231         /*
1232          * We've already verified that the config is valid earlier. If things go
1233          * wrong in either enable or disable the most likely reason is an IO
1234          * error from the device. In this case there is no good recovery
1235          * strategy. Just make sure to disable everything and leave the device
1236          * in a sane state.  With a bit of luck the device might come back to
1237          * life again later and userspace can try again.
1238          */
1239         iio_buffer_deactivate_all(indio_dev);
1240
1241 err_free_config:
1242         iio_free_scan_mask(indio_dev, new_config.scan_mask);
1243         return ret;
1244 }
1245
1246 int iio_update_buffers(struct iio_dev *indio_dev,
1247                        struct iio_buffer *insert_buffer,
1248                        struct iio_buffer *remove_buffer)
1249 {
1250         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1251         int ret;
1252
1253         if (insert_buffer == remove_buffer)
1254                 return 0;
1255
1256         if (insert_buffer &&
1257             (insert_buffer->direction == IIO_BUFFER_DIRECTION_OUT))
1258                 return -EINVAL;
1259
1260         mutex_lock(&iio_dev_opaque->info_exist_lock);
1261         mutex_lock(&indio_dev->mlock);
1262
1263         if (insert_buffer && iio_buffer_is_active(insert_buffer))
1264                 insert_buffer = NULL;
1265
1266         if (remove_buffer && !iio_buffer_is_active(remove_buffer))
1267                 remove_buffer = NULL;
1268
1269         if (!insert_buffer && !remove_buffer) {
1270                 ret = 0;
1271                 goto out_unlock;
1272         }
1273
1274         if (indio_dev->info == NULL) {
1275                 ret = -ENODEV;
1276                 goto out_unlock;
1277         }
1278
1279         ret = __iio_update_buffers(indio_dev, insert_buffer, remove_buffer);
1280
1281 out_unlock:
1282         mutex_unlock(&indio_dev->mlock);
1283         mutex_unlock(&iio_dev_opaque->info_exist_lock);
1284
1285         return ret;
1286 }
1287 EXPORT_SYMBOL_GPL(iio_update_buffers);
1288
1289 void iio_disable_all_buffers(struct iio_dev *indio_dev)
1290 {
1291         iio_disable_buffers(indio_dev);
1292         iio_buffer_deactivate_all(indio_dev);
1293 }
1294
1295 static ssize_t iio_buffer_store_enable(struct device *dev,
1296                                        struct device_attribute *attr,
1297                                        const char *buf,
1298                                        size_t len)
1299 {
1300         int ret;
1301         bool requested_state;
1302         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
1303         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
1304         bool inlist;
1305
1306         ret = kstrtobool(buf, &requested_state);
1307         if (ret < 0)
1308                 return ret;
1309
1310         mutex_lock(&indio_dev->mlock);
1311
1312         /* Find out if it is in the list */
1313         inlist = iio_buffer_is_active(buffer);
1314         /* Already in desired state */
1315         if (inlist == requested_state)
1316                 goto done;
1317
1318         if (requested_state)
1319                 ret = __iio_update_buffers(indio_dev, buffer, NULL);
1320         else
1321                 ret = __iio_update_buffers(indio_dev, NULL, buffer);
1322
1323 done:
1324         mutex_unlock(&indio_dev->mlock);
1325         return (ret < 0) ? ret : len;
1326 }
1327
1328 static ssize_t iio_buffer_show_watermark(struct device *dev,
1329                                          struct device_attribute *attr,
1330                                          char *buf)
1331 {
1332         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
1333
1334         return sysfs_emit(buf, "%u\n", buffer->watermark);
1335 }
1336
1337 static ssize_t iio_buffer_store_watermark(struct device *dev,
1338                                           struct device_attribute *attr,
1339                                           const char *buf,
1340                                           size_t len)
1341 {
1342         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
1343         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
1344         unsigned int val;
1345         int ret;
1346
1347         ret = kstrtouint(buf, 10, &val);
1348         if (ret)
1349                 return ret;
