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
  24 #include <linux/iio/iio.h>
  25 #include "iio_core.h"
  26 #include <linux/iio/sysfs.h>
  27 #include <linux/iio/buffer.h>
  28
  29 static const char * const iio_endian_prefix[] = {
  30         [IIO_BE] = "be",
  31         [IIO_LE] = "le",
  32 };
  33
  34 /**
  35  * iio_buffer_read_first_n_outer() - chrdev read for buffer access
  36  *
  37  * This function relies on all buffer implementations having an
  38  * iio_buffer as their first element.
  39  **/
  40 ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
  41                                       size_t n, loff_t *f_ps)
  42 {
  43         struct iio_dev *indio_dev = filp->private_data;
  44         struct iio_buffer *rb = indio_dev->buffer;
  45
  46         if (!rb || !rb->access->read_first_n)
  47                 return -EINVAL;
  48         return rb->access->read_first_n(rb, n, buf);
  49 }
  50
  51 /**
  52  * iio_buffer_poll() - poll the buffer to find out if it has data
  53  */
  54 unsigned int iio_buffer_poll(struct file *filp,
  55                              struct poll_table_struct *wait)
  56 {
  57         struct iio_dev *indio_dev = filp->private_data;
  58         struct iio_buffer *rb = indio_dev->buffer;
  59
  60         poll_wait(filp, &rb->pollq, wait);
  61         if (rb->stufftoread)
  62                 return POLLIN | POLLRDNORM;
  63         /* need a way of knowing if there may be enough data... */
  64         return 0;
  65 }
  66
  67 void iio_buffer_init(struct iio_buffer *buffer)
  68 {
  69         INIT_LIST_HEAD(&buffer->demux_list);
  70         init_waitqueue_head(&buffer->pollq);
  71 }
  72 EXPORT_SYMBOL(iio_buffer_init);
  73
  74 static ssize_t iio_show_scan_index(struct device *dev,
  75                                    struct device_attribute *attr,
  76                                    char *buf)
  77 {
  78         return sprintf(buf, "%u\n", to_iio_dev_attr(attr)->c->scan_index);
  79 }
  80
  81 static ssize_t iio_show_fixed_type(struct device *dev,
  82                                    struct device_attribute *attr,
  83                                    char *buf)
  84 {
  85         struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
  86         u8 type = this_attr->c->scan_type.endianness;
  87
  88         if (type == IIO_CPU) {
  89 #ifdef __LITTLE_ENDIAN
  90                 type = IIO_LE;
  91 #else
  92                 type = IIO_BE;
  93 #endif
  94         }
  95         return sprintf(buf, "%s:%c%d/%d>>%u\n",
  96                        iio_endian_prefix[type],
  97                        this_attr->c->scan_type.sign,
  98                        this_attr->c->scan_type.realbits,
  99                        this_attr->c->scan_type.storagebits,
 100                        this_attr->c->scan_type.shift);
 101 }
 102
 103 static ssize_t iio_scan_el_show(struct device *dev,
 104                                 struct device_attribute *attr,
 105                                 char *buf)
 106 {
 107         int ret;
 108         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 109
 110         ret = test_bit(to_iio_dev_attr(attr)->address,
 111                        indio_dev->buffer->scan_mask);
 112
 113         return sprintf(buf, "%d\n", ret);
 114 }
 115
 116 static int iio_scan_mask_clear(struct iio_buffer *buffer, int bit)
 117 {
 118         clear_bit(bit, buffer->scan_mask);
 119         return 0;
 120 }
 121
 122 static ssize_t iio_scan_el_store(struct device *dev,
 123                                  struct device_attribute *attr,
 124                                  const char *buf,
 125                                  size_t len)
 126 {
 127         int ret;
 128         bool state;
 129         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 130         struct iio_buffer *buffer = indio_dev->buffer;
 131         struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
 132
 133         ret = strtobool(buf, &state);
 134         if (ret < 0)
 135                 return ret;
 136         mutex_lock(&indio_dev->mlock);
 137         if (iio_buffer_enabled(indio_dev)) {
 138                 ret = -EBUSY;
 139                 goto error_ret;
 140         }
 141         ret = iio_scan_mask_query(indio_dev, buffer, this_attr->address);
 142         if (ret < 0)
 143                 goto error_ret;
 144         if (!state && ret) {
 145                 ret = iio_scan_mask_clear(buffer, this_attr->address);
 146                 if (ret)
 147                         goto error_ret;
