tools/iio/iio_generic_buffer.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Industrialio buffer test code.
   3  *
   4  * Copyright (c) 2008 Jonathan Cameron
   5  *
   6  * This program is primarily intended as an example application.
   7  * Reads the current buffer setup from sysfs and starts a short capture
   8  * from the specified device, pretty printing the result after appropriate
   9  * conversion.
  10  *
  11  * Command line parameters
  12  * generic_buffer -n <device_name> -t <trigger_name>
  13  * If trigger name is not specified the program assumes you want a dataready
  14  * trigger associated with the device and goes looking for it.
  15  */
  16
  17 #include <unistd.h>
  18 #include <stdlib.h>
  19 #include <dirent.h>
  20 #include <fcntl.h>
  21 #include <stdio.h>
  22 #include <errno.h>
  23 #include <sys/stat.h>
  24 #include <sys/dir.h>
  25 #include <linux/types.h>
  26 #include <string.h>
  27 #include <poll.h>
  28 #include <endian.h>
  29 #include <getopt.h>
  30 #include <inttypes.h>
  31 #include <stdbool.h>
  32 #include <signal.h>
  33 #include <sys/ioctl.h>
  34 #include <linux/iio/buffer.h>
  35 #include "iio_utils.h"
  36
  37 /**
  38  * enum autochan - state for the automatic channel enabling mechanism
  39  */
  40 enum autochan {
  41         AUTOCHANNELS_DISABLED,
  42         AUTOCHANNELS_ENABLED,
  43         AUTOCHANNELS_ACTIVE,
  44 };
  45
  46 /**
  47  * size_from_channelarray() - calculate the storage size of a scan
  48  * @channels:           the channel info array
  49  * @num_channels:       number of channels
  50  *
  51  * Has the side effect of filling the channels[i].location values used
  52  * in processing the buffer output.
  53  **/
  54 static int size_from_channelarray(struct iio_channel_info *channels, int num_channels)
  55 {
  56         int bytes = 0;
  57         int i = 0;
  58
  59         while (i < num_channels) {
  60                 if (bytes % channels[i].bytes == 0)
  61                         channels[i].location = bytes;
  62                 else
  63                         channels[i].location = bytes - bytes % channels[i].bytes
  64                                                + channels[i].bytes;
  65
  66                 bytes = channels[i].location + channels[i].bytes;
  67                 i++;
  68         }
  69
  70         return bytes;
  71 }
  72
  73 static void print1byte(uint8_t input, struct iio_channel_info *info)
  74 {
  75         /*
  76          * Shift before conversion to avoid sign extension
  77          * of left aligned data
  78          */
  79         input >>= info->shift;
  80         input &= info->mask;
  81         if (info->is_signed) {
  82                 int8_t val = (int8_t)(input << (8 - info->bits_used)) >>
  83                              (8 - info->bits_used);
  84                 printf("%05f ", ((float)val + info->offset) * info->scale);
  85         } else {
  86                 printf("%05f ", ((float)input + info->offset) * info->scale);
  87         }
  88 }
  89
  90 static void print2byte(uint16_t input, struct iio_channel_info *info)
  91 {
  92         /* First swap if incorrect endian */
  93         if (info->be)
  94                 input = be16toh(input);
  95         else
  96                 input = le16toh(input);
  97
  98         /*
  99          * Shift before conversion to avoid sign extension
 100          * of left aligned data
 101          */
 102         input >>= info->shift;
 103         input &= info->mask;
 104         if (info->is_signed) {
 105                 int16_t val = (int16_t)(input << (16 - info->bits_used)) >>
 106                               (16 - info->bits_used);
 107                 printf("%05f ", ((float)val + info->offset) * info->scale);
 108         } else {
 109                 printf("%05f ", ((float)input + info->offset) * info->scale);
 110         }
 111 }
 112
 113 static void print4byte(uint32_t input, struct iio_channel_info *info)
 114 {
 115         /* First swap if incorrect endian */
 116         if (info->be)
 117                 input = be32toh(input);
 118         else
 119                 input = le32toh(input);
 120
 121         /*
 122          * Shift before conversion to avoid sign extension
 123          * of left aligned data
 124          */
 125         input >>= info->shift;
 126         input &= info->mask;
