X-Git-Url: http://git.osdn.net/view?a=blobdiff_plain;f=control.c;h=7d942fdfab48557a412089f649544edb0816f30e;hb=b24d6584ce3c44cdb5ba9ebe6aa525ff7ecd477c;hp=811270debb43ffec2de3d4555752f884a39dab81;hpb=816bba686f5c70100cf825b3894e808f58e30ab8;p=android-x86%2Fhardware-intel-libsensors.git

diff --git a/control.c b/control.c
index 811270d..7d942fd 100644
--- a/control.c
+++ b/control.c
@@ -2,14 +2,21 @@
  * Copyright (C) 2014 Intel Corporation.
  */
 
+#include <stdlib.h>
+#include <ctype.h>
 #include <fcntl.h>
+#include <pthread.h>
+#include <time.h>
 #include <sys/epoll.h>
-#include <math.h>
+#include <sys/socket.h>
 #include <utils/Log.h>
 #include <hardware/sensors.h>
 #include "control.h"
 #include "enumeration.h"
 #include "utils.h"
+#include "transform.h"
+#include "calibration.h"
+#include "description.h"
 
 /* Currently active sensors count, per device */
 static int poll_sensors_per_dev[MAX_DEVICES];	/* poll-mode sensors */
@@ -19,37 +26,77 @@ static int device_fd[MAX_DEVICES];   /* fd on the /dev/iio:deviceX file */
 
 static int poll_fd; /* epoll instance covering all enabled sensors */
 
-/* Timestamp for the moment when we last exited a poll operation */
-static int64_t last_poll_exit_ts;
-
-/* Cap the time between poll operations to this, to counter runaway polls */
-#define POLL_MIN_INTERVAL 10000 /* uS */
-
 static int active_poll_sensors; /* Number of enabled poll-mode sensors */
 
+/* We use pthread condition variables to get worker threads out of sleep */
+static pthread_cond_t  thread_release_cond	[MAX_SENSORS];
+static pthread_mutex_t thread_release_mutex	[MAX_SENSORS];
+
+/*
+ * 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	0x00010000
+
+/* When polling try to compensate for the iio overhead in
+ * order to try to get a frequency closer to the advertised one
+ */
+#define OVERHEAD_THRESHOLD 0.97
+#define ENABLE_BUFFER_RETRIES 10
+#define ENABLE_BUFFER_RETRY_DELAY_MS 10
 
 static int enable_buffer(int dev_num, int enabled)
 {
 	char sysfs_path[PATH_MAX];
+	int ret, retries, millisec;
+	struct timespec req = {0};
+
+	retries = ENABLE_BUFFER_RETRIES;
+	millisec = ENABLE_BUFFER_RETRY_DELAY_MS;
+	req.tv_sec = 0;
+	req.tv_nsec = millisec * 1000000L;
 
 	sprintf(sysfs_path, ENABLE_PATH, dev_num);
 
-	/* Low level, non-multiplexed, enable/disable routine */
-	return sysfs_write_int(sysfs_path, enabled);
+	while (retries--) {
+		/* Low level, non-multiplexed, enable/disable routine */
+		ret = sysfs_write_int(sysfs_path, enabled);
+		if (ret > 0)
+			break;
+
+		ALOGE("Failed enabling buffer, retrying");
+		nanosleep(&req, (struct timespec *)NULL);
+	}
+
+	if (ret < 0) {
+		ALOGE("Could not enable buffer\n");
+		return -EIO;
+	}
+
+	return 0;
 }
 
 
-static int setup_trigger(int dev_num, const char* trigger_val)
+static void setup_trigger (int s, const char* trigger_val)
 {
 	char sysfs_path[PATH_MAX];
 
-	sprintf(sysfs_path, TRIGGER_PATH, dev_num);
+	sprintf(sysfs_path, TRIGGER_PATH, sensor_info[s].dev_num);
 
-	return sysfs_write_str(sysfs_path, trigger_val);
+	if (trigger_val[0] != '\n')
+		ALOGI("Setting S%d (%s) trigger to %s\n", s,
+			sensor_info[s].friendly_name, trigger_val);
+
+	sysfs_write_str(sysfs_path, trigger_val);
+
+	sensor_info[s].selected_trigger = trigger_val;
 }
 
 
-static void refresh_sensor_report_maps(int dev_num)
+void build_sensor_report_maps(int dev_num)
 {
 	/*
 	 * Read sysfs files from a iio device's scan_element directory, and
@@ -69,21 +116,19 @@ static void refresh_sensor_report_maps(int dev_num)
 	int c;
 	int n;
 	int i;
-	int ch_enabled;
 	int ch_index;
 	char* ch_spec;
 	char spec_buf[MAX_TYPE_SPEC_LEN];
 	struct datum_info_t* ch_info;
 	int size;
 	char sysfs_path[PATH_MAX];
-	int active_channels;
+	int known_channels;
 	int offset;
-	int channel_count;
 	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 };
 
-	active_channels = 0;
+	known_channels = 0;
 
 	/* For each sensor that is linked to this device */
 	for (s=0; s<sensor_count; s++) {
@@ -92,26 +137,9 @@ static void refresh_sensor_report_maps(int dev_num)
 
 		i = sensor_info[s].catalog_index;
 
-		/* Read channel status through syfs attributes */
+		/* Read channel details through sysfs attributes */
 		for (c=0; c<sensor_info[s].num_channels; c++) {
 
-			/* Read _en file */
-			sprintf(sysfs_path, CHANNEL_PATH "%s",
-				sensor_info[s].dev_num,
-				sensor_catalog[i].channel[c].en_path);
-
-			n = sysfs_read_int(sysfs_path, &ch_enabled);
-
-			if (n == -1) {
-				ALOGW(	"Failed to read _en flag: %s\n",
-				sysfs_path);
-				continue;
-			}
-
-			if (!ch_enabled != 1) {
-				sensor_info[s].channel[c].size = 0;
-			}
-
 			/* Read _type file */
 			sprintf(sysfs_path, CHANNEL_PATH "%s",
 				sensor_info[s].dev_num,
@@ -147,21 +175,37 @@ static void refresh_sensor_report_maps(int dev_num)
 					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;
 
-			active_channels++;
+			known_channels++;
+		}
+
+		/* 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_info[s].num_channels; c++) {
+			sprintf(sysfs_path, CHANNEL_PATH "%s",
+				sensor_info[s].dev_num,
+				sensor_catalog[i].channel[c].en_path);
+			sysfs_write_int(sysfs_path, 1);
 		}
 	}
 
-	ALOGI("Found %d enabled channels for iio device %d\n", active_channels,
-		dev_num);
+	ALOGI("Found %d channels on iio device %d\n", known_channels, dev_num);
 
 	/*
-	 * Now that we know which channels are enabled, their sizes and their
+	 * 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
@@ -200,33 +244,54 @@ int adjust_counters (int s, int enabled)
 	 */
 
 	int dev_num = sensor_info[s].dev_num;
+	int catalog_index = sensor_info[s].catalog_index;
+	int sensor_type = sensor_catalog[catalog_index].type;
 
 	/* Refcount per sensor, in terms of enable count */
 	if (enabled) {
 		ALOGI("Enabling sensor %d (iio device %d: %s)\n",
-			s, dev_num, sensor_info[s].internal_name);
+			s, dev_num, sensor_info[s].friendly_name);
 
 		sensor_info[s].enable_count++;
 
-		if (sensor_info[s].enable_count != 1)
+		if (sensor_info[s].enable_count > 1)
 			return 0; /* The sensor was, and remains, in use */
+
+		switch (sensor_type) {
+			case SENSOR_TYPE_MAGNETIC_FIELD:
+				compass_read_data(&sensor_info[s]);
+				break;
+
+			case SENSOR_TYPE_GYROSCOPE:
+			case SENSOR_TYPE_GYROSCOPE_UNCALIBRATED:
+				gyro_cal_init(&sensor_info[s]);
+				break;
+		}
 	} else {
 		if (sensor_info[s].enable_count == 0)
 			return -1; /* Spurious disable call */
 
-		ALOGI("Disabling sensor %d (iio device %d)\n", s, dev_num);
+		ALOGI("Disabling sensor %d (iio device %d: %s)\n", s, dev_num,
+		      sensor_info[s].friendly_name);
 
 		sensor_info[s].enable_count--;
 
 		if (sensor_info[s].enable_count > 0)
 			return 0; /* The sensor was, and remains, in use */
 
-		/* Sensor disabled, clear up pending data */
-
+		/* Sensor disabled, lower report available flag */
 		sensor_info[s].report_pending = 0;
-		memset(sensor_info[s].report_buffer, 0, MAX_SENSOR_REPORT_SIZE);
+
+		if (sensor_type == SENSOR_TYPE_MAGNETIC_FIELD)
+			compass_store_data(&sensor_info[s]);
 	}
 
+
+	/* If uncalibrated type and pair is already active don't adjust counters */
+	if (sensor_type == SENSOR_TYPE_GYROSCOPE_UNCALIBRATED &&
+		sensor_info[sensor_info[s].pair_idx].enable_count != 0)
+			return 0;
+
 	/* We changed the state of a sensor - adjust per iio device counters */
 
 	/* If this is a regular event-driven sensor */
@@ -252,78 +317,277 @@ int adjust_counters (int s, int enabled)
 }
 
 
+static int get_field_count (int s)
+{
+	int catalog_index = sensor_info[s].catalog_index;
+	int sensor_type	  = sensor_catalog[catalog_index].type;
+
+	switch (sensor_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_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 */
+			return 1;
+
+		case SENSOR_TYPE_ROTATION_VECTOR:
+			return  4;
+
+		default:
+			ALOGE("Unknown sensor type!\n");
+			return 0;			/* Drop sample */
+	}
+}
+
+
+static void time_add(struct timespec *out, struct timespec *in, int64_t ns)
+{
+	int64_t target_ts = 1000000000LL * in->tv_sec + in->tv_nsec + ns;
+
+	out->tv_sec = target_ts / 1000000000;
+	out->tv_nsec = target_ts % 1000000000;
+}
+
+
+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;
+	struct sensors_event_t data = {0};
+	int c;
+	int ret;
+	struct timespec entry_time;
+	struct timespec target_time;
+	int64_t period;
+
+	ALOGI("Entering data acquisition thread S%d (%s): rate(%f), minDelay(%ld), maxDelay(%ld)\n",
+		s, sensor_info[s].friendly_name, sensor_info[s].sampling_rate,
+		sensor_desc[s].minDelay, sensor_desc[s].maxDelay);
+
+	if (s < 0 || s >= sensor_count) {
+		ALOGE("Invalid sensor handle!\n");
+		return NULL;
+	}
+
+	if (!sensor_info[s].sampling_rate) {
+		ALOGE("Zero rate in acquisition routine for sensor %d\n", s);
+		return NULL;
+	}
+
+	num_fields = get_field_count(s);
+
+	/*
+	 * 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]);
+
+	while (1) {
+		/* Pinpoint the moment we start sampling */
+		clock_gettime(CLOCK_REALTIME, &entry_time);
+
+		ALOGV("Acquiring sample data for sensor %d through sysfs\n", s);
+
+		/* Read values through sysfs */
+		for (c=0; c<num_fields; c++) {
+			data.data[c] = acquire_immediate_value(s, c);
+
+			/* Check and honor termination requests */
+			if (sensor_info[s].thread_data_fd[1] == -1)
+				goto exit;
+
+			ALOGV("\tfield %d: %f\n", c, data.data[c]);
+
+		}
+
+		/* If the sample looks good */
+		if (sensor_info[s].ops.finalize(s, &data)) {
+
+			/* Pipe it for transmission to poll loop */
+			ret = write(	sensor_info[s].thread_data_fd[1],
+					data.data,
+					num_fields * sizeof(float));
+		}
+
+		/* Check and honor termination requests */
+		if (sensor_info[s].thread_data_fd[1] == -1)
+			goto exit;
+
+
+		period = (int64_t) (1000000000.0/ sensor_info[s].sampling_rate);
+		period = period * OVERHEAD_THRESHOLD;
+		time_add(&target_time, &entry_time, period);
+
+		/*
+		 * 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);
+
+		/* Check and honor termination requests */
+		if (sensor_info[s].thread_data_fd[1] == -1)
+				goto exit;
+	}
+
+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_cond_init(&thread_release_cond[s], NULL);
+	ret = pthread_mutex_init(&thread_release_mutex[s], NULL);
+
+	/* Create a pipe for inter thread communication */
+	ret = pipe(sensor_info[s].thread_data_fd);
+
+	incoming_data_fd = sensor_info[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);
+
+	/* Create and start worker thread */
+	ret = pthread_create(	&sensor_info[s].acquisition_thread,
+				NULL,
+				acquisition_routine,
+				(void*) (size_t) s);
+}
+
+
+static void stop_acquisition_thread (int s)
+{
+	int incoming_data_fd = sensor_info[s].thread_data_fd[0];
+	int outgoing_data_fd = sensor_info[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_info[s].thread_data_fd[0] = -1;
+	sensor_info[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_info[s].acquisition_thread, NULL);
+
+	/* Clean up our sensor descriptor */
+	sensor_info[s].acquisition_thread = -1;
+
+	/* Delete condition variable and mutex */
+	pthread_cond_destroy(&thread_release_cond[s]);
+	pthread_mutex_destroy(&thread_release_mutex[s]);
+}
+
+
 int sensor_activate(int s, int enabled)
 {
-	char sysfs_path[PATH_MAX];
 	char device_name[PATH_MAX];
-	char trigger_name[MAX_NAME_SIZE + 16];
-	int c;
 	struct epoll_event ev = {0};
 	int dev_fd;
 	int ret;
 	int dev_num = sensor_info[s].dev_num;
-	int i = sensor_info[s].catalog_index;
 	int is_poll_sensor = !sensor_info[s].num_channels;
 
-	ret = adjust_counters(s, enabled);
+	/* Prepare the report timestamp field for the first event, see set_report_ts method */
+	sensor_info[s].report_ts = 0;
 
-	/* If the operation was neutral in terms of state, we're done */
-	if (ret <= 0)
-		return ret;
+	/* If we want to activate gyro calibrated and gyro uncalibrated is activated
+	 * Deactivate gyro uncalibrated - Uncalibrated releases handler
+	 * Activate gyro calibrated     - Calibrated has handler
+	 * Reactivate gyro uncalibrated - Uncalibrated gets data from calibrated */
 
-	if (!is_poll_sensor) {
-		/* Changes have to be made while the buffer is turned off */
-		enable_buffer(dev_num, 0);
+	/* If we want to deactivate gyro calibrated and gyro uncalibrated is active
+	 * Deactivate gyro uncalibrated - Uncalibrated no longer gets data from handler
+	 * Deactivate gyro calibrated   - Calibrated releases handler
+	 * Reactivate gyro uncalibrated - Uncalibrated has handler */
 
-		/* Configure trigger */
-		switch (trig_sensors_per_dev[dev_num]) {
-			case 0:
-				setup_trigger(dev_num, "none");
-				break;
+	if (sensor_catalog[sensor_info[s].catalog_index].type == SENSOR_TYPE_GYROSCOPE &&
+		sensor_info[s].pair_idx && sensor_info[sensor_info[s].pair_idx].enable_count != 0) {
 
-			case 1:
-				sprintf(trigger_name, "%s-dev%d",
-					sensor_info[s].internal_name, dev_num);
+				sensor_activate(sensor_info[s].pair_idx, 0);
+				ret = sensor_activate(s, enabled);
+				sensor_activate(sensor_info[s].pair_idx, 1);
+				return ret;
+	}
 
-				setup_trigger(dev_num, trigger_name);
-				break;
+	ret = adjust_counters(s, enabled);
 
-			default:
-				/* The trigger is already set */
-				break;
-		}
+	/* If the operation was neutral in terms of state, we're done */
+	if (ret <= 0)
+		return ret;
 
-		/*
-		 * Turn channels associated to this sensor on or off, and update
-		 * the channels maps for all sensors associated to this device.
-		 */
-		for (c=0;c<sensor_info[s].num_channels; c++) {
-			sprintf(sysfs_path, CHANNEL_PATH "%s",
-				sensor_info[s].dev_num,
-				sensor_catalog[i].channel[c].en_path);
 
-			sysfs_write_int(sysfs_path, enabled);
-		}
+	if (!is_poll_sensor) {
+
+		/* Stop sampling */
+		enable_buffer(dev_num, 0);
+		setup_trigger(s, "\n");
 
-		/* If there's at least one sensor left */
+		/* If there's at least one sensor enabled on this iio device */
 		if (trig_sensors_per_dev[dev_num]) {
-			refresh_sensor_report_maps(dev_num);
+
+			/* Start sampling */
+			setup_trigger(s, sensor_info[s].init_trigger_name);
 			enable_buffer(dev_num, 1);
 		}
 	}
 
 	/*
 	 * Make sure we have a fd on the character device ; conversely, close
-	 * the fd if no one is using associated sensor anymore. The assumption
+	 * 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 hold a fd on the device.
+	 * hardware block while someone holds a fd on the device.
 	 */
 	dev_fd = device_fd[dev_num];
 
-	switch (poll_sensors_per_dev[dev_num] +	trig_sensors_per_dev[dev_num]) {
+	if (!enabled) {
+		if (is_poll_sensor)
+			stop_acquisition_thread(s);
 
-		case 0:
-			if (dev_fd != -1) {
+		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.
@@ -333,76 +597,198 @@ int sensor_activate(int s, int enabled)
 				close(dev_fd);
 				device_fd[dev_num] = -1;
 			}
-			return 0;
 
-		case 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);
+		/* If we recorded a trail of samples for filtering, delete it */
+		if (sensor_info[s].history) {
+			free(sensor_info[s].history);
+			sensor_info[s].history = NULL;
+			sensor_info[s].history_size = 0;
+			if (sensor_info[s].history_sum) {
+				free(sensor_info[s].history_sum);
+				sensor_info[s].history_sum = NULL;
+			}
+		}
+
+		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);
+			return -1;
+		}
 
-			if (dev_fd == -1) {
-				ALOGE("Could not open fd on %s (%s)\n",
-				      device_name, strerror(errno));
+		ALOGV("Opened %s: fd=%d\n", device_name, dev_fd);
+
+		if (!is_poll_sensor) {
+
+			/* 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;
 			}
 
-			ALOGV("Opened %s: fd=%d\n", device_name, dev_fd);
+			/* Note: poll-mode fds are not readable */
+		}
+	}
 
-			device_fd[dev_num] = dev_fd;
-			break;
+	/* Ensure that on-change sensors send at least one event after enable */
+	sensor_info[s].prev_val = -1;
 
-		default:
-			break;
-	}
+	if (is_poll_sensor)
+		start_acquisition_thread(s);
 
-	if (!is_poll_sensor && trig_sensors_per_dev[dev_num] == 1) {
+	return 0;
+}
 
-		/* 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);
+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.
+	 */
+	int catalog_index = sensor_info[s].catalog_index;
+
+	if (sensor_catalog[catalog_index].type != SENSOR_TYPE_ACCELEROMETER)
+		return 0;
+
+	if (sensor_info[s].sampling_rate < 25)
+		return 0;
+
+	return 1;
+}
 
-		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 */
+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_info[s].dev_num == dev_num &&
+		    sensor_info[s].enable_count &&
+		    sensor_info[s].num_channels &&
+		    (!sensor_info[s].motion_trigger_name[0] ||
+		     !sensor_info[s].report_initialized ||
+		     is_fast_accelerometer(s))
+		    )
+			return; /* Nope */
+
+	/* Record which particular sensors need to switch */
+
+	for (s=0; s<MAX_SENSORS; s++)
+		if (sensor_info[s].dev_num == dev_num &&
+		    sensor_info[s].enable_count &&
+		    sensor_info[s].num_channels &&
+		    !(sensor_info[s].quirks & QUIRK_CONTINUOUS_DRIVER) &&
+		    sensor_info[s].selected_trigger !=
+			sensor_info[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_info[s].motion_trigger_name);
 	}
 
-	return 0;
+	enable_buffer(dev_num, 1);
 }
 
+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_info[s].report_ts && sensor_info[s].sampling_rate &&
+		REPORTING_MODE(sensor_desc[s].flags) == SENSOR_FLAG_CONTINUOUS_MODE)
+	{
+		period = (int64_t) (1000000000LL / sensor_info[s].sampling_rate);
+		maxTs = sensor_info[s].report_ts + period;
+		sensor_info[s].report_ts = (ts < maxTs ? ts : maxTs);
+	} else {
+		sensor_info[s].report_ts = ts;
+	}
+}
 
 static int integrate_device_report(int dev_num)
 {
 	int len;
 	int s,c;
-	unsigned char buf[MAX_SENSOR_REPORT_SIZE * MAX_SENSORS] = { 0 };
-	int dr_offset;
+	unsigned char buf[MAX_SENSOR_REPORT_SIZE] = { 0 };
 	int sr_offset;
 	unsigned char *target;
 	unsigned char *source;
 	int size;
-	int expected_size = 0;
+	int64_t ts;
 
-	if (dev_num < 0 || dev_num >= MAX_DEVICES)
-		return -1;
+	/* There's an incoming report on the specified iio device char dev fd */
 
-	/* There's an incoming report on the specified fd */
+	if (dev_num < 0 || dev_num >= MAX_DEVICES) {
+		ALOGE("Event reported on unexpected iio device %d\n", dev_num);
+		return -1;
+	}
 
-	for (s=0; s<MAX_SENSORS; s++)
-		if (sensor_info[s].enable_count &&
-		    sensor_info[s].dev_num == dev_num)
-			for (c=0; c<sensor_info[s].num_channels; c++)
-				expected_size += sensor_info[s].channel[c].size;
+	if (device_fd[dev_num] == -1) {
+		ALOGE("Ignoring stale report on iio device %d\n", dev_num);
+		return -1;
+	}
 
-	if (expected_size == 0)
-		return 0;
+	ts = get_timestamp();
 
-	len = read(device_fd[dev_num], buf, expected_size);
+	len = read(device_fd[dev_num], buf, MAX_SENSOR_REPORT_SIZE);
 
 	if (len == -1) {
 		ALOGE("Could not read report from iio device %d (%s)\n",
@@ -412,11 +798,12 @@ static int integrate_device_report(int dev_num)
 
 	ALOGV("Read %d bytes from iio device %d\n", len, dev_num);
 
-	dr_offset = 0;
+	/* Map device report to sensor reports */
 
 	for (s=0; s<MAX_SENSORS; s++)
-		if (sensor_info[s].enable_count &&
-		    sensor_info[s].dev_num == dev_num) {
+		if (sensor_info[s].dev_num == dev_num &&
+		    sensor_info[s].enable_count) {
+
 			sr_offset = 0;
 
 			/* Copy data from device to sensor report buffer */
@@ -434,146 +821,191 @@ static int integrate_device_report(int dev_num)
 				sr_offset += size;
 			}
 
-			ALOGV("Sensor %d report available (%d bytes)\n",
-				s, sr_offset);
+			ALOGV("Sensor %d report available (%d bytes)\n", s,
+			      sr_offset);
 
+			set_report_ts(s, ts);
 			sensor_info[s].report_pending = 1;
+			sensor_info[s].report_initialized = 1;
 		}
 
+	/* Tentatively switch to an any-motion trigger if conditions are met */
+	enable_motion_trigger(dev_num);
+
 	return 0;
 }
 
 
-static float acquire_immediate_value(int s, int c)
+static int propagate_sensor_report(int s, struct sensors_event_t  *data)
 {
-	char sysfs_path[PATH_MAX];
-	float val;
-	int ret;
-	int dev_num = sensor_info[s].dev_num;
-	int i = sensor_info[s].catalog_index;
-	const char* raw_path = sensor_catalog[i].channel[c].raw_path;
-	const char* input_path = sensor_catalog[i].channel[c].input_path;
-	float scale = sensor_info[s].scale;
-	float offset = sensor_info[s].offset;
+	/* There's a sensor report pending for this sensor ; transmit it */
 
-	/* Acquire a sample value for sensor s / channel c through sysfs */
+	int catalog_index = sensor_info[s].catalog_index;
+	int sensor_type	  = sensor_catalog[catalog_index].type;
+	int num_fields	  = get_field_count(s);
+	int c;
+	unsigned char* current_sample;
 
-	if (input_path[0]) {
-		sprintf(sysfs_path, BASE_PATH "%s", dev_num, input_path);
-		ret = sysfs_read_float(sysfs_path, &val);
+	/* If there's nothing to return... we're done */
+	if (!num_fields)
+		return 0;
 
-		if (!ret) {
-			return val;
-		}
-	};
 
-	if (!raw_path[0])
-		return 0;
+	/* Only return uncalibrated event if also gyro active */
+	if (sensor_type == SENSOR_TYPE_GYROSCOPE_UNCALIBRATED &&
+		sensor_info[sensor_info[s].pair_idx].enable_count != 0)
+			return 0;
 
-	sprintf(sysfs_path, BASE_PATH "%s", dev_num, raw_path);
-	ret = sysfs_read_float(sysfs_path, &val);
+	memset(data, 0, sizeof(sensors_event_t));
 
-	if (ret == -1)
-		return 0;
+	data->version	= sizeof(sensors_event_t);
+	data->sensor	= s;
+	data->type	= sensor_type;
+	data->timestamp = sensor_info[s].report_ts;
 
-	return (val + offset) * scale;
-}
+	ALOGV("Sample on sensor %d (type %d):\n", s, sensor_type);
 
+	current_sample = sensor_info[s].report_buffer;
 
-static void propagate_sensor_report(int s, struct sensors_event_t* data)
-{
-	/* There's a sensor report pending for this sensor ; transmit it */
+	/* If this is a poll sensor */
+	if (!sensor_info[s].num_channels) {
+		/* Use the data provided by the acquisition thread */
+		ALOGV("Reporting data from worker thread for S%d\n", s);
+		memcpy(data->data, current_sample, num_fields * sizeof(float));
+		return 1;
+	}
 
-	int catalog_index = sensor_info[s].catalog_index;
-	int sensor_type = sensor_catalog[catalog_index].type;
-	int num_fields;
-	int c;
-	unsigned char* current_sample;
-	int sample_size;
-	struct datum_info_t* sample_type;
-	int64_t s64;
-	float val;
+	/* Convert the data into the expected Android-level format */
+	for (c=0; c<num_fields; c++) {
 
-	memset(data, 0, sizeof(sensors_event_t));
+		data->data[c] = sensor_info[s].ops.transform
+							(s, c, current_sample);
 
-	data->version = sizeof(sensors_event_t);
-	data->sensor = s;
-	data->type = sensor_type;
-	data->timestamp = get_timestamp();
+		ALOGV("\tfield %d: %f\n", c, data->data[c]);
+		current_sample += sensor_info[s].channel[c].size;
+	}
 
-	switch (sensor_type) {
-		case SENSOR_TYPE_ACCELEROMETER:		/* m/s^2	*/
-		case SENSOR_TYPE_MAGNETIC_FIELD:	/* micro-tesla	*/
-		case SENSOR_TYPE_ORIENTATION:		/* degrees	*/
-		case SENSOR_TYPE_GYROSCOPE:		/* radians/s	*/
-			num_fields = 3;
-			break;
+	/*
+	 * 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 sensor_info[s].ops.finalize(s, data);
+}
 
-		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 */
-			num_fields = 1;
-			break;
 
-		case SENSOR_TYPE_ROTATION_VECTOR:
-			num_fields = 4;
-			break;
+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.
+	 */
 
-		case SENSOR_TYPE_DEVICE_PRIVATE_BASE:	/* hidden for now */
-			num_fields = 0;
-			break;
+	int s;
+	int64_t current_ts;
+	int64_t target_ts;
+	int64_t period;
 
-		default:
-			ALOGE("Unknown sensor type!\n");
-			num_fields = 0;
-			break;
-	}
+	for (s=0; s<sensor_count; s++) {
 
-	ALOGV("Sample on sensor %d (type %d):\n", s, sensor_type);
+		/* Ignore disabled sensors */
+		if (!sensor_info[s].enable_count)
+			continue;
 
-	/* If we're dealing with a poll-mode sensor */
-	if (!sensor_info[s].num_channels) {
+		/* If the sensor is continuously firing, leave it alone */
+		if (	sensor_info[s].selected_trigger !=
+			sensor_info[s].motion_trigger_name)
+			continue;
 
-		/* Read values through sysfs rather than from a report buffer */
-		for (c=0; c<num_fields; c++) {
-			val = acquire_immediate_value(s, c);
+		/* If we haven't seen a sample, there's nothing to duplicate */
+		if (!sensor_info[s].report_initialized)
+			continue;
+
+		/* If a sample was recently buffered, leave it alone too */
+		if (sensor_info[s].report_pending)
+			continue;
 
-			data->data[c] = transform_sample(sensor_type, c, val);
+		/* We also need a valid sampling rate to be configured */
+		if (!sensor_info[s].sampling_rate)
+			continue;
 
-			ALOGV("\tfield %d: %f\n", c, data->data[c]);
-		}
-		return;
-	}
+		period = (int64_t) (1000000000.0/ sensor_info[s].sampling_rate);
 
-	/* Convert the data into the expected Android-level format */
+		current_ts = get_timestamp();
+		target_ts = sensor_info[s].report_ts + period;
 
-	current_sample = sensor_info[s].report_buffer;
+		if (target_ts <= current_ts) {
+			/* Mark the sensor for event generation */
+			set_report_ts(s, current_ts);
+			sensor_info[s].report_pending = 1;
+		}
+	}
+}
 
-	for (c=0; c<num_fields; c++) {
-		sample_size	=  sensor_info[s].channel[c].size;
-		sample_type	= &sensor_info[s].channel[c].type_info;
 
-		s64 = sample_as_int64(current_sample, sample_type);
+static void integrate_thread_report (uint32_t tag)
+{
+	int s = tag - THREAD_REPORT_TAG_BASE;
+	int len;
+	int expected_len;
 
-		val = (sensor_info[s].offset + s64) * sensor_info[s].scale;
+	expected_len = get_field_count(s) * sizeof(float);
 
-		data->data[c] = transform_sample(sensor_type, c, val);
+	len = read(sensor_info[s].thread_data_fd[0],
+		   sensor_info[s].report_buffer,
+		   expected_len);
 
-		ALOGV("\tfield %d: %f\n", c, data->data[c]);
-		current_sample += sample_size;
+	if (len == expected_len) {
+		set_report_ts(s, get_timestamp());
+		sensor_info[s].report_pending = 1;
 	}
 }
 
 
-static int get_poll_time (void)
+static int get_poll_wait_timeout (void)
 {
-	if (!active_poll_sensors)
-		return -1;	/* Infinite wait */
+	/*
+	 * 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 have have to deal with "terse" drivers 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 (sensor_info[s].enable_count &&
+		    sensor_info[s].selected_trigger ==
+		    sensor_info[s].motion_trigger_name &&
+		    sensor_info[s].sampling_rate) {
+			period = (int64_t) (1000000000.0 /
+						sensor_info[s].sampling_rate);
+
+			if (sensor_info[s].report_ts + period < target_ts)
+				target_ts = sensor_info[s].report_ts + period;
+		}
+
+	/* If we don't have such a driver to deal with */
+	if (target_ts == INT64_MAX)
+		return -1; /* Infinite wait */
 
-	return 100;	/* ms ... this needs to be dynamic */
+	ms_to_wait = (target_ts - get_timestamp()) / 1000000;
+
+	/* If the target timestamp is already behind us, don't wait */
+	if (ms_to_wait < 1)
+		return 0;
+
+	return ms_to_wait;
 }
 
 
@@ -582,60 +1014,253 @@ int sensor_poll(struct sensors_event_t* data, int count)
 	int s;
 	int i;
 	int nfds;
-	int delta;
 	struct epoll_event ev[MAX_DEVICES];
+	int returned_events;
+	int event_count;
+	int uncal_start;
 
 	/* Get one or more events from our collection of sensors */
 
-return_first_available_sensor_report:
+return_available_sensor_reports:
 
-	/* If there's at least one available report */
-	for (s=0; s<sensor_count; s++)
-		if (sensor_info[s].report_pending) {
+	/* Synthetize duplicate samples if needed */
+	synthetize_duplicate_samples();
+
+	returned_events = 0;
 
-			/* Return that up */
-			propagate_sensor_report(s, data);
+	/* Check our sensor collection for available reports */
+	for (s=0; s<sensor_count && returned_events < count; s++)
+		if (sensor_info[s].report_pending) {
+			event_count = 0;
+			/* Lower flag */
 			sensor_info[s].report_pending = 0;
-			ALOGV("Report on sensor %d\n", s);
-			return 1;
+
+			/* Report this event if it looks OK */
+			event_count = propagate_sensor_report(s, &data[returned_events]);
+
+			/* Duplicate only if both cal & uncal are active */
+			if (sensor_catalog[sensor_info[s].catalog_index].type == SENSOR_TYPE_GYROSCOPE &&
+					sensor_info[s].pair_idx && sensor_info[sensor_info[s].pair_idx].enable_count != 0) {
+					struct gyro_cal* gyro_data = (struct gyro_cal*) sensor_info[s].cal_data;
+
+					memcpy(&data[returned_events + event_count], &data[returned_events],
+							sizeof(struct sensors_event_t) * event_count);
+
+					uncal_start = returned_events + event_count;
+					for (i = 0; i < event_count; i++) {
+						data[uncal_start + i].type = SENSOR_TYPE_GYROSCOPE_UNCALIBRATED;
+						data[uncal_start + i].sensor = sensor_info[s].pair_idx;
+
+						data[uncal_start + i].data[0] = data[returned_events + i].data[0] + gyro_data->bias_x;
+						data[uncal_start + i].data[1] = data[returned_events + i].data[1] + gyro_data->bias_y;
+						data[uncal_start + i].data[2] = data[returned_events + i].data[2] + gyro_data->bias_z;
+
+						data[uncal_start + i].uncalibrated_gyro.bias[0] = gyro_data->bias_x;
+						data[uncal_start + i].uncalibrated_gyro.bias[1] = gyro_data->bias_y;
+						data[uncal_start + i].uncalibrated_gyro.bias[2] = gyro_data->bias_z;
+					}
+					event_count <<= 1;
+			}
+			sensor_info[sensor_info[s].pair_idx].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.
+			 */
 		}
 
-	/* Keep a minimum time interval between poll operations */
-	delta = (get_timestamp() - last_poll_exit_ts)/1000;
+	if (returned_events)
+		return returned_events;
 
-	if (delta > 0 && delta < POLL_MIN_INTERVAL)
-		usleep(POLL_MIN_INTERVAL - delta);
+await_event:
 
 	ALOGV("Awaiting sensor data\n");
 
-	nfds = epoll_wait(poll_fd, ev, MAX_DEVICES, get_poll_time());
+	nfds = epoll_wait(poll_fd, ev, MAX_DEVICES, get_poll_wait_timeout());
 
-	last_poll_exit_ts = get_timestamp();
+	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 devices for which a report is available */
+	/* For each of the signalled sources */
 	for (i=0; i<nfds; i++)
 		if (ev[i].events == EPOLLIN)
-			/* Read report */
-			integrate_device_report(ev[i].data.u32);
-
-	/* It's a good time to invalidate poll-mode sensor values */
-	for (s=0; s<sensor_count; s++)
-		if (!sensor_info[s].num_channels && sensor_info[s].enable_count)
-			sensor_info[s].report_pending = 1;
+			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;
+
+				default:
+					ALOGW("Unexpected event source!\n");
+					break;
+			}
 
-	goto return_first_available_sensor_report;
+	goto return_available_sensor_reports;
 }
 
 
-int sensor_set_delay(int handle, int64_t ns)
+int sensor_set_delay(int s, int64_t ns)
 {
 	/* Set the rate at which a specific sensor should report events */
-	/* Continuous reports: accelerometer, gyroscope */
-	/* On change with minimum delay between events: ALS, proximity */
-	/* See sensors.h for indication on sensor trigger modes */
-	return -1;
+
+	/* See Android sensors.h for indication on sensor trigger modes */
+
+	char sysfs_path[PATH_MAX];
+	char avail_sysfs_path[PATH_MAX];
+	int dev_num		=	sensor_info[s].dev_num;
+	int i			=	sensor_info[s].catalog_index;
+	const char *prefix	=	sensor_catalog[i].tag;
+	float new_sampling_rate; /* Granted sampling rate after arbitration   */
+	float cur_sampling_rate; /* Currently used sampling rate	      */
+	int per_sensor_sampling_rate;
+	int per_device_sampling_rate;
+	int32_t min_delay_us = sensor_desc[s].minDelay;
+	max_delay_t max_delay_us = sensor_desc[s].maxDelay;
+	float min_supported_rate = max_delay_us ? (1000000.0f / max_delay_us) : 1;
+	float max_supported_rate = 
+		(min_delay_us && min_delay_us != -1) ? (1000000.0f / min_delay_us) : 0;
+	char freqs_buf[100];
+	char* cursor;
+	int n;
+	float sr;
+
+	if (!ns) {
+		ALOGE("Rejecting zero delay request on sensor %d\n", s);
+		return -EINVAL;
+	}
+
+	new_sampling_rate = 1000000000LL/ns;
+
+	/*
+	 * Artificially limit ourselves to 1 Hz or higher. This is mostly to
+	 * avoid setting up the stage for divisions by zero.
+	 */
+	if (new_sampling_rate < min_supported_rate)
+		new_sampling_rate = min_supported_rate;
+
+	if (max_supported_rate &&
+		new_sampling_rate > max_supported_rate) {
+		new_sampling_rate = max_supported_rate;
+	}
+
+	sensor_info[s].sampling_rate = new_sampling_rate;
+
+	/* If we're dealing with a poll-mode sensor */
+	if (!sensor_info[s].num_channels) {
+		/* Interrupt current sleep so the new sampling gets used */
+		pthread_cond_signal(&thread_release_cond[s]);
+		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;
+	}
+
+	/* 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_info[n].dev_num == dev_num &&
+			    sensor_info[n].num_channels &&
+			    sensor_info[n].enable_count &&
+			    sensor_info[n].sampling_rate > new_sampling_rate)
+				new_sampling_rate= sensor_info[n].sampling_rate;
+
+	/* Check if we have contraints on allowed sampling rates */
+
+	sprintf(avail_sysfs_path, DEVICE_AVAIL_FREQ_PATH, dev_num);
+
+	if (sysfs_read_str(avail_sysfs_path, freqs_buf, sizeof(freqs_buf)) > 0){
+		cursor = freqs_buf;
+
+		/* Decode allowed sampling rates string, ex: "10 20 50 100" */
+
+		/* While we're not at the end of the string */
+		while (*cursor && cursor[0]) {
+
+			/* Decode a single value */
+			sr = strtod(cursor, NULL);
+
+			/* If this matches the selected rate, we're happy */
+			if (new_sampling_rate == sr)
+				break;
+
+			/*
+			 * 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 > new_sampling_rate) {
+				new_sampling_rate = sr;
+				break;
+			}
+
+			/* Skip digits */
+			while (cursor[0] && !isspace(cursor[0]))
+				cursor++;
+
+			/* Skip spaces */
+			while (cursor[0] && isspace(cursor[0]))
+					cursor++;
+		}
+	}
+
+
+	if (max_supported_rate &&
+		new_sampling_rate > max_supported_rate) {
+		new_sampling_rate = max_supported_rate;
+	}
+
+
+	/* If the desired rate is already active we're all set */
+	if (new_sampling_rate == cur_sampling_rate)
+		return 0;
+
+	ALOGI("Sensor %d sampling rate set to %g\n", s, new_sampling_rate);
+
+	if (trig_sensors_per_dev[dev_num])
+		enable_buffer(dev_num, 0);
+
+	sysfs_write_float(sysfs_path, new_sampling_rate);
+
+	/* Switch back to continuous sampling for accelerometer based games */
+	if (is_fast_accelerometer(s) && sensor_info[s].selected_trigger !=
+					sensor_info[s].init_trigger_name)
+		setup_trigger(s, sensor_info[s].init_trigger_name);
+
+	if (trig_sensors_per_dev[dev_num])
+		enable_buffer(dev_num, 1);
+
+	return 0;
 }
 
 
@@ -650,6 +1275,7 @@ int allocate_control_data (void)
 
 	if (poll_fd == -1) {
 		ALOGE("Can't create epoll instance for iio sensors!\n");
+		return -1;
 	}
 
 	return poll_fd;