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最近项目计步器传感器概率性没有值，就顺道研究下传感器框架。今天主要说下native层的框架
native层框架的实现路径
/frameworks/native/services/sensorservice/
文件大概有下面几个
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主入口是main_sensorservice.cpp,主要是把这个远程服务发布出去
int main(int /*argc*/, char** /*argv*/) {
SensorService::publishAndJoinThreadPool();
return 0;
}
看看这个SensorService的构造函数,主要是注册了一些sensor的服务，可以看到他获取的设备SensorDevice
SensorService继承结构.png
void SensorService::onFirstRef()
{
ALOGD("nuSensorService starting...");
SensorDevice& dev(SensorDevice::getInstance());
if (dev.initCheck() == NO_ERROR) {
sensor_t const* list;
ssize_t count = dev.getSensorList(&list); //获取sensor列表
if (count > 0) {
ssize_t orientationIndex = -1;
bool hasGyro = false, hasAccel = false, hasMag = false;
uint32_t virtualSensorsNeeds =
(1< 0) {
batchingSupported = true;
break;
}
}
if (batchingSupported) {
// Increase socket buffer size to a max of 100 KB for batching capabilities.
mSocketBufferSize = MAX_SOCKET_BUFFER_SIZE_BATCHED;
} else {
mSocketBufferSize = SOCKET_BUFFER_SIZE_NON_BATCHED;
}
// Compare the socketBufferSize value against the system limits and limit
// it to maxSystemSocketBufferSize if necessary.
FILE *fp = fopen("/proc/sys/net/core/wmem_max", "r");
char line[128];
if (fp != NULL && fgets(line, sizeof(line), fp) != NULL) {
line[sizeof(line) - 1] = '\0';
size_t maxSystemSocketBufferSize;
sscanf(line, "%zu", &maxSystemSocketBufferSize);
if (mSocketBufferSize > maxSystemSocketBufferSize) {
mSocketBufferSize = maxSystemSocketBufferSize;
}
}
if (fp) {
fclose(fp);
}
mWakeLockAcquired = false;
mLooper = new Looper(false);
const size_t minBufferSize = SensorEventQueue::MAX_RECEIVE_BUFFER_EVENT_COUNT;
mSensorEventBuffer = new sensors_event_t[minBufferSize];
mSensorEventScratch = new sensors_event_t[minBufferSize];
mMapFlushEventsToConnections = new SensorEventConnection const * [minBufferSize];
mCurrentOperatingMode = NORMAL;
mNextSensorRegIndex = 0;
for (int i = 0; i < SENSOR_REGISTRATIONS_BUF_SIZE; ++i) {
mLastNSensorRegistrations.push();
}
mInitCheck = NO_ERROR;
mAckReceiver = new SensorEventAckReceiver(this);
mAckReceiver->run("SensorEventAckReceiver", PRIORITY_URGENT_DISPLAY);
run("SensorService", PRIORITY_URGENT_DISPLAY);
}
}
}
SensorDevice主要构架了hal层的接口和module的接口，hal接口跟硬件相关，而module则更高层一点
SensorDevice::SensorDevice()
: mSensorDevice(0), //hal层接口
mSensorModule(0) //module
{
status_t err = hw_get_module(SENSORS_HARDWARE_MODULE_ID,
(hw_module_t const**)&mSensorModule);
ALOGE_IF(err, "couldn't load %s module (%s)",
SENSORS_HARDWARE_MODULE_ID, strerror(-err));
if (mSensorModule) {
err = sensors_open_1(&mSensorModule->common, &mSensorDevice); //打开设备
ALOGE_IF(err, "couldn't open device for module %s (%s)",
SENSORS_HARDWARE_MODULE_ID, strerror(-err));
if (mSensorDevice) {
if (mSensorDevice->common.version == SENSORS_DEVICE_API_VERSION_1_1 ||
mSensorDevice->common.version == SENSORS_DEVICE_API_VERSION_1_2) {
ALOGE(">>>> WARNING <<< Upgrade sensor HAL to version 1_3");
}
sensor_t const* list; //sensor list
ssize_t count = mSensorModule->get_sensors_list(mSensorModule, &list);
mActivationCount.setCapacity(count);
Info model;
for (size_t i=0 ; iactivate(
reinterpret_cast(mSensorDevice),
list[i].handle, 0);
}
}
}
}
在SensorService的threadLoop来获取传感器数据，使用poll来获取数据
bool SensorService::threadLoop()
{
ALOGD("nuSensorService thread starting...");
// each virtual sensor could generate an event per "real" event, that's why we need
// to size numEventMax much smaller than MAX_RECEIVE_BUFFER_EVENT_COUNT.