 127         if (info->is_signed) {
 128                 int32_t val = (int32_t)(input << (32 - info->bits_used)) >>
 129                               (32 - info->bits_used);
 130                 printf("%05f ", ((float)val + info->offset) * info->scale);
 131         } else {
 132                 printf("%05f ", ((float)input + info->offset) * info->scale);
 133         }
 134 }
 135
 136 static void print8byte(uint64_t input, struct iio_channel_info *info)
 137 {
 138         /* First swap if incorrect endian */
 139         if (info->be)
 140                 input = be64toh(input);
 141         else
 142                 input = le64toh(input);
 143
 144         /*
 145          * Shift before conversion to avoid sign extension
 146          * of left aligned data
 147          */
 148         input >>= info->shift;
 149         input &= info->mask;
 150         if (info->is_signed) {
 151                 int64_t val = (int64_t)(input << (64 - info->bits_used)) >>
 152                               (64 - info->bits_used);
 153                 /* special case for timestamp */
 154                 if (info->scale == 1.0f && info->offset == 0.0f)
 155                         printf("%" PRId64 " ", val);
 156                 else
 157                         printf("%05f ",
 158                                ((float)val + info->offset) * info->scale);
 159         } else {
 160                 printf("%05f ", ((float)input + info->offset) * info->scale);
 161         }
 162 }
 163
 164 /**
 165  * process_scan() - print out the values in SI units
 166  * @data:               pointer to the start of the scan
 167  * @channels:           information about the channels.
 168  *                      Note: size_from_channelarray must have been called first
 169  *                            to fill the location offsets.
 170  * @num_channels:       number of channels
 171  **/
 172 static void process_scan(char *data, struct iio_channel_info *channels,
 173                          int num_channels)
 174 {
 175         int k;
 176
 177         for (k = 0; k < num_channels; k++)
 178                 switch (channels[k].bytes) {
 179                         /* only a few cases implemented so far */
 180                 case 1:
 181                         print1byte(*(uint8_t *)(data + channels[k].location),
 182                                    &channels[k]);
 183                         break;
 184                 case 2:
 185                         print2byte(*(uint16_t *)(data + channels[k].location),
 186                                    &channels[k]);
 187                         break;
 188                 case 4:
 189                         print4byte(*(uint32_t *)(data + channels[k].location),
 190                                    &channels[k]);
 191                         break;
 192                 case 8:
 193                         print8byte(*(uint64_t *)(data + channels[k].location),
 194                                    &channels[k]);
 195                         break;
 196                 default:
 197                         break;
 198                 }
 199         printf("\n");
 200 }
 201
 202 static int enable_disable_all_channels(char *dev_dir_name, int buffer_idx, int enable)
 203 {
 204         const struct dirent *ent;
 205         char scanelemdir[256];
 206         DIR *dp;
 207         int ret;
 208
 209         snprintf(scanelemdir, sizeof(scanelemdir),
 210                  FORMAT_SCAN_ELEMENTS_DIR, dev_dir_name, buffer_idx);
 211         scanelemdir[sizeof(scanelemdir)-1] = '\0';
 212
 213         dp = opendir(scanelemdir);
 214         if (!dp) {
 215                 fprintf(stderr, "Enabling/disabling channels: can't open %s\n",
 216                         scanelemdir);
 217                 return -EIO;
 218         }
 219
 220         ret = -ENOENT;
 221         while (ent = readdir(dp), ent) {
 222                 if (iioutils_check_suffix(ent->d_name, "_en")) {
 223                         printf("%sabling: %s\n",
 224                                enable ? "En" : "Dis",
 225                                ent->d_name);
 226                         ret = write_sysfs_int(ent->d_name, scanelemdir,
 227                                               enable);
 228                         if (ret < 0)
 229                                 fprintf(stderr, "Failed to enable/disable %s\n",
