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/*
* Copyright (C) 2016 The Android Open Source Project
*
* 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.
*/
#ifndef _CHRE_SENSOR_H_
#define _CHRE_SENSOR_H_
/**
* API dealing with sensor interaction in the Context Hub Runtime
* Environment.
*
* This includes the definition of our sensor types and the ability to
* configure them for receiving events.
*/
#include <stdbool.h>
#include <stdint.h>
// For CHRE_EVENT_SENSOR_FIRST_EVENT and CHRE_EVENT_SENSOR_LAST_EVENT
#include "chre_event.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* The CHRE_SENSOR_TYPE_* defines are the sensor types supported.
*
* Unless otherwise noted, each of these sensor types is based off of a
* corresponding sensor type in the Android API's sensors.h interface.
* For a given CHRE_SENSOR_TYPE_FOO, it corresponds to the SENSOR_TYPE_FOO in
* hardware/libhardware/include/hardware/sensors.h of the Android code base.
*
* Unless otherwise noted below, a CHRE_SENSOR_TYPE_FOO should be assumed
* to work the same as the Android SENSOR_TYPE_FOO, as documented in the
* sensors.h documentation and as detailed within the Android Compatibility
* Definition Document.
*
* Note that every sensor will generate CHRE_EVENT_SENSOR_SAMPLING_CHANGE
* events, so it is not listed with each individual sensor.
*/
/**
* Accelerometer.
*
* Generates: CHRE_EVENT_SENSOR_ACCELEROMETER_DATA
*
* @see CHRE_EVENT_SENSOR_ACCELEROMETER_DATA
*/
#define CHRE_SENSOR_TYPE_ACCELEROMETER UINT8_C(1)
/**
* Instantaneous motion detection.
*
* Generates: CHRE_EVENT_SENSOR_INSTANT_MOTION_DETECT_DATA
*
* This is a one-shot sensor.
*
* This does not have a direct analogy within sensors.h. This is similar
* to SENSOR_TYPE_MOTION_DETECT, but this triggers instantly upon any
* motion, instead of waiting for a period of continuous motion.
*/
#define CHRE_SENSOR_TYPE_INSTANT_MOTION_DETECT UINT8_C(2)
/**
* Stationary detection.
*
* Generates: CHRE_EVENT_SENSOR_STATIONARY_DETECT_DATA
*
* This is a one-shot sensor.
*/
#define CHRE_SENSOR_TYPE_STATIONARY_DETECT UINT8_C(3)
/**
* Gyroscope.
*
* Generates: CHRE_EVENT_SENSOR_GYROSCOPE_DATA and
* CHRE_EVENT_SENSOR_GYROSCOPE_BIAS_INFO
*
* Note that the GYROSCOPE_DATA is always the calibrated data, and not
* raw data.
*/
#define CHRE_SENSOR_TYPE_GYROSCOPE UINT8_C(6)
/**
* Magnetometer.
*
* Generates: CHRE_EVENT_SENSOR_GEOMAGNETIC_FIELD_DATA and
* CHRE_EVENT_SENSOR_GEOMAGNETIC_FIELD_BIAS_INFO
*
* Note that the GEOMAGNETIC_FIELD_DATA is always the calibrated data, and not
* raw data.
*/
#define CHRE_SENSOR_TYPE_GEOMAGNETIC_FIELD UINT8_C(8)
/**
* Barometric pressure sensor.
*
* Generates: CHRE_EVENT_SENSOR_PRESSURE_DATA
*/
#define CHRE_SENSOR_TYPE_PRESSURE UINT8_C(10)
/**
* Ambient light sensor.
*
* Generates: CHRE_EVENT_SENSOR_LIGHT_DATA
*/
#define CHRE_SENSOR_TYPE_LIGHT UINT8_C(12)
/**
* Proximity detection.
*
* Generates: CHRE_EVENT_SENSOR_PROXIMITY_DATA
*
* This is an on-change sensor.
