text: /*
  // Copyright (c) 2015 Intel Corporation
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  */
  
  #include <stdlib.h>
  #include <ctype.h>
  #include <fcntl.h>
  #include <unistd.h>
  #include <pthread.h>
  #include <time.h>
  #include <math.h>
  #include <sys/epoll.h>
  #include <sys/ioctl.h>
  #include <sys/socket.h>
  #include <utils/Log.h>
  #include <hardware/sensors.h>
  #include <linux/ioctl.h>
  #include "control.h"
  #include "enumeration.h"
  #include "utils.h"
  #include "transform.h"
  #include "calibration.h"
  #include "description.h"
  #include "filtering.h"
  #ifndef __NO_EVENTS__
  #include <linux/iio/events.h>
  #include <linux/iio/types.h>
  #endif
  #include <errno.h>
  
  /* Currently active sensors count, per device */
  static int poll_sensors_per_dev[MAX_DEVICES];		/* poll-mode sensors				*/
  static int trig_sensors_per_dev[MAX_DEVICES];		/* trigger, event based				*/
  
  static int device_fd[MAX_DEVICES];			/* fd on the /dev/iio:deviceX file		*/
  static int events_fd[MAX_DEVICES];			/* fd on the /sys/bus/iio/devices/iio:deviceX/events/<event_name> file */
  static int has_iio_ts[MAX_DEVICES];			/* ts channel available on this iio dev		*/
  static int expected_dev_report_size[MAX_DEVICES];	/* expected iio scan len			*/
  static int poll_fd;					/* epoll instance covering all enabled sensors	*/
  
  static int active_poll_sensors;				/* Number of enabled poll-mode sensors		*/
  
  static int flush_event_fd[2];				/* Pipe used for flush signaling */
  
  /* We use pthread condition variables to get worker threads out of sleep */
  static pthread_condattr_t thread_cond_attr	[MAX_SENSORS];
  static pthread_cond_t     thread_release_cond	[MAX_SENSORS];
  static pthread_mutex_t    thread_release_mutex	[MAX_SENSORS];
  
  #define FLUSH_REPORT_TAG			900
  /*
   * We associate tags to each of our poll set entries. These tags have the following values:
   * - a iio device number if the fd is a iio character device fd
   * - THREAD_REPORT_TAG_BASE + sensor handle if the fd is the receiving end of a pipe used by a sysfs data acquisition thread
   */
  #define THREAD_REPORT_TAG_BASE		1000
  
  /* If buffer enable fails, we may want to retry a few times before giving up */
  #define ENABLE_BUFFER_RETRIES		3
  #define ENABLE_BUFFER_RETRY_DELAY_MS	10
  
  
  inline int is_enabled (int s)
  {
  	return sensor[s].directly_enabled || sensor[s].ref_count;
  }
  
  
  static int check_state_change (int s, int enabled, int from_virtual)
  {
  	if (enabled) {
  		if (sensor[s].directly_enabled)
  			return 0;			/* We're being enabled but already were directly activated: no change. */
  
  		if (!from_virtual)
  			sensor[s].directly_enabled = 1;	/* We're being directly enabled */
  
  		if (sensor[s].ref_count)
  			return 0;			/* We were already indirectly enabled */
  
  		return 1; 				/* Do continue enabling this sensor */
  	}
  
  	if (!is_enabled(s))
  		return 0;				/* We are being disabled but already were: no change */
  
  	if (from_virtual && sensor[s].directly_enabled)
  		return 0;				/* We're indirectly disabled but the base is still active */
  
  	sensor[s].directly_enabled = 0;			/* We're now directly disabled */
  
  	if (!from_virtual && sensor[s].ref_count)
  		return 0;				/* We still have ref counts */
  
  	return 1;					/* Do continue disabling this sensor */
  }
  
  
  static int enable_buffer (int dev_num, int enabled)
  {
  	char sysfs_path[PATH_MAX];
  	int retries = ENABLE_BUFFER_RETRIES;
  
  	sprintf(sysfs_path, ENABLE_PATH, dev_num);
  
  	while (retries) {
  		/* Low level, non-multiplexed, enable/disable routine */
  		if (sysfs_write_int(sysfs_path, enabled) > 0)
  			return 0;
  
  		ALOGE("Failed enabling buffer on dev%d, retrying", dev_num);
  		usleep(ENABLE_BUFFER_RETRY_DELAY_MS*1000);
  		retries--;
  	}
  
  	ALOGE("Could not enable buffer\n");
  	return -EIO;
  }
  
  
  static int setup_trigger (int s, const char* trigger_val)
  {
  	char sysfs_path[PATH_MAX];
  	int ret = -1, attempts = 5;
  
  	sprintf(sysfs_path, TRIGGER_PATH, sensor[s].dev_num);
  
  	if (trigger_val[0] != '\n')
  		ALOGI("Setting S%d (%s) trigger to %s\n", s, sensor[s].friendly_name, trigger_val);
  
  	while (ret == -1 && attempts) {
  		ret = sysfs_write_str(sysfs_path, trigger_val);
  		attempts--;
  	}
  
  	if (ret != -1)
  		sensor[s].selected_trigger = trigger_val;
  	else
  		ALOGE("Setting S%d (%s) trigger to %s FAILED.\n", s, sensor[s].friendly_name, trigger_val);
  	return ret;
  }
  
  static int enable_event(int dev_num, const char *name, int enabled)
  {
  	char sysfs_path[PATH_MAX];
  
  	sprintf(sysfs_path, EVENTS_PATH "%s", dev_num, name);
  	return sysfs_write_int(sysfs_path, enabled);
  }
  
  static int enable_sensor(int dev_num, const char *tag, int enabled)
  {
  	char sysfs_path[PATH_MAX];
  
  	sprintf(sysfs_path, SENSOR_ENABLE_PATH, dev_num, tag);
  	return sysfs_write_int(sysfs_path, enabled);
  }
  
  static void enable_iio_timestamp (int dev_num, int known_channels)
  {
  	/* Check if we have a dedicated iio timestamp channel */
  
  	char spec_buf[MAX_TYPE_SPEC_LEN];
  	char sysfs_path[PATH_MAX];
  	int n;
  
  	sprintf(sysfs_path, CHANNEL_PATH "%s", dev_num, "in_timestamp_type");
  
  	n = sysfs_read_str(sysfs_path, spec_buf, sizeof(spec_buf));
  
  	if (n <= 0)
  		return;
  
  	if (strcmp(spec_buf, "le:s64/64>>0"))
  		return;
  
  	/* OK, type is int64_t as expected, in little endian representation */
  
  	sprintf(sysfs_path, CHANNEL_PATH"%s", dev_num, "in_timestamp_index");
  
  	if (sysfs_read_int(sysfs_path, &n))
  		return;
  
  	/* Check that the timestamp comes after the other fields we read */
  	if (n != known_channels)
  		return;
  
  	/* Try enabling that channel */
  	sprintf(sysfs_path, CHANNEL_PATH "%s", dev_num, "in_timestamp_en");
  
  	sysfs_write_int(sysfs_path, 1);
  
  	if (sysfs_read_int(sysfs_path, &n))
  		return;
  
  	if (n) {
  		ALOGI("Detected timestamp channel on iio device %d\n", dev_num);
  		has_iio_ts[dev_num] = 1;
  	}
  }
  
  
  static int decode_type_spec (const char type_buf[MAX_TYPE_SPEC_LEN], datum_info_t *type_info)
  {
  	/* Return size in bytes for this type specification, or -1 in error */
  	char sign;
  	char endianness;
  	unsigned int realbits, storagebits, shift;
  	int tokens;
  
  	/* Valid specs: "le:u10/16>>0", "le:s16/32>>0" or "le:s32/32>>0" */
  
  	tokens = sscanf(type_buf, "%ce:%c%u/%u>>%u", &endianness, &sign, &realbits, &storagebits, &shift);
  
  	if (tokens != 5 || (endianness != 'b' && endianness != 'l') || (sign != 'u' && sign != 's') ||
  	    realbits > storagebits || (storagebits != 16 && storagebits != 32 && storagebits != 64)) {
  			ALOGE("Invalid iio channel type spec: %s\n", type_buf);
  			return -1;
  	}
  
  	type_info->endianness	=		endianness;
  	type_info->sign		=		sign;
  	type_info->realbits	=	(short)	realbits;
  	type_info->storagebits	=	(short)	storagebits;
  	type_info->shift	=	(short)	shift;
  
  	return storagebits / 8;
  }
  
  
  void build_sensor_report_maps (int dev_num)
  {
  	/*
  	 * Read sysfs files from a iio device's scan_element directory, and build a couple of tables from that data. These tables will tell, for
  	 * each sensor, where to gather relevant data in a device report, i.e. the structure that we read from the /dev/iio:deviceX file in order to
  	 * sensor report, itself being the data that we return to Android when a sensor poll completes. The mapping should be straightforward in the
  	 * case where we have a single sensor active per iio device but, this is not the general case. In general several sensors can be handled
  	 * through a single iio device, and the _en, _index and _type syfs entries all concur to paint a picture of what the structure of the
  	 * device report is.
  	 */
  
  	int s;
  	int c;
  	int n;
  	int i;
  	int ch_index;
  	char* ch_spec;
  	char spec_buf[MAX_TYPE_SPEC_LEN];
  	datum_info_t* ch_info;
  	int size;
  	char sysfs_path[PATH_MAX];
  	int known_channels;
  	int offset;
  	int channel_size_from_index[MAX_SENSORS * MAX_CHANNELS] = { 0 };
  	int sensor_handle_from_index[MAX_SENSORS * MAX_CHANNELS] = { 0 };
  	int channel_number_from_index[MAX_SENSORS * MAX_CHANNELS] = { 0 };
  
  	known_channels = 0;
  
  	/* For each sensor that is linked to this device */
  	for (s=0; s<sensor_count; s++) {
  		if (sensor[s].dev_num != dev_num)
  			continue;
  
  		i = sensor[s].catalog_index;
  
  		/* Read channel details through sysfs attributes */
  		for (c=0; c<sensor[s].num_channels; c++) {
  
  			/* Read _type file */
  			sprintf(sysfs_path, CHANNEL_PATH "%s", sensor[s].dev_num, sensor_catalog[i].channel[c].type_path);
  
  			n = sysfs_read_str(sysfs_path, spec_buf, sizeof(spec_buf));
  
  			if (n == -1) {
  					ALOGW(	"Failed to read type: %s\n", sysfs_path);
  					continue;
  			}
  
  			ch_spec = sensor[s].channel[c].type_spec;
  
  			memcpy(ch_spec, spec_buf, sizeof(spec_buf));
  
  			ch_info = &sensor[s].channel[c].type_info;
  
  			size = decode_type_spec(ch_spec, ch_info);
  
  			/* Read _index file */
  			sprintf(sysfs_path, CHANNEL_PATH "%s", sensor[s].dev_num, sensor_catalog[i].channel[c].index_path);
  
  			n = sysfs_read_int(sysfs_path, &ch_index);
  
  			if (n == -1) {
  					ALOGW(	"Failed to read index: %s\n", sysfs_path);
  					continue;
  			}
  
  			if (ch_index >= MAX_SENSORS) {
  				ALOGE("Index out of bounds!: %s\n", sysfs_path);
  				continue;
  			}
  
  			/* Record what this index is about */
  
  			sensor_handle_from_index [ch_index] = s;
  			channel_number_from_index[ch_index] = c;
  			channel_size_from_index  [ch_index] = size;
  
  			known_channels++;
  		}
  
  		sensor_update_max_range(s);
  
  		/* Stop sampling - if we are recovering from hal restart */
                  enable_buffer(dev_num, 0);
                  setup_trigger(s, "\n");
  
  		/* Turn on channels we're aware of */
  		for (c=0;c<sensor[s].num_channels; c++) {
  			sprintf(sysfs_path, CHANNEL_PATH "%s", sensor[s].dev_num, sensor_catalog[i].channel[c].en_path);
  			sysfs_write_int(sysfs_path, 1);
  		}
  	}
  
  	ALOGI("Found %d channels on iio device %d\n", known_channels, dev_num);
  
  	/*
  	 * Now that we know which channels are defined, their sizes and their ordering, update channels offsets within device report. Note: there
  	 * is a possibility that several sensors share the same index, with their data fields being isolated by masking and shifting as specified
  	 * through the real bits and shift values in type attributes. This case is not currently supported. Also, the code below assumes no hole in
  	 * the sequence of indices, so it is dependent on discovery of all sensors.
  	 */
  	 offset = 0;
  
  	 for (i=0; i<MAX_SENSORS * MAX_CHANNELS; i++) {
  		s =	sensor_handle_from_index[i];
  		c =	channel_number_from_index[i];
  		size = 	channel_size_from_index[i];
  
  		if (!size)
  			continue;
  
  		ALOGI("S%d C%d : offset %d, size %d, type %s\n", s, c, offset, size, sensor[s].channel[c].type_spec);
  
  		sensor[s].channel[c].offset	= offset;
  		sensor[s].channel[c].size		= size;
  
  		offset += size;
  	 }
  
  	/* Enable the timestamp channel if there is one available */
  	enable_iio_timestamp(dev_num, known_channels);
  
  	/* Add padding and timestamp size if it's enabled on this iio device */
  	if (has_iio_ts[dev_num])
  		offset = (offset+7)/8*8 + sizeof(int64_t);
  
  	expected_dev_report_size[dev_num] = offset;
  	ALOGI("Expecting %d scan length on iio dev %d\n", offset, dev_num);
  
  	if (expected_dev_report_size[dev_num] > MAX_DEVICE_REPORT_SIZE) {
  		ALOGE("Unexpectedly large scan buffer on iio dev%d: %d bytes\n", dev_num, expected_dev_report_size[dev_num]);
  
  		expected_dev_report_size[dev_num] = MAX_DEVICE_REPORT_SIZE;
  	}
  }
  
  
  int adjust_counters (int s, int enabled, int from_virtual)
  {
  	/*
  	 * Adjust counters based on sensor enable action. Return values are:
  	 *  0 if the operation was completed and we're all set
  	 *  1 if we toggled the state of the sensor and there's work left
  	 * -1 in case of an error
  	 */
  
  	int dev_num = sensor[s].dev_num;
  
  	if (!check_state_change(s, enabled, from_virtual))
  		return 0; /* The state of the sensor remains the same: we're done */
  
  	if (enabled) {
  		ALOGI("Enabling sensor %d (iio device %d: %s)\n", s, dev_num, sensor[s].friendly_name);
  
  		switch (sensor[s].type) {
  			case SENSOR_TYPE_ACCELEROMETER:
  				accel_cal_init(s);
  				break;
  
  			case SENSOR_TYPE_MAGNETIC_FIELD:
  				compass_read_data(s);
  				break;
  
  			case SENSOR_TYPE_GYROSCOPE:
  				gyro_cal_init(s);
  				break;
  		}
  	} else {
  		ALOGI("Disabling sensor %d (iio device %d: %s)\n", s, dev_num, sensor[s].friendly_name);
  
  		/* Sensor disabled, lower report available flag */
  		sensor[s].report_pending = 0;
  
  		/* Save calibration data to persistent storage */
  		switch (sensor[s].type) {
  			case SENSOR_TYPE_ACCELEROMETER:
  				accel_cal_store(s);
  				break;
  
  			case SENSOR_TYPE_MAGNETIC_FIELD:
  				compass_store_data(s);
  				break;
  
  			case SENSOR_TYPE_GYROSCOPE:
  				gyro_store_data(s);
  				break;
  		}
  	}
  
  	/* We changed the state of a sensor: adjust device ref counts */
  
  	switch(sensor[s].mode) {
  	case MODE_TRIGGER:
  		if (enabled)
  			trig_sensors_per_dev[dev_num]++;
  		else
  			trig_sensors_per_dev[dev_num]--;
  
  		return 1;
  	case MODE_POLL:
  		if (enabled) {
  			active_poll_sensors++;
  			poll_sensors_per_dev[dev_num]++;
  			return 1;
  		} else {
  			active_poll_sensors--;
  			poll_sensors_per_dev[dev_num]--;
  			return 1;
  		}
  	case MODE_EVENT:
  		return 1;
  	default:
  		/* Invalid sensor mode */
  		return -1;
  	}
  }
  
  
  static int get_field_count (int s, size_t *field_size)
  {
  	*field_size = sizeof(float);
  
  	switch (sensor[s].type) {
  		case SENSOR_TYPE_ACCELEROMETER:		/* m/s^2	*/
  		case SENSOR_TYPE_MAGNETIC_FIELD:	/* micro-tesla	*/
  		case SENSOR_TYPE_ORIENTATION:		/* degrees	*/
  		case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
  		case SENSOR_TYPE_GYROSCOPE:		/* radians/s	*/
  			return 3;
  
  		case SENSOR_TYPE_INTERNAL_INTENSITY:
  		case SENSOR_TYPE_INTERNAL_ILLUMINANCE:
  		case SENSOR_TYPE_LIGHT:			/* SI lux units */
  		case SENSOR_TYPE_AMBIENT_TEMPERATURE:	/* °C		*/
  		case SENSOR_TYPE_TEMPERATURE:		/* °C		*/
  		case SENSOR_TYPE_PROXIMITY:		/* centimeters	*/
  		case SENSOR_TYPE_PRESSURE:		/* hecto-pascal */
  		case SENSOR_TYPE_RELATIVE_HUMIDITY:	/* percent */
  		case SENSOR_TYPE_STEP_DETECTOR:		/* event: always 1 */
  			return 1;
  
  		case SENSOR_TYPE_ROTATION_VECTOR:
  			return 4;
  
  		case SENSOR_TYPE_STEP_COUNTER:		/* number of steps */
  			*field_size = sizeof(uint64_t);
  			return 1;
  		default:
  			ALOGE("Unknown sensor type!\n");
  			return 0;			/* Drop sample */
  	}
  }
  
  /*
   *  CTS acceptable thresholds:
   *	EventGapVerification.java: (th <= 1.8)
   *	FrequencyVerification.java: (0.9)*(expected freq) => (th <= 1.1111)
   */
  #define THRESHOLD 1.10
  #define MAX_DELAY 500000000 /* 500 ms */
  
  void set_report_ts(int s, int64_t ts)
  {
  	int64_t maxTs, period;
  
  	/*
  	*  A bit of a hack to please a bunch of cts tests. They
  	*  expect the timestamp to be exacly according to the set-up
  	*  frequency but if we're simply getting the timestamp at hal level
  	*  this may not be the case. Perhaps we'll get rid of this when
  	*  we'll be reading the timestamp from the iio channel for all sensors
  	*/
  	if (sensor[s].report_ts && sensor[s].sampling_rate &&
  		REPORTING_MODE(sensor_desc[s].flags) == SENSOR_FLAG_CONTINUOUS_MODE)
  	{
  		period = (int64_t) (1000000000.0 / sensor[s].sampling_rate);
  		maxTs = sensor[s].report_ts + THRESHOLD * period;
  		/* If we're too far behind get back on track */
  		if (ts - maxTs >= MAX_DELAY)
  			maxTs = ts;
  		sensor[s].report_ts = (ts < maxTs ? ts : maxTs);
  	} else {
  		sensor[s].report_ts = ts;
  	}
  }
  
  static void* acquisition_routine (void* param)
  {
  	/*
  	 * Data acquisition routine run in a dedicated thread, covering a single sensor. This loop will periodically retrieve sampling data through
  	 * sysfs, then package it as a sample and transfer it to our master poll loop through a report fd. Checks for a cancellation signal quite
  	 * frequently, as the thread may be disposed of at any time. Note that Bionic does not provide pthread_cancel / pthread_testcancel...
  	 */
  
  	int s = (int) (size_t) param;
  	int num_fields;
  	sensors_event_t data = {0};
  	int c;
  	int ret;
  	struct timespec target_time;
  	int64_t timestamp, period, start, stop;
  	size_t field_size;
  
  	if (s < 0 || s >= sensor_count) {
  		ALOGE("Invalid sensor handle!\n");
  		return NULL;
  	}
  
  	ALOGI("Entering S%d (%s) data acquisition thread: rate:%g\n", s, sensor[s].friendly_name, sensor[s].sampling_rate);
  
  	if (sensor[s].sampling_rate <= 0) {
  		ALOGE("Invalid rate in acquisition routine for sensor %d: %g\n", s, sensor[s].sampling_rate);
  		return NULL;
  	}
  
  	/* Initialize data fields that will be shared by all sensor reports */
  	data.version	= sizeof(sensors_event_t);
  	data.sensor	= s;
  	data.type	= sensor_desc[s].type;
  
  	num_fields = get_field_count(s, &field_size);
  
  	/*
  	 * Each condition variable is associated to a mutex that has to be locked by the thread that's waiting on it. We use these condition
  	 * variables to get the acquisition threads out of sleep quickly after the sampling rate is adjusted, or the sensor is disabled.
  	 */
  	pthread_mutex_lock(&thread_release_mutex[s]);
  
  	/* Pinpoint the moment we start sampling */
  	timestamp = get_timestamp_monotonic();
  
  	/* Check and honor termination requests */
  	while (sensor[s].thread_data_fd[1] != -1) {
  		start = get_timestamp_boot();
  
  		/* Read values through sysfs */
  		for (c=0; c<num_fields; c++) {
  			if (field_size == sizeof(uint64_t))
  				data.u64.data[c] = acquire_immediate_uint64_value(s, c);
  			else
  				data.data[c] = acquire_immediate_float_value(s, c);
  
  			/* Check and honor termination requests */
  			if (sensor[s].thread_data_fd[1] == -1)
  				goto exit;
  		}
  		stop = get_timestamp_boot();
  		set_report_ts(s, start/2 + stop/2);
  		data.timestamp = sensor[s].report_ts;
  		/* If the sample looks good */
  		if (sensor[s].ops.finalize(s, &data)) {
  
  			/* Pipe it for transmission to poll loop */
  			ret = write(sensor[s].thread_data_fd[1], &data, sizeof(sensors_event_t));
  
  			if (ret != sizeof(sensors_event_t))
  				ALOGE("S%d write failure: wrote %zd, got %d\n", s, sizeof(sensors_event_t), ret);
  		}
  
  		/* Check and honor termination requests */
  		if (sensor[s].thread_data_fd[1] == -1)
  			goto exit;
  
  		/* Recalculate period assuming sensor[s].sampling_rate can be changed dynamically during the thread run */
  		if (sensor[s].sampling_rate <= 0) {
  			ALOGE("Unexpected sampling rate for sensor %d: %g\n", s, sensor[s].sampling_rate);
  			goto exit;
  		}
  
  		period = (int64_t) (1000000000.0 / sensor[s].sampling_rate);
  		timestamp += period;
  		set_timestamp(&target_time, timestamp);
  
  		/* Wait until the sampling time elapses, or a rate change is signaled, or a thread exit is requested */
  		ret = pthread_cond_timedwait(&thread_release_cond[s], &thread_release_mutex[s], &target_time);
  	}
  
  exit:
  	ALOGV("Acquisition thread for S%d exiting\n", s);
  	pthread_mutex_unlock(&thread_release_mutex[s]);
  	pthread_exit(0);
  	return NULL;
  }
  
  
  static void start_acquisition_thread (int s)
  {
  	int incoming_data_fd;
  	int ret;
  
  	struct epoll_event ev = {0};
  
  	ALOGV("Initializing acquisition context for sensor %d\n", s);
  
  	/* Create condition variable and mutex for quick thread release */
  	ret = pthread_condattr_init(&thread_cond_attr[s]);
  	ret = pthread_condattr_setclock(&thread_cond_attr[s], CLOCK_MONOTONIC);
  	ret = pthread_cond_init(&thread_release_cond[s], &thread_cond_attr[s]);
  	ret = pthread_mutex_init(&thread_release_mutex[s], NULL);
  
  	/* Create a pipe for inter thread communication */
  	ret = pipe(sensor[s].thread_data_fd);
  
  	incoming_data_fd = sensor[s].thread_data_fd[0];
  
  	ev.events = EPOLLIN;
  	ev.data.u32 = THREAD_REPORT_TAG_BASE + s;
  
  	/* Add incoming side of pipe to our poll set, with a suitable tag */
  	ret = epoll_ctl(poll_fd, EPOLL_CTL_ADD, incoming_data_fd , &ev);
  	if (ret == -1) {
  		ALOGE("Failed adding %d to poll set (%s)\n",
  			incoming_data_fd, strerror(errno));
  	}
  
  	/* Create and start worker thread */
  	ret = pthread_create(&sensor[s].acquisition_thread, NULL, acquisition_routine, (void*) (size_t) s);
  }
  
  
  static void stop_acquisition_thread (int s)
  {
  	int incoming_data_fd = sensor[s].thread_data_fd[0];
  	int outgoing_data_fd = sensor[s].thread_data_fd[1];
  
  	ALOGV("Tearing down acquisition context for sensor %d\n", s);
  
  	/* Delete the incoming side of the pipe from our poll set */
  	epoll_ctl(poll_fd, EPOLL_CTL_DEL, incoming_data_fd, NULL);
  
  	/* Mark the pipe ends as invalid ; that's a cheap exit flag */
  	sensor[s].thread_data_fd[0] = -1;
  	sensor[s].thread_data_fd[1] = -1;
  
  	/* Close both sides of our pipe */
  	close(incoming_data_fd);
  	close(outgoing_data_fd);
  
  	/* Stop acquisition thread and clean up thread handle */
  	pthread_cond_signal(&thread_release_cond[s]);
  	pthread_join(sensor[s].acquisition_thread, NULL);
  
  	/* Clean up our sensor descriptor */
  	sensor[s].acquisition_thread = -1;
  
  	/* Delete condition variable and mutex */
  	pthread_cond_destroy(&thread_release_cond[s]);
  	pthread_mutex_destroy(&thread_release_mutex[s]);
  }
  
  
  static int is_fast_accelerometer (int s)
  {
  	/*
  	 * Some games don't react well to accelerometers using any-motion triggers. Even very low thresholds seem to trip them, and they tend to
  	 * request fairly high event rates. Favor continuous triggers if the sensor is an accelerometer and uses a sampling rate of at least 25.
  	 */
  
  	if (sensor[s].type != SENSOR_TYPE_ACCELEROMETER)
  		return 0;
  
  	if (sensor[s].sampling_rate < 25)
  		return 0;
  
  	return 1;
  }
  
  
  static void tentative_switch_trigger (int s)
  {
  	/*
  	 * Under certain situations it may be beneficial to use an alternate trigger:
  	 *
  	 * - for applications using the accelerometer with high sampling rates, prefer the continuous trigger over the any-motion one, to avoid
  	 *   jumps related to motion thresholds
  	 */
  
  	if (is_fast_accelerometer(s) && !(sensor[s].quirks & QUIRK_TERSE_DRIVER) && sensor[s].selected_trigger == sensor[s].motion_trigger_name)
  		setup_trigger(s, sensor[s].init_trigger_name);
  }
  
  
  static float get_group_max_sampling_rate (int s)
  {
  	/* Review the sampling rates of linked sensors and return the maximum */
  
  	int i, vi;
  
  	float arbitrated_rate = 0;
  
  	if (is_enabled(s))
  		arbitrated_rate = sensor[s].requested_rate;
  
  	/* If any of the currently active sensors built on top of this one need a higher sampling rate, switch to this rate */
  	for (i = 0; i < sensor_count; i++)
  		for (vi = 0; vi < sensor[i].base_count; vi++)
  			if (sensor[i].base[vi] == s && is_enabled(i) && sensor[i].requested_rate > arbitrated_rate)	/* If sensor i depends on sensor s */
  				arbitrated_rate = sensor[i].requested_rate;
  
  	/* If any of the currently active sensors we rely on is using a higher sampling rate, switch to this rate */
  	for (vi = 0; vi < sensor[s].base_count; vi++) {
  		i = sensor[s].base[vi];
  		if (is_enabled(i) && sensor[i].requested_rate > arbitrated_rate)
  			arbitrated_rate = sensor[i].requested_rate;
  	}
  
  	return arbitrated_rate;
  }
  
  extern float sensor_get_max_freq (int s);
  
  static float select_closest_available_rate(int s, float requested_rate)
  {
  	float sr;
  	int j;
  	float selected_rate = 0;
  	float max_rate_from_prop = sensor_get_max_freq(s);
  
  	if (!sensor[s].avail_freqs_count)
  		return requested_rate;
  
  	for (j = 0; j < sensor[s].avail_freqs_count; j++) {
  
  		sr = sensor[s].avail_freqs[j];
  
  		/* If this matches the selected rate, we're happy.  Have some tolerance for rounding errors and avoid needless jumps to higher rates */
  		if ((fabs(requested_rate - sr) <= 0.01) && (sr <= max_rate_from_prop)) {
  			return sr;
  		}
  
  		/* Select rate if it's less than max freq */
  		if ((sr > selected_rate) && (sr <= max_rate_from_prop)) {
  			selected_rate = sr;
  		}
  
  		/*
  		 * If we reached a higher value than the desired rate, adjust selected rate so it matches the first higher available one and
  		 * stop parsing - this makes the assumption that rates are sorted by increasing value in the allowed frequencies string.
  		 */
  		if (sr > requested_rate) {
  			return selected_rate;
  		}
  	}
  
  	/* Check for wrong values */
  	if (selected_rate < 0.1) {
  		return requested_rate;
  	} else {
  		return selected_rate;
  	}
  }
  
  static int sensor_set_rate (int s, float requested_rate)
  {
  	/* Set the rate at which a specific sensor should report events. See Android sensors.h for indication on sensor trigger modes */
  
  	char sysfs_path[PATH_MAX];
  	int dev_num		=	sensor[s].dev_num;
  	int i			=	sensor[s].catalog_index;
  	const char *prefix	=	sensor_catalog[i].tag;
  	int per_sensor_sampling_rate;
  	int per_device_sampling_rate;
  	int n;
  	float sr;
  	float group_max_sampling_rate;
  	float cur_sampling_rate; /* Currently used sampling rate	      */
  	float arb_sampling_rate; /* Granted sampling rate after arbitration   */
  	char hrtimer_sampling_path[PATH_MAX];
  	char trigger_path[PATH_MAX];
  
  	ALOGV("Sampling rate %g requested on sensor %d (%s)\n", requested_rate, s, sensor[s].friendly_name);
  
  	sensor[s].requested_rate = requested_rate;
  
  	arb_sampling_rate = requested_rate;
  
  	if (arb_sampling_rate < sensor[s].min_supported_rate) {
  		ALOGV("Sampling rate %g too low for %s, using %g instead\n", arb_sampling_rate, sensor[s].friendly_name, sensor[s].min_supported_rate);
  		arb_sampling_rate = sensor[s].min_supported_rate;
  	}
  
  	/* If one of the linked sensors uses a higher rate, adopt it */
  	group_max_sampling_rate = get_group_max_sampling_rate(s);
  
  	if (arb_sampling_rate < group_max_sampling_rate) {
  		ALOGV("Using %s sampling rate to %g too due to dependency\n", sensor[s].friendly_name, arb_sampling_rate);
  		arb_sampling_rate = group_max_sampling_rate;
  	}
  
  	if (sensor[s].max_supported_rate && arb_sampling_rate > sensor[s].max_supported_rate) {
  		ALOGV("Sampling rate %g too high for %s, using %g instead\n", arb_sampling_rate, sensor[s].friendly_name, sensor[s].max_supported_rate);
  		arb_sampling_rate = sensor[s].max_supported_rate;
  	}
  
  	sensor[s].sampling_rate = arb_sampling_rate;
  
  	/* If the sensor is virtual, we're done */
  	if (sensor[s].is_virtual)
  		return 0;
  
  	/* If we're dealing with a poll-mode sensor */
  	if (sensor[s].mode == MODE_POLL) {
  		if (is_enabled(s))
  			pthread_cond_signal(&thread_release_cond[s]); /* Wake up thread so the new sampling rate gets used */
  		return 0;
  	}
  
  	sprintf(sysfs_path, SENSOR_SAMPLING_PATH, dev_num, prefix);
  
  	if (sysfs_read_float(sysfs_path, &cur_sampling_rate) != -1) {
  		per_sensor_sampling_rate = 1;
  		per_device_sampling_rate = 0;
  	} else {
  		per_sensor_sampling_rate = 0;
  
  		sprintf(sysfs_path, DEVICE_SAMPLING_PATH, dev_num);
  
  		if (sysfs_read_float(sysfs_path, &cur_sampling_rate) != -1)
  			per_device_sampling_rate = 1;
  		else
  			per_device_sampling_rate = 0;
  	}
  
  	if (!per_sensor_sampling_rate && !per_device_sampling_rate) {
  		ALOGE("No way to adjust sampling rate on sensor %d\n", s);
  		return -ENOSYS;
  	}
  
  	if (sensor[s].hrtimer_trigger_name[0] != '\0') {
  		snprintf(trigger_path, PATH_MAX, "%s%s%d/", IIO_DEVICES, "trigger", sensor[s].trigger_nr);
  		snprintf(hrtimer_sampling_path, PATH_MAX, "%s%s", trigger_path, "sampling_frequency");
  		/* Enforce frequency update when software trigger
  		 * frequency and current sampling rate are different */
  		if (sysfs_read_float(hrtimer_sampling_path, &sr) != -1 && sr != cur_sampling_rate)
  			cur_sampling_rate = -1;
  	} else {
  		arb_sampling_rate = select_closest_available_rate(s, arb_sampling_rate);
  	}
  
  	/* Record the rate that was agreed upon with the sensor taken in isolation ; this avoid uncontrolled ripple effects between colocated sensor rates */
  	sensor[s].semi_arbitrated_rate = arb_sampling_rate;
  
  	/* Coordinate with others active sensors on the same device, if any */
  	if (per_device_sampling_rate)
  		for (n=0; n<sensor_count; n++)
  			if (n != s && sensor[n].dev_num == dev_num && sensor[n].num_channels && is_enabled(n) &&
  				sensor[n].semi_arbitrated_rate > arb_sampling_rate) {
  				ALOGV("Sampling rate shared between %s and %s, using %g instead of %g\n", sensor[s].friendly_name, sensor[n].friendly_name,
  													  sensor[n].semi_arbitrated_rate, arb_sampling_rate);
  				arb_sampling_rate = sensor[n].semi_arbitrated_rate;
  			}
  
  	sensor[s].sampling_rate = arb_sampling_rate;
  
  	/* Update actual sampling rate field for this sensor and others which may be sharing the same sampling rate */
  	if (per_device_sampling_rate)
  		for (n=0; n<sensor_count; n++)
  			if (sensor[n].dev_num == dev_num && n != s && sensor[n].num_channels)
  				sensor[n].sampling_rate = arb_sampling_rate;
  
  	/* If the desired rate is already active we're all set */
  	if (arb_sampling_rate == cur_sampling_rate)
  		return 0;
  
  	ALOGI("Sensor %d (%s) sampling rate set to %g\n", s, sensor[s].friendly_name, arb_sampling_rate);
  
  	if (sensor[s].hrtimer_trigger_name[0] != '\0')
  		sysfs_write_float(hrtimer_sampling_path, ceilf(arb_sampling_rate));
  
  	if (trig_sensors_per_dev[dev_num])
  		enable_buffer(dev_num, 0);
  
  	if (sensor[s].hrtimer_trigger_name[0] != '\0') {
  		sysfs_write_float(sysfs_path, select_closest_available_rate(s, arb_sampling_rate));
  	} else {
  		sysfs_write_float(sysfs_path, arb_sampling_rate);
  	}
  
  	/* Check if it makes sense to use an alternate trigger */
  	tentative_switch_trigger(s);
  
  	if (trig_sensors_per_dev[dev_num])
  		enable_buffer(dev_num, 1);
  
  	return 0;
  }
  
  
  static void reapply_sampling_rates (int s)
  {
  	/*
  	 * The specified sensor was either enabled or disabled. Other sensors in the same group may have constraints related to this sensor
  	 * sampling rate on their own sampling rate, so reevaluate them by retrying to use their requested sampling rate, rather than the one
  	 * that ended up being used after arbitration.
  	 */
  
  	int i, j, base;
  
  	if (sensor[s].is_virtual) {
  		/* Take care of downwards dependencies */
  		for (i=0; i<sensor[s].base_count; i++) {
  			base = sensor[s].base[i];
  			sensor_set_rate(base, sensor[base].requested_rate);
  		}
  		return;
  	}
  
  	/* Upwards too */
  	for (i=0; i<sensor_count; i++)
  		for (j=0; j<sensor[i].base_count; j++)
  			if (sensor[i].base[j] == s) /* If sensor i depends on sensor s */
  				sensor_set_rate(i, sensor[i].requested_rate);
  }
  
  
  static int sensor_activate_virtual (int s, int enabled, int from_virtual)
  {
  	int i, base;
  
  	sensor[s].event_count = 0;
  	sensor[s].meta_data_pending = 0;
  
  	if (!check_state_change(s, enabled, from_virtual))
  		return 0;	/* The state of the sensor remains the same ; we're done */
  
  	if (enabled)
  		ALOGI("Enabling sensor %d (%s)\n", s, sensor[s].friendly_name);
  	else
  		ALOGI("Disabling sensor %d (%s)\n", s, sensor[s].friendly_name);
  
  	sensor[s].report_pending = 0;
  
  	for (i=0; i<sensor[s].base_count; i++) {
  
  		base = sensor[s].base[i];
  		sensor_activate(base, enabled, 1);
  
  		if (enabled)
  			sensor[base].ref_count++;
  		else
  			sensor[base].ref_count--;
  	}
  
  	/* Reevaluate sampling rates of linked sensors */
  	reapply_sampling_rates(s);
  	return 0;
  }
  
  
  int sensor_activate (int s, int enabled, int from_virtual)
  {
  	char device_name[PATH_MAX];
  	struct epoll_event ev = {0};
  	int dev_fd, event_fd;
  	int ret, c, d;
  	int dev_num = sensor[s].dev_num;
  	size_t field_size;
  	int catalog_index = sensor[s].catalog_index;
  
  	if (sensor[s].is_virtual)
  		return sensor_activate_virtual(s, enabled, from_virtual);
  
  	/* Prepare the report timestamp field for the first event, see set_report_ts method */
  	sensor[s].report_ts = 0;
  
  	ret = adjust_counters(s, enabled, from_virtual);
  
  	/* If the operation was neutral in terms of state, we're done */
  	if (ret <= 0)
  		return ret;
  
  	sensor[s].event_count = 0;
  	sensor[s].meta_data_pending = 0;
  
  	if (enabled)
  		setup_noise_filtering(s);	/* Initialize filtering data if required */
  
  	if (sensor[s].mode == MODE_TRIGGER) {
  
  		/* Stop sampling */
  		enable_buffer(dev_num, 0);
  		setup_trigger(s, "\n");
  
  		/* If there's at least one sensor enabled on this iio device */
  		if (trig_sensors_per_dev[dev_num]) {
  
  			/* Start sampling */
  			if (sensor[s].hrtimer_trigger_name[0] != '\0')
  				setup_trigger(s, sensor[s].hrtimer_trigger_name);
  			else
  				setup_trigger(s, sensor[s].init_trigger_name);
  
  			enable_buffer(dev_num, 1);
  		}
  	} else if (sensor[s].mode == MODE_POLL) {
  		if (sensor[s].needs_enable) {
  			enable_sensor(dev_num, sensor_catalog[catalog_index].tag, enabled);
  		}
  	}
  
  	/*
  	 * Make sure we have a fd on the character device ; conversely, close the fd if no one is using associated sensors anymore. The assumption
  	 * here is that the underlying driver will power on the relevant hardware block while someone holds a fd on the device.
  	 */
  	dev_fd = device_fd[dev_num];
  
  	if (!enabled) {
  		if (sensor[s].mode == MODE_POLL)
  			stop_acquisition_thread(s);
  
  		if (dev_fd != -1 && !poll_sensors_per_dev[dev_num] && !trig_sensors_per_dev[dev_num]) {
  				/* Stop watching this fd. This should be a no-op in case this fd was not in the poll set. */
  				epoll_ctl(poll_fd, EPOLL_CTL_DEL, dev_fd, NULL);
  
  				close(dev_fd);
  				device_fd[dev_num] = -1;
  		}
  
  		if (sensor[s].mode == MODE_EVENT) {
  			event_fd = events_fd[dev_num];
  
  			for (c = 0; c < sensor_catalog[catalog_index].num_channels; c++) {
  				for (d = 0; d < sensor_catalog[catalog_index].channel[c].num_events; d++)
  					enable_event(dev_num, sensor_catalog[catalog_index].channel[c].event[d].ev_en_path, enabled);
  			}
  
  			epoll_ctl(poll_fd, EPOLL_CTL_DEL, event_fd, NULL);
  			close(event_fd);
  			events_fd[dev_num] = -1;
  
  		}
  
  		/* Release any filtering data we may have accumulated */
  		release_noise_filtering_data(s);
  
  		/* Reevaluate sampling rates of linked sensors */
  		reapply_sampling_rates(s);
  		return 0;
  	}
  
  	if (dev_fd == -1) {
  		/* First enabled sensor on this iio device */
  		sprintf(device_name, DEV_FILE_PATH, dev_num);
  		dev_fd = open(device_name, O_RDONLY | O_NONBLOCK);
  
  		device_fd[dev_num] = dev_fd;
  
  		if (dev_fd == -1) {
  			ALOGE("Could not open fd on %s (%s)\n", device_name, strerror(errno));
  			adjust_counters(s, 0, from_virtual);
  			return -1;
  		}
  
  		ALOGV("Opened %s: fd=%d\n", device_name, dev_fd);
  
  		if (sensor[s].mode == MODE_TRIGGER) {
  
  			/* Add this iio device fd to the set of watched fds */
  			ev.events = EPOLLIN;
  			ev.data.u32 = dev_num;
  
  			ret = epoll_ctl(poll_fd, EPOLL_CTL_ADD, dev_fd, &ev);
  
  			if (ret == -1) {
  				ALOGE("Failed adding %d to poll set (%s)\n", dev_fd, strerror(errno));
  				return -1;
  			}
  
  			/* Note: poll-mode fds are not readable */
  #ifdef __NO_EVENTS__
  		}
  #else
  		} else if (sensor[s].mode == MODE_EVENT) {
  			event_fd = events_fd[dev_num];
  
  			ret = ioctl(dev_fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
  			if (ret == -1 || event_fd == -1) {
  				ALOGE("Failed to retrieve event_fd from %d (%s)\n", dev_fd, strerror(errno));
  				return -1;
  			}
  			events_fd[dev_num] = event_fd;
  			ALOGV("Opened fd=%d to receive events\n", event_fd);
  
  			/* Add this event fd to the set of watched fds */
  			ev.events = EPOLLIN;
  			ev.data.u32 = dev_num;
  
  			ret = epoll_ctl(poll_fd, EPOLL_CTL_ADD, event_fd, &ev);
  			if (ret == -1) {
  				ALOGE("Failed adding %d to poll set (%s)\n", event_fd, strerror(errno));
  				return -1;
  			}
  			for (c = 0; c < sensor_catalog[catalog_index].num_channels; c++) {
  				int d;
  				for (d = 0; d < sensor_catalog[catalog_index].channel[c].num_events; d++)
  					enable_event(dev_num, sensor_catalog[catalog_index].channel[c].event[d].ev_en_path, enabled);
  			}
  
  			if (!poll_sensors_per_dev[dev_num] && !trig_sensors_per_dev[dev_num]) {
  				close(dev_fd);
  				device_fd[dev_num] = -1;
  			}
  		}
  #endif
  	}
  
  	/* Ensure that on-change sensors send at least one event after enable */
  	get_field_count(s, &field_size);
  	if (field_size == sizeof(uint64_t))
  		sensor[s].prev_val.data64 = -1;
  	else
  		sensor[s].prev_val.data = -1;
  
  	if (sensor[s].mode == MODE_POLL)
  		start_acquisition_thread(s);
  
  	/* Reevaluate sampling rates of linked sensors */
  	reapply_sampling_rates(s);
  
  	return 0;
  }
  
  
  static void enable_motion_trigger (int dev_num)
  {
  	/*
  	 * In the ideal case, we enumerate two triggers per iio device ; the default (periodically firing) trigger, and another one (the motion
  	 * trigger) that only fires up when motion is detected. This second one allows for lesser energy consumption, but requires periodic sample
  	 * duplication at the HAL level for sensors that Android defines as continuous. This "duplicate last sample" logic can only be engaged
  	 * once we got a first sample for the driver, so we start with the default trigger when an iio device is first opened, then adjust the
  	 * trigger when we got events for all active sensors. Unfortunately in the general case several sensors can be associated to a given iio
  	 * device, they can independently be controlled, and we have to adjust the trigger in use at the iio device level depending on whether or
  	 * not appropriate conditions are met at the sensor level.
  	 */
  
  	int s;
  	int i;
  	int active_sensors = trig_sensors_per_dev[dev_num];
  	int candidate[MAX_SENSORS];
  	int candidate_count = 0;
  
  	if  (!active_sensors)
  		return;
  
  	/* Check that all active sensors are ready to switch */
  
  	for (s=0; s<MAX_SENSORS; s++)
  		if (sensor[s].dev_num == dev_num && is_enabled(s) && sensor[s].num_channels &&
  		    (!sensor[s].motion_trigger_name[0] || !sensor[s].report_initialized || is_fast_accelerometer(s) ||
  		     (sensor[s].quirks & QUIRK_FORCE_CONTINUOUS)))
  			return; /* Nope */
  
  	/* Record which particular sensors need to switch */
  
  	for (s=0; s<MAX_SENSORS; s++)
  		if (sensor[s].dev_num == dev_num && is_enabled(s) && sensor[s].num_channels && sensor[s].selected_trigger != sensor[s].motion_trigger_name)
  				candidate[candidate_count++] = s;
  
  	if (!candidate_count)
  		return;
  
  	/* Now engage the motion trigger for sensors which aren't using it */
  
  	enable_buffer(dev_num, 0);
  
  	for (i=0; i<candidate_count; i++) {
  		s = candidate[i];
  		setup_trigger(s, sensor[s].motion_trigger_name);
  	}
  
  	enable_buffer(dev_num, 1);
  }
  
  static void stamp_reports (int dev_num, int64_t ts)
  {
  	int s;
  
  	for (s=0; s<MAX_SENSORS; s++)
  		if (sensor[s].dev_num == dev_num && is_enabled(s) && sensor[s].mode != MODE_POLL) {
  			if (sensor[s].quirks & QUIRK_SPOTTY)
  				set_report_ts(s, ts);
  			else
  				sensor[s].report_ts = ts;
  		}
  }
  
  
  static int integrate_device_report_from_dev(int dev_num, int fd)
  {
  	int len;
  	int s,c;
  	unsigned char buf[MAX_DEVICE_REPORT_SIZE] = { 0 };
  	int sr_offset;
  	unsigned char *target;
  	unsigned char *source;
  	int size;
  	int64_t ts = 0;
  	int ts_offset = 0;	/* Offset of iio timestamp, if provided */
  	int64_t boot_to_rt_delta;
  
  	/* There's an incoming report on the specified iio device char dev fd */
  	if (fd == -1) {
  		ALOGE("Ignoring stale report on iio device %d\n", dev_num);
  		return -1;
  	}
  
  	len = read(fd, buf, expected_dev_report_size[dev_num]);
  
  	if (len == -1) {
  		ALOGE("Could not read report from iio device %d (%s)\n", dev_num, strerror(errno));
  		return -1;
  	}
  
  	ALOGV("Read %d bytes from iio device %d\n", len, dev_num);
  
  	/* Map device report to sensor reports */
  
  	for (s=0; s<MAX_SENSORS; s++)
  		if (sensor[s].dev_num == dev_num && is_enabled(s)) {
  
  			sr_offset = 0;
  
  			/* Copy data from device to sensor report buffer */
  			for (c=0; c<sensor[s].num_channels; c++) {
  
  				target = sensor[s].report_buffer + sr_offset;
  
  				source = buf + sensor[s].channel[c].offset;
  
  				size = sensor[s].channel[c].size;
  
  				memcpy(target, source, size);
  
  				sr_offset += size;
  			}
  
  			ALOGV("Sensor %d report available (%d bytes)\n", s, sr_offset);
  
  			sensor[s].report_pending = DATA_TRIGGER;
  			sensor[s].report_initialized = 1;
  
  		}
  
  	/* Tentatively switch to an any-motion trigger if conditions are met */
  	enable_motion_trigger(dev_num);
  
  	/* If no iio timestamp channel was detected for this device, bail out */
  	if (!has_iio_ts[dev_num]) {
  		stamp_reports(dev_num, get_timestamp_boot());
  		return 0;
  	}
  
  	/* Don't trust the timestamp channel in any-motion mode */
  	for (s=0; s<MAX_SENSORS; s++)
  		if (sensor[s].dev_num == dev_num && is_enabled(s) && sensor[s].selected_trigger == sensor[s].motion_trigger_name) {
  			stamp_reports(dev_num, get_timestamp_boot());
  			return 0;
  		}
  
  	/* Align on a 64 bits boundary */
  	ts_offset = expected_dev_report_size[dev_num] - sizeof(int64_t);
  
  	/* If we read an amount of data consistent with timestamp presence */
  	if (len == expected_dev_report_size[dev_num])
  		ts = *(int64_t*) (buf + ts_offset);
  
  	if (ts == 0) {
  		ALOGV("Unreliable timestamp channel on iio dev %d\n", dev_num);
  		stamp_reports(dev_num, get_timestamp_boot());
  		return 0;
  	}
  
  	ALOGV("Driver timestamp on iio device %d: ts=%jd\n", dev_num, ts);
  
  	boot_to_rt_delta = get_timestamp_boot() - get_timestamp_realtime();
  
  	stamp_reports(dev_num, ts + boot_to_rt_delta);
  
  	return 0;
  }
  
  #ifndef __NO_EVENTS__
  static int integrate_device_report_from_event(int dev_num, int fd)
  {
  	int len, s;
  	int64_t ts;
  	struct iio_event_data event;
  	int64_t boot_to_rt_delta = get_timestamp_boot() - get_timestamp_realtime();
  
  	/* There's an incoming report on the specified iio device char dev fd */
  	if (fd == -1) {
  		ALOGE("Ignoring stale report on event fd %d of device %d\n",
  			fd, dev_num);
  		return -1;
  	}
  
  	len = read(fd, &event, sizeof(event));
  
  	if (len == -1) {
  		ALOGE("Could not read event from fd %d of device %d (%s)\n",
  			fd, dev_num, strerror(errno));
  		return -1;
  	}
  
  	ts = event.timestamp + boot_to_rt_delta;
  
  	ALOGV("Read event %lld from fd %d of iio device %d - ts %jd\n", event.id, fd, dev_num, ts);
  
  	/* Map device report to sensor reports */
  	for (s = 0; s < MAX_SENSORS; s++)
  		if (sensor[s].dev_num == dev_num &&
  		    is_enabled(s)) {
  			sensor[s].event_id = event.id;
  			sensor[s].report_ts = ts;
  			sensor[s].report_pending = 1;
  			sensor[s].report_initialized = 1;
  			ALOGV("Sensor %d report available (1 byte)\n", s);
  		}
  	return 0;
  }
  #endif
  
  static int integrate_device_report(int dev_num)
  {
  	int ret = 0;
  
  	if (dev_num < 0 || dev_num >= MAX_DEVICES) {
  		ALOGE("Event reported on unexpected iio device %d\n", dev_num);
  		return -1;
  	}
  
  #ifndef __NO_EVENTS__
  	if (events_fd[dev_num] != -1) {
  		ret = integrate_device_report_from_event(dev_num, events_fd[dev_num]);
  		if (ret < 0)
  			return ret;
  	}
  #endif
  
  	if (device_fd[dev_num] != -1)
  		ret = integrate_device_report_from_dev(dev_num, device_fd[dev_num]);
  
  	return ret;
  }
  
  static int propagate_vsensor_report (int s, sensors_event_t *data)
  {
  	/* There's a new report stored in sensor.sample for this sensor; transmit it */
  
  	memcpy(data, &sensor[s].sample, sizeof(sensors_event_t));
  
  	data->sensor	= s;
  	data->type	= sensor_desc[s].type; /* sensor_desc[s].type can differ from sensor[s].type ; internal types are remapped */
  	return 1;
  }
  
  
  static int propagate_sensor_report (int s, sensors_event_t *data)
  {
  	/* There's a sensor report pending for this sensor ; transmit it */
  
  	size_t field_size;
  	int num_fields	  = get_field_count(s, &field_size);
  	int c;
  	unsigned char* current_sample;
  	int ret;
  
  	/* If there's nothing to return... we're done */
  	if (!num_fields)
  		return 0;
  
  	ALOGV("Sample on sensor %d (type %d):\n", s, sensor[s].type);
  
  	if (sensor[s].mode == MODE_POLL) {
  		/* We received a good sample but we're not directly enabled so we'll drop */
  		if (!sensor[s].directly_enabled)
  			return 0;
  		/* Use the data provided by the acquisition thread */
  		ALOGV("Reporting data from worker thread for S%d\n", s);
  		memcpy(data, &sensor[s].sample, sizeof(sensors_event_t));
  		data->timestamp = sensor[s].report_ts;
  		return 1;
  	}
  
  	memset(data, 0, sizeof(sensors_event_t));
  
  	data->version	= sizeof(sensors_event_t);
  	data->sensor	= s;
  	data->type	= sensor_desc[s].type;	/* sensor_desc[s].type can differ from sensor[s].type ; internal types are remapped */
  	data->timestamp = sensor[s].report_ts;
  
  #ifndef __NO_EVENTS__
  	if (sensor[s].mode == MODE_EVENT) {
  		ALOGV("Reporting event\n");
  		/* Android requires events to return 1.0 */
  		int dir = IIO_EVENT_CODE_EXTRACT_DIR(sensor[s].event_id);
  		switch (sensor[s].type) {
  			case SENSOR_TYPE_PROXIMITY:
  				if (dir == IIO_EV_DIR_FALLING)
  					data->data[0] = 0.0;
  				else
  					data->data[0] = 1.0;
  				break;
  			default:
  				data->data[0] = 1.0;
  				break;
  
  		}
  		data->data[1] = 0.0;
  		data->data[2] = 0.0;
  		return 1;
  	}
  #endif
  
  	/* Convert the data into the expected Android-level format */
  
  	current_sample = sensor[s].report_buffer;
  
  	for (c=0; c<num_fields; c++) {
  
  		data->data[c] = sensor[s].ops.transform (s, c, current_sample);
  
  		ALOGV("\tfield %d: %g\n", c, data->data[c]);
  		current_sample += sensor[s].channel[c].size;
  	}
  
  	ret = sensor[s].ops.finalize(s, data);
  
  	/* We will drop samples if the sensor is not directly enabled */
  	if (!sensor[s].directly_enabled)
  		return 0;
  
  	/* The finalize routine, in addition to its late sample processing duty, has the final say on whether or not the sample gets sent to Android */
  	return ret;
  }
  
  
  static void synthetize_duplicate_samples (void)
  {
  	/*
  	 * Some sensor types (ex: gyroscope) are defined as continuously firing by Android, despite the fact that
  	 * we can be dealing with iio drivers that only report events for new samples. For these we generate reports
  	 * periodically, duplicating the last data we got from the driver. This is not necessary for polling sensors.
  	 */
  
  	int s;
  	int64_t current_ts;
  	int64_t target_ts;
  	int64_t period;
  
  	for (s=0; s<sensor_count; s++) {
  
  		/* Ignore disabled sensors */
  		if (!is_enabled(s))
  			continue;
  
  		/* If the sensor is continuously firing, leave it alone */
  		if (sensor[s].selected_trigger != sensor[s].motion_trigger_name)
  			continue;
  
  		/* If we haven't seen a sample, there's nothing to duplicate */
  		if (!sensor[s].report_initialized)
  			continue;
  
  		/* If a sample was recently buffered, leave it alone too */
  		if (sensor[s].report_pending)
  			continue;
  
  		/* We also need a valid sampling rate to be configured */
  		if (!sensor[s].sampling_rate)
  			continue;
  
  		period = (int64_t) (1000000000.0 / sensor[s].sampling_rate);
  
  		current_ts = get_timestamp_boot();
  		target_ts = sensor[s].report_ts + period;
  
  		if (target_ts <= current_ts) {
  			/* Mark the sensor for event generation */
  			set_report_ts(s, current_ts);
  			sensor[s].report_pending = DATA_DUPLICATE;
  		}
  	}
  }
  
  
  static void integrate_thread_report (uint32_t tag)
  {
  	int s = tag - THREAD_REPORT_TAG_BASE;
  	int len;
  
  	len = read(sensor[s].thread_data_fd[0], &sensor[s].sample, sizeof(sensors_event_t));
  
  	if (len == sizeof(sensors_event_t))
  		sensor[s].report_pending = DATA_SYSFS;
  }
  
  
  static int get_poll_wait_timeout (void)
  {
  	/*
  	 * Compute an appropriate timeout value, in ms, for the epoll_wait call that's going to await
  	 * for iio device reports and incoming reports from our sensor sysfs data reader threads.
  	 */
  
  	int s;
  	int64_t target_ts = INT64_MAX;
  	int64_t ms_to_wait;
  	int64_t period;
  
  	/*
  	 * Check if we're dealing with a driver that only send events when there is motion, despite the fact that the associated Android sensor
  	 * type is continuous rather than on-change. In that case we have to duplicate events. Check deadline for the nearest upcoming event.
  	 */
  	for (s=0; s<sensor_count; s++)
  		if (is_enabled(s) && sensor[s].selected_trigger == sensor[s].motion_trigger_name && sensor[s].sampling_rate) {
  			period = (int64_t) (1000000000.0 / sensor[s].sampling_rate);
  
  			if (sensor[s].report_ts + period < target_ts)
  				target_ts = sensor[s].report_ts + period;
  		}
  
  	/* If we don't have such a driver to deal with */
  	if (target_ts == INT64_MAX)
  		return -1; /* Infinite wait */
  
  	ms_to_wait = (target_ts - get_timestamp_boot()) / 1000000;
  
  	/* If the target timestamp is already behind us, don't wait */
  	if (ms_to_wait < 1)
  		return 0;
  
  	return ms_to_wait;
  }
  
  
  int sensor_poll (sensors_event_t* data, int count)
  {
  	int s;
  	int i;
  	int nfds;
  	struct epoll_event ev[MAX_DEVICES];
  	int returned_events;
  	int event_count;
  
  	/* Get one or more events from our collection of sensors */
  return_available_sensor_reports:
  
  	/* Synthetize duplicate samples if needed */
  	synthetize_duplicate_samples();
  
  	returned_events = 0;
  
  	/* Check our sensor collection for available reports */
  	for (s=0; s<sensor_count && returned_events < count; s++) {
  
  		if (sensor[s].report_pending) {
  			event_count = 0;
  
  			if (sensor[s].is_virtual)
  				event_count = propagate_vsensor_report(s, &data[returned_events]);
  			else
  				/* Report this event if it looks OK */
  				event_count = propagate_sensor_report(s, &data[returned_events]);
  
  			/* Lower flag */
  			sensor[s].report_pending = 0;
  			returned_events += event_count;
  
  			/*
  			 * If the sample was deemed invalid or unreportable, e.g. had the same value as the previously reported
  			 * value for a 'on change' sensor, silently drop it.
  			 */
  		}
  
  		while (sensor[s].meta_data_pending) {
  			/* See sensors.h on these */
  			data[returned_events].version = META_DATA_VERSION;
  			data[returned_events].sensor = 0;
  			data[returned_events].type = SENSOR_TYPE_META_DATA;
  			data[returned_events].reserved0 = 0;
  			data[returned_events].timestamp = 0;
  			data[returned_events].meta_data.sensor = s;
  			data[returned_events].meta_data.what = META_DATA_FLUSH_COMPLETE;
  			returned_events++;
  			sensor[s].meta_data_pending--;
  		}
  	}
  
  	if (returned_events)
  		return returned_events;
  
  await_event:
  
  	ALOGV("Awaiting sensor data\n");
  
  	nfds = epoll_wait(poll_fd, ev, MAX_DEVICES, get_poll_wait_timeout());
  
  	if (nfds == -1) {
  		ALOGE("epoll_wait returned -1 (%s)\n", strerror(errno));
  		goto await_event;
  	}
  
  	ALOGV("%d fds signalled\n", nfds);
  
  	/* For each of the signalled sources */
  	for (i=0; i<nfds; i++)
  		if (ev[i].events == EPOLLIN)
  			switch (ev[i].data.u32) {
  				case 0 ... MAX_DEVICES-1:
  					/* Read report from iio char dev fd */
  					integrate_device_report(ev[i].data.u32);
  					break;
  
  				case THREAD_REPORT_TAG_BASE ...
  				     THREAD_REPORT_TAG_BASE + MAX_SENSORS-1:
  					/* Get report from acquisition thread */
  					integrate_thread_report(ev[i].data.u32);
  					break;
  				case FLUSH_REPORT_TAG:
  					{
  						char flush_event_content;
  						read(flush_event_fd[0], &flush_event_content, sizeof(flush_event_content));
  						break;
  					}
  
  				default:
  					ALOGW("Unexpected event source!\n");
  					break;
  			}
  
  	goto return_available_sensor_reports;
  }
  
  
  int sensor_set_delay (int s, int64_t ns)
  {
  	float requested_sampling_rate;
  
  	if (ns <= 0) {
  		ALOGE("Invalid delay requested on sensor %d: %jd\n", s, ns);
  		return -EINVAL;
  	}
  
  	requested_sampling_rate = 1000000000.0 / ns;
  
  	ALOGV("Entering set delay S%d (%s): current rate: %g, requested: %g\n", s, sensor[s].friendly_name, sensor[s].sampling_rate, requested_sampling_rate);
  
  	/*
  	 * Only try to adjust the low level sampling rate if it's different from the current one, as set by the HAL. This saves a few sysfs
  	 * reads and writes as well as buffer enable/disable operations, since at the iio level most drivers require the buffer to be turned off
  	 * in order to accept a sampling rate change. Of course that implies that this field has to be kept up to date and that only this library
  	 * is changing the sampling rate.
  	 */
  
  	if (requested_sampling_rate != sensor[s].sampling_rate)
  		return sensor_set_rate(s, requested_sampling_rate);
  
  	return 0;
  }
  
  
  int sensor_flush (int s)
  {
  	char flush_event_content = 0;
  	/* If one shot or not enabled return -EINVAL */
  	if (sensor_desc[s].flags & SENSOR_FLAG_ONE_SHOT_MODE || !is_enabled(s))
  		return -EINVAL;
  
  	sensor[s].meta_data_pending++;
  	write(flush_event_fd[1], &flush_event_content, sizeof(flush_event_content));
  	return 0;
  }
  
  
  int allocate_control_data (void)
  {
  	int i, ret;
  	struct epoll_event ev = {0};
  
  	for (i=0; i<MAX_DEVICES; i++) {
  		device_fd[i] = -1;
  		events_fd[i] = -1;
  	}
  
  	poll_fd = epoll_create(MAX_DEVICES);
  
  	if (poll_fd == -1) {
  		ALOGE("Can't create epoll instance for iio sensors!\n");
  		return -1;
  	}
  
  	ret = pipe(flush_event_fd);
  	if (ret) {
  		ALOGE("Cannot create flush_event_fd");
  		return -1;
  	}
  
  	ev.events = EPOLLIN;
  	ev.data.u32 = FLUSH_REPORT_TAG;
  	ret = epoll_ctl(poll_fd, EPOLL_CTL_ADD, flush_event_fd[0] , &ev);
  	if (ret == -1) {
  		ALOGE("Failed adding %d to poll set (%s)\n",
  			flush_event_fd[0], strerror(errno));
  		return -1;
  	}
  
  	return poll_fd;
  }
  
  
  void delete_control_data (void)
  {
  }
  