Android Sensor Input型別 (四) Native Sensor HAL
阿新 • • 發佈：2021-07-13
msm8909平臺上 Sensor HAL的實現
程式碼路徑：code/hardware/qcom/sensors/
├── 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
主要裝置結構
sensor_t
struct sensor_t { const char* name; //!< sensor名稱 By: jixuan const char* vendor; //!< 廠商名 By: jixuan int version; int handle int type; //!< 型別標識 By: jixuan float maxRange; float resolution; //!< 解析度 即報告數值的最大差異範圍 By: jixuan float power; int32_t minDelay; uint32_t fifoReservedEventCount; uint32_t fifoMaxEventCount; //!< 型別字串 Note By: yujixuan const char* stringType; //!< 許可權 Note By: yujixuan const char* requiredPermission; void* reserved[2]; };
sensor_moudule_t
struct sensors_module_t { struct hw_module_t common; //!< hw_module_t 基礎結構 >! NoteBy: yujixuan int (*get_sensors_list)(struct sensors_module_t* module, struct sensor_t const** list); //!< 拓展介面，獲取sensor 列表 >! NoteBy:yujixuan int (*set_operation_mode)(unsigned int mode); //!< 操作設定sensor mode >! NoteBy: yujixuan }; //!< 定義 名為HMI的 hw_module_t 結構體（可以轉型為包含它的具體裝置型別，首地址保持相同），get_module 獲取它 >! NoteBy: yujixuan struct sensors_module_t HAL_MODULE_INFO_SYM = { common: { tag: HARDWARE_MODULE_TAG, //!< 固定名 >! NoteBy: yujixuan version_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: yujixuan dso: 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 //!< 只有一個open函式，它的作用是返回具體的 device >! NoteBy: yujixuan }; //!< 開啟一個新的sensor 例項 填充具體的hw_device_t>! NoteBy: yujixuan
open函式實現：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;
#else
dev->device.common.version = SENSORS_DEVICE_API_VERSION_0_1;
#endif
dev->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 例項，首先new了一個sensors_poll_context_t 的device ，然後設定該device，並返回 給到呼叫者；
針對 sensors_poll_context_t 下面內容會做具體分析；
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；
可以看到它是通過NativeSensorManger 來做具體的Hal層訪問；
Sensor服務使用者程式不能直接訪問，通過NativeSensorManager來訪問。 (note: nativeSensorManager是指在HAL中的管理sensor的裝置結構，需要區別於Android Framework中的SensorManager)
裡面使用了NativeSensorManager，sensors__get_sensors_list函式中呼叫單例模式建立了一個例項sm，通過呼叫其中的成員函式獲取感測器列表，並返回，返回值對應的sensor_t結構體；NativeSensorManager統一管理著所有的感測器、物理和虛擬感測器；
SensorHAL 解析
Native Sensor Hal框架中，最為主要的內容即是 open函式中對device的回撥設定；簡單的可以理解為是上層函式與呼叫底層驅動的橋接；
所以在Hal這個層次應著重分析這塊內容；，由上可知，當前的程式碼裡是通過sensors_poll_context_t來定義一個device； 以下是 sensors_poll_context_t 的內容：
sensors_poll_context_t
struct sensors_poll_context_t {
// extension for sensors_poll_device_1, must be first
struct sensors_poll_device_1_ext_t device;// must be first
//!< 必須放在首個位置，它是個聯合體，首個屬性是 hw_device_t； >! NoteBy: yujixuan
sensors_poll_context_t();
~sensors_poll_context_t();
//!<struct同樣有建構函式，解構函式，完成重要的初始化功能 >! NoteBy: yujixuan
int 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;
};
通過open函式返回的的是hw_device_t，實際是傳入的地址值；只要保證，包含此結構，且sensors_poll_device_1_ext_t放在首位，可以向上轉型回具體的sensor
裝置device；
實際device的函式呼叫 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);
};
通過sensors_poll_device_1_ext_t也可以看出，實際sensors_poll_context_t 可以是sensors_poll_device_t
這是面向物件 多型的思想方式； 獲取到的device根據具體的型別，再轉換為具體的 device進行函式呼叫；
實際device的函式呼叫 都是拓展的；比如上面的 activate； setDelay； pollEvents；等；
在open函式中，new一個例項物件；sensors_poll_context_t會呼叫其建構函式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);
//!< 獲取sensor個數; 與sensor構成的連結串列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;
}
建構函式中，通過NativeSensorManager 獲取了sensor 列表；
通過struct SensorContext *context;
context = sm.getInfoByHandle(slist[i].handle);
維繫記錄了handle對應的SensorContext物件指標的控制代碼；SensorContext 的結構如下：
SensorContext
struct SensorContext {
char name[SYSFS_MAXLEN]; // name of the sensor
char vendor[SYSFS_MAXLEN]; // vendor of the sensor
char enable_path[PATH_MAX]; // the control path of this sensor
char data_path[PATH_MAX]; // the data path to get sensor events
struct sensor_t *sensor; // point to the sensor_t structure in the sensor list
SensorBase *driver; // point to the sensor driver instance
int data_fd; // the file descriptor of the data device node
int enable; // indicate if the sensor is enabled
bool is_virtual; // indicate if this is a virtual sensor
int64_t delay_ns; // the poll delay setting of this sensor
int64_t latency_ns; // the max report latency of this sensor
struct listnode dep_list; // the background sensor type needed for this sensor
struct listnode listener; // the head of listeners of this sensor
};
從上可以看出： SensorContext中的 SensorBase *driver; 指向了具體的sensor例項；
在建構函式中，還完成了pollfd即mPollFds用來監聽senso時用的檔案描述符；
open函式的後面的部分，也就是對sensors_poll_context_t 拓展的那些方法的連結；
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函式分析
這裡分析下，最重要的一個函式 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;
//!< 這裡就用到了 向上轉型；將sensor_poll_device_t 轉為 sensor_poll_context_t >! NoteBy: yujixuan
return 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 sensor
mPollFds[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 return
do {
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;
}
主要函式：sm.readEvents(slist[i].handle, data, count);
NativeSensorManager::readEvents中呼叫了：
nb = list->driver->readEvents(data, count);
list->driver是一個SensorBase結構體，SensorBase結構體的函式readEvents，
這裡就需要聯合 nativesensormanger的實現來看具體的讀取流程；