*/
#define CHRE_SENSOR_TYPE_PROXIMITY UINT8_C(13)
/**
* Base value for all of the data events for sensors.
*
* The value for a data event FOO is
* CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_FOO
*
* This allows for easy mapping, and also explains why there are gaps
* in our values since we don't have all possible sensor types assigned.
*/
#define CHRE_EVENT_SENSOR_DATA_EVENT_BASE CHRE_EVENT_SENSOR_FIRST_EVENT
/**
* nanoappHandleEvent argument: struct chreSensorThreeAxisData
*
* The data can be interpreted using the 'x', 'y', and 'z' fields within
* 'readings', or by the 3D array 'v' (v[0] == x; v[1] == y; v[2] == z).
*
* All values are in SI units (m/s^2) and measure the acceleration of the
* device minus the force of gravity.
*/
#define CHRE_EVENT_SENSOR_ACCELEROMETER_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_ACCELEROMETER)
/**
* nanoappHandleEvent argument: struct chreSensorOccurrenceData
*
* Since this is a one-shot sensor, after this event is delivered to the
* nanoapp, the sensor automatically goes into DONE mode. Sensors of this
* type must be configured with a ONE_SHOT mode.
*/
#define CHRE_EVENT_SENSOR_INSTANT_MOTION_DETECT_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_INSTANT_MOTION_DETECT)
/**
* nanoappHandleEvent argument: struct chreSensorOccurrenceData
*
* Since this is a one-shot sensor, after this event is delivered to the
* nanoapp, the sensor automatically goes into DONE mode. Sensors of this
* type must be configured with a ONE_SHOT mode.
*/
#define CHRE_EVENT_SENSOR_STATIONARY_DETECT_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_STATIONARY_DETECT)
/**
* nanoappHandleEvent argument: struct chreSensorThreeAxisData
*
* The data can be interpreted using the 'x', 'y', and 'z' fields within
* 'readings', or by the 3D array 'v' (v[0] == x; v[1] == y; v[2] == z).
*
* All values are in radians/second and measure the rate of rotation
* around the X, Y and Z axis.
*/
#define CHRE_EVENT_SENSOR_GYROSCOPE_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_GYROSCOPE)
/**
* nanoappHandleEvent argument: struct chreSensorThreeAxisData
*
* The data can be interpreted using the 'x', 'y', and 'z' fields within
* 'readings', or by the 3D array 'v' (v[0] == x; v[1] == y; v[2] == z).
*
* All values are in micro-Tesla (uT) and measure the geomagnetic
* field in the X, Y and Z axis.
*/
#define CHRE_EVENT_SENSOR_GEOMAGNETIC_FIELD_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_GEOMAGNETIC_FIELD)
/**
* nanoappHandleEvent argument: struct chreSensorFloatData
*
* The data can be interpreted using the 'pressure' field within 'readings'.
* This value is in hectopascals (hPa).
*/
#define CHRE_EVENT_SENSOR_PRESSURE_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_PRESSURE)
/**
* nanoappHandleEvent argument: struct chreSensorFloatData
*
* The data can be interpreted using the 'light' field within 'readings'.
* This value is in SI lux units.
*/
#define CHRE_EVENT_SENSOR_LIGHT_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_LIGHT)
/**
* nanoappHandleEvent argument: struct chreSensorByteData
*
* The data is interpreted from the following fields in 'readings':
* o 'isNear': If set to 1, we are nearby (on the order of centimeters);
* if set to 0, we are far.
* o 'invalid': If set to 1, this is not a valid reading of this data.
*
* As an on-change sensor, there is an event generated upon configuring
* this sensor. This is when we might get an 'invalid' reading. Thus,
* this field must be checked on the first event before interpreting 'isNear'.
*/
#define CHRE_EVENT_SENSOR_PROXIMITY_DATA \
(CHRE_EVENT_SENSOR_DATA_EVENT_BASE + CHRE_SENSOR_TYPE_PROXIMITY)
/**
* First value for sensor events which are not data from the sensor.
