sensor__HAl分析(头文件)

首先看下sensor的hal层头文件：hardware\libhardware\include\hardware

typedef struct {
    union {
        float v[3];
        struct {
            float x;
            float y;
            float z;
        };
        struct {
            float azimuth;
            float pitch;
            float roll;
        };
    };
    int8_t status;
    uint8_t reserved[3];
} sensors_vec_t;

/**
 * Union of the various types of sensor data
 * that can be returned.
 */
typedef struct sensors_event_t {
    /* must be sizeof(struct sensors_event_t) */
    int32_t version;

    /* sensor identifier */
    int32_t sensor;

    /* sensor type */
    int32_t type;

    /* reserved */
    int32_t reserved0;

    /* time is in nanosecond */
    int64_t timestamp;

    union {
        float           data[16];

        /* acceleration values are in meter per second per second (m/s^2) */
        sensors_vec_t   acceleration;

        /* magnetic vector values are in micro-Tesla (uT) */
        sensors_vec_t   magnetic;

        /* orientation values are in degrees */
        sensors_vec_t   orientation;

        /* gyroscope values are in rad/s */
        sensors_vec_t   gyro;

        /* temperature is in degrees centigrade (Celsius) */
        float           temperature;

        /* distance in centimeters */
        float           distance;

        /* light in SI lux units */
        float           light;

        /* pressure in hectopascal (hPa) */
        float           pressure;

        /* relative humidity in percent */
        float           relative_humidity;
    };
    uint32_t        reserved1[4];
} sensors_event_t;



struct sensor_t;

/**
 * Every hardware module must have a data structure named HAL_MODULE_INFO_SYM
 * and the fields of this data structure must begin with hw_module_t
 * followed by module specific information.
 */
struct sensors_module_t {
    struct hw_module_t common;

    /**
     * Enumerate all available sensors. The list is returned in "list".
     * @return number of sensors in the list
     */
    int (*get_sensors_list)(struct sensors_module_t* module,
            struct sensor_t const** list);
};

struct sensor_t {
    /* name of this sensors */
    const char*     name;
    /* vendor of the hardware part */
    const char*     vendor;
    /* version of the hardware part + driver. The value of this field
     * must increase when the driver is updated in a way that changes the
     * output of this sensor. This is important for fused sensors when the
     * fusion algorithm is updated.
     */    
    int             version;
    /* handle that identifies this sensors. This handle is used to activate
     * and deactivate this sensor. The value of the handle must be 8 bits
     * in this version of the API. 
     */
    int             handle;
    /* this sensor's type. */
    int             type;
    /* maximaum range of this sensor's value in SI units */
    float           maxRange;
    /* smallest difference between two values reported by this sensor */
    float           resolution;
    /* rough estimate of this sensor's power consumption in mA */
    float           power;
    /* minimum delay allowed between events in microseconds. A value of zero
     * means that this sensor doesn't report events at a constant rate, but
     * rather only when a new data is available */
    int32_t         minDelay;
    /* reserved fields, must be zero */
    void*           reserved[8];
};


/**
 * Every device data structure must begin with hw_device_t
 * followed by module specific public methods and attributes.
 */
struct sensors_poll_device_t {
    struct hw_device_t common;

    /** Activate/deactivate one sensor.
     *
     * @param handle is the handle of the sensor to change.
     * @param enabled set to 1 to enable, or 0 to disable the sensor.
     *
     * @return 0 on success, negative errno code otherwise
     */
    int (*activate)(struct sensors_poll_device_t *dev,
            int handle, int enabled);

    /**
     * Set the delay between sensor events in nanoseconds for a given sensor.
     *
     * 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.
     *
     * @return 0 if successful, < 0 on error
     */
    int (*setDelay)(struct sensors_poll_device_t *dev,
            int handle, int64_t 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.
     * This function should never return 0 (no event).
     *
     */
    int (*poll)(struct sensors_poll_device_t *dev,
            sensors_event_t* data, int count);
};

/** convenience API for opening and closing a device */

static inline int sensors_open(const struct hw_module_t* module,
        struct sensors_poll_device_t** device) {
    return module->methods->open(module,
            SENSORS_HARDWARE_POLL, (struct hw_device_t**)device);
}

static inline int sensors_close(struct sensors_poll_device_t* device) {
    return device->common.close(&device->common);
}

__END_DECLS

主要包括sensors_vec_t、sensors_event_t、sensors_module_t、sensor_t、sensors_poll_device_t几个结构

sensors_vec_t主要是上传的数据，里面包括一个union结构，包含各种上传数据的一个数据封装，都是三个float

sensors_event_t主要是以一个事件的形式上传从sensor获取的数据，里面也有一个union，包含的是各种各样的传感器的数据，其中type是sensor的类型，sensor是一个标识

sensors_module_t是hw_module_t的一个封装，提供一个get_sensors_list获取该平台可提供的所有sensor

sensor_t用来描述一个sensor

sensors_poll_device_t是hw_device_t的一个封装。提供了3个方法activate、setDelay、poll

activate用来启动和停止sensor

setDelay用来设置延时

poll用来监听sensor上是否有数据