 230                                         ent->d_name);
 231                 }
 232         }
 233
 234         if (closedir(dp) == -1) {
 235                 perror("Enabling/disabling channels: "
 236                        "Failed to close directory");
 237                 return -errno;
 238         }
 239         return 0;
 240 }
 241
 242 static void print_usage(void)
 243 {
 244         fprintf(stderr, "Usage: generic_buffer [options]...\n"
 245                 "Capture, convert and output data from IIO device buffer\n"
 246                 "  -a         Auto-activate all available channels\n"
 247                 "  -A         Force-activate ALL channels\n"
 248                 "  -b <n>     The buffer which to open (by index), default 0\n"
 249                 "  -c <n>     Do n conversions, or loop forever if n < 0\n"
 250                 "  -e         Disable wait for event (new data)\n"
 251                 "  -g         Use trigger-less mode\n"
 252                 "  -l <n>     Set buffer length to n samples\n"
 253                 "  --device-name -n <name>\n"
 254                 "  --device-num -N <num>\n"
 255                 "        Set device by name or number (mandatory)\n"
 256                 "  --trigger-name -t <name>\n"
 257                 "  --trigger-num -T <num>\n"
 258                 "        Set trigger by name or number\n"
 259                 "  -w <n>     Set delay between reads in us (event-less mode)\n");
 260 }
 261
 262 static enum autochan autochannels = AUTOCHANNELS_DISABLED;
 263 static char *dev_dir_name = NULL;
 264 static char *buf_dir_name = NULL;
 265 static int buffer_idx = 0;
 266 static bool current_trigger_set = false;
 267
 268 static void cleanup(void)
 269 {
 270         int ret;
 271
 272         /* Disable trigger */
 273         if (dev_dir_name && current_trigger_set) {
 274                 /* Disconnect the trigger - just write a dummy name. */
 275                 ret = write_sysfs_string("trigger/current_trigger",
 276                                          dev_dir_name, "NULL");
 277                 if (ret < 0)
 278                         fprintf(stderr, "Failed to disable trigger: %s\n",
 279                                 strerror(-ret));
 280                 current_trigger_set = false;
 281         }
 282
 283         /* Disable buffer */
 284         if (buf_dir_name) {
 285                 ret = write_sysfs_int("enable", buf_dir_name, 0);
 286                 if (ret < 0)
 287                         fprintf(stderr, "Failed to disable buffer: %s\n",
 288                                 strerror(-ret));
 289         }
 290
 291         /* Disable channels if auto-enabled */
 292         if (dev_dir_name && autochannels == AUTOCHANNELS_ACTIVE) {
 293                 ret = enable_disable_all_channels(dev_dir_name, buffer_idx, 0);
 294                 if (ret)
 295                         fprintf(stderr, "Failed to disable all channels\n");
 296                 autochannels = AUTOCHANNELS_DISABLED;
 297         }
 298 }
 299
 300 static void sig_handler(int signum)
 301 {
 302         fprintf(stderr, "Caught signal %d\n", signum);
 303         cleanup();
 304         exit(-signum);
 305 }
 306
 307 static void register_cleanup(void)
 308 {
 309         struct sigaction sa = { .sa_handler = sig_handler };
 310         const int signums[] = { SIGINT, SIGTERM, SIGABRT };
 311         int ret, i;
 312
 313         for (i = 0; i < ARRAY_SIZE(signums); ++i) {
 314                 ret = sigaction(signums[i], &sa, NULL);
 315                 if (ret) {
 316                         perror("Failed to register signal handler");
 317                         exit(-1);
 318                 }
 319         }
 320 }
 321
 322 static const struct option longopts[] = {
 323         { "device-name",        1, 0, 'n' },
 324         { "device-num",         1, 0, 'N' },
 325         { "trigger-name",       1, 0, 't' },
 326         { "trigger-num",        1, 0, 'T' },
 327         { },
 328 };
 329
 330 int main(int argc, char **argv)
 331 {
 332         long long num_loops = 2;
 333         unsigned long timedelay = 1000000;
 334         unsigned long buf_len = 128;
 335
 336         ssize_t i;
 337         unsigned long long j;
 338         unsigned long toread;
 339         int ret, c;
 340         struct stat st;
 341         int fd = -1;
 342         int buf_fd = -1;
 343
 344         int num_channels = 0;
 345         char *trigger_name = NULL, *device_name = NULL;
 346
 347         char *data = NULL;
 348         ssize_t read_size;
 349         int dev_num = -1, trig_num = -1;
 350         char *buffer_access = NULL;
 351         int scan_size;
 352         int noevents = 0;
 353         int notrigger = 0;
 354         char *dummy;
 355         bool force_autochannels = false;
 356
 357         struct iio_channel_info *channels = NULL;
 358
 359         register_cleanup();
 360
 361         while ((c = getopt_long(argc, argv, "aAb:c:egl:n:N:t:T:w:?", longopts,
 362                                 NULL)) != -1) {
 363                 switch (c) {
 364                 case 'a':
 365                         autochannels = AUTOCHANNELS_ENABLED;
 366                         break;
 367                 case 'A':
 368                         autochannels = AUTOCHANNELS_ENABLED;
 369                         force_autochannels = true;
 370                         break;
 371                 case 'b':
 372                         errno = 0;
 373                         buffer_idx = strtoll(optarg, &dummy, 10);
 374                         if (errno) {
 375                                 ret = -errno;
 376                                 goto error;
 377                         }
 378                         if (buffer_idx < 0) {
 379                                 ret = -ERANGE;
 380                                 goto error;
 381                         }
 382
 383                         break;
 384                 case 'c':
 385                         errno = 0;
 386                         num_loops = strtoll(optarg, &dummy, 10);
 387                         if (errno) {
 388                                 ret = -errno;
 389                                 goto error;
 390                         }
 391
 392                         break;
 393                 case 'e':
 394                         noevents = 1;
 395                         break;
 396                 case 'g':
 397                         notrigger = 1;
 398                         break;
 399                 case 'l':
 400                         errno = 0;
 401                         buf_len = strtoul(optarg, &dummy, 10);
 402                         if (errno) {
 403                                 ret = -errno;
 404                                 goto error;
 405                         }
 406
 407                         break;
 408                 case 'n':
 409                         device_name = strdup(optarg);
 410                         break;
 411                 case 'N':
 412                         errno = 0;
 413                         dev_num = strtoul(optarg, &dummy, 10);
 414                         if (errno) {
 415                                 ret = -errno;
 416                                 goto error;
 417                         }
 418                         break;
 419                 case 't':
 420                         trigger_name = strdup(optarg);
 421                         break;
 422                 case 'T':
 423                         errno = 0;
 424                         trig_num = strtoul(optarg, &dummy, 10);
 425                         if (errno)
 426                                 return -errno;
 427                         break;
 428                 case 'w':
 429                         errno = 0;
 430                         timedelay = strtoul(optarg, &dummy, 10);
 431                         if (errno) {
 432                                 ret = -errno;
 433                                 goto error;
 434                         }
 435                         break;
 436                 case '?':
 437                         print_usage();
 438                         ret = -1;
 439                         goto error;
 440                 }
 441         }
 442
 443         /* Find the device requested */
 444         if (dev_num < 0 && !device_name) {
 445                 fprintf(stderr, "Device not set\n");
 446                 print_usage();
 447                 ret = -1;
 448                 goto error;
 449         } else if (dev_num >= 0 && device_name) {
 450                 fprintf(stderr, "Only one of --device-num or --device-name needs to be set\n");
 451                 print_usage();
 452                 ret = -1;
 453                 goto error;
 454         } else if (dev_num < 0) {
 455                 dev_num = find_type_by_name(device_name, "iio:device");
 456                 if (dev_num < 0) {
 457                         fprintf(stderr, "Failed to find the %s\n", device_name);
 458                         ret = dev_num;
 459                         goto error;
 460                 }
 461         }
 462         printf("iio device number being used is %d\n", dev_num);
 463
 464         ret = asprintf(&dev_dir_name, "%siio:device%d", iio_dir, dev_num);
 465         if (ret < 0)
 466                 return -ENOMEM;
 467         /* Fetch device_name if specified by number */
 468         if (!device_name) {
 469                 device_name = malloc(IIO_MAX_NAME_LENGTH);
 470                 if (!device_name) {
 471                         ret = -ENOMEM;
 472                         goto error;
 473                 }
 474                 ret = read_sysfs_string("name", dev_dir_name, device_name);
 475                 if (ret < 0) {
 476                         fprintf(stderr, "Failed to read name of device %d\n", dev_num);
 477                         goto error;
 478                 }
 479         }
 480
 481         if (notrigger) {
 482                 printf("trigger-less mode selected\n");
 483         } else if (trig_num >= 0) {
 484                 char *trig_dev_name;
 485                 ret = asprintf(&trig_dev_name, "%strigger%d", iio_dir, trig_num);
 486                 if (ret < 0) {
 487                         return -ENOMEM;
 488                 }
 489                 trigger_name = malloc(IIO_MAX_NAME_LENGTH);
 490                 ret = read_sysfs_string("name", trig_dev_name, trigger_name);
 491                 free(trig_dev_name);
 492                 if (ret < 0) {
 493                         fprintf(stderr, "Failed to read trigger%d name from\n", trig_num);
 494                         return ret;
 495                 }
 496                 printf("iio trigger number being used is %d\n", trig_num);
 497         } else {
 498                 if (!trigger_name) {
 499                         /*
 500                          * Build the trigger name. If it is device associated
 501                          * its name is <device_name>_dev[n] where n matches
 502                          * the device number found above.
 503                          */
 504                         ret = asprintf(&trigger_name,
 505                                        "%s-dev%d", device_name, dev_num);
 506                         if (ret < 0) {
 507                                 ret = -ENOMEM;
 508                                 goto error;
 509                         }
 510                 }
 511
 512                 /* Look for this "-devN" trigger */
 513                 trig_num = find_type_by_name(trigger_name, "trigger");
 514                 if (trig_num < 0) {
 515                         /* OK try the simpler "-trigger" suffix instead */
 516                         free(trigger_name);
 517                         ret = asprintf(&trigger_name,
 518                                        "%s-trigger", device_name);
 519                         if (ret < 0) {
 520                                 ret = -ENOMEM;
 521                                 goto error;
 522                         }
 523                 }
 524
 525                 trig_num = find_type_by_name(trigger_name, "trigger");
 526                 if (trig_num < 0) {
 527                         fprintf(stderr, "Failed to find the trigger %s\n",
 528                                 trigger_name);
 529                         ret = trig_num;
 530                         goto error;
 531                 }
 532
 533                 printf("iio trigger number being used is %d\n", trig_num);
 534         }
 535
 536         /*
 537          * Parse the files in scan_elements to identify what channels are
 538          * present
 539          */
 540         ret = build_channel_array(dev_dir_name, buffer_idx, &channels, &num_channels);
 541         if (ret) {
 542                 fprintf(stderr, "Problem reading scan element information\n"
 543                         "diag %s\n", dev_dir_name);
 544                 goto error;
 545         }
 546         if (num_channels && autochannels == AUTOCHANNELS_ENABLED &&
 547             !force_autochannels) {
 548                 fprintf(stderr, "Auto-channels selected but some channels "
 549                         "are already activated in sysfs\n");
 550                 fprintf(stderr, "Proceeding without activating any channels\n");
 551         }
 552
 553         if ((!num_channels && autochannels == AUTOCHANNELS_ENABLED) ||
 554             (autochannels == AUTOCHANNELS_ENABLED && force_autochannels)) {
 555                 fprintf(stderr, "Enabling all channels\n");
 556
 557                 ret = enable_disable_all_channels(dev_dir_name, buffer_idx, 1);
 558                 if (ret) {
 559                         fprintf(stderr, "Failed to enable all channels\n");
 560                         goto error;
 561                 }
 562
 563                 /* This flags that we need to disable the channels again */
 564                 autochannels = AUTOCHANNELS_ACTIVE;
 565
 566                 ret = build_channel_array(dev_dir_name, buffer_idx, &channels,
 567                                           &num_channels);
 568                 if (ret) {
 569                         fprintf(stderr, "Problem reading scan element "
 570                                 "information\n"
 571                                 "diag %s\n", dev_dir_name);
 572                         goto error;
 573                 }
 574                 if (!num_channels) {
 575                         fprintf(stderr, "Still no channels after "
 576                                 "auto-enabling, giving up\n");
 577                         goto error;
 578                 }
 579         }
 580
 581         if (!num_channels && autochannels == AUTOCHANNELS_DISABLED) {
 582                 fprintf(stderr,
 583                         "No channels are enabled, we have nothing to scan.\n");
 584                 fprintf(stderr, "Enable channels manually in "
 585                         FORMAT_SCAN_ELEMENTS_DIR
 586                         "/*_en or pass -a to autoenable channels and "
 587                         "try again.\n", dev_dir_name, buffer_idx);
 588                 ret = -ENOENT;
 589                 goto error;
 590         }
 591
 592         /*
 593          * Construct the directory name for the associated buffer.
 594          * As we know that the lis3l02dq has only one buffer this may
 595          * be built rather than found.
 596          */
 597         ret = asprintf(&buf_dir_name,
 598                        "%siio:device%d/buffer%d", iio_dir, dev_num, buffer_idx);
 599         if (ret < 0) {
 600                 ret = -ENOMEM;
 601                 goto error;
 602         }
 603
 604         if (stat(buf_dir_name, &st)) {
 605                 fprintf(stderr, "Could not stat() '%s', got error %d: %s\n",
 606                         buf_dir_name, errno, strerror(errno));
 607                 ret = -errno;
 608                 goto error;
 609         }
 610
 611         if (!S_ISDIR(st.st_mode)) {
 612                 fprintf(stderr, "File '%s' is not a directory\n", buf_dir_name);
 613                 ret = -EFAULT;
 614                 goto error;
 615         }
 616
 617         if (!notrigger) {
 618                 printf("%s %s\n", dev_dir_name, trigger_name);
 619                 /*
 620                  * Set the device trigger to be the data ready trigger found
 621                  * above
 622                  */
 623                 ret = write_sysfs_string_and_verify("trigger/current_trigger",
 624                                                     dev_dir_name,
 625                                                     trigger_name);
 626                 if (ret < 0) {
 627                         fprintf(stderr,
 628                                 "Failed to write current_trigger file\n");
 629                         goto error;
 630                 }
 631         }
 632
 633         ret = asprintf(&buffer_access, "/dev/iio:device%d", dev_num);
 634         if (ret < 0) {
 635                 ret = -ENOMEM;
 636                 goto error;
 637         }
 638
 639         /* Attempt to open non blocking the access dev */
 640         fd = open(buffer_access, O_RDONLY | O_NONBLOCK);
 641         if (fd == -1) { /* TODO: If it isn't there make the node */
 642                 ret = -errno;
 643                 fprintf(stderr, "Failed to open %s\n", buffer_access);
 644                 goto error;
 645         }
 646
 647         /* specify for which buffer index we want an FD */
 648         buf_fd = buffer_idx;
 649
 650         ret = ioctl(fd, IIO_BUFFER_GET_FD_IOCTL, &buf_fd);
 651         if (ret == -1 || buf_fd == -1) {
 652                 ret = -errno;
 653                 if (ret == -ENODEV || ret == -EINVAL)
 654                         fprintf(stderr,
 655                                 "Device does not have this many buffers\n");
 656                 else
 657                         fprintf(stderr, "Failed to retrieve buffer fd\n");
 658
 659                 goto error;
 660         }
 661
 662         /* Setup ring buffer parameters */
 663         ret = write_sysfs_int("length", buf_dir_name, buf_len);
 664         if (ret < 0)
 665                 goto error;
 666
 667         /* Enable the buffer */
 668         ret = write_sysfs_int("enable", buf_dir_name, 1);
 669         if (ret < 0) {
 670                 fprintf(stderr,
 671                         "Failed to enable buffer '%s': %s\n",
 672                         buf_dir_name, strerror(-ret));
 673                 goto error;
 674         }
 675
 676         scan_size = size_from_channelarray(channels, num_channels);
 677         data = malloc(scan_size * buf_len);
 678         if (!data) {
 679                 ret = -ENOMEM;
 680                 goto error;
 681         }
 682
 683         /**
 684          * This check is being done here for sanity reasons, however it
 685          * should be omitted under normal operation.
 686          * If this is buffer0, we check that we get EBUSY after this point.
 687          */
 688         if (buffer_idx == 0) {
 689                 errno = 0;
 690                 read_size = read(fd, data, 1);
 691                 if (read_size > -1 || errno != EBUSY) {
 692                         ret = -EFAULT;
 693                         perror("Reading from '%s' should not be possible after ioctl()");
 694                         goto error;
 695                 }
 696         }
 697
 698         /* close now the main chardev FD and let the buffer FD work */
 699         if (close(fd) == -1)
 700                 perror("Failed to close character device file");
 701         fd = -1;
 702
 703         for (j = 0; j < num_loops || num_loops < 0; j++) {
 704                 if (!noevents) {
 705                         struct pollfd pfd = {
 706                                 .fd = buf_fd,
 707                                 .events = POLLIN,
 708                         };
 709
 710                         ret = poll(&pfd, 1, -1);
 711                         if (ret < 0) {
 712                                 ret = -errno;
 713                                 goto error;
 714                         } else if (ret == 0) {
 715                                 continue;
 716                         }
 717
 718                         toread = buf_len;
 719                 } else {
 720                         usleep(timedelay);
 721                         toread = 64;
 722                 }
 723
 724                 read_size = read(buf_fd, data, toread * scan_size);
 725                 if (read_size < 0) {
 726                         if (errno == EAGAIN) {
 727                                 fprintf(stderr, "nothing available\n");
 728                                 continue;
 729                         } else {
 730                                 break;
 731                         }
 732                 }
 733                 for (i = 0; i < read_size / scan_size; i++)
 734                         process_scan(data + scan_size * i, channels,
 735                                      num_channels);
 736         }
 737
 738 error:
 739         cleanup();
 740
 741         if (fd >= 0 && close(fd) == -1)
 742                 perror("Failed to close character device");
 743         if (buf_fd >= 0 && close(buf_fd) == -1)
 744                 perror("Failed to close buffer");
 745         free(buffer_access);
 746         free(data);
 747         free(buf_dir_name);
 748         for (i = num_channels - 1; i >= 0; i--) {
 749                 free(channels[i].name);
 750                 free(channels[i].generic_name);
 751         }
 752         free(channels);
 753         free(trigger_name);
 754         free(device_name);
 755         free(dev_dir_name);
 756
 757         return ret;
 758 }