1350         if (!val)
1351                 return -EINVAL;
1352
1353         mutex_lock(&indio_dev->mlock);
1354
1355         if (val > buffer->length) {
1356                 ret = -EINVAL;
1357                 goto out;
1358         }
1359
1360         if (iio_buffer_is_active(buffer)) {
1361                 ret = -EBUSY;
1362                 goto out;
1363         }
1364
1365         buffer->watermark = val;
1366 out:
1367         mutex_unlock(&indio_dev->mlock);
1368
1369         return ret ? ret : len;
1370 }
1371
1372 static ssize_t iio_dma_show_data_available(struct device *dev,
1373                                                 struct device_attribute *attr,
1374                                                 char *buf)
1375 {
1376         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
1377
1378         return sysfs_emit(buf, "%zu\n", iio_buffer_data_available(buffer));
1379 }
1380
1381 static ssize_t direction_show(struct device *dev,
1382                               struct device_attribute *attr,
1383                               char *buf)
1384 {
1385         struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
1386
1387         switch (buffer->direction) {
1388         case IIO_BUFFER_DIRECTION_IN:
1389                 return sysfs_emit(buf, "in\n");
1390         case IIO_BUFFER_DIRECTION_OUT:
1391                 return sysfs_emit(buf, "out\n");
1392         default:
1393                 return -EINVAL;
1394         }
1395 }
1396
1397 static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
1398                    iio_buffer_write_length);
1399 static struct device_attribute dev_attr_length_ro = __ATTR(length,
1400         S_IRUGO, iio_buffer_read_length, NULL);
1401 static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
1402                    iio_buffer_show_enable, iio_buffer_store_enable);
1403 static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
1404                    iio_buffer_show_watermark, iio_buffer_store_watermark);
1405 static struct device_attribute dev_attr_watermark_ro = __ATTR(watermark,
1406         S_IRUGO, iio_buffer_show_watermark, NULL);
1407 static DEVICE_ATTR(data_available, S_IRUGO,
1408                 iio_dma_show_data_available, NULL);
1409 static DEVICE_ATTR_RO(direction);
1410
1411 /*
1412  * When adding new attributes here, put the at the end, at least until
1413  * the code that handles the length/length_ro & watermark/watermark_ro
1414  * assignments gets cleaned up. Otherwise these can create some weird
1415  * duplicate attributes errors under some setups.
1416  */
1417 static struct attribute *iio_buffer_attrs[] = {
1418         &dev_attr_length.attr,
1419         &dev_attr_enable.attr,
1420         &dev_attr_watermark.attr,
1421         &dev_attr_data_available.attr,
1422         &dev_attr_direction.attr,
1423 };
1424
1425 #define to_dev_attr(_attr) container_of(_attr, struct device_attribute, attr)
1426
1427 static struct attribute *iio_buffer_wrap_attr(struct iio_buffer *buffer,
1428                                               struct attribute *attr)
1429 {
1430         struct device_attribute *dattr = to_dev_attr(attr);
1431         struct iio_dev_attr *iio_attr;
1432
1433         iio_attr = kzalloc(sizeof(*iio_attr), GFP_KERNEL);
1434         if (!iio_attr)
1435                 return NULL;
1436
1437         iio_attr->buffer = buffer;
1438         memcpy(&iio_attr->dev_attr, dattr, sizeof(iio_attr->dev_attr));
1439         iio_attr->dev_attr.attr.name = kstrdup_const(attr->name, GFP_KERNEL);
1440         if (!iio_attr->dev_attr.attr.name) {
1441                 kfree(iio_attr);
1442                 return NULL;
1443         }
1444
1445         sysfs_attr_init(&iio_attr->dev_attr.attr);
1446
1447         list_add(&iio_attr->l, &buffer->buffer_attr_list);
1448
1449         return &iio_attr->dev_attr.attr;
1450 }
1451
1452 static int iio_buffer_register_legacy_sysfs_groups(struct iio_dev *indio_dev,
1453                                                    struct attribute **buffer_attrs,
1454                                                    int buffer_attrcount,
1455                                                    int scan_el_attrcount)
1456 {
1457         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1458         struct attribute_group *group;
1459         struct attribute **attrs;
1460         int ret;
1461
1462         attrs = kcalloc(buffer_attrcount + 1, sizeof(*attrs), GFP_KERNEL);
1463         if (!attrs)
1464                 return -ENOMEM;
1465
1466         memcpy(attrs, buffer_attrs, buffer_attrcount * sizeof(*attrs));
1467
1468         group = &iio_dev_opaque->legacy_buffer_group;
1469         group->attrs = attrs;
1470         group->name = "buffer";
1471
1472         ret = iio_device_register_sysfs_group(indio_dev, group);
1473         if (ret)
1474                 goto error_free_buffer_attrs;
1475
1476         attrs = kcalloc(scan_el_attrcount + 1, sizeof(*attrs), GFP_KERNEL);
1477         if (!attrs) {
1478                 ret = -ENOMEM;
1479                 goto error_free_buffer_attrs;
1480         }
1481
1482         memcpy(attrs, &buffer_attrs[buffer_attrcount],
1483                scan_el_attrcount * sizeof(*attrs));
1484
1485         group = &iio_dev_opaque->legacy_scan_el_group;
1486         group->attrs = attrs;
1487         group->name = "scan_elements";
1488
1489         ret = iio_device_register_sysfs_group(indio_dev, group);
1490         if (ret)
1491                 goto error_free_scan_el_attrs;
1492
1493         return 0;
1494
1495 error_free_scan_el_attrs:
1496         kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
1497 error_free_buffer_attrs:
1498         kfree(iio_dev_opaque->legacy_buffer_group.attrs);
1499
1500         return ret;
1501 }
1502
1503 static void iio_buffer_unregister_legacy_sysfs_groups(struct iio_dev *indio_dev)
1504 {
1505         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1506
1507         kfree(iio_dev_opaque->legacy_buffer_group.attrs);
1508         kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
1509 }
1510
1511 static int iio_buffer_chrdev_release(struct inode *inode, struct file *filep)
1512 {
1513         struct iio_dev_buffer_pair *ib = filep->private_data;
1514         struct iio_dev *indio_dev = ib->indio_dev;
1515         struct iio_buffer *buffer = ib->buffer;
1516
1517         wake_up(&buffer->pollq);
1518
1519         kfree(ib);
1520         clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
1521         iio_device_put(indio_dev);
1522
1523         return 0;
1524 }
1525
1526 static const struct file_operations iio_buffer_chrdev_fileops = {
1527         .owner = THIS_MODULE,
1528         .llseek = noop_llseek,
1529         .read = iio_buffer_read,
1530         .write = iio_buffer_write,
1531         .poll = iio_buffer_poll,
1532         .release = iio_buffer_chrdev_release,
1533 };
1534
1535 static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg)
1536 {
1537         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1538         int __user *ival = (int __user *)arg;
1539         struct iio_dev_buffer_pair *ib;
1540         struct iio_buffer *buffer;
1541         int fd, idx, ret;
1542
1543         if (copy_from_user(&idx, ival, sizeof(idx)))
1544                 return -EFAULT;
1545
1546         if (idx >= iio_dev_opaque->attached_buffers_cnt)
1547                 return -ENODEV;
1548
1549         iio_device_get(indio_dev);
1550
1551         buffer = iio_dev_opaque->attached_buffers[idx];
1552
1553         if (test_and_set_bit(IIO_BUSY_BIT_POS, &buffer->flags)) {
1554                 ret = -EBUSY;
1555                 goto error_iio_dev_put;
1556         }
1557
1558         ib = kzalloc(sizeof(*ib), GFP_KERNEL);
1559         if (!ib) {
1560                 ret = -ENOMEM;
1561                 goto error_clear_busy_bit;
1562         }
1563
1564         ib->indio_dev = indio_dev;
1565         ib->buffer = buffer;
1566
1567         fd = anon_inode_getfd("iio:buffer", &iio_buffer_chrdev_fileops,
1568                               ib, O_RDWR | O_CLOEXEC);
1569         if (fd < 0) {
1570                 ret = fd;
1571                 goto error_free_ib;
1572         }
1573
1574         if (copy_to_user(ival, &fd, sizeof(fd))) {
1575                 /*
1576                  * "Leak" the fd, as there's not much we can do about this
1577                  * anyway. 'fd' might have been closed already, as
1578                  * anon_inode_getfd() called fd_install() on it, which made
1579                  * it reachable by userland.
1580                  *
1581                  * Instead of allowing a malicious user to play tricks with
1582                  * us, rely on the process exit path to do any necessary
1583                  * cleanup, as in releasing the file, if still needed.
1584                  */
1585                 return -EFAULT;
1586         }
1587
1588         return 0;
1589
1590 error_free_ib:
1591         kfree(ib);
1592 error_clear_busy_bit:
1593         clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
1594 error_iio_dev_put:
1595         iio_device_put(indio_dev);
1596         return ret;
1597 }
1598
1599 static long iio_device_buffer_ioctl(struct iio_dev *indio_dev, struct file *filp,
1600                                     unsigned int cmd, unsigned long arg)
1601 {
1602         switch (cmd) {
1603         case IIO_BUFFER_GET_FD_IOCTL:
1604                 return iio_device_buffer_getfd(indio_dev, arg);
1605         default:
1606                 return IIO_IOCTL_UNHANDLED;
1607         }
1608 }
1609
1610 static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
1611                                              struct iio_dev *indio_dev,
1612                                              int index)
1613 {
1614         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1615         struct iio_dev_attr *p;
1616         struct attribute **attr;
1617         int ret, i, attrn, scan_el_attrcount, buffer_attrcount;
1618         const struct iio_chan_spec *channels;
1619
1620         buffer_attrcount = 0;
1621         if (buffer->attrs) {
1622                 while (buffer->attrs[buffer_attrcount] != NULL)
1623                         buffer_attrcount++;
1624         }
1625
1626         scan_el_attrcount = 0;
1627         INIT_LIST_HEAD(&buffer->buffer_attr_list);
1628         channels = indio_dev->channels;
1629         if (channels) {
1630                 /* new magic */
1631                 for (i = 0; i < indio_dev->num_channels; i++) {
1632                         if (channels[i].scan_index < 0)
1633                                 continue;
1634
1635                         /* Verify that sample bits fit into storage */
1636                         if (channels[i].scan_type.storagebits <
1637                             channels[i].scan_type.realbits +
1638                             channels[i].scan_type.shift) {
1639                                 dev_err(&indio_dev->dev,
1640                                         "Channel %d storagebits (%d) < shifted realbits (%d + %d)\n",
1641                                         i, channels[i].scan_type.storagebits,
1642                                         channels[i].scan_type.realbits,
1643                                         channels[i].scan_type.shift);
1644                                 ret = -EINVAL;
1645                                 goto error_cleanup_dynamic;
1646                         }
1647
1648                         ret = iio_buffer_add_channel_sysfs(indio_dev, buffer,
1649                                                          &channels[i]);
1650                         if (ret < 0)
1651                                 goto error_cleanup_dynamic;
1652                         scan_el_attrcount += ret;
1653                         if (channels[i].type == IIO_TIMESTAMP)
1654                                 iio_dev_opaque->scan_index_timestamp =
1655                                         channels[i].scan_index;
1656                 }
1657                 if (indio_dev->masklength && buffer->scan_mask == NULL) {
1658                         buffer->scan_mask = bitmap_zalloc(indio_dev->masklength,
1659                                                           GFP_KERNEL);
1660                         if (buffer->scan_mask == NULL) {
1661                                 ret = -ENOMEM;
1662                                 goto error_cleanup_dynamic;
1663                         }
1664                 }
1665         }
1666
1667         attrn = buffer_attrcount + scan_el_attrcount + ARRAY_SIZE(iio_buffer_attrs);
1668         attr = kcalloc(attrn + 1, sizeof(*attr), GFP_KERNEL);
1669         if (!attr) {
1670                 ret = -ENOMEM;
1671                 goto error_free_scan_mask;
1672         }
1673
1674         memcpy(attr, iio_buffer_attrs, sizeof(iio_buffer_attrs));
1675         if (!buffer->access->set_length)
1676                 attr[0] = &dev_attr_length_ro.attr;
1677
1678         if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
1679                 attr[2] = &dev_attr_watermark_ro.attr;
1680
1681         if (buffer->attrs)
1682                 memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
1683                        sizeof(struct attribute *) * buffer_attrcount);
1684
1685         buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);
1686         buffer->buffer_group.attrs = attr;
1687
1688         for (i = 0; i < buffer_attrcount; i++) {
1689                 struct attribute *wrapped;
1690
1691                 wrapped = iio_buffer_wrap_attr(buffer, attr[i]);
1692                 if (!wrapped) {
1693                         ret = -ENOMEM;
1694                         goto error_free_buffer_attrs;
1695                 }
1696                 attr[i] = wrapped;
1697         }
1698
1699         attrn = 0;
1700         list_for_each_entry(p, &buffer->buffer_attr_list, l)
1701                 attr[attrn++] = &p->dev_attr.attr;
1702
1703         buffer->buffer_group.name = kasprintf(GFP_KERNEL, "buffer%d", index);
1704         if (!buffer->buffer_group.name) {
1705                 ret = -ENOMEM;
1706                 goto error_free_buffer_attrs;
1707         }
1708
1709         ret = iio_device_register_sysfs_group(indio_dev, &buffer->buffer_group);
1710         if (ret)
1711                 goto error_free_buffer_attr_group_name;
1712
1713         /* we only need to register the legacy groups for the first buffer */
1714         if (index > 0)
1715                 return 0;
1716
1717         ret = iio_buffer_register_legacy_sysfs_groups(indio_dev, attr,
1718                                                       buffer_attrcount,
1719                                                       scan_el_attrcount);
1720         if (ret)
1721                 goto error_free_buffer_attr_group_name;
1722
1723         return 0;
1724
1725 error_free_buffer_attr_group_name:
1726         kfree(buffer->buffer_group.name);
1727 error_free_buffer_attrs:
1728         kfree(buffer->buffer_group.attrs);
1729 error_free_scan_mask:
1730         bitmap_free(buffer->scan_mask);
1731 error_cleanup_dynamic:
1732         iio_free_chan_devattr_list(&buffer->buffer_attr_list);
1733
1734         return ret;
1735 }
1736
1737 static void __iio_buffer_free_sysfs_and_mask(struct iio_buffer *buffer,
1738                                              struct iio_dev *indio_dev,
1739                                              int index)
1740 {
1741         if (index == 0)
1742                 iio_buffer_unregister_legacy_sysfs_groups(indio_dev);
1743         bitmap_free(buffer->scan_mask);
1744         kfree(buffer->buffer_group.name);
1745         kfree(buffer->buffer_group.attrs);
1746         iio_free_chan_devattr_list(&buffer->buffer_attr_list);
1747 }
1748
1749 int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
1750 {
1751         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1752         const struct iio_chan_spec *channels;
1753         struct iio_buffer *buffer;
1754         int ret, i, idx;
1755         size_t sz;
1756
1757         channels = indio_dev->channels;
1758         if (channels) {
1759                 int ml = indio_dev->masklength;
1760
1761                 for (i = 0; i < indio_dev->num_channels; i++)
1762                         ml = max(ml, channels[i].scan_index + 1);
1763                 indio_dev->masklength = ml;
1764         }
1765
1766         if (!iio_dev_opaque->attached_buffers_cnt)
1767                 return 0;
1768
1769         for (idx = 0; idx < iio_dev_opaque->attached_buffers_cnt; idx++) {
1770                 buffer = iio_dev_opaque->attached_buffers[idx];
1771                 ret = __iio_buffer_alloc_sysfs_and_mask(buffer, indio_dev, idx);
1772                 if (ret)
1773                         goto error_unwind_sysfs_and_mask;
1774         }
1775
1776         sz = sizeof(*(iio_dev_opaque->buffer_ioctl_handler));
1777         iio_dev_opaque->buffer_ioctl_handler = kzalloc(sz, GFP_KERNEL);
1778         if (!iio_dev_opaque->buffer_ioctl_handler) {
1779                 ret = -ENOMEM;
1780                 goto error_unwind_sysfs_and_mask;
1781         }
1782
1783         iio_dev_opaque->buffer_ioctl_handler->ioctl = iio_device_buffer_ioctl;
1784         iio_device_ioctl_handler_register(indio_dev,
1785                                           iio_dev_opaque->buffer_ioctl_handler);
1786
1787         return 0;
1788
1789 error_unwind_sysfs_and_mask:
1790         while (idx--) {
1791                 buffer = iio_dev_opaque->attached_buffers[idx];
1792                 __iio_buffer_free_sysfs_and_mask(buffer, indio_dev, idx);
1793         }
1794         return ret;
1795 }
1796
1797 void iio_buffers_free_sysfs_and_mask(struct iio_dev *indio_dev)
1798 {
1799         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1800         struct iio_buffer *buffer;
1801         int i;
1802
1803         if (!iio_dev_opaque->attached_buffers_cnt)
1804                 return;
1805
1806         iio_device_ioctl_handler_unregister(iio_dev_opaque->buffer_ioctl_handler);
1807         kfree(iio_dev_opaque->buffer_ioctl_handler);
1808
1809         for (i = iio_dev_opaque->attached_buffers_cnt - 1; i >= 0; i--) {
1810                 buffer = iio_dev_opaque->attached_buffers[i];
1811                 __iio_buffer_free_sysfs_and_mask(buffer, indio_dev, i);
1812         }
1813 }
1814
1815 /**
1816  * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
1817  * @indio_dev: the iio device
1818  * @mask: scan mask to be checked
1819  *
1820  * Return true if exactly one bit is set in the scan mask, false otherwise. It
1821  * can be used for devices where only one channel can be active for sampling at
1822  * a time.
1823  */
1824 bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
1825         const unsigned long *mask)
1826 {
1827         return bitmap_weight(mask, indio_dev->masklength) == 1;
1828 }
1829 EXPORT_SYMBOL_GPL(iio_validate_scan_mask_onehot);
1830
1831 static const void *iio_demux(struct iio_buffer *buffer,
1832                                  const void *datain)
1833 {
1834         struct iio_demux_table *t;
1835
1836         if (list_empty(&buffer->demux_list))
1837                 return datain;
1838         list_for_each_entry(t, &buffer->demux_list, l)
1839                 memcpy(buffer->demux_bounce + t->to,
1840                        datain + t->from, t->length);
1841
1842         return buffer->demux_bounce;
1843 }
1844
1845 static int iio_push_to_buffer(struct iio_buffer *buffer, const void *data)
1846 {
1847         const void *dataout = iio_demux(buffer, data);
1848         int ret;
1849
1850         ret = buffer->access->store_to(buffer, dataout);
1851         if (ret)
1852                 return ret;
1853
1854         /*
1855          * We can't just test for watermark to decide if we wake the poll queue
1856          * because read may request less samples than the watermark.
1857          */
1858         wake_up_interruptible_poll(&buffer->pollq, EPOLLIN | EPOLLRDNORM);
1859         return 0;
1860 }
1861
1862 /**
1863  * iio_push_to_buffers() - push to a registered buffer.
1864  * @indio_dev:          iio_dev structure for device.
1865  * @data:               Full scan.
1866  */
1867 int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data)
1868 {
1869         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1870         int ret;
1871         struct iio_buffer *buf;
1872
1873         list_for_each_entry(buf, &iio_dev_opaque->buffer_list, buffer_list) {
1874                 ret = iio_push_to_buffer(buf, data);
1875                 if (ret < 0)
1876                         return ret;
1877         }
1878
1879         return 0;
1880 }
1881 EXPORT_SYMBOL_GPL(iio_push_to_buffers);
1882
1883 /**
1884  * iio_push_to_buffers_with_ts_unaligned() - push to registered buffer,
1885  *    no alignment or space requirements.
1886  * @indio_dev:          iio_dev structure for device.
1887  * @data:               channel data excluding the timestamp.
1888  * @data_sz:            size of data.
1889  * @timestamp:          timestamp for the sample data.
1890  *
1891  * This special variant of iio_push_to_buffers_with_timestamp() does
1892  * not require space for the timestamp, or 8 byte alignment of data.
1893  * It does however require an allocation on first call and additional
1894  * copies on all calls, so should be avoided if possible.
1895  */
1896 int iio_push_to_buffers_with_ts_unaligned(struct iio_dev *indio_dev,
1897                                           const void *data,
1898                                           size_t data_sz,
1899                                           int64_t timestamp)
1900 {
1901         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1902
1903         /*
1904          * Conservative estimate - we can always safely copy the minimum
1905          * of either the data provided or the length of the destination buffer.
1906          * This relaxed limit allows the calling drivers to be lax about
1907          * tracking the size of the data they are pushing, at the cost of
1908          * unnecessary copying of padding.
1909          */
1910         data_sz = min_t(size_t, indio_dev->scan_bytes, data_sz);
1911         if (iio_dev_opaque->bounce_buffer_size !=  indio_dev->scan_bytes) {
1912                 void *bb;
1913
1914                 bb = devm_krealloc(&indio_dev->dev,
1915                                    iio_dev_opaque->bounce_buffer,
1916                                    indio_dev->scan_bytes, GFP_KERNEL);
1917                 if (!bb)
1918                         return -ENOMEM;
1919                 iio_dev_opaque->bounce_buffer = bb;
1920                 iio_dev_opaque->bounce_buffer_size = indio_dev->scan_bytes;
1921         }
1922         memcpy(iio_dev_opaque->bounce_buffer, data, data_sz);
1923         return iio_push_to_buffers_with_timestamp(indio_dev,
1924                                                   iio_dev_opaque->bounce_buffer,
1925                                                   timestamp);
1926 }
1927 EXPORT_SYMBOL_GPL(iio_push_to_buffers_with_ts_unaligned);
1928
1929 /**
1930  * iio_buffer_release() - Free a buffer's resources
1931  * @ref: Pointer to the kref embedded in the iio_buffer struct
1932  *
1933  * This function is called when the last reference to the buffer has been
1934  * dropped. It will typically free all resources allocated by the buffer. Do not
1935  * call this function manually, always use iio_buffer_put() when done using a
1936  * buffer.
1937  */
1938 static void iio_buffer_release(struct kref *ref)
1939 {
1940         struct iio_buffer *buffer = container_of(ref, struct iio_buffer, ref);
1941
1942         buffer->access->release(buffer);
1943 }
1944
1945 /**
1946  * iio_buffer_get() - Grab a reference to the buffer
1947  * @buffer: The buffer to grab a reference for, may be NULL
1948  *
1949  * Returns the pointer to the buffer that was passed into the function.
1950  */
1951 struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer)
1952 {
1953         if (buffer)
1954                 kref_get(&buffer->ref);
1955
1956         return buffer;
1957 }
1958 EXPORT_SYMBOL_GPL(iio_buffer_get);
1959
1960 /**
1961  * iio_buffer_put() - Release the reference to the buffer
1962  * @buffer: The buffer to release the reference for, may be NULL
1963  */
1964 void iio_buffer_put(struct iio_buffer *buffer)
1965 {
1966         if (buffer)
1967                 kref_put(&buffer->ref, iio_buffer_release);
1968 }
1969 EXPORT_SYMBOL_GPL(iio_buffer_put);
1970
1971 /**
1972  * iio_device_attach_buffer - Attach a buffer to a IIO device
1973  * @indio_dev: The device the buffer should be attached to
1974  * @buffer: The buffer to attach to the device
1975  *
1976  * Return 0 if successful, negative if error.
1977  *
1978  * This function attaches a buffer to a IIO device. The buffer stays attached to
1979  * the device until the device is freed. For legacy reasons, the first attached
1980  * buffer will also be assigned to 'indio_dev->buffer'.
1981  * The array allocated here, will be free'd via the iio_device_detach_buffers()
1982  * call which is handled by the iio_device_free().
1983  */
1984 int iio_device_attach_buffer(struct iio_dev *indio_dev,
1985                              struct iio_buffer *buffer)
1986 {
1987         struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
1988         struct iio_buffer **new, **old = iio_dev_opaque->attached_buffers;
1989         unsigned int cnt = iio_dev_opaque->attached_buffers_cnt;
1990
1991         cnt++;
1992
1993         new = krealloc(old, sizeof(*new) * cnt, GFP_KERNEL);
1994         if (!new)
1995                 return -ENOMEM;
1996         iio_dev_opaque->attached_buffers = new;
1997
1998         buffer = iio_buffer_get(buffer);
1999
2000         /* first buffer is legacy; attach it to the IIO device directly */
2001         if (!indio_dev->buffer)
2002                 indio_dev->buffer = buffer;
2003
2004         iio_dev_opaque->attached_buffers[cnt - 1] = buffer;
2005         iio_dev_opaque->attached_buffers_cnt = cnt;
2006
2007         return 0;
2008 }
2009 EXPORT_SYMBOL_GPL(iio_device_attach_buffer);