本文主要是介绍Android Sensor Input类型 (四) Sensor HAL 实现，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
msm8909 Sensor HAL
代码路径：code/hardware/qcom/sensors/
核心作用：封装对 sensor的方法，不直接通过本地C库直接访问
├── Accelerometer.cpp
├── AccelSensor.h
├── AkmSensor.cpp
├── AkmSensor.h
├── algo
├── Android.mk
├── Bmp180.cpp
├── CalibrationManager.cpp
├── CalibrationManager.h
├── CalibrationModule.h
├── calmodule.cfg
├── CompassSensor.cpp
├── CompassSensor.h
├── Gyroscope.cpp
├── GyroSensor.h
├── InputEventReader.cpp
├── InputEventReader.h
├── LICENSE
├── LightSensor.cpp
├── LightSensor.h
├── NativeSensorManager.cpp
├── NativeSensorManager.h
├── PressureSensor.h
├── ProximitySensor.cpp
├── ProximitySensor.h
├── SensorBase.cpp
├── SensorBase.h
├── sensors.cpp
├── sensors_extension.h
├── sensors.h
├── sensors_XML.cpp
├── sensors_XML.h
├── SignificantMotion.cpp
├── SignificantMotion.h
├── VirtualSensor.cpp
└── VirtualSensor.h
重要文件有：
sensors.cpp
sensors.cpp 中提供数据机构架构，提供 hw_device_t 封装； 让其他层可以获得这个结构，得以使用其中的方法；
通过实现的结构可以发现，所有的操作都使用了， NativeSensorManager用来做具体的操作
NativeSensorManager.cpp
Native SensorManager 是个class，继承Singleton； 单例模式，只存在一个对象；
即被多次定义引用的对象 sm； 它的存在是统一管理sensor HAL的sensor访问；
将存在的sensor统一存在数组里，不针对sensor具体类型； 是HAL的实际操作者；
SensorBase.cpp
VirtualSensor.cpp
sensors主要设备结构
sensor_t
struct sensor_t {const char* name;//!< sensor名称 By: jixuanconst char* vendor;//!< 厂商名 By: jixuan int version;int handleint type;//!< 类型标识 By: jixuanfloat maxRange;float resolution;//!< 解析度 即报告数值的最大差异范围 By: jixuan float power;int32_t minDelay;uint32_t fifoReservedEventCount;uint32_t fifoMaxEventCount;//!< 类型字符串 Note By: yujixuan const char* stringType;//!< 权限 Note By: yujixuan const char* requiredPermission;void* reserved[2];
};
sensor_moudule_t
struct sensors_module_t {struct hw_module_t common;//!< hw_module_t 基础结构 >! NoteBy: yujixuan int (*get_sensors_list)(struct sensors_module_t* module,struct sensor_t const** list);//!< 拓展接口，获取sensor 列表 >! NoteBy:yujixuanint (*set_operation_mode)(unsigned int mode);//!< 操作设置sensor mode >! NoteBy: yujixuan
};//!< 定义 名为HMI的 hw_module_t 结构体（可以转型为包含它的具体设备类型，首地址保持相同），get_module 获取它 >! NoteBy: yujixuan
struct sensors_module_t HAL_MODULE_INFO_SYM = {common: {tag: HARDWARE_MODULE_TAG, //!< 固定名 >! NoteBy: yujixuanversion_major: 1,version_minor: 0,id: SENSORS_HARDWARE_MODULE_ID, name: "Quic Sensor module",author: "Quic",methods: &sensors_module_methods, //!< hw_module_t 必要填充的方法 >! NoteBy: yujixuandso: NULL,reserved: {0},},get_sensors_list: sensors__get_sensors_list, //!< sensor_module_t 拓展的方法 >! NoteBy: yujixuan
};
static struct hw_module_methods_t sensors_module_methods = {open: open_sensors //!< 只有一个open函数，它的作用是返回具体的 device >! NoteBy: yujixuan
};
//!< 打开一个新的sensor 实例 填充具体的hw_device_t>! NoteBy: yujixuan
open函数实现：open_sensors
#define HAL_MODULE_INFO_SYM HMI
#define HAL_MODULE_INFO_SYM_AS_STR "HMI"static int open_sensors(const struct hw_module_t* module, const char*,struct hw_device_t** device)
{int status = -EINVAL;sensors_poll_context_t *dev = new sensors_poll_context_t();NativeSensorManager& sm(NativeSensorManager::getInstance());memset(&dev->device, 0, sizeof(sensors_poll_device_1_ext_t));dev->device.common.tag = HARDWARE_DEVICE_TAG;
#if defined(SENSORS_DEVICE_API_VERSION_1_3)ALOGI("Sensors device API version 1.3 supported\n");dev->device.common.version = SENSORS_DEVICE_API_VERSION_1_3;
#elsedev->device.common.version = SENSORS_DEVICE_API_VERSION_0_1;
#endifdev->device.common.module = const_cast<hw_module_t*>(module);dev->device.common.close = poll__close;dev->device.activate = poll__activate;dev->device.setDelay = poll__setDelay;dev->device.poll = poll__poll;dev->device.calibrate = poll_calibrate;
#if defined(SENSORS_DEVICE_API_VERSION_1_3)dev->device.batch = poll__batch;dev->device.flush = poll__flush;
#endif*device = &dev->device.common;status = 0;return status;
}
open_sensors新的sensor 实例，首先new了一个sensors_poll_context_t 的device ，然后设置该device，并返回 给到调用者；
针对 sensors_poll_context_t 下面内容会做具体分析；
static int sensors__get_sensors_list(struct sensors_module_t*,struct sensor_t const** list)
{NativeSensorManager& sm(NativeSensorManager::getInstance());return sm.getSensorList(list);
}
拓展的sensors_module_t 中添加了 get_sensor_list方法；
可以看到它是通过NativeSensorManger 来做具体的Hal层访问；
Sensor服务用户程序不能直接访问，通过NativeSensorManager来访问。 (note: nativeSensorManager是指在HAL中的管理sensor的设备结构，需要区别于Android Framework中的SensorManager)
里面使用了NativeSensorManager，sensors__get_sensors_list函数中调用单例模式创建了一个实例sm，通过调用其中的成员函数获取传感器列表，并返回，返回值对应的sensor_t结构体；NativeSensorManager统一管理着所有的传感器、物理和虚拟传感器；
SensorHAL 解析
Native Sensor Hal框架中，最为主要的内容即是 open函数中对device的回调设置；简单的可以理解为是上层函数与调用底层驱动的桥接；
所以在Hal这个层次应着重分析这块内容；，由上可知，当前的代码里是通过sensors_poll_context_t来定义一个device； 以下是 sensors_poll_context_t 的内容：
sensors_poll_context_t
struct sensors_poll_context_t {// extension for sensors_poll_device_1, must be firststruct sensors_poll_device_1_ext_t device;// must be first//!< 必须放在首个位置，它是个联合体，首个属性是 hw_device_t； >! NoteBy: yujixuansensors_poll_context_t();~sensors_poll_context_t();//!<struct同样有构造函数，析构函数，完成重要的初始化功能 >! NoteBy: yujixuanint activate(int handle, int enabled);int setDelay(int handle, int64_t ns);int pollEvents(sensors_event_t* data, int count);int calibrate(int handle, cal_cmd_t *para);int batch(int handle, int sample_ns, int latency_ns);int flush(int handle);private:static const size_t wake = MAX_SENSORS;static const char WAKE_MESSAGE = 'W';struct pollfd mPollFds[MAX_SENSORS+1];int mWritePipeFd;SensorBase* mSensors[MAX_SENSORS];mutable Mutex mLock;
};
通过open函数返回的的是hw_device_t，实际是传入的地址值；只要保证，包含此结构，且sensors_poll_device_1_ext_t放在首位，可以向上转型回具体的sensor
设备device；
实际device的函数调用 都是拓展的；比如上面的 activate； setDelay； pollEvents；等；
struct sensors_poll_device_1_ext_t {union {struct sensors_poll_device_1 aosp;struct {struct hw_device_t common;int (*activate)(struct sensors_poll_device_t *dev,int handle, int enabled);int (*setDelay)(struct sensors_poll_device_t *dev,int handle, int64_t period_ns);int (*poll)(struct sensors_poll_device_t *dev,sensors_event_t* data, int count);int (*batch)(struct sensors_poll_device_1* dev,int handle, int flags, int64_t period_ns, int64_t timeout);int (*flush)(struct sensors_poll_device_1* dev, int handle);void (*reserved_procs[8])(void);};};struct sensors_poll_device_t {struct hw_device_t common;int (*activate)(struct sensors_poll_device_t *dev,int sensor_handle, int enabled);int (*setDelay)(struct sensors_poll_device_t *dev,int sensor_handle, int64_t sampling_period_ns);int (*poll)(struct sensors_poll_device_t *dev,sensors_event_t* data, int count);
};
通过sensors_poll_device_1_ext_t也可以看出，实际sensors_poll_context_t 可以是sensors_poll_device_t
这是面向对象 多态的思想方式； 获取到的device根据具体的类型，再转换为具体的 device进行函数调用；
实际device的函数调用 都是拓展的；比如上面的 activate； setDelay； pollEvents；等；
在open函数中，new一个实例对象；sensors_poll_context_t会调用其构造函数完成最重要的初始化功能，如下：
sensors_poll_context_t::sensors_poll_context_t()
{int number;int i;const struct sensor_t *slist; const struct SensorContext *context;NativeSensorManager& sm(NativeSensorManager::getInstance());number = sm.getSensorList(&slist);//!< 获取sensor个数; 与sensor构成的链表list >! NoteBy: yujixuan/* use the dynamic sensor list */for (i = 0; i < number; i++) {context = sm.getInfoByHandle(slist[i].handle);mPollFds[i].fd = (context == NULL) ? -1 : context->data_fd;mPollFds[i].events = POLLIN;mPollFds[i].revents = 0;}ALOGI("The avaliable sensor handle number is %d",i);int wakeFds[2];int result = pipe(wakeFds);ALOGE_IF(result<0, "error creating wake pipe (%s)", strerror(errno));fcntl(wakeFds[0], F_SETFL, O_NONBLOCK);fcntl(wakeFds[1], F_SETFL, O_NONBLOCK);mWritePipeFd = wakeFds[1];mPollFds[number].fd = wakeFds[0];mPollFds[number].events = POLLIN;mPollFds[number].revents = 0;
}
构造函数中，通过NativeSensorManager 获取了sensor 列表；
通过struct SensorContext *context;
context = sm.getInfoByHandle(slist[i].handle);
维系记录了handle对应的SensorContext对象指针的句柄；SensorContext 的结构如下：
SensorContext
struct SensorContext {char name[SYSFS_MAXLEN]; // name of the sensorchar vendor[SYSFS_MAXLEN]; // vendor of the sensorchar enable_path[PATH_MAX]; // the control path of this sensorchar data_path[PATH_MAX]; // the data path to get sensor eventsstruct sensor_t *sensor; // point to the sensor_t structure in the sensor listSensorBase *driver; // point to the sensor driver instanceint data_fd; // the file descriptor of the data device nodeint enable; // indicate if the sensor is enabledbool is_virtual; // indicate if this is a virtual sensorint64_t delay_ns; // the poll delay setting of this sensorint64_t latency_ns; // the max report latency of this sensorstruct listnode dep_list; // the background sensor type needed for this sensorstruct listnode listener; // the head of listeners of this sensor
};
从上可以看出： SensorContext中的 SensorBase *driver; 指向了具体的sensor实例；
在构造函数中，还完成了pollfd即mPollFds用来监听senso时用的文件描述符；
open函数的后面的部分，也就是对sensors_poll_context_t 拓展的那些方法的链接；
比如：
dev->device.common.close = poll__close;dev->device.activate = poll__activate;dev->device.setDelay = poll__setDelay;dev->device.poll = poll__poll;dev->device.calibrate = poll_calibrate;
poll函数分析
这里分析下，最重要的一个函数 poll__poll；
static int poll__poll(struct sensors_poll_device_t *dev,sensors_event_t* data, int count) {sensors_poll_context_t *ctx = (sensors_poll_context_t *)dev;//!< 这里就用到了 向上转型；将sensor_poll_device_t 转为 sensor_poll_context_t >! NoteBy: yujixuanreturn ctx->pollEvents(data, count);//!< 返回pollEvents >! NoteBy: yujixuan
}
int sensors_poll_context_t::pollEvents(sensors_event_t* data, int count)
{int nbEvents = 0;int n = 0;NativeSensorManager& sm(NativeSensorManager::getInstance());const sensor_t *slist;int number = sm.getSensorList(&slist);do {// see if we have some leftover from the last poll()for (int i = 0 ; count && i < number ; i++) {if ((mPollFds[i].revents & POLLIN) || (sm.hasPendingEvents(slist[i].handle))) {Mutex::Autolock _l(mLock);int nb = sm.readEvents(slist[i].handle, data, count);if (nb < 0) {ALOGE("readEvents failed.(%d)", errno);return nb;}if (nb <= count) {// no more data for this sensormPollFds[i].revents = 0;}count -= nb;nbEvents += nb;data += nb;}}if (count) {// we still have some room, so try to see if we can get// some events immediately or just wait if we don't have// anything to returndo {n = poll(mPollFds, number + 1, nbEvents ? 0 : -1);} while (n < 0 && errno == EINTR);if (n<0) {ALOGE("poll() failed (%s)", strerror(errno));return -errno;}if (mPollFds[number].revents & POLLIN) {char msg;int result = read(mPollFds[number].fd, &msg, 1);ALOGE_IF(result<0, "error reading from wake pipe (%s)", strerror(errno));ALOGE_IF(msg != WAKE_MESSAGE, "unknown message on wake queue (0x%02x)", int(msg));mPollFds[number].revents = 0;}}// if we have events and space, go read them} while (n && count);return nbEvents;
}
主要函数：sm.readEvents(slist[i].handle, data, count);
NativeSensorManager::readEvents中调用了：
nb = list->driver->readEvents(data, count);
list->driver是一个SensorBase结构体，SensorBase结构体的函数readEvents，
这里就需要联合 nativesensormanger的实现来看具体的读取流程；
nativesensormanger相关内容，在后续的内容中分析；
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