control.c

   1 /*
   2  * Copyright (C) 2014 Intel Corporation.
   3  */
   4
   5 #include <fcntl.h>
   6 #include <sys/epoll.h>
   7 #include <sys/socket.h>
   8 #include <utils/Log.h>
   9 #include <hardware/sensors.h>
  10 #include "control.h"
  11 #include "enumeration.h"
  12 #include "utils.h"
  13 #include "transform.h"
  14
  15 /* Currently active sensors count, per device */
  16 static int poll_sensors_per_dev[MAX_DEVICES];   /* poll-mode sensors */
  17 static int trig_sensors_per_dev[MAX_DEVICES];   /* trigger, event based */
  18
  19 static int device_fd[MAX_DEVICES];   /* fd on the /dev/iio:deviceX file */
  20
  21 static int poll_fd; /* epoll instance covering all enabled sensors */
  22
  23 static int poll_socket_pair[2]; /* used to unblock the poll loop */
  24
  25 /* Timestamp for the moment when we last exited a poll operation */
  26 static int64_t last_poll_exit_ts;
  27
  28 static int active_poll_sensors; /* Number of enabled poll-mode sensors */
  29
  30 /* Cap the time between poll operations to this, to counter runaway polls */
  31 #define POLL_MIN_INTERVAL 10000 /* uS */
  32
  33 #define INVALID_DEV_NUM ((uint32_t) -1)
  34
  35
  36 static int enable_buffer(int dev_num, int enabled)
  37 {
  38         char sysfs_path[PATH_MAX];
  39
  40         sprintf(sysfs_path, ENABLE_PATH, dev_num);
  41
  42         /* Low level, non-multiplexed, enable/disable routine */
  43         return sysfs_write_int(sysfs_path, enabled);
  44 }
  45
  46
  47 static int setup_trigger(int dev_num, const char* trigger_val)
  48 {
  49         char sysfs_path[PATH_MAX];
  50
  51         sprintf(sysfs_path, TRIGGER_PATH, dev_num);
  52
  53         return sysfs_write_str(sysfs_path, trigger_val);
  54 }
  55
  56
  57 static void refresh_sensor_report_maps(int dev_num)
  58 {
  59         /*
  60          * Read sysfs files from a iio device's scan_element directory, and
  61          * build a couple of tables from that data. These tables will tell, for
  62          * each sensor, where to gather relevant data in a device report, i.e.
  63          * the structure that we read from the /dev/iio:deviceX file in order to
  64          * sensor report, itself being the data that we return to Android when a
  65          * sensor poll completes. The mapping should be straightforward in the
  66          * case where we have a single sensor active per iio device but, this is
  67          * not the general case. In general several sensors can be handled
  68          * through a single iio device, and the _en, _index and _type syfs
  69          * entries all concur to paint a picture of what the structure of the
  70          * device report is.
  71          */
  72
  73         int s;
  74         int c;
  75         int n;
  76         int i;
  77         int ch_enabled;
  78         int ch_index;
  79         char* ch_spec;
  80         char spec_buf[MAX_TYPE_SPEC_LEN];
  81         struct datum_info_t* ch_info;
  82         int size;
  83         char sysfs_path[PATH_MAX];
  84         int active_channels;
  85         int offset;
  86         int channel_count;
  87         int channel_size_from_index[MAX_SENSORS * MAX_CHANNELS] = { 0 };
  88         int sensor_handle_from_index[MAX_SENSORS * MAX_CHANNELS] = { 0 };
  89         int channel_number_from_index[MAX_SENSORS * MAX_CHANNELS] = { 0 };
  90
  91         active_channels = 0;
  92
  93         /* For each sensor that is linked to this device */
  94         for (s=0; s<sensor_count; s++) {
  95                 if (sensor_info[s].dev_num != dev_num)
  96                         continue;
  97
  98                 i = sensor_info[s].catalog_index;
  99
 100                 /* Read channel status through syfs attributes */
 101                 for (c=0; c<sensor_info[s].num_channels; c++) {
 102
 103                         /* Read _en file */
 104                         sprintf(sysfs_path, CHANNEL_PATH "%s",
 105                                 sensor_info[s].dev_num,
 106                                 sensor_catalog[i].channel[c].en_path);
 107
 108                         n = sysfs_read_int(sysfs_path, &ch_enabled);
 109
 110                         if (n == -1) {
 111                                 ALOGW(  "Failed to read _en flag: %s\n",
 112                                 sysfs_path);
 113                                 continue;
 114                         }
 115
 116                         if (!ch_enabled != 1) {
 117                                 sensor_info[s].channel[c].size = 0;
 118                         }
 119
 120                         /* Read _type file */
 121                         sprintf(sysfs_path, CHANNEL_PATH "%s",
 122                                 sensor_info[s].dev_num,
 123                                 sensor_catalog[i].channel[c].type_path);
 124
 125                         n = sysfs_read_str(sysfs_path, spec_buf,
 126                                                 sizeof(spec_buf));
 127
 128                         if (n == -1) {
 129                                         ALOGW(  "Failed to read type: %s\n",
 130                                         sysfs_path);
 131                                         continue;
 132                                 }
 133
 134                         ch_spec = sensor_info[s].channel[c].type_spec;
 135
 136                         memcpy(ch_spec, spec_buf, sizeof(spec_buf));
 137
 138                         ch_info = &sensor_info[s].channel[c].type_info;
 139
 140                         size = decode_type_spec(ch_spec, ch_info);
 141
 142                         /* Read _index file */
 143                         sprintf(sysfs_path, CHANNEL_PATH "%s",
 144                                 sensor_info[s].dev_num,
 145                                 sensor_catalog[i].channel[c].index_path);
 146
 147                         n = sysfs_read_int(sysfs_path, &ch_index);
 148
 149                         if (n == -1) {
 150                                         ALOGW(  "Failed to read index: %s\n",
 151                                                 sysfs_path);
 152                                         continue;
 153                                 }
 154
 155                         if (ch_index >= MAX_SENSORS) {
 156                                 ALOGE("Index out of bounds!: %s\n", sysfs_path);
 157                                 continue;
 158                         }
 159
 160                         /* Record what this index is about */
 161
 162                         sensor_handle_from_index [ch_index] = s;
 163                         channel_number_from_index[ch_index] = c;
 164                         channel_size_from_index  [ch_index] = size;
 165
 166                         active_channels++;
 167                 }
 168         }
 169
 170         ALOGI("Found %d enabled channels for iio device %d\n", active_channels,
 171                 dev_num);
 172
 173         /*
 174          * Now that we know which channels are enabled, their sizes and their
 175          * ordering, update channels offsets within device report. Note: there
 176          * is a possibility that several sensors share the same index, with
 177          * their data fields being isolated by masking and shifting as specified
 178          * through the real bits and shift values in type attributes. This case
 179          * is not currently supported. Also, the code below assumes no hole in
 180          * the sequence of indices, so it is dependent on discovery of all
 181          * sensors.
 182          */
 183          offset = 0;
 184          for (i=0; i<MAX_SENSORS * MAX_CHANNELS; i++) {
 185                 s =     sensor_handle_from_index[i];
 186                 c =     channel_number_from_index[i];
 187                 size =  channel_size_from_index[i];
 188
 189                 if (!size)
 190                         continue;
 191
 192                 ALOGI("S%d C%d : offset %d, size %d, type %s\n",
 193                       s, c, offset, size, sensor_info[s].channel[c].type_spec);
 194
 195                 sensor_info[s].channel[c].offset        = offset;
 196                 sensor_info[s].channel[c].size          = size;
 197
 198                 offset += size;
 199          }
 200 }
 201
 202
 203 int adjust_counters (int s, int enabled)
 204 {
 205         /*
 206          * Adjust counters based on sensor enable action. Return values are:
 207          * -1 if there's an inconsistency: abort action in this case
 208          *  0 if the operation was completed and we're all set
 209          *  1 if we toggled the state of the sensor and there's work left
 210          */
 211
 212         int dev_num = sensor_info[s].dev_num;
 213
 214         /* Refcount per sensor, in terms of enable count */
 215         if (enabled) {
 216                 ALOGI("Enabling sensor %d (iio device %d: %s)\n",
 217                         s, dev_num, sensor_info[s].internal_name);
 218
 219                 sensor_info[s].enable_count++;
 220
 221                 if (sensor_info[s].enable_count != 1)
 222                         return 0; /* The sensor was, and remains, in use */
 223         } else {
 224                 if (sensor_info[s].enable_count == 0)
 225                         return -1; /* Spurious disable call */
 226
 227                 ALOGI("Disabling sensor %d (iio device %d)\n", s, dev_num);
 228
 229                 sensor_info[s].enable_count--;
 230
 231                 if (sensor_info[s].enable_count > 0)
 232                         return 0; /* The sensor was, and remains, in use */
 233
 234                 /* Sensor disabled, clear up pending data */
 235
 236                 sensor_info[s].report_pending = 0;
 237                 memset(sensor_info[s].report_buffer, 0, MAX_SENSOR_REPORT_SIZE);
 238         }
 239
 240         /* We changed the state of a sensor - adjust per iio device counters */
 241
 242         /* If this is a regular event-driven sensor */
 243         if (sensor_info[s].num_channels) {
 244
 245                         if (enabled)
 246                                 trig_sensors_per_dev[dev_num]++;
 247                         else
 248                                 trig_sensors_per_dev[dev_num]--;
 249
 250                         return 1;
 251                 }
 252
 253         if (enabled) {
 254                 active_poll_sensors++;
 255                 poll_sensors_per_dev[dev_num]++;
 256                 return 1;
 257         }
 258
 259         active_poll_sensors--;
 260         poll_sensors_per_dev[dev_num]--;
 261         return 1;
 262 }
 263
 264
 265 int sensor_activate(int s, int enabled)
 266 {
 267         char sysfs_path[PATH_MAX];
 268         char device_name[PATH_MAX];
 269         char trigger_name[MAX_NAME_SIZE + 16];
 270         int c;
 271         struct epoll_event ev = {0};
 272         int dev_fd;
 273         int ret;
 274         int dev_num = sensor_info[s].dev_num;
 275         int i = sensor_info[s].catalog_index;
 276         int is_poll_sensor = !sensor_info[s].num_channels;
 277
 278         ret = adjust_counters(s, enabled);
 279
 280         /* If the operation was neutral in terms of state, we're done */
 281         if (ret <= 0)
 282                 return ret;
 283
 284         if (!is_poll_sensor) {
 285                 /* Changes have to be made while the buffer is turned off */
 286                 enable_buffer(dev_num, 0);
 287
 288                 /* Configure trigger */
 289                 switch (trig_sensors_per_dev[dev_num]) {
 290                         case 0:
 291                                 setup_trigger(dev_num, "none");
 292                                 break;
 293
 294                         case 1:
 295                                 sprintf(trigger_name, "%s-dev%d",
 296                                         sensor_info[s].internal_name, dev_num);
 297
 298                                 setup_trigger(dev_num, trigger_name);
 299                                 break;
 300
 301                         default:
 302                                 /* The trigger is already set */
 303                                 break;
 304                 }
 305
 306                 /*
 307                  * Turn channels associated to this sensor on or off, and update
 308                  * the channels maps for all sensors associated to this device.
 309                  */
 310                 for (c=0;c<sensor_info[s].num_channels; c++) {
 311                         sprintf(sysfs_path, CHANNEL_PATH "%s",
 312                                 sensor_info[s].dev_num,
 313                                 sensor_catalog[i].channel[c].en_path);
 314
 315                         sysfs_write_int(sysfs_path, enabled);
 316                 }
 317
 318                 /* If there's at least one sensor left */
 319                 if (trig_sensors_per_dev[dev_num]) {
 320                         refresh_sensor_report_maps(dev_num);
 321                         enable_buffer(dev_num, 1);
 322                 }
 323         }
 324
 325         /*
 326          * Make sure we have a fd on the character device ; conversely, close
 327          * the fd if no one is using associated sensor anymore. The assumption
 328          * here is that the underlying driver will power on the relevant
 329          * hardware block while someone hold a fd on the device.
 330          */
 331         dev_fd = device_fd[dev_num];
 332
 333         if (!enabled) {
 334                 if (dev_fd != -1 && !poll_sensors_per_dev[dev_num] &&
 335                         !trig_sensors_per_dev[dev_num]) {
 336                                 /*
 337                                  * Stop watching this fd. This should be a no-op
 338                                  * in case this fd was not in the poll set.
 339                                  */
 340                                 epoll_ctl(poll_fd, EPOLL_CTL_DEL, dev_fd, NULL);
 341
 342                                 close(dev_fd);
 343                                 device_fd[dev_num] = -1;
 344                         }
 345                 return 0;
 346         }
 347
 348         if (dev_fd == -1) {
 349                 /* First enabled sensor on this iio device */
 350                 sprintf(device_name, DEV_FILE_PATH, dev_num);
 351                 dev_fd = open(device_name, O_RDONLY | O_NONBLOCK);
 352
 353                 device_fd[dev_num] = dev_fd;
 354
 355                 if (dev_fd == -1) {
 356                         ALOGE("Could not open fd on %s (%s)\n",
 357                               device_name, strerror(errno));
 358                         adjust_counters(s, 0);
 359                         return -1;
 360                 }
 361
 362                 ALOGV("Opened %s: fd=%d\n", device_name, dev_fd);
 363
 364                 if (!is_poll_sensor) {
 365
 366                         /* Add this iio device fd to the set of watched fds */
 367                         ev.events = EPOLLIN;
 368                         ev.data.u32 = dev_num;
 369
 370                         ret = epoll_ctl(poll_fd, EPOLL_CTL_ADD, dev_fd, &ev);
 371
 372                         if (ret == -1) {
 373                                 ALOGE(  "Failed adding %d to poll set (%s)\n",
 374                                         dev_fd, strerror(errno));
 375                                 return -1;
 376                         }
 377
 378                         /* Note: poll-mode fds are not readable */
 379                 }
 380         }
 381
 382         /* Release the polling loop so an updated timeout gets used */
 383         write(poll_socket_pair[1], "", 1);
 384
 385         return 0;
 386 }
 387
 388
 389 static int integrate_device_report(int dev_num)
 390 {
 391         int len;
 392         int s,c;
 393         unsigned char buf[MAX_SENSOR_REPORT_SIZE * MAX_SENSORS] = { 0 };
 394         int sr_offset;
 395         unsigned char *target;
 396         unsigned char *source;
 397         int size;
 398         int expected_size = 0;
 399
 400         /* There's an incoming report on the specified fd */
 401
 402         if (dev_num < 0 || dev_num >= MAX_DEVICES ||
 403                 !trig_sensors_per_dev[dev_num]) {
 404                 ALOGE("Event reported on unexpected iio device %d\n", dev_num);
 405                 return -1;
 406         }
 407
 408         for (s=0; s<MAX_SENSORS; s++)
 409                 if (sensor_info[s].dev_num == dev_num)
 410                         for (c=0; c<sensor_info[s].num_channels; c++)
 411                                 expected_size += sensor_info[s].channel[c].size;
 412
 413         len = read(device_fd[dev_num], buf, expected_size);
 414
 415         if (len == -1) {
 416                 ALOGE("Could not read report from iio device %d (%s)\n",
 417                       dev_num, strerror(errno));
 418                 return -1;
 419         }
 420
 421         ALOGV("Read %d bytes from iio device %d\n", len, dev_num);
 422
 423         for (s=0; s<MAX_SENSORS; s++)
 424                 if (sensor_info[s].dev_num == dev_num) {
 425                         sr_offset = 0;
 426
 427                         /* Copy data from device to sensor report buffer */
 428                         for (c=0; c<sensor_info[s].num_channels; c++) {
 429
 430                                 target = sensor_info[s].report_buffer +
 431                                         sr_offset;
 432
 433                                 source = buf + sensor_info[s].channel[c].offset;
 434
 435                                 size = sensor_info[s].channel[c].size;
 436
 437                                 memcpy(target, source, size);
 438
 439                                 sr_offset += size;
 440                         }
 441
 442                         if (sensor_info[s].enable_count) {
 443                                 ALOGV("Sensor %d report available (%d bytes)\n",
 444                                       s, sr_offset);
 445
 446                                 sensor_info[s].report_pending = 1;
 447                         }
 448                 }
 449
 450         return 0;
 451 }
 452
 453
 454 static float acquire_immediate_value(int s, int c)
 455 {
 456         char sysfs_path[PATH_MAX];
 457         float val;
 458         int ret;
 459         int dev_num = sensor_info[s].dev_num;
 460         int i = sensor_info[s].catalog_index;
 461         const char* raw_path = sensor_catalog[i].channel[c].raw_path;
 462         const char* input_path = sensor_catalog[i].channel[c].input_path;
 463         float scale = sensor_info[s].scale;
 464         float offset = sensor_info[s].offset;
 465
 466         /* Acquire a sample value for sensor s / channel c through sysfs */
 467
 468         if (input_path[0]) {
 469                 sprintf(sysfs_path, BASE_PATH "%s", dev_num, input_path);
 470                 ret = sysfs_read_float(sysfs_path, &val);
 471
 472                 if (!ret) {
 473                         return val;
 474                 }
 475         };
 476
 477         if (!raw_path[0])
 478                 return 0;
 479
 480         sprintf(sysfs_path, BASE_PATH "%s", dev_num, raw_path);
 481         ret = sysfs_read_float(sysfs_path, &val);
 482
 483         if (ret == -1)
 484                 return 0;
 485
 486         return (val + offset) * scale;
 487 }
 488
 489
 490 static void propagate_sensor_report(int s, struct sensors_event_t* data)
 491 {
 492         /* There's a sensor report pending for this sensor ; transmit it */
 493
 494         int catalog_index = sensor_info[s].catalog_index;
 495         int sensor_type = sensor_catalog[catalog_index].type;
 496         int num_fields;
 497         int c;
 498         unsigned char* current_sample;
 499
 500         memset(data, 0, sizeof(sensors_event_t));
 501
 502         data->version = sizeof(sensors_event_t);
 503         data->sensor = s;
 504         data->type = sensor_type;
 505         data->timestamp = get_timestamp();
 506
 507         switch (sensor_type) {
 508                 case SENSOR_TYPE_ACCELEROMETER:         /* m/s^2        */
 509                 case SENSOR_TYPE_MAGNETIC_FIELD:        /* micro-tesla  */
 510                 case SENSOR_TYPE_ORIENTATION:           /* degrees      */
 511                 case SENSOR_TYPE_GYROSCOPE:             /* radians/s    */
 512                         num_fields = 3;
 513                         break;
 514
 515                 case SENSOR_TYPE_LIGHT:                 /* SI lux units */
 516                 case SENSOR_TYPE_AMBIENT_TEMPERATURE:   /* °C          */
 517                 case SENSOR_TYPE_TEMPERATURE:           /* °C          */
 518                 case SENSOR_TYPE_PROXIMITY:             /* centimeters  */
 519                 case SENSOR_TYPE_PRESSURE:              /* hecto-pascal */
 520                 case SENSOR_TYPE_RELATIVE_HUMIDITY:     /* percent */
 521                         num_fields = 1;
 522                         break;
 523
 524                 case SENSOR_TYPE_ROTATION_VECTOR:
 525                         num_fields = 4;
 526                         break;
 527
 528                 case SENSOR_TYPE_DEVICE_PRIVATE_BASE:   /* hidden for now */
 529                         num_fields = 0;
 530                         break;
 531
 532                 default:
 533                         ALOGE("Unknown sensor type!\n");
 534                         num_fields = 0;
 535                         break;
 536         }
 537
 538         ALOGV("Sample on sensor %d (type %d):\n", s, sensor_type);
 539
 540         /* If we're dealing with a poll-mode sensor */
 541         if (!sensor_info[s].num_channels) {
 542
 543                 /* Read values through sysfs rather than from a report buffer */
 544                 for (c=0; c<num_fields; c++) {
 545
 546                         data->data[c] = acquire_immediate_value(s, c);
 547
 548                         ALOGV("\tfield %d: %f\n", c, data->data[c]);
 549                 }
 550
 551                 finalize_sample(s, data);
 552                 return;
 553         }
 554
 555         /* Convert the data into the expected Android-level format */
 556
 557         current_sample = sensor_info[s].report_buffer;
 558
 559         for (c=0; c<num_fields; c++) {
 560
 561                 data->data[c] = transform_sample(s, c, current_sample);
 562
 563                 ALOGV("\tfield %d: %f\n", c, data->data[c]);
 564                 current_sample += sensor_info[s].channel[c].size;
 565         }
 566
 567         finalize_sample(s, data);
 568 }
 569
 570
 571 static int get_poll_time (void)
 572 {
 573         if (!active_poll_sensors)
 574                 return -1;      /* Infinite wait */
 575
 576         return 100;     /* ms ... this needs to be dynamic */
 577 }
 578
 579
 580 static void acknowledge_release (void)
 581 {
 582         /* A write to our socket circuit was performed to release epoll */
 583         char buf;
 584         read(poll_socket_pair[0], &buf, 1);
 585 }
 586
 587
 588 int sensor_poll(struct sensors_event_t* data, int count)
 589 {
 590         int s;
 591         int i;
 592         int nfds;
 593         int delta;
 594         struct epoll_event ev[MAX_DEVICES];
 595
 596         /* Get one or more events from our collection of sensors */
 597
 598 return_first_available_sensor_report:
 599
 600         /* If there's at least one available report */
 601         for (s=0; s<sensor_count; s++)
 602                 if (sensor_info[s].report_pending) {
 603
 604                         /* Return that up */
 605                         propagate_sensor_report(s, data);
 606                         sensor_info[s].report_pending = 0;
 607                         ALOGV("Report on sensor %d\n", s);
 608                         return 1;
 609                 }
 610 await_event:
 611
 612         /* Keep a minimum time interval between poll operations */
 613         delta = (get_timestamp() - last_poll_exit_ts)/1000;
 614
 615         if (delta > 0 && delta < POLL_MIN_INTERVAL)
 616                 usleep(POLL_MIN_INTERVAL - delta);
 617
 618         ALOGV("Awaiting sensor data\n");
 619
 620         nfds = epoll_wait(poll_fd, ev, MAX_DEVICES, get_poll_time());
 621
 622         last_poll_exit_ts = get_timestamp();
 623
 624         if (nfds == -1) {
 625                 ALOGI("epoll_wait returned -1 (%s)\n", strerror(errno));
 626                 goto await_event;
 627         }
 628
 629         ALOGV("%d fds signalled\n", nfds);
 630
 631         /* For each of the devices for which a report is available */
 632         for (i=0; i<nfds; i++)
 633                 if (ev[i].events == EPOLLIN) {
 634                         if (ev[i].data.u32 == INVALID_DEV_NUM) {
 635                                 acknowledge_release();
 636                                 goto await_event;
 637                         } else
 638                                 /* Read report */
 639                                 integrate_device_report(ev[i].data.u32);
 640                 }
 641
 642         /* It's a good time to invalidate poll-mode sensor values */
 643         if (active_poll_sensors)
 644                 for (s=0; s<sensor_count; s++)
 645                         if (sensor_info[s].enable_count &&
 646                                 !sensor_info[s].num_channels)
 647                                         sensor_info[s].report_pending = 1;
 648
 649         goto return_first_available_sensor_report;
 650 }
 651
 652
 653 int sensor_set_delay(int s, int64_t ns)
 654 {
 655         /* Set the rate at which a specific sensor should report events */
 656
 657         /* See Android sensors.h for indication on sensor trigger modes */
 658
 659         char sysfs_path[PATH_MAX];
 660         int dev_num             =       sensor_info[s].dev_num;
 661         int i                   =       sensor_info[s].catalog_index;
 662         const char *prefix      =       sensor_catalog[i].tag;
 663         int new_sampling_rate   =       (int) (1000000000L/ns);
 664         int cur_sampling_rate;
 665
 666         ALOGI("sensor_set_delay: sampling rate set to %d\n", new_sampling_rate);
 667
 668         sprintf(sysfs_path, COMMON_SAMPLING_PATH, dev_num, prefix);
 669
 670         if (sysfs_read_int(sysfs_path, &cur_sampling_rate) != -1)
 671                 if (new_sampling_rate != cur_sampling_rate) {
 672
 673                         if (trig_sensors_per_dev[dev_num])
 674                                 enable_buffer(dev_num, 0);
 675
 676                         sysfs_write_int(sysfs_path, new_sampling_rate);
 677
 678                         if (trig_sensors_per_dev[dev_num])
 679                                 enable_buffer(dev_num, 1);
 680         }
 681
 682         sensor_info[s].sampling_rate = new_sampling_rate;
 683
 684         /* Release the polling loop so an updated timeout value gets used */
 685         write(poll_socket_pair[1], "", 1);
 686
 687         return 0;
 688 }
 689
 690
 691 int allocate_control_data (void)
 692 {
 693         int i;
 694         struct epoll_event ev = {0};
 695
 696         for (i=0; i<MAX_DEVICES; i++)
 697                 device_fd[i] = -1;
 698
 699         poll_fd = epoll_create(MAX_DEVICES);
 700
 701         if (poll_fd == -1) {
 702                 ALOGE("Can't create epoll instance for iio sensors!\n");
 703                 return -1;
 704         }
 705
 706         /* Create and add "unblocking" fd to the set of watched fds */
 707
 708         if (socketpair(AF_UNIX, SOCK_STREAM, 0, poll_socket_pair) == -1) {
 709                 ALOGE("Can't create socket pair for iio sensors!\n");
 710                 close(poll_fd);
 711                 return -1;
 712         }
 713
 714         ev.events = EPOLLIN;
 715         ev.data.u32 = INVALID_DEV_NUM;
 716
 717         epoll_ctl(poll_fd, EPOLL_CTL_ADD, poll_socket_pair[0], &ev);
 718
 719         return poll_fd;
 720 }
 721
 722
 723 void delete_control_data (void)
 724 {
 725 }