// in practice, this is too aggressive, but guaranteed to be enough.
const size_t minBufferSize = SensorEventQueue::MAX_RECEIVE_BUFFER_EVENT_COUNT;
const size_t numEventMax = minBufferSize / (1 + mVirtualSensorList.size());
SensorDevice& device(SensorDevice::getInstance());
const size_t vcount = mVirtualSensorList.size();
const int halVersion = device.getHalDeviceVersion();
do {
ssize_t count = device.poll(mSensorEventBuffer, numEventMax);
//poll获取数据，数据保存到mSensorEventBuffer
if (count < 0) {
ALOGE("sensor poll failed (%s)", strerror(-count));
break;
}
// Reset sensors_event_t.flags to zero for all events in the buffer.
for (int i = 0; i < count; i++) {
mSensorEventBuffer[i].flags = 0;
}
// Make a copy of the connection vector as some connections may be removed during the
// course of this loop (especially when one-shot sensor events are present in the
// sensor_event buffer). Promote all connections to StrongPointers before the lock is
// acquired. If the destructor of the sp gets called when the lock is acquired, it may
// result in a deadlock as ~SensorEventConnection() needs to acquire mLock again for
// cleanup. So copy all the strongPointers to a vector before the lock is acquired.
SortedVector< sp > activeConnections;
populateActiveConnections(&activeConnections);
Mutex::Autolock _l(mLock);
// Poll has returned. Hold a wakelock if one of the events is from a wake up sensor. The
// rest of this loop is under a critical section protected by mLock. Acquiring a wakeLock,
// sending events to clients (incrementing SensorEventConnection::mWakeLockRefCount) should
// not be interleaved with decrementing SensorEventConnection::mWakeLockRefCount and
// releasing the wakelock.
bool bufferHasWakeUpEvent = false;
for (int i = 0; i < count; i++) {
if (isWakeUpSensorEvent(mSensorEventBuffer[i])) {
bufferHasWakeUpEvent = true;
break;
}
}
if (bufferHasWakeUpEvent && !mWakeLockAcquired) {
setWakeLockAcquiredLocked(true);
}
recordLastValueLocked(mSensorEventBuffer, count);
// handle virtual sensors
if (count && vcount) {
sensors_event_t const * const event = mSensorEventBuffer;
const size_t activeVirtualSensorCount = mActiveVirtualSensors.size();
if (activeVirtualSensorCount) {
size_t k = 0;
SensorFusion& fusion(SensorFusion::getInstance());
if (fusion.isEnabled()) {
for (size_t i=0 ; i= minBufferSize) {
ALOGE("buffer too small to hold all events: "
"count=%zd, k=%zu, size=%zu",
count, k, minBufferSize);
break;
}
sensors_event_t out;
SensorInterface* si = mActiveVirtualSensors.valueAt(j);
if (si->process(&out, event[i])) {
mSensorEventBuffer[count + k] = out;
k++;
}
}
}
if (k) {
// record the last synthesized values
recordLastValueLocked(&mSensorEventBuffer[count], k);
count += k;
// sort the buffer by time-stamps
sortEventBuffer(mSensorEventBuffer, count);
}
}
}
// handle backward compatibility for RotationVector sensor
if (halVersion < SENSORS_DEVICE_API_VERSION_1_0) {
for (int i = 0; i < count; i++) {
if (mSensorEventBuffer[i].type == SENSOR_TYPE_ROTATION_VECTOR) {
// All the 4 components of the quaternion should be available
// No heading accuracy. Set it to -1
mSensorEventBuffer[i].data[4] = -1;
}
}
}
// Map flush_complete_events in the buffer to SensorEventConnections which called
// flush on the hardware sensor. mapFlushEventsToConnections[i] will be the
// SensorEventConnection mapped to the corresponding flush_complete_event in
// mSensorEventBuffer[i] if such a mapping exists (NULL otherwise).
