Docs: Removing contents now on source.android.com
Bug: 10134622
Change-Id: Ief5a53f1b5e5eff9ade45763d895029428266980
diff --git a/include/hardware/sensors.h b/include/hardware/sensors.h
index 4c13848..2abca72 100644
--- a/include/hardware/sensors.h
+++ b/include/hardware/sensors.h
@@ -35,6 +35,12 @@
#define SENSORS_DEVICE_API_VERSION_1_1 HARDWARE_DEVICE_API_VERSION_2(1, 1, SENSORS_HEADER_VERSION)
/**
+ * Please see the Sensors section of source.android.com for an
+ * introduction to and detailed descriptions of Android sensor types:
+ * http://source.android.com/devices/sensors/index.html
+ */
+
+/**
* The id of this module
*/
#define SENSORS_HARDWARE_MODULE_ID "sensors"
@@ -74,74 +80,14 @@
META_DATA_VERSION /* always last, leave auto-assigned */
};
-/**
- * Definition of the axis used by the sensor HAL API
- *
- * This API is relative to the screen of the device in its default orientation,
- * that is, if the device can be used in portrait or landscape, this API
- * is only relative to the NATURAL orientation of the screen. In other words,
- * the axis are not swapped when the device's screen orientation changes.
- * Higher level services /may/ perform this transformation.
- *
- * x<0 x>0
- * ^
- * |
- * +-----------+--> y>0
- * | |
- * | |
- * | |
- * | | / z<0
- * | | /
- * | | /
- * O-----------+/
- * |[] [ ] []/
- * +----------/+ y<0
- * /
- * /
- * |/ z>0 (toward the sky)
- *
- * O: Origin (x=0,y=0,z=0)
- *
- */
-
-/*
- * Interaction with suspend mode
- *
- * Unless otherwise noted, an enabled sensor shall not prevent the
- * SoC to go into suspend mode. It is the responsibility of applications
- * to keep a partial wake-lock should they wish to receive sensor
- * events while the screen is off. While in suspend mode, and unless
- * otherwise noted (batch mode, sensor particularities, ...), enabled sensors'
- * events are lost.
- *
- * Note that conceptually, the sensor itself is not de-activated while in
- * suspend mode -- it's just that the data it returns are lost. As soon as
- * the SoC gets out of suspend mode, operations resume as usual. Of course,
- * in practice sensors shall be disabled while in suspend mode to
- * save power, unless batch mode is active, in which case they must
- * continue fill their internal FIFO (see the documentation of batch() to
- * learn how suspend interacts with batch mode).
- *
- * In batch mode, and only when the flag SENSORS_BATCH_WAKE_UPON_FIFO_FULL is
- * set and supported, the specified sensor must be able to wake-up the SoC and
- * be able to buffer at least 10 seconds worth of the requested sensor events.
- *
- * There are notable exceptions to this behavior, which are sensor-dependent
- * (see sensor types definitions below)
- *
- *
- * The sensor type documentation below specifies the wake-up behavior of
- * each sensor:
- * wake-up: yes this sensor must wake-up the SoC to deliver events
- * wake-up: no this sensor shall not wake-up the SoC, events are dropped
- *
- */
-
/*
* Sensor type
*
* Each sensor has a type which defines what this sensor measures and how
- * measures are reported. All types are defined below.
+ * measures are reported. See the Base sensors and Composite sensors lists
+ * for complete descriptions:
+ * http://source.android.com/devices/sensors/base_triggers.html
+ * http://source.android.com/devices/sensors/composite_sensors.html
*
* Device manufacturers (OEMs) can define their own sensor types, for
* their private use by applications or services provided by them. Such
@@ -156,47 +102,6 @@
#define SENSOR_TYPE_DEVICE_PRIVATE_BASE 0x10000
/*
- * Sensor fusion and virtual sensors
- *
- * Many sensor types are or can be implemented as virtual sensors from
- * physical sensors on the device. For instance the rotation vector sensor,
- * orientation sensor, step-detector, step-counter, etc...
- *
- * From the point of view of this API these virtual sensors MUST appear as
- * real, individual sensors. It is the responsibility of the driver and HAL
- * to make sure this is the case.
- *
- * In particular, all sensors must be able to function concurrently.
- * For example, if defining both an accelerometer and a step counter,
- * then both must be able to work concurrently.
- */
-
-/*
- * Trigger modes
- *
- * Sensors can report events in different ways called trigger modes,
- * each sensor type has one and only one trigger mode associated to it.
- * Currently there are four trigger modes defined:
- *
- * continuous: events are reported at a constant rate defined by setDelay().
- * eg: accelerometers, gyroscopes.
- * on-change: events are reported only if the sensor's value has changed.
- * setDelay() is used to set a lower limit to the reporting
- * period (minimum time between two events).
- * The HAL must return an event immediately when an on-change
- * sensor is activated.
- * eg: proximity, light sensors
- * one-shot: upon detection of an event, the sensor deactivates itself and
- * then sends a single event. Order matters to avoid race
- * conditions. No other event is sent until the sensor get
- * reactivated. setDelay() is ignored.
- * eg: significant motion sensor
- * special: see details in the sensor type specification below
- *
- */
-
-
-/*
* SENSOR_TYPE_META_DATA
* trigger-mode: n/a
* wake-up sensor: n/a
@@ -237,30 +142,6 @@
* All values are in SI units (m/s^2) and measure the acceleration of the
* device minus the force of gravity.
*
- * Acceleration sensors return sensor events for all 3 axes at a constant
- * rate defined by setDelay().
- *
- * x: Acceleration on the x-axis
- * y: Acceleration on the y-axis
- * z: Acceleration on the z-axis
- *
- * Note that the readings from the accelerometer include the acceleration
- * due to gravity (which is opposite to the direction of the gravity vector).
- *
- * Examples:
- * The norm of <x, y, z> should be close to 0 when in free fall.
- *
- * When the device lies flat on a table and is pushed on its left side
- * toward the right, the x acceleration value is positive.
- *
- * When the device lies flat on a table, the acceleration value is +9.81,
- * which correspond to the acceleration of the device (0 m/s^2) minus the
- * force of gravity (-9.81 m/s^2).
- *
- * When the device lies flat on a table and is pushed toward the sky, the
- * acceleration value is greater than +9.81, which correspond to the
- * acceleration of the device (+A m/s^2) minus the force of
- * gravity (-9.81 m/s^2).
*/
#define SENSOR_TYPE_ACCELEROMETER (1)
@@ -272,12 +153,6 @@
* All values are in micro-Tesla (uT) and measure the geomagnetic
* field in the X, Y and Z axis.
*
- * Returned values include calibration mechanisms such that the vector is
- * aligned with the magnetic declination and heading of the earth's
- * geomagnetic field.
- *
- * Magnetic Field sensors return sensor events for all 3 axes at a constant
- * rate defined by setDelay().
*/
#define SENSOR_TYPE_GEOMAGNETIC_FIELD (2)
#define SENSOR_TYPE_MAGNETIC_FIELD SENSOR_TYPE_GEOMAGNETIC_FIELD
@@ -286,39 +161,11 @@
* SENSOR_TYPE_ORIENTATION
* trigger-mode: continuous
* wake-up sensor: no
- *
+ *
* All values are angles in degrees.
- *
+ *
* Orientation sensors return sensor events for all 3 axes at a constant
* rate defined by setDelay().
- *
- * azimuth: angle between the magnetic north direction and the Y axis, around
- * the Z axis (0<=azimuth<360).
- * 0=North, 90=East, 180=South, 270=West
- *
- * pitch: Rotation around X axis (-180<=pitch<=180), with positive values when
- * the z-axis moves toward the y-axis.
- *
- * roll: Rotation around Y axis (-90<=roll<=90), with positive values when
- * the x-axis moves towards the z-axis.
- *
- * Note: For historical reasons the roll angle is positive in the clockwise
- * direction (mathematically speaking, it should be positive in the
- * counter-clockwise direction):
- *
- * Z
- * ^
- * (+roll) .--> |
- * / |
- * | | roll: rotation around Y axis
- * X <-------(.)
- * Y
- * note that +Y == -roll
- *
- *
- *
- * Note: This definition is different from yaw, pitch and roll used in aviation
- * where the X axis is along the long side of the plane (tail to nose).
*/
#define SENSOR_TYPE_ORIENTATION (3)
@@ -328,17 +175,7 @@
* wake-up sensor: no
*
* All values are in radians/second and measure the rate of rotation
- * around the X, Y and Z axis. The coordinate system is the same as is
- * used for the acceleration sensor. Rotation is positive in the
- * counter-clockwise direction (right-hand rule). That is, an observer
- * looking from some positive location on the x, y or z axis at a device
- * positioned on the origin would report positive rotation if the device
- * appeared to be rotating counter clockwise. Note that this is the
- * standard mathematical definition of positive rotation and does not agree
- * with the definition of roll given earlier.
- * The range should at least be 17.45 rad/s (ie: ~1000 deg/s).
- *
- * automatic gyro-drift compensation is allowed but not required.
+ * around the X, Y and Z axis.
*/
#define SENSOR_TYPE_GYROSCOPE (4)
@@ -368,10 +205,7 @@
* trigger-mode: on-change
* wake-up sensor: yes
*
- * The distance value is measured in centimeters. Note that some proximity
- * sensors only support a binary "close" or "far" measurement. In this case,
- * the sensor should report its maxRange value in the "far" state and a value
- * less than maxRange in the "near" state.
+ * The value corresponds to the distance to the nearest object in centimeters.
*/
#define SENSOR_TYPE_PROXIMITY (8)
@@ -381,10 +215,7 @@
* wake-up sensor: no
*
* A gravity output indicates the direction of and magnitude of gravity in
- * the devices's coordinates. On Earth, the magnitude is 9.8 m/s^2.
- * Units are m/s^2. The coordinate system is the same as is used for the
- * acceleration sensor. When the device is at rest, the output of the
- * gravity sensor should be identical to that of the accelerometer.
+ * the devices's coordinates.
*/
#define SENSOR_TYPE_GRAVITY (9)
@@ -395,13 +226,6 @@
*
* Indicates the linear acceleration of the device in device coordinates,
* not including gravity.
- *
- * The output is conceptually:
- * output of TYPE_ACCELERATION - output of TYPE_GRAVITY
- *
- * Readings on all axes should be close to 0 when device lies on a table.
- * Units are m/s^2.
- * The coordinate system is the same as is used for the acceleration sensor.
*/
#define SENSOR_TYPE_LINEAR_ACCELERATION (10)
@@ -412,46 +236,7 @@
* wake-up sensor: no
*
* The rotation vector symbolizes the orientation of the device relative to the
- * East-North-Up coordinates frame. It is usually obtained by integration of
- * accelerometer, gyroscope and magnetometer readings.
- *
- * The East-North-Up coordinate system is defined as a direct orthonormal basis
- * where:
- * - X points east and is tangential to the ground.
- * - Y points north and is tangential to the ground.
- * - Z points towards the sky and is perpendicular to the ground.
- *
- * The orientation of the phone is represented by the rotation necessary to
- * align the East-North-Up coordinates with the phone's coordinates. That is,
- * applying the rotation to the world frame (X,Y,Z) would align them with the
- * phone coordinates (x,y,z).
- *
- * The rotation can be seen as rotating the phone by an angle theta around
- * an axis rot_axis to go from the reference (East-North-Up aligned) device
- * orientation to the current device orientation.
- *
- * The rotation is encoded as the 4 (reordered) components of a unit quaternion:
- * sensors_event_t.data[0] = rot_axis.x*sin(theta/2)
- * sensors_event_t.data[1] = rot_axis.y*sin(theta/2)
- * sensors_event_t.data[2] = rot_axis.z*sin(theta/2)
- * sensors_event_t.data[3] = cos(theta/2)
- * where
- * - rot_axis.x,y,z are the North-East-Up coordinates of a unit length vector
- * representing the rotation axis
- * - theta is the rotation angle
- *
- * The quaternion must be of norm 1 (it is a unit quaternion). Failure to ensure
- * this will cause erratic client behaviour.
- *
- * In addition, this sensor reports an estimated heading accuracy.
- * sensors_event_t.data[4] = estimated_accuracy (in radians)
- * The heading error must be less than estimated_accuracy 95% of the time
- *
- * This sensor must use a gyroscope and an accelerometer as main orientation
- * change input.
- *
- * This sensor can also include magnetometer input to make up for gyro drift,
- * but it cannot be implemented using only a magnetometer.
+ * East-North-Up coordinates frame.
*/
#define SENSOR_TYPE_ROTATION_VECTOR (11)
@@ -481,35 +266,6 @@
*
* Similar to SENSOR_TYPE_MAGNETIC_FIELD, but the hard iron calibration is
* reported separately instead of being included in the measurement.
- * Factory calibration and temperature compensation should still be applied to
- * the "uncalibrated" measurement.
- * Separating away the hard iron calibration estimation allows the system to
- * better recover from bad hard iron estimation.
- *
- * All values are in micro-Tesla (uT) and measure the ambient magnetic
- * field in the X, Y and Z axis. Assumptions that the the magnetic field
- * is due to the Earth's poles should be avoided.
- *
- * The uncalibrated_magnetic event contains
- * - 3 fields for uncalibrated measurement: x_uncalib, y_uncalib, z_uncalib.
- * Each is a component of the measured magnetic field, with soft iron
- * and temperature compensation applied, but not hard iron calibration.
- * These values should be continuous (no re-calibration should cause a jump).
- * - 3 fields for hard iron bias estimates: x_bias, y_bias, z_bias.
- * Each field is a component of the estimated hard iron calibration.
- * They represent the offsets to apply to the calibrated readings to obtain
- * uncalibrated readings (x_uncalib ~= x_calibrated + x_bias)
- * These values are expected to jump as soon as the estimate of the hard iron
- * changes, and they should be stable the rest of the time.
- *
- * If this sensor is present, then the corresponding
- * SENSOR_TYPE_MAGNETIC_FIELD must be present and both must return the
- * same sensor_t::name and sensor_t::vendor.
- *
- * Minimum filtering should be applied to this sensor. In particular, low pass
- * filters should be avoided.
- *
- * See SENSOR_TYPE_MAGNETIC_FIELD for more information
*/
#define SENSOR_TYPE_MAGNETIC_FIELD_UNCALIBRATED (14)
@@ -519,21 +275,7 @@
* wake-up sensor: no
*
* Similar to SENSOR_TYPE_ROTATION_VECTOR, but not using the geomagnetic
- * field. Therefore the Y axis doesn't point north, but instead to some other
- * reference. That reference is allowed to drift by the same order of
- * magnitude than the gyroscope drift around the Z axis.
- *
- * This sensor does not report an estimated heading accuracy:
- * sensors_event_t.data[4] is reserved and should be set to 0
- *
- * In the ideal case, a phone rotated and returning to the same real-world
- * orientation should report the same game rotation vector
- * (without using the earth's geomagnetic field).
- *
- * This sensor must be based on a gyroscope. It cannot be implemented using
- * a magnetometer.
- *
- * see SENSOR_TYPE_ROTATION_VECTOR for more details
+ * field.
*/
#define SENSOR_TYPE_GAME_ROTATION_VECTOR (15)
@@ -543,44 +285,10 @@
* wake-up sensor: no
*
* All values are in radians/second and measure the rate of rotation
- * around the X, Y and Z axis. An estimation of the drift on each axis is
- * reported as well.
- *
- * No gyro-drift compensation shall be performed.
- * Factory calibration and temperature compensation should still be applied
- * to the rate of rotation (angular speeds).
- *
- * The coordinate system is the same as is
- * used for the acceleration sensor. Rotation is positive in the
- * counter-clockwise direction (right-hand rule). That is, an observer
- * looking from some positive location on the x, y or z axis at a device
- * positioned on the origin would report positive rotation if the device
- * appeared to be rotating counter clockwise. Note that this is the
- * standard mathematical definition of positive rotation and does not agree
- * with the definition of roll given earlier.
- * The range should at least be 17.45 rad/s (ie: ~1000 deg/s).
- *
- * Content of an uncalibrated_gyro event: (units are rad/sec)
- * x_uncalib : angular speed (w/o drift compensation) around the X axis
- * y_uncalib : angular speed (w/o drift compensation) around the Y axis
- * z_uncalib : angular speed (w/o drift compensation) around the Z axis
- * x_bias : estimated drift around X axis in rad/s
- * y_bias : estimated drift around Y axis in rad/s
- * z_bias : estimated drift around Z axis in rad/s
- *
- * IMPLEMENTATION NOTES:
- *
- * If the implementation is not able to estimate the drift, then this
- * sensor MUST NOT be reported by this HAL. Instead, the regular
- * SENSOR_TYPE_GYROSCOPE is used without drift compensation.
- *
- * If this sensor is present, then the corresponding
- * SENSOR_TYPE_GYROSCOPE must be present and both must return the
- * same sensor_t::name and sensor_t::vendor.
+ * around the X, Y and Z axis.
*/
#define SENSOR_TYPE_GYROSCOPE_UNCALIBRATED (16)
-
/*
* SENSOR_TYPE_SIGNIFICANT_MOTION
* trigger-mode: one-shot
@@ -589,45 +297,6 @@
* A sensor of this type triggers an event each time significant motion
* is detected and automatically disables itself.
* The only allowed value to return is 1.0.
- *
- * A significant motion is a motion that might lead to a change in the user
- * location.
- * Examples of such motions are:
- * walking, biking, sitting in a moving car, coach or train.
- * Examples of situations that should not trigger significant motion:
- * - phone in pocket and person is not moving
- * - phone is on a table, even if the table shakes a bit due to nearby traffic
- * or washing machine
- *
- * A note on false positive / false negative / power consumption tradeoff
- * - The goal of this sensor is to save power.
- * - Triggering an event when the user is not moving (false positive) is costly
- * in terms of power, so it should be avoided.
- * - Not triggering an event when the user is moving (false negative) is
- * acceptable as long as it is not done repeatedly. If the user has been
- * walking for 10 seconds, not triggering an event within those 10 seconds
- * is not acceptable.
- *
- * IMPORTANT NOTE: this sensor type is very different from other types
- * in that it must work when the screen is off without the need of
- * holding a partial wake-lock and MUST allow the SoC to go into suspend.
- * When significant motion is detected, the sensor must awaken the SoC and
- * the event be reported.
- *
- * If a particular hardware cannot support this mode of operation then this
- * sensor type MUST NOT be reported by the HAL. ie: it is not acceptable
- * to "emulate" this sensor in the HAL.
- *
- * The whole point of this sensor type is to save power by keeping the
- * SoC in suspend mode when the device is at rest.
- *
- * When the sensor is not activated, it must also be deactivated in the
- * hardware: it must not wake up the SoC anymore, even in case of
- * significant motion.
- *
- * setDelay() has no effect and is ignored.
- * Once a "significant motion" event is returned, a sensor of this type
- * must disables itself automatically, as if activate(..., 0) had been called.
*/
#define SENSOR_TYPE_SIGNIFICANT_MOTION (17)
@@ -639,21 +308,8 @@
* wake-up sensor: no
*
* A sensor of this type triggers an event each time a step is taken
- * by the user. The only allowed value to return is 1.0 and an event is
- * generated for each step. Like with any other event, the timestamp
- * indicates when the event (here the step) occurred, this corresponds to when
- * the foot hit the ground, generating a high variation in acceleration.
- *
- * While this sensor operates, it shall not disrupt any other sensors, in
- * particular, but not limited to, the accelerometer; which might very well
- * be in use as well.
- *
- * This sensor must be low power. That is, if the step detection cannot be
- * done in hardware, this sensor should not be defined. Also, when the
- * step detector is activated and the accelerometer is not, only steps should
- * trigger interrupts (not accelerometer data).
- *
- * setDelay() has no impact on this sensor type
+ * by the user. The only allowed value to return is 1.0 and an event
+ * is generated for each step.
*/
#define SENSOR_TYPE_STEP_DETECTOR (18)
@@ -667,46 +323,6 @@
* A sensor of this type returns the number of steps taken by the user since
* the last reboot while activated. The value is returned as a uint64_t and is
* reset to zero only on a system / android reboot.
- *
- * The timestamp of the event is set to the time when the first step
- * for that event was taken.
- * See SENSOR_TYPE_STEP_DETECTOR for the signification of the time of a step.
- *
- * The minimum size of the hardware's internal counter shall be 16 bits
- * (this restriction is here to avoid too frequent wake-ups when the
- * delay is very large).
- *
- * IMPORTANT NOTE: this sensor type is different from other types
- * in that it must work when the screen is off without the need of
- * holding a partial wake-lock and MUST allow the SoC to go into suspend.
- * Unlike other sensors, while in suspend mode this sensor must stay active,
- * no events are reported during that time but, steps continue to be
- * accounted for; an event will be reported as soon as the SoC resumes if
- * the timeout has expired.
- *
- * In other words, when the screen is off and the device allowed to
- * go into suspend mode, we don't want to be woken up, regardless of the
- * setDelay() value, but the steps shall continue to be counted.
- *
- * The driver must however ensure that the internal step count never
- * overflows. It is allowed in this situation to wake the SoC up so the
- * driver can do the counter maintenance.
- *
- * While this sensor operates, it shall not disrupt any other sensors, in
- * particular, but not limited to, the accelerometer; which might very well
- * be in use as well.
- *
- * If a particular hardware cannot support these modes of operation then this
- * sensor type MUST NOT be reported by the HAL. ie: it is not acceptable
- * to "emulate" this sensor in the HAL.
- *
- * This sensor must be low power. That is, if the step detection cannot be
- * done in hardware, this sensor should not be defined. Also, when the
- * step counter is activated and the accelerometer is not, only steps should
- * trigger interrupts (not accelerometer data).
- *
- * The whole point of this sensor type is to save power by keeping the
- * SoC in suspend mode when the device is at rest.
*/
#define SENSOR_TYPE_STEP_COUNTER (19)
@@ -718,18 +334,6 @@
*
* Similar to SENSOR_TYPE_ROTATION_VECTOR, but using a magnetometer instead
* of using a gyroscope.
- *
- * This sensor must be based on a magnetometer. It cannot be implemented using
- * a gyroscope, and gyroscope input cannot be used by this sensor, as the
- * goal of this sensor is to be low power.
- * The accelerometer can be (and usually is) used.
- *
- * Just like SENSOR_TYPE_ROTATION_VECTOR, this sensor reports an estimated
- * heading accuracy:
- * sensors_event_t.data[4] = estimated_accuracy (in radians)
- * The heading error must be less than estimated_accuracy 95% of the time
- *
- * see SENSOR_TYPE_ROTATION_VECTOR for more details
*/
#define SENSOR_TYPE_GEOMAGNETIC_ROTATION_VECTOR (20)
@@ -966,7 +570,9 @@
/*
* sensors_poll_device_t is used with SENSORS_DEVICE_API_VERSION_0_1
* and is present for backward binary and source compatibility.
- * (see documentation of the hooks in struct sensors_poll_device_1 below)
+ * See the Sensors HAL interface section for complete descriptions of the
+ * following functions:
+ * http://source.android.com/devices/sensors/index.html#hal
*/
struct sensors_poll_device_t {
struct hw_device_t common;
@@ -991,70 +597,24 @@
struct {
struct hw_device_t common;
- /* Activate/de-activate one sensor.
+ /* Activate/de-activate one sensor. Return 0 on success, negative
*
* handle is the handle of the sensor to change.
* enabled set to 1 to enable, or 0 to disable the sensor.
*
- * if enabled is set to 1, the sensor is activated even if
- * setDelay() wasn't called before. In this case, a default rate
- * should be used.
- *
- * unless otherwise noted in the sensor types definitions, an
- * activated sensor never prevents the SoC to go into suspend
- * mode; that is, the HAL shall not hold a partial wake-lock on
- * behalf of applications.
- *
- * one-shot sensors de-activate themselves automatically upon
- * receiving an event and they must still accept to be deactivated
- * through a call to activate(..., ..., 0).
- *
- * if "enabled" is 1 and the sensor is already activated, this
- * function is a no-op and succeeds.
- *
- * if "enabled" is 0 and the sensor is already de-activated,
- * this function is a no-op and succeeds.
- *
- * return 0 on success, negative errno code otherwise
+ * Return 0 on success, negative errno code otherwise.
*/
int (*activate)(struct sensors_poll_device_t *dev,
int handle, int enabled);
/**
* Set the events's period in nanoseconds for a given sensor.
- *
- * What the period_ns parameter means depends on the specified
- * sensor's trigger mode:
- *
- * continuous: setDelay() sets the sampling rate.
- * on-change: setDelay() limits the delivery rate of events
- * one-shot: setDelay() is ignored. it has no effect.
- * special: see specific sensor type definitions
- *
- * For continuous and on-change sensors, if the requested value is
- * less than sensor_t::minDelay, then it's silently clamped to
- * sensor_t::minDelay unless sensor_t::minDelay is 0, in which
- * case it is clamped to >= 1ms.
- *
- * setDelay will not be called when the sensor is in batching mode.
- * In this case, batch() will be called with the new period.
- *
- * @return 0 if successful, < 0 on error
*/
int (*setDelay)(struct sensors_poll_device_t *dev,
int handle, int64_t period_ns);
/**
* Returns an array of sensor data.
- * This function must block until events are available.
- *
- * return the number of events read on success, or -errno in case
- * of an error.
- *
- * The number of events returned in data must be less or equal
- * to the "count" argument.
- *
- * This function shall never return 0 (no event).
*/
int (*poll)(struct sensors_poll_device_t *dev,
sensors_event_t* data, int count);
@@ -1063,200 +623,9 @@
/*
- * Enables batch mode for the given sensor and sets the delay between events
- *
- * A timeout value of zero disables batch mode for the given sensor.
- *
- * The period_ns parameter is equivalent to calling setDelay() -- this
- * function both enables or disables the batch mode AND sets the events's
- * period in nanosecond. See setDelay() above for a detailed explanation of
- * the period_ns parameter.
- *
- * BATCH MODE:
- * -----------
- * In non-batch mode, all sensor events must be reported as soon as they
- * are detected. For example, an accelerometer activated at 50Hz will
- * trigger interrupts 50 times per second.
- * While in batch mode, sensor events do not need to be reported as soon
- * as they are detected. They can be temporarily stored in batches and
- * reported in batches, as long as no event is delayed by more than
- * "timeout" nanoseconds. That is, all events since the previous batch
- * are recorded and returned all at once. This allows to reduce the amount
- * of interrupts sent to the SoC, and allow the SoC to switch to a lower
- * power state (Idle) while the sensor is capturing and batching data.
- *
- * setDelay() is not affected and it behaves as usual.
- *
- * Each event has a timestamp associated with it, the timestamp
- * must be accurate and correspond to the time at which the event
- * physically happened.
- *
- * Batching does not modify the behavior of poll(): batches from different
- * sensors can be interleaved and split. As usual, all events from the same
- * sensor are time-ordered.
- *
- * BEHAVIOUR OUTSIDE OF SUSPEND MODE:
- * ----------------------------------
- *
- * When the SoC is awake (not in suspend mode), events must be reported in
- * batches at least every "timeout". No event shall be dropped or lost.
- * If internal h/w FIFOs fill-up before the timeout, then events are
- * reported at that point to ensure no event is lost.
- *
- *
- * NORMAL BEHAVIOR IN SUSPEND MODE:
- * ---------------------------------
- *
- * By default, batch mode doesn't significantly change the interaction with
- * suspend mode. That is, sensors must continue to allow the SoC to
- * go into suspend mode and sensors must stay active to fill their
- * internal FIFO. In this mode, when the FIFO fills up, it shall wrap
- * around (basically behave like a circular buffer, overwriting events).
- * As soon as the SoC comes out of suspend mode, a batch is produced with
- * as much as the recent history as possible, and batch operation
- * resumes as usual.
- *
- * The behavior described above allows applications to record the recent
- * history of a set of sensor while keeping the SoC into suspend. It
- * also allows the hardware to not have to rely on a wake-up interrupt line.
- *
- * WAKE_UPON_FIFO_FULL BEHAVIOR IN SUSPEND MODE:
- * ----------------------------------------------
- *
- * There are cases, however, where an application cannot afford to lose
- * any events, even when the device goes into suspend mode.
- * For a given rate, if a sensor has the capability to store at least 10
- * seconds worth of events in its FIFO and is able to wake up the Soc, it
- * can implement an optional secondary mode: the WAKE_UPON_FIFO_FULL mode.
- *
- * The caller will set the SENSORS_BATCH_WAKE_UPON_FIFO_FULL flag to
- * activate this mode. If the sensor does not support this mode, batch()
- * will fail when the flag is set.
- *
- * When running with the WAKE_UPON_FIFO_FULL flag set, no events can be
- * lost. When the FIFO is getting full, the sensor must wake up the SoC from
- * suspend and return a batch before the FIFO fills-up.
- * Depending on the device, it might take a few miliseconds for the SoC to
- * entirely come out of suspend and start flushing the FIFO. Enough head
- * room must be allocated in the FIFO to allow the device to entirely come
- * out of suspend without the FIFO overflowing (no events shall be lost).
- *
- * Implementing the WAKE_UPON_FIFO_FULL mode is optional.
- * If the hardware cannot support this mode, or if the physical
- * FIFO is so small that the device would never be allowed to go into
- * suspend for at least 10 seconds, then this function MUST fail when
- * the flag SENSORS_BATCH_WAKE_UPON_FIFO_FULL is set, regardless of
- * the value of the timeout parameter.
- *
- *
- * DRY RUN:
- * --------
- *
- * If the flag SENSORS_BATCH_DRY_RUN is set, this function returns
- * without modifying the batch mode or the event period and has no side
- * effects, but returns errors as usual (as it would if this flag was
- * not set). This flag is used to check if batch mode is available for a
- * given configuration -- in particular for a given sensor at a given rate.
- *
- *
- * Return values:
- * --------------
- *
- * Because sensors must be independent, the return value must not depend
- * on the state of the system (whether another sensor is on or not),
- * nor on whether the flag SENSORS_BATCH_DRY_RUN is set (in other words,
- * if a batch call with SENSORS_BATCH_DRY_RUN is successful,
- * the same call without SENSORS_BATCH_DRY_RUN must succeed as well).
- *
- * When timeout is not 0:
- * If successful, 0 is returned.
- * If the specified sensor doesn't support batch mode, return -EINVAL.
- * If the specified sensor's trigger-mode is one-shot, return -EINVAL.
- * If WAKE_UPON_FIFO_FULL is specified and the specified sensor's internal
- * FIFO is too small to store at least 10 seconds worth of data at the
- * given rate, -EINVAL is returned. Note that as stated above, this has to
- * be determined at compile time, and not based on the state of the
- * system.
- * If some other constraints above cannot be satisfied, return -EINVAL.
- *
- * Note: the timeout parameter, when > 0, has no impact on whether this
- * function succeeds or fails.
- *
- * When timeout is 0:
- * The caller will never set the wake_upon_fifo_full flag.
- * The function must succeed, and batch mode must be deactivated.
- *
- * Independently of whether DRY_RUN is specified, When the call to batch()
- * fails, no state should be changed. In particular, a failed call to
- * batch() should not change the rate of the sensor. Example:
- * setDelay(..., 10ms)
- * batch(..., 20ms, ...) fails
- * rate should stay 10ms.
- *
- *
- * IMPLEMENTATION NOTES:
- * ---------------------
- *
- * Batch mode, if supported, should happen at the hardware level,
- * typically using hardware FIFOs. In particular, it SHALL NOT be
- * implemented in the HAL, as this would be counter productive.
- * The goal here is to save significant amounts of power.
- *
- * In some implementations, events from several sensors can share the
- * same physical FIFO. In that case, all events in the FIFO can be sent and
- * processed by the HAL as soon as one batch must be reported.
- * For example, if the following sensors are activated:
- * - accelerometer batched with timeout = 20s
- * - gyroscope batched with timeout = 5s
- * then the accelerometer batches can be reported at the same time the
- * gyroscope batches are reported (every 5 seconds)
- *
- * Batch mode can be enabled or disabled at any time, in particular
- * while the specified sensor is already enabled, and this shall not
- * result in the loss of events.
- *
- * COMPARATIVE IMPORTANCE OF BATCHING FOR DIFFERENT SENSORS:
- * ---------------------------------------------------------
- *
- * On platforms on which hardware fifo size is limited, the system designers
- * might have to choose how much fifo to reserve for each sensor. To help
- * with this choice, here is a list of applications made possible when
- * batching is implemented on the different sensors.
- *
- * High value: Low power pedestrian dead reckoning
- * Target batching time: 20 seconds to 1 minute
- * Sensors to batch:
- * - Step detector
- * - Rotation vector or game rotation vector at 5Hz
- * Gives us step and heading while letting the SoC go to Suspend.
- *
- * High value: Medium power activity/gesture recognition
- * Target batching time: 3 seconds
- * Sensors to batch: accelerometer between 20Hz and 50Hz
- * Allows recognizing arbitrary activities and gestures without having
- * to keep the SoC fully awake while the data is collected.
- *
- * Medium-high value: Interrupt load reduction
- * Target batching time: < 1 second
- * Sensors to batch: any high frequency sensor.
- * If the gyroscope is set at 800Hz, even batching just 10 gyro events can
- * reduce the number of interrupts from 800/second to 80/second.
- *
- * Medium value: Continuous low frequency data collection
- * Target batching time: > 1 minute
- * Sensors to batch: barometer, humidity sensor, other low frequency
- * sensors.
- * Allows creating monitoring applications at low power.
- *
- * Medium value: Continuous full-sensors collection
- * Target batching time: > 1 minute
- * Sensors to batch: all, at high frequencies
- * Allows full collection of sensor data while leaving the SoC in
- * suspend mode. Only to consider if fifo space is not an issue.
- *
- * In each of the cases above, if WAKE_UPON_FIFO_FULL is implemented, the
- * applications might decide to let the SoC go to suspend, allowing for even
- * more power savings.
+ * Enables batch mode for the given sensor and sets the delay between events.
+ * See the Batching sensor results page for details:
+ * http://source.android.com/devices/sensors/batching.html
*/
int (*batch)(struct sensors_poll_device_1* dev,
int handle, int flags, int64_t period_ns, int64_t timeout);
@@ -1264,29 +633,7 @@
/*
* Flush adds a META_DATA_FLUSH_COMPLETE event (sensors_event_meta_data_t)
* to the end of the "batch mode" FIFO for the specified sensor and flushes
- * the FIFO; those events are delivered as usual (i.e.: as if the batch
- * timeout had expired) and removed from the FIFO.
- *
- * See the META_DATA_FLUSH_COMPLETE section for details about the
- * META_DATA_FLUSH_COMPLETE event.
- *
- * The flush happens asynchronously (i.e.: this function must return
- * immediately).
- *
- * If the implementation uses a single FIFO for several sensors, that
- * FIFO is flushed and the META_DATA_FLUSH_COMPLETE event is added only
- * for the specified sensor.
- *
- * If the specified sensor wasn't in batch mode, flush succeeds and
- * promptly sends a META_DATA_FLUSH_COMPLETE event for that sensor.
- *
- * If the FIFO was empty at the time of the call, flush returns
- * 0 (success) and promptly sends a META_DATA_FLUSH_COMPLETE event
- * for that sensor.
- *
- * If the specified sensor wasn't enabled, flush returns -EINVAL.
- *
- * return 0 on success, negative errno code otherwise.
+ * the FIFO.
*/
int (*flush)(struct sensors_poll_device_1* dev, int handle);