*
* Unlike the data event values, these other event values don't have any
* mapping to sensor types.
*/
#define CHRE_EVENT_SENSOR_OTHER_EVENTS_BASE \
(CHRE_EVENT_SENSOR_FIRST_EVENT + 0x0100)
/**
* nanoappHandleEvent argument: struct chreSensorSamplingChangeEvent
*
* Indicates that the interval and/or the latency which this sensor is
* sampling at has changed.
*/
#define CHRE_EVENT_SENSOR_SAMPLING_CHANGE \
(CHRE_EVENT_SENSOR_OTHER_EVENTS_BASE + 0)
/**
* nanoappHandleEvent argument: struct chreSensorThreeAxisData
*
* The data can be interpreted using the 'x_bias', 'y_bias', and 'z_bias'
* field within 'readings', or by the 3D array 'bias' (bias[0] == x_bias;
* bias[1] == y_bias; bias[2] == z_bias).
*
* All values are in radians/second and measure the rate of rotation
* around the X, Y and Z axis.
*/
#define CHRE_EVENT_SENSOR_GYROSCOPE_BIAS_INFO \
(CHRE_EVENT_SENSOR_OTHER_EVENTS_BASE + 1)
/**
* nanoappHandleEvent argument: struct chreSensorThreeAxisData
*
* The data can be interpreted using the 'x_bias', 'y_bias', and 'z_bias'
* field within 'readings', or by the 3D array 'bias' (bias[0] == x_bias;
* bias[1] == y_bias; bias[2] == z_bias).
*
* All values are in micro-Tesla (uT) and measure the geomagnetic
* field in the X, Y and Z axis.
*/
#define CHRE_EVENT_SENSOR_GEOMAGNETIC_FIELD_BIAS_INFO \
(CHRE_EVENT_SENSOR_OTHER_EVENTS_BASE + 2)
#if CHRE_EVENT_SENSOR_GEOMAGNETIC_FIELD_BIAS_INFO > CHRE_EVENT_SENSOR_LAST_EVENT
#error Too many sensor events.
#endif
/**
* Value indicating we want the smallest possible latency for a sensor.
*
* This literally translates to 0 nanoseconds for the chreSensorConfigure()
* argument. While we won't get exactly 0 nanoseconds, the CHRE will
* queue up this event As Soon As Possible.
*/
#define CHRE_SENSOR_LATENCY_ASAP UINT64_C(0)
/**
* Special value indicating non-importance of the interval.
*
* @see chreSensorConfigure
* @see chreSensorSamplingStatus
*/
#define CHRE_SENSOR_INTERVAL_DEFAULT UINT64_C(-1)
/**
* Special value indicating non-importance of the latency.
*
* @see chreSensorConfigure
* @see chreSensorSamplingStatus
*/
#define CHRE_SENSOR_LATENCY_DEFAULT UINT64_C(-1)
// This is used to define elements of enum chreSensorConfigureMode.
#define CHRE_SENSOR_CONFIGURE_RAW_POWER_ON (1 << 0)
// This is used to define elements of enum chreSensorConfigureMode.
#define CHRE_SENSOR_CONFIGURE_RAW_REPORT_CONTINUOUS (1 << 1)
// This is used to define elements of enum chreSensorConfigureMode.
#define CHRE_SENSOR_CONFIGURE_RAW_REPORT_ONE_SHOT (2 << 1)
/**
* Modes we can configure a sensor to use.
*
* Our mode will affect not only how/if we receive events, but
* also whether or not the sensor will be powered on our behalf.
*
* @see chreSensorConfigure
*/
enum chreSensorConfigureMode {
/**
* Get events from the sensor.
*
* Power: Turn on if not already on.
* Reporting: Continuous. Send each new event as it comes (subject to
* batching and latency).