for (int i = 0; i < count; ++i) {
mMapFlushEventsToConnections[i] = NULL;
if (mSensorEventBuffer[i].type == SENSOR_TYPE_META_DATA) {
const int sensor_handle = mSensorEventBuffer[i].meta_data.sensor;
SensorRecord* rec = mActiveSensors.valueFor(sensor_handle);
if (rec != NULL) {
mMapFlushEventsToConnections[i] = rec->getFirstPendingFlushConnection();
rec->removeFirstPendingFlushConnection();
}
}
}
// Send our events to clients. Check the state of wake lock for each client and release the
// lock if none of the clients need it.
bool needsWakeLock = false;
size_t numConnections = activeConnections.size();
for (size_t i=0 ; i < numConnections; ++i) {
if (activeConnections[i] != 0) {
//通过activeConnections发送传感器事件
activeConnections[i]->sendEvents(mSensorEventBuffer, count, mSensorEventScratch,
mMapFlushEventsToConnections);
needsWakeLock |= activeConnections[i]->needsWakeLock();
// If the connection has one-shot sensors, it may be cleaned up after first trigger.
// Early check for one-shot sensors.
if (activeConnections[i]->hasOneShotSensors()) {
cleanupAutoDisabledSensorLocked(activeConnections[i], mSensorEventBuffer,
count);
}
}
}
if (mWakeLockAcquired && !needsWakeLock) {
setWakeLockAcquiredLocked(false);
}
} while (!Thread::exitPending());
ALOGW("Exiting SensorService::threadLoop => aborting...");
abort();
return false;
}
说下几个关键的数据结构
/hardware/libhardware/include/hardware/
sensor_t 用来保存sensor的结构。常用来做指针，指向一个sensor list。
struct sensor_t {
/* Name of this sensor.
* All sensors of the same "type" must have a different "name".
*/
const char* name; //传感器名字
/* vendor of the hardware part */
const char* vendor; //定制商
/* 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 reference
* this sensor throughout the HAL API.
*/
int handle; //用于区分sensor
/* this sensor's type. */
int type; //类型
/* maximum range of this sensor's value in SI units */
float maxRange; //最大范围
/* smallest difference between two values reported by this sensor */
float resolution; //最小取分值
/* rough estimate of this sensor's power consumption in mA */
float power; //耗电
/* this value depends on the reporting mode:
*
* continuous: minimum sample period allowed in microseconds
* on-change : 0
* one-shot :-1
* special : 0, unless otherwise noted
*/
int32_t minDelay;
/* number of events reserved for this sensor in the batch mode FIFO.
* If there is a dedicated FIFO for this sensor, then this is the
* size of this FIFO. If the FIFO is shared with other sensors,
* this is the size reserved for that sensor and it can be zero.
*/
uint32_t fifoReservedEventCount;
/* maximum number of events of this sensor that could be batched.
* This is especially relevant when the FIFO is shared between
* several sensors; this value is then set to the size of that FIFO.
*/
uint32_t fifoMaxEventCount;
/* type of this sensor as a string. Set to corresponding
* SENSOR_STRING_TYPE_*.
* When defining an OEM specific sensor or sensor manufacturer specific
* sensor, use your reserve domain name as a prefix.
* ex: com.google.glass.onheaddetector
* For sensors of known type, the android framework might overwrite this
* string automatically.