 148         } else if (state && !ret) {
 149                 ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
 150                 if (ret)
 151                         goto error_ret;
 152         }
 153
 154 error_ret:
 155         mutex_unlock(&indio_dev->mlock);
 156
 157         return ret < 0 ? ret : len;
 158
 159 }
 160
 161 static ssize_t iio_scan_el_ts_show(struct device *dev,
 162                                    struct device_attribute *attr,
 163                                    char *buf)
 164 {
 165         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 166         return sprintf(buf, "%d\n", indio_dev->buffer->scan_timestamp);
 167 }
 168
 169 static ssize_t iio_scan_el_ts_store(struct device *dev,
 170                                     struct device_attribute *attr,
 171                                     const char *buf,
 172                                     size_t len)
 173 {
 174         int ret;
 175         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 176         bool state;
 177
 178         ret = strtobool(buf, &state);
 179         if (ret < 0)
 180                 return ret;
 181
 182         mutex_lock(&indio_dev->mlock);
 183         if (iio_buffer_enabled(indio_dev)) {
 184                 ret = -EBUSY;
 185                 goto error_ret;
 186         }
 187         indio_dev->buffer->scan_timestamp = state;
 188         indio_dev->scan_timestamp = state;
 189 error_ret:
 190         mutex_unlock(&indio_dev->mlock);
 191
 192         return ret ? ret : len;
 193 }
 194
 195 static int iio_buffer_add_channel_sysfs(struct iio_dev *indio_dev,
 196                                         const struct iio_chan_spec *chan)
 197 {
 198         int ret, attrcount = 0;
 199         struct iio_buffer *buffer = indio_dev->buffer;
 200
 201         ret = __iio_add_chan_devattr("index",
 202                                      chan,
 203                                      &iio_show_scan_index,
 204                                      NULL,
 205                                      0,
 206                                      0,
 207                                      &indio_dev->dev,
 208                                      &buffer->scan_el_dev_attr_list);
 209         if (ret)
 210                 goto error_ret;
 211         attrcount++;
 212         ret = __iio_add_chan_devattr("type",
 213                                      chan,
 214                                      &iio_show_fixed_type,
 215                                      NULL,
 216                                      0,
 217                                      0,
 218                                      &indio_dev->dev,
 219                                      &buffer->scan_el_dev_attr_list);
 220         if (ret)
 221                 goto error_ret;
 222         attrcount++;
 223         if (chan->type != IIO_TIMESTAMP)
 224                 ret = __iio_add_chan_devattr("en",
 225                                              chan,
 226                                              &iio_scan_el_show,
 227                                              &iio_scan_el_store,
 228                                              chan->scan_index,
 229                                              0,
 230                                              &indio_dev->dev,
 231                                              &buffer->scan_el_dev_attr_list);
 232         else
 233                 ret = __iio_add_chan_devattr("en",
 234                                              chan,
 235                                              &iio_scan_el_ts_show,
 236                                              &iio_scan_el_ts_store,
 237                                              chan->scan_index,
 238                                              0,
 239                                              &indio_dev->dev,
 240                                              &buffer->scan_el_dev_attr_list);
 241         attrcount++;
 242         ret = attrcount;
 243 error_ret:
 244         return ret;
 245 }
 246
 247 static void iio_buffer_remove_and_free_scan_dev_attr(struct iio_dev *indio_dev,
 248                                                      struct iio_dev_attr *p)
 249 {
 250         kfree(p->dev_attr.attr.name);
 251         kfree(p);
 252 }
 253
 254 static void __iio_buffer_attr_cleanup(struct iio_dev *indio_dev)
 255 {
 256         struct iio_dev_attr *p, *n;
 257         struct iio_buffer *buffer = indio_dev->buffer;
 258
 259         list_for_each_entry_safe(p, n,