*/
CHRE_SENSOR_CONFIGURE_MODE_CONTINUOUS =
(CHRE_SENSOR_CONFIGURE_RAW_POWER_ON |
CHRE_SENSOR_CONFIGURE_RAW_REPORT_CONTINUOUS),
/**
* Get a single event from the sensor and then become DONE.
*
* Once the event is sent, the sensor automatically
* changes to CHRE_SENSOR_CONFIGURE_MODE_DONE mode.
*
* Power: Turn on if not already on.
* Reporting: One shot. Send the next event and then be DONE.
*/
CHRE_SENSOR_CONFIGURE_MODE_ONE_SHOT =
(CHRE_SENSOR_CONFIGURE_RAW_POWER_ON |
CHRE_SENSOR_CONFIGURE_RAW_REPORT_ONE_SHOT),
/**
* Get events from a sensor that are generated for other apps.
*
* This is considered passive because the sensor will not be powered
* on for the sake of our nanoapp. If and only if another app in
* the system has requested this sensor power on will we get events.
*
* This can be useful for something which is interested in seeing data,
* but not interested enough to be responsible for powering on the sensor.
*
* Power: Do not power the sensor on our behalf.
* Reporting: Continuous. Send each event as it comes.
*/
CHRE_SENSOR_CONFIGURE_MODE_PASSIVE_CONTINUOUS =
CHRE_SENSOR_CONFIGURE_RAW_REPORT_CONTINUOUS,
/**
* Get a single event from a sensor that is generated for other apps.
*
* See CHRE_SENSOR_CONFIGURE_MODE_PASSIVE_CONTINUOUS for more details
* on what be "passive" means.
*
* Power: Do not power the sensor on our behalf.
* Reporting: One shot. Send only the next event and then be DONE.
*/
CHRE_SENSOR_CONFIGURE_MODE_PASSIVE_ONE_SHOT =
CHRE_SENSOR_CONFIGURE_RAW_REPORT_ONE_SHOT,
/**
* Indicate we are done using this sensor and no longer interested in it.
*
* See chreSensorConfigure for more details on expressing interest or
* lack of interest in a sensor.
*
* Power: Do not power the sensor on our behalf.
* Reporting: None.
*/
CHRE_SENSOR_CONFIGURE_MODE_DONE = 0,
};
/**
* A structure containing information about a Sensor.
*
* See documentation of individual fields below.
*/
struct chreSensorInfo {
/**
* The name of the sensor.
*
* A text name, useful for logging/debugging, describing the Sensor. This
* is not assured to be unique (i.e. there could be multiple sensors with
* the name "Temperature").
*
* CHRE implementations may not set this as NULL. An empty
* string, while discouraged, is legal.
*/
const char *sensorName;
/**
* One of the CHRE_SENSOR_TYPE_* defines above.
*/
uint8_t sensorType;
/**
* Flag indicating if this sensor is on-change.
*
* An on-change sensor only generates events when underlying state
* changes. This has the same meaning as on-change does in the Android
* Sensors HAL. See sensors.h for much more details.
*
* A value of 1 indicates this is on-change. 0 indicates this is not
* on-change.
*/
uint8_t isOnChange : 1;
/**
* Flag indicating if this sensor is one-shot.
*
* A one-shot sensor only triggers a single event, and then automatically
* disables itself.
*
* A value of 1 indicates this is on-change. 0 indicates this is not
* on-change.
*/
uint8_t isOneShot : 1;
uint8_t unusedFlags : 6;
};
/**
* Header used in every structure containing batchable data from a sensor.
*
* The typical structure for sensor data looks like:
*
* struct chreSensorTypeData {
* struct chreSensorDataHeader header;
* struct {
* uint32_t timestampDelta;
* union {
* <type> value;
* <type> interpretation0;
* <type> interpretation1;
* };
* } readings[1];
* };
*
* Despite 'readings' being declared as an array of 1 element,
* an instance of the struct will actually have 'readings' as
* an array of header.readingCount elements (which may be 1).
* The 'timestampDelta' is in relation to the previous 'readings' (or
* the baseTimestamp for readings[0]. So,
* Timestamp for readings[0] == header.baseTimestamp +
* readings[0].timestampDelta.
* Timestamp for readings[1] == timestamp for readings[0] +
* readings[1].timestampDelta.
* And thus, in order to determine the timestamp for readings[N], it's
* necessary to process through all of the N-1 readings. The advantage,
* though, is that our entire readings can span an arbitrary length of time,
* just as long as any two consecutive readings differ by no more than
* 4.295 seconds (timestampDelta, like all time in the CHRE, is in
* nanoseconds).
*
* If a sensor has batched readings where two consecutive readings differ by
* more than 4.295 seconds, the CHRE will split them across multiple
* instances of the struct, and send multiple events.
*
* The value from the sensor is typically expressed in a union,
* allowing a generic access to the data ('value'), along with
* differently named access giving a more natural interpretation
* of the data for the specific sensor types which use this
* structure. This allows, for example, barometer code to
* reference readings[N].pressure, and an ambient light sensor
* to reference readings[N].light, while both use the same
* structure.
*/
struct chreSensorDataHeader {
/**
* The base timestamp, in nanoseconds.
*/
uint64_t baseTimestamp;
/**
* The handle of the sensor producing this event.
*/
uint32_t sensorHandle;
/**
* The number elements in the 'readings' array.
*
* This must be at least 1.
*/
uint16_t readingCount;
/**
* Reserved bytes.
*
* These must be 0.
*/
uint8_t reserved[2];
};
/**
* Data for a sensor which reports on three axes.
*
* This is used by CHRE_EVENT_SENSOR_DATA, CHRE_EVENT_SENSOR_GYROSCOPE_DATA,
* CHRE_EVENT_SENSOR_GYROSCOPE_BIAS_INFO,
* CHRE_EVENT_SENSOR_GEOMAGNETIC_FIELD_DATA, and
* CHRE_EVENT_SENSOR_GEOMAGNETIC_FIELD_BIAS_INFO.
*/
struct chreSensorThreeAxisData {
/**
* @see chreSensorDataHeader
*/
struct chreSensorDataHeader header;
struct {
/**
* @see chreSensorDataHeader
*/
uint32_t timestampDelta;
union {
float values[3];
float v[3];
struct {
float x;
float y;
float z;
};
float bias[3];
struct {
float x_bias;
float y_bias;
float z_bias;
};
};
} readings[1];
};
/**
* Data from a sensor where we only care about a event occurring.
*
* This is a bit unusual in that our readings have no data in addition
* to the timestamp. But since we only care about the occurrence, we
* don't need to know anything else.
*
* Used by: CHRE_EVENT_SENSOR_INSTANT_MOTION_DETECT_DATA and
* CHRE_EVENT_SENSOR_STATIONARY_DETECT_DATA.
*/
struct chreSensorOccurrenceData {
struct chreSensorDataHeader header;
struct {
uint32_t timestampDelta;
// This space intentionally left blank.
// Only the timestamp is meaningful here, there
// is no additional data.
} readings[1];
};
/**
* CHRE_EVENT_SENSOR_LIGHT_DATA and CHRE_EVENT_SENSOR_PRESSURE_DATA.
*/
struct chreSensorFloatData {
struct chreSensorDataHeader header;
struct {
uint32_t timestampDelta;
union {
float value;
float light; // lux
float pressure; // hectopascals (hPa)
};
} readings[1];
};
/**
* CHRE_EVENT_SENSOR_PROXIMITY_DATA.
*/
struct chreSensorByteData {
struct chreSensorDataHeader header;
struct {
uint32_t timestampDelta;
union {
uint8_t value;
struct {
uint8_t isNear : 1;
uint8_t invalid : 1;
uint8_t padding0 : 6;
};
};
} readings[1];
};
/**
* The status of a sensor's sampling configuration.
*/
struct chreSensorSamplingStatus {
/**
* The interval, in nanoseconds, at which the sensor is now sampling.
*
* If this is CHRE_SENSOR_INTERVAL_DEFAULT, then a sampling interval
* isn't meaningful for this sensor.
*
* Note that if 'enabled' is false, this value is not meaningful.
*/
uint64_t interval;
/**
* The latency, in nanoseconds, at which the senor is now reporting.
*
* If this is CHRE_SENSOR_LATENCY_DEFAULT, then a latency
* isn't meaningful for this sensor.
*
* Note that if 'enabled' is false, this value is not meaningful.
*/
uint64_t latency;
/**
* True if the sensor is actively powered and sampling; false otherwise.
*/
bool enabled;
};
/**
* The nanoappHandleEvent argument for CHRE_EVENT_SENSOR_SAMPLING_CHANGE.
*
* Note that only at least one of 'interval' or 'latency' must be
* different than it was prior to this event. Thus, one of these
* fields may be (but doesn't need to be) the same as before.
*/
struct chreSensorSamplingStatusEvent {
/**
* The handle of the sensor which has experienced a change in sampling.
*/
uint32_t sensorHandle;
/**
* The new sampling status.
*
* At least one of the field in this struct will be different from
* the previous sampling status event.
*/
struct chreSensorSamplingStatus status;
};
/**
* Find the default sensor for a given sensor type.
*
* @param sensorType One of the CHRE_SENSOR_TYPE_* constants.
* @param handle If a sensor is found, then the memory will be filled with
* the value for the sensor's handle. This argument must be non-NULL.
* @returns true if a sensor was found, false otherwise.
*/
bool chreSensorFindDefault(uint8_t sensorType, uint32_t *handle);
/**
* Get the chreSensorInfo struct for a given sensor.
*
* @param sensorHandle The sensor handle, as obtained from
* chreSensorFindDefault() or passed to nanoappHandleEvent().
* @param info If the sensor is valid, then this memory will be filled with
* the SensorInfo contents for this sensor. This argument must be
* non-NULL.
* @returns true if the senor handle is valid and 'info' was filled in;
* false otherwise.
*/
bool chreGetSensorInfo(uint32_t sensorHandle, struct chreSensorInfo *info);
/**
* Get the chreSensorSamplingStatus struct for a given sensor.
*
* Note that this may be different from what was requested in
* chreSensorConfigure(), for multiple reasons. It's possible that the sensor
* does not exactly support the interval requested in chreSensorConfigure(), so
* a faster one was chosen.
*
* It's also possible that there is another user of this sensor who has
* requested a faster interval and/or lower latency. This latter scenario
* should be noted, because it means the sensor rate can change due to no
* interaction from this nanoapp. Note that the
* CHRE_EVENT_SENSOR_SAMPLING_CHANGE event will trigger in this case, so it's
* not necessary to poll for such a change.
*
* @param sensorHandle The sensor handle, as obtained from
* chreSensorFindDefault() or passed to nanoappHandleEvent().
* @param status If the sensor is valid, then this memory will be filled with
* the sampling status contents for this sensor. This argument must be
* non-NULL.
* @returns true if the senor handle is valid and 'status' was filled in;
* false otherwise.
*/
bool chreGetSensorSamplingStatus(uint32_t sensorHandle,
struct chreSensorSamplingStatus *status);
/**
* Configures a given sensor at a specific interval and latency and mode.
*
* If this sensor's chreSensorInfo has isOneShot set to 1,
* then the mode must be one of the ONE_SHOT modes, or this method will fail.
*
* The CHRE wants to power as few sensors as possible, in keeping with its
* low power design. As such, it only turns on sensors when there are clients
* actively interested in that sensor data, and turns off sensors as soon as
* there are no clients interested in them. Calling this method generally
* indicates an interest, and using CHRE_SENSOR_CONFIGURE_MODE_DONE shows
* when we are no longer interested.