*/
const char* stringType; //类型
/* permission required to see this sensor, register to it and receive data.
* Set to "" if no permission is required. Some sensor types like the
* heart rate monitor have a mandatory require_permission.
* For sensors that always require a specific permission, like the heart
* rate monitor, the android framework might overwrite this string
* automatically.
*/
const char* requiredPermission; //权限
/* This value is defined only for continuous mode and on-change sensors. It is the delay between
* two sensor events corresponding to the lowest frequency that this sensor supports. When lower
* frequencies are requested through batch()/setDelay() the events will be generated at this
* frequency instead. It can be used by the framework or applications to estimate when the batch
* FIFO may be full.
*
* NOTE: 1) period_ns is in nanoseconds where as maxDelay/minDelay are in microseconds.
* continuous, on-change: maximum sampling period allowed in microseconds.
* one-shot, special : 0
* 2) maxDelay should always fit within a 32 bit signed integer. It is declared as 64 bit
* on 64 bit architectures only for binary compatibility reasons.
* Availability: SENSORS_DEVICE_API_VERSION_1_3
*/
#ifdef __LP64__
int64_t maxDelay;
#else
int32_t maxDelay; //最大延迟
#endif
/* Flags for sensor. See SENSOR_FLAG_* above. Only the least significant 32 bits are used here.
* It is declared as 64 bit on 64 bit architectures only for binary compatibility reasons.
* Availability: SENSORS_DEVICE_API_VERSION_1_3
*/
#ifdef __LP64__
uint64_t flags;
#else
uint32_t flags;
#endif
/* reserved fields, must be zero */
void* reserved[2];
};
对应的sensor 类是，封装了获取结构体数据的方法
/frameworks/native/libs/gui/Sensor.cpp
sensor
sensor的注册接口HardwareSensor,注册是生成了一个list结构mSensorList和一个map结构mSensorMap，mSensorList用于保存所有Sensor，mSensorMap保存handle到HardwareSensor的映射表。
Sensor SensorService::registerSensor(SensorInterface* s)
{
sensors_event_t event;
memset(&event, 0, sizeof(event));
const Sensor sensor(s->getSensor());
// add to the sensor list (returned to clients)
mSensorList.add(sensor);
// add to our handle->SensorInterface mapping
mSensorMap.add(sensor.getHandle(), s);
// create an entry in the mLastEventSeen array
mLastEventSeen.add(sensor.getHandle(), NULL);
return sensor;
}
class HardwareSensor : public SensorInterface
{
SensorDevice& mSensorDevice;
Sensor mSensor;
public:
HardwareSensor(const sensor_t& sensor);
virtual ~HardwareSensor();
virtual bool process(sensors_event_t* outEvent,
const sensors_event_t& event);
virtual status_t activate(void* ident, bool enabled);
virtual status_t batch(void* ident, int handle, int flags, int64_t samplingPeriodNs,
int64_t maxBatchReportLatencyNs);
virtual status_t setDelay(void* ident, int handle, int64_t ns);
virtual status_t flush(void* ident, int handle);
virtual Sensor getSensor() const;
virtual bool isVirtual() const { return false; }
virtual void autoDisable(void *ident, int handle);
};
还有一个比较重要的是SensorEventConnection，他的函数sendEvents用来发送sensor数据给framework层
class SensorEventConnection : public BnSensorEventConnection, public LooperCallback {
friend class SensorService;
virtual ~SensorEventConnection();
virtual void onFirstRef();
virtual sp getSensorChannel() const;
virtual status_t enableDisable(int handle, bool enabled, nsecs_t samplingPeriodNs,
nsecs_t maxBatchReportLatencyNs, int reservedFlags);
virtual status_t setEventRate(int handle, nsecs_t samplingPeriodNs);
virtual status_t flush();
// Count the number of flush complete events which are about to be dropped in the buffer.