 260                                  &buffer->scan_el_dev_attr_list, l)
 261                 iio_buffer_remove_and_free_scan_dev_attr(indio_dev, p);
 262 }
 263
 264 static const char * const iio_scan_elements_group_name = "scan_elements";
 265
 266 int iio_buffer_register(struct iio_dev *indio_dev,
 267                         const struct iio_chan_spec *channels,
 268                         int num_channels)
 269 {
 270         struct iio_dev_attr *p;
 271         struct attribute **attr;
 272         struct iio_buffer *buffer = indio_dev->buffer;
 273         int ret, i, attrn, attrcount, attrcount_orig = 0;
 274
 275         if (buffer->attrs)
 276                 indio_dev->groups[indio_dev->groupcounter++] = buffer->attrs;
 277
 278         if (buffer->scan_el_attrs != NULL) {
 279                 attr = buffer->scan_el_attrs->attrs;
 280                 while (*attr++ != NULL)
 281                         attrcount_orig++;
 282         }
 283         attrcount = attrcount_orig;
 284         INIT_LIST_HEAD(&buffer->scan_el_dev_attr_list);
 285         if (channels) {
 286                 /* new magic */
 287                 for (i = 0; i < num_channels; i++) {
 288                         /* Establish necessary mask length */
 289                         if (channels[i].scan_index >
 290                             (int)indio_dev->masklength - 1)
 291                                 indio_dev->masklength
 292                                         = indio_dev->channels[i].scan_index + 1;
 293
 294                         ret = iio_buffer_add_channel_sysfs(indio_dev,
 295                                                          &channels[i]);
 296                         if (ret < 0)
 297                                 goto error_cleanup_dynamic;
 298                         attrcount += ret;
 299                         if (channels[i].type == IIO_TIMESTAMP)
 300                                 indio_dev->scan_index_timestamp =
 301                                         channels[i].scan_index;
 302                 }
 303                 if (indio_dev->masklength && buffer->scan_mask == NULL) {
 304                         buffer->scan_mask = kcalloc(BITS_TO_LONGS(indio_dev->masklength),
 305                                                     sizeof(*buffer->scan_mask),
 306                                                     GFP_KERNEL);
 307                         if (buffer->scan_mask == NULL) {
 308                                 ret = -ENOMEM;
 309                                 goto error_cleanup_dynamic;
 310                         }
 311                 }
 312         }
 313
 314         buffer->scan_el_group.name = iio_scan_elements_group_name;
 315
 316         buffer->scan_el_group.attrs = kcalloc(attrcount + 1,
 317                                               sizeof(buffer->scan_el_group.attrs[0]),
 318                                               GFP_KERNEL);
 319         if (buffer->scan_el_group.attrs == NULL) {
 320                 ret = -ENOMEM;
 321                 goto error_free_scan_mask;
 322         }
 323         if (buffer->scan_el_attrs)
 324                 memcpy(buffer->scan_el_group.attrs, buffer->scan_el_attrs,
 325                        sizeof(buffer->scan_el_group.attrs[0])*attrcount_orig);
 326         attrn = attrcount_orig;
 327
 328         list_for_each_entry(p, &buffer->scan_el_dev_attr_list, l)
 329                 buffer->scan_el_group.attrs[attrn++] = &p->dev_attr.attr;
 330         indio_dev->groups[indio_dev->groupcounter++] = &buffer->scan_el_group;
 331
 332         return 0;
 333
 334 error_free_scan_mask:
 335         kfree(buffer->scan_mask);
 336 error_cleanup_dynamic:
 337         __iio_buffer_attr_cleanup(indio_dev);
 338
 339         return ret;
 340 }
 341 EXPORT_SYMBOL(iio_buffer_register);
 342
 343 void iio_buffer_unregister(struct iio_dev *indio_dev)
 344 {
 345         kfree(indio_dev->buffer->scan_mask);
 346         kfree(indio_dev->buffer->scan_el_group.attrs);
 347         __iio_buffer_attr_cleanup(indio_dev);
 348 }
 349 EXPORT_SYMBOL(iio_buffer_unregister);
 350
 351 ssize_t iio_buffer_read_length(struct device *dev,
 352                                struct device_attribute *attr,
 353                                char *buf)
 354 {
 355         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 356         struct iio_buffer *buffer = indio_dev->buffer;
 357
 358         if (buffer->access->get_length)
 359                 return sprintf(buf, "%d\n",
 360                                buffer->access->get_length(buffer));
 361
 362         return 0;
 363 }
 364 EXPORT_SYMBOL(iio_buffer_read_length);
 365
 366 ssize_t iio_buffer_write_length(struct device *dev,
 367                                 struct device_attribute *attr,
 368                                 const char *buf,
 369                                 size_t len)
 370 {
 371         int ret;
 372         ulong val;
 373         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 374         struct iio_buffer *buffer = indio_dev->buffer;
 375
 376         ret = strict_strtoul(buf, 10, &val);
 377         if (ret)
 378                 return ret;
 379
 380         if (buffer->access->get_length)
 381                 if (val == buffer->access->get_length(buffer))
 382                         return len;
 383
 384         mutex_lock(&indio_dev->mlock);
 385         if (iio_buffer_enabled(indio_dev)) {
 386                 ret = -EBUSY;
 387         } else {
 388                 if (buffer->access->set_length)
 389                         buffer->access->set_length(buffer, val);
 390                 ret = 0;
 391         }
 392         mutex_unlock(&indio_dev->mlock);
 393
 394         return ret ? ret : len;
 395 }
 396 EXPORT_SYMBOL(iio_buffer_write_length);
 397
 398 ssize_t iio_buffer_store_enable(struct device *dev,
 399                                 struct device_attribute *attr,
 400                                 const char *buf,
 401                                 size_t len)
 402 {
 403         int ret;
 404         bool requested_state, current_state;
 405         int previous_mode;
 406         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 407         struct iio_buffer *buffer = indio_dev->buffer;
 408
 409         mutex_lock(&indio_dev->mlock);
 410         previous_mode = indio_dev->currentmode;
 411         requested_state = !(buf[0] == '0');
 412         current_state = iio_buffer_enabled(indio_dev);
 413         if (current_state == requested_state) {
 414                 printk(KERN_INFO "iio-buffer, current state requested again\n");
 415                 goto done;
 416         }
 417         if (requested_state) {
 418                 if (indio_dev->setup_ops->preenable) {
 419                         ret = indio_dev->setup_ops->preenable(indio_dev);
 420                         if (ret) {
 421                                 printk(KERN_ERR
 422                                        "Buffer not started:"
 423                                        "buffer preenable failed\n");
 424                                 goto error_ret;
 425                         }
 426                 }
 427                 if (buffer->access->request_update) {
 428                         ret = buffer->access->request_update(buffer);
 429                         if (ret) {
 430                                 printk(KERN_INFO
 431                                        "Buffer not started:"
 432                                        "buffer parameter update failed\n");
 433                                 goto error_ret;
 434                         }
 435                 }
 436                 /* Definitely possible for devices to support both of these.*/
 437                 if (indio_dev->modes & INDIO_BUFFER_TRIGGERED) {
 438                         if (!indio_dev->trig) {
 439                                 printk(KERN_INFO
 440                                        "Buffer not started: no trigger\n");
 441                                 ret = -EINVAL;
 442                                 goto error_ret;
 443                         }
 444                         indio_dev->currentmode = INDIO_BUFFER_TRIGGERED;
 445                 } else if (indio_dev->modes & INDIO_BUFFER_HARDWARE)
 446                         indio_dev->currentmode = INDIO_BUFFER_HARDWARE;
 447                 else { /* should never be reached */
 448                         ret = -EINVAL;
 449                         goto error_ret;
 450                 }
 451
 452                 if (indio_dev->setup_ops->postenable) {
 453                         ret = indio_dev->setup_ops->postenable(indio_dev);
 454                         if (ret) {
 455                                 printk(KERN_INFO
 456                                        "Buffer not started:"
 457                                        "postenable failed\n");
 458                                 indio_dev->currentmode = previous_mode;
 459                                 if (indio_dev->setup_ops->postdisable)
 460                                         indio_dev->setup_ops->
 461                                                 postdisable(indio_dev);
 462                                 goto error_ret;
 463                         }
 464                 }
 465         } else {
 466                 if (indio_dev->setup_ops->predisable) {
 467                         ret = indio_dev->setup_ops->predisable(indio_dev);
 468                         if (ret)
 469                                 goto error_ret;
 470                 }
 471                 indio_dev->currentmode = INDIO_DIRECT_MODE;
 472                 if (indio_dev->setup_ops->postdisable) {
 473                         ret = indio_dev->setup_ops->postdisable(indio_dev);
 474                         if (ret)
 475                                 goto error_ret;
 476                 }
 477         }
 478 done:
 479         mutex_unlock(&indio_dev->mlock);
 480         return len;
 481
 482 error_ret:
 483         mutex_unlock(&indio_dev->mlock);
 484         return ret;
 485 }
 486 EXPORT_SYMBOL(iio_buffer_store_enable);
 487
 488 ssize_t iio_buffer_show_enable(struct device *dev,
 489                                struct device_attribute *attr,
 490                                char *buf)
 491 {
 492         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 493         return sprintf(buf, "%d\n", iio_buffer_enabled(indio_dev));
 494 }
 495 EXPORT_SYMBOL(iio_buffer_show_enable);
 496
 497 /* note NULL used as error indicator as it doesn't make sense. */
 498 static const unsigned long *iio_scan_mask_match(const unsigned long *av_masks,
 499                                           unsigned int masklength,
 500                                           const unsigned long *mask)
 501 {
 502         if (bitmap_empty(mask, masklength))
 503                 return NULL;
 504         while (*av_masks) {
 505                 if (bitmap_subset(mask, av_masks, masklength))
 506                         return av_masks;
 507                 av_masks += BITS_TO_LONGS(masklength);
 508         }
 509         return NULL;
 510 }
 511
 512 static int iio_compute_scan_bytes(struct iio_dev *indio_dev, const long *mask,
 513                                   bool timestamp)
 514 {
 515         const struct iio_chan_spec *ch;
 516         unsigned bytes = 0;
 517         int length, i;
 518
 519         /* How much space will the demuxed element take? */
 520         for_each_set_bit(i, mask,
 521                          indio_dev->masklength) {
 522                 ch = iio_find_channel_from_si(indio_dev, i);
 523                 length = ch->scan_type.storagebits / 8;
 524                 bytes = ALIGN(bytes, length);
 525                 bytes += length;
 526         }
 527         if (timestamp) {
 528                 ch = iio_find_channel_from_si(indio_dev,
 529                                               indio_dev->scan_index_timestamp);
 530                 length = ch->scan_type.storagebits / 8;
 531                 bytes = ALIGN(bytes, length);
 532                 bytes += length;
 533         }
 534         return bytes;
 535 }
 536
 537 int iio_sw_buffer_preenable(struct iio_dev *indio_dev)
 538 {
 539         struct iio_buffer *buffer = indio_dev->buffer;
 540         dev_dbg(&indio_dev->dev, "%s\n", __func__);
 541
 542         /* How much space will the demuxed element take? */
 543         indio_dev->scan_bytes =
 544                 iio_compute_scan_bytes(indio_dev, buffer->scan_mask,
 545                                        buffer->scan_timestamp);
 546         buffer->access->set_bytes_per_datum(buffer, indio_dev->scan_bytes);
 547
 548         /* What scan mask do we actually have ?*/
 549         if (indio_dev->available_scan_masks)
 550                 indio_dev->active_scan_mask =
 551                         iio_scan_mask_match(indio_dev->available_scan_masks,
 552                                             indio_dev->masklength,
 553                                             buffer->scan_mask);
 554         else
 555                 indio_dev->active_scan_mask = buffer->scan_mask;
 556         iio_update_demux(indio_dev);
 557
 558         if (indio_dev->info->update_scan_mode)
 559                 return indio_dev->info
 560                         ->update_scan_mode(indio_dev,
 561                                            indio_dev->active_scan_mask);
 562         return 0;
 563 }
 564 EXPORT_SYMBOL(iio_sw_buffer_preenable);
 565
 566 /**
 567  * iio_scan_mask_set() - set particular bit in the scan mask
 568  * @buffer: the buffer whose scan mask we are interested in
 569  * @bit: the bit to be set.
 570  **/
 571 int iio_scan_mask_set(struct iio_dev *indio_dev,
 572                       struct iio_buffer *buffer, int bit)
 573 {
 574         const unsigned long *mask;
 575         unsigned long *trialmask;
 576
 577         trialmask = kmalloc(sizeof(*trialmask)*
 578                             BITS_TO_LONGS(indio_dev->masklength),
 579                             GFP_KERNEL);
 580
 581         if (trialmask == NULL)
 582                 return -ENOMEM;
 583         if (!indio_dev->masklength) {
 584                 WARN_ON("trying to set scanmask prior to registering buffer\n");
 585                 kfree(trialmask);
 586                 return -EINVAL;
 587         }
 588         bitmap_copy(trialmask, buffer->scan_mask, indio_dev->masklength);
 589         set_bit(bit, trialmask);
 590
 591         if (indio_dev->available_scan_masks) {
 592                 mask = iio_scan_mask_match(indio_dev->available_scan_masks,
 593                                            indio_dev->masklength,
 594                                            trialmask);
 595                 if (!mask) {
 596                         kfree(trialmask);
 597                         return -EINVAL;
 598                 }
 599         }
 600         bitmap_copy(buffer->scan_mask, trialmask, indio_dev->masklength);
 601
 602         kfree(trialmask);
 603
 604         return 0;
 605 };
 606 EXPORT_SYMBOL_GPL(iio_scan_mask_set);
 607
 608 int iio_scan_mask_query(struct iio_dev *indio_dev,
 609                         struct iio_buffer *buffer, int bit)
 610 {
 611         if (bit > indio_dev->masklength)
 612                 return -EINVAL;
 613
 614         if (!buffer->scan_mask)
 615                 return 0;
 616
 617         return test_bit(bit, buffer->scan_mask);
 618 };
 619 EXPORT_SYMBOL_GPL(iio_scan_mask_query);
 620
 621 /**
 622  * struct iio_demux_table() - table describing demux memcpy ops
 623  * @from:       index to copy from
 624  * @to: index to copy to
 625  * @length:     how many bytes to copy
 626  * @l:          list head used for management
 627  */
 628 struct iio_demux_table {
 629         unsigned from;
 630         unsigned to;
 631         unsigned length;
 632         struct list_head l;
 633 };
 634
 635 static unsigned char *iio_demux(struct iio_buffer *buffer,
 636                                  unsigned char *datain)
 637 {
 638         struct iio_demux_table *t;
 639
 640         if (list_empty(&buffer->demux_list))
 641                 return datain;
 642         list_for_each_entry(t, &buffer->demux_list, l)
 643                 memcpy(buffer->demux_bounce + t->to,
 644                        datain + t->from, t->length);
 645
 646         return buffer->demux_bounce;
 647 }
 648
 649 int iio_push_to_buffer(struct iio_buffer *buffer, unsigned char *data,
 650                        s64 timestamp)
 651 {
 652         unsigned char *dataout = iio_demux(buffer, data);
 653
 654         return buffer->access->store_to(buffer, dataout, timestamp);
 655 }
 656 EXPORT_SYMBOL_GPL(iio_push_to_buffer);
 657
 658 static void iio_buffer_demux_free(struct iio_buffer *buffer)
 659 {
 660         struct iio_demux_table *p, *q;
 661         list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
 662                 list_del(&p->l);
 663                 kfree(p);
 664         }
 665 }
 666
 667 int iio_update_demux(struct iio_dev *indio_dev)
 668 {
 669         const struct iio_chan_spec *ch;
 670         struct iio_buffer *buffer = indio_dev->buffer;
 671         int ret, in_ind = -1, out_ind, length;
 672         unsigned in_loc = 0, out_loc = 0;
 673         struct iio_demux_table *p;
 674
 675         /* Clear out any old demux */
 676         iio_buffer_demux_free(buffer);
 677         kfree(buffer->demux_bounce);
 678         buffer->demux_bounce = NULL;
 679
 680         /* First work out which scan mode we will actually have */
 681         if (bitmap_equal(indio_dev->active_scan_mask,
 682                          buffer->scan_mask,
 683                          indio_dev->masklength))
 684                 return 0;
 685
 686         /* Now we have the two masks, work from least sig and build up sizes */
 687         for_each_set_bit(out_ind,
 688                          indio_dev->active_scan_mask,
 689                          indio_dev->masklength) {
 690                 in_ind = find_next_bit(indio_dev->active_scan_mask,
 691                                        indio_dev->masklength,
 692                                        in_ind + 1);
 693                 while (in_ind != out_ind) {
 694                         in_ind = find_next_bit(indio_dev->active_scan_mask,
 695                                                indio_dev->masklength,
 696                                                in_ind + 1);
 697                         ch = iio_find_channel_from_si(indio_dev, in_ind);
 698                         length = ch->scan_type.storagebits/8;
 699                         /* Make sure we are aligned */
 700                         in_loc += length;
 701                         if (in_loc % length)
 702                                 in_loc += length - in_loc % length;
 703                 }
 704                 p = kmalloc(sizeof(*p), GFP_KERNEL);
 705                 if (p == NULL) {
 706                         ret = -ENOMEM;
 707                         goto error_clear_mux_table;
 708                 }
 709                 ch = iio_find_channel_from_si(indio_dev, in_ind);
 710                 length = ch->scan_type.storagebits/8;
 711                 if (out_loc % length)
 712                         out_loc += length - out_loc % length;
 713                 if (in_loc % length)
 714                         in_loc += length - in_loc % length;
 715                 p->from = in_loc;
 716                 p->to = out_loc;
 717                 p->length = length;
 718                 list_add_tail(&p->l, &buffer->demux_list);
 719                 out_loc += length;
 720                 in_loc += length;
 721         }
 722         /* Relies on scan_timestamp being last */
 723         if (buffer->scan_timestamp) {
 724                 p = kmalloc(sizeof(*p), GFP_KERNEL);
 725                 if (p == NULL) {
 726                         ret = -ENOMEM;
 727                         goto error_clear_mux_table;
 728                 }
 729                 ch = iio_find_channel_from_si(indio_dev,
 730                         indio_dev->scan_index_timestamp);
 731                 length = ch->scan_type.storagebits/8;
 732                 if (out_loc % length)
 733                         out_loc += length - out_loc % length;
 734                 if (in_loc % length)
 735                         in_loc += length - in_loc % length;
 736                 p->from = in_loc;
 737                 p->to = out_loc;
 738                 p->length = length;
 739                 list_add_tail(&p->l, &buffer->demux_list);
 740                 out_loc += length;
 741                 in_loc += length;
 742         }
 743         buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
 744         if (buffer->demux_bounce == NULL) {
 745                 ret = -ENOMEM;
 746                 goto error_clear_mux_table;
 747         }
 748         return 0;
 749
 750 error_clear_mux_table:
 751         iio_buffer_demux_free(buffer);
 752
 753         return ret;
 754 }
 755 EXPORT_SYMBOL_GPL(iio_update_demux);