*
* Thus, each initial Configure of a sensor (per nanoapp) needs to eventually
* have a DONE call made, either directly or on its behalf. Subsequent calls
* to a Configure method within the same nanoapp, when there has been no DONE
* in between, still only require a single DONE call.
*
* For example, the following is valid usage:
* <code>
* chreSensorConfigure(myHandle, mode, interval0, latency0);
* [...]
* chreSensorConfigure(myHandle, mode, interval1, latency0);
* [...]
* chreSensorConfigure(myHandle, mode, interval1, latency1);
* [...]
* chreSensorConfigureModeOnly(myHandle, CHRE_SENSOR_CONFIGURE_MODE_DONE);
* </code>
*
* The first call to Configure is the one which creates the requirement
* to eventually call with DONE. The subsequent calls are just changing the
* interval/latency. They have not changed the fact that this nanoapp is
* still interested in output from the sensor 'myHandle'. Thus, only one
* single call for DONE is needed.
*
* There is a special case. One-shot sensors, sensors which
* just trigger a single event and never trigger again, implicitly go into
* DONE mode after that single event triggers. Thus, the
* following are legitimate usages:
* <code>
* chreSensorConfigure(myHandle, MODE_ONE_SHOT, rate, latency);
* [...]
* [myHandle triggers an event]
* [no need to configure to DONE].
* </code>
*
* And:
* <code>
* chreSensorConfigure(myHandle, MODE_ONE_SHOT, rate, latency);
* [...]
* chreSensorConfigureModeOnly(myHandle, MODE_DONE);
* [we cancelled myHandle before it ever triggered an event]
* </code>
*
* Note that while PASSIVE modes, by definition, don't express
* an interest in powering the sensor, DONE is still necessary
* to silence the event reporting.
*
* @param sensorHandle The handle to the sensor, as obtained from
* chreSensorFindDefault().
* @param mode The mode to use. See descriptions within the
* chreSensorConfigureMode enum.
* @param interval The interval, in nanoseconds, at which we want events from
* the sensor. On success, the sensor will be set to 'interval', or a value
* less than 'interval'. There is a special value
* CHRE_SENSOR_INTERVAL_DEFAULT, in which we don't express a preference for
* the interval, and allow the sensor to chose what it wants. Note that
* due to batching, we may receive events less frequently than
* 'interval'.
* @param latency The maximum latency, in nanoseconds, allowed before the
* CHRE begins delivery of an event. This will control how many events
* can be queued by the sensor before requiring a delivery event.
* Latency is defined as the "timestamp when event is queued by the CHRE"
* minus "timestamp of oldest unsent data reading".
* There is a special value CHRE_SENSOR_LATENCY_DEFAULT, in which we don't
* express a preference for the latency, and allow the sensor to chose what
* it wants.
* Note that there is no assurance of how long it will take an event to
* get through a CHRE's queueing system, and thus there is no ability to
* request a minimum time from the occurrence of a phenomenon to when the
* nanoapp receives the information. The current CHRE API has no
* real-time elements, although future versions may introduce some to
* help with this issue.
* @returns true if the configuration succeeded, false otherwise.
*
* @see chreSensorConfigureMode
* @see chreSensorFindDefault
* @see chreSensorInfo
*/
bool chreSensorConfigure(uint32_t sensorHandle,
enum chreSensorConfigureMode mode,
uint64_t interval, uint64_t latency);
/**
* Short cut for chreSensorConfigure where we only want to change the mode.
*
* @see chreSensorConfigure
*/
inline bool chreSensorConfigureModeOnly(uint32_t sensorHandle,
enum chreSensorConfigureMode mode) {
return chreSensorConfigure(sensorHandle,
mode,
CHRE_SENSOR_INTERVAL_DEFAULT,
CHRE_SENSOR_LATENCY_DEFAULT);
}
#ifdef __cplusplus
}
#endif
#endif /* _CHRE_SENSOR_H_ */