// Increment mPendingFlushEventsToSend in mSensorInfo. These flush complete events will be
// sent separately before the next batch of events.
void countFlushCompleteEventsLocked(sensors_event_t const* scratch, int numEventsDropped);
// Check if there are any wake up events in the buffer. If yes, return the index of the
// first wake_up sensor event in the buffer else return -1. This wake_up sensor event will
// have the flag WAKE_UP_SENSOR_EVENT_NEEDS_ACK set. Exactly one event per packet will have
// the wake_up flag set. SOCK_SEQPACKET ensures that either the entire packet is read or
// dropped.
int findWakeUpSensorEventLocked(sensors_event_t const* scratch, int count);
// Send pending flush_complete events. There may have been flush_complete_events that are
// dropped which need to be sent separately before other events. On older HALs (1_0) this
// method emulates the behavior of flush().
void sendPendingFlushEventsLocked();
// Writes events from mEventCache to the socket.
void writeToSocketFromCache();
// Compute the approximate cache size from the FIFO sizes of various sensors registered for
// this connection. Wake up and non-wake up sensors have separate FIFOs but FIFO may be
// shared amongst wake-up sensors and non-wake up sensors.
int computeMaxCacheSizeLocked() const;
// When more sensors register, the maximum cache size desired may change. Compute max cache
// size, reallocate memory and copy over events from the older cache.
void reAllocateCacheLocked(sensors_event_t const* scratch, int count);
// LooperCallback method. If there is data to read on this fd, it is an ack from the
// app that it has read events from a wake up sensor, decrement mWakeLockRefCount.
// If this fd is available for writing send the data from the cache.
virtual int handleEvent(int fd, int events, void* data);
// Increment mPendingFlushEventsToSend for the given sensor handle.
void incrementPendingFlushCount(int32_t handle);
// Add or remove the file descriptor associated with the BitTube to the looper. If mDead is
// set to true or there are no more sensors for this connection, the file descriptor is
// removed if it has been previously added to the Looper. Depending on the state of the
// connection FD may be added to the Looper. The flags to set are determined by the internal
// state of the connection. FDs are added to the looper when wake-up sensors are registered
// (to poll for acknowledgements) and when write fails on the socket when there are too many
// error and the other end hangs up or when this client unregisters for this connection.
void updateLooperRegistration(const sp& looper);
void updateLooperRegistrationLocked(const sp& looper);
sp const mService;
sp mChannel;
uid_t mUid;
mutable Mutex mConnectionLock;
// Number of events from wake up sensors which are still pending and haven't been delivered
// to the corresponding application. It is incremented by one unit for each write to the
// socket.
uint32_t mWakeLockRefCount;
// If this flag is set to true, it means that the file descriptor associated with the
// BitTube has been added to the Looper in SensorService. This flag is typically set when
// this connection has wake-up sensors associated with it or when write has failed on this
// connection and we're storing some events in the cache.
bool mHasLooperCallbacks;
// If there are any errors associated with the Looper this flag is set to true and
// mWakeLockRefCount is reset to zero. needsWakeLock method will always return false, if
// this flag is set.
bool mDead;
bool mDataInjectionMode;
struct FlushInfo {
// The number of flush complete events dropped for this sensor is stored here.
// They are sent separately before the next batch of events.
int mPendingFlushEventsToSend;
// Every activate is preceded by a flush. Only after the first flush complete is
// received, the events for the sensor are sent on that *connection*.
bool mFirstFlushPending;
FlushInfo() : mPendingFlushEventsToSend(0), mFirstFlushPending(false) {}
};
// protected by SensorService::mLock. Key for this vector is the sensor handle.
KeyedVector mSensorInfo;
sensors_event_t *mEventCache;
int mCacheSize, mMaxCacheSize;
String8 mPackageName;
const String16 mOpPackageName;
#if DEBUG_CONNECTIONS
int mEventsReceived, mEventsSent, mEventsSentFromCache;
int mTotalAcksNeeded, mTotalAcksReceived;
#endif
public:
SensorEventConnection(const sp& service, uid_t uid, String8 packageName,
bool isDataInjectionMode, const String16& opPackageName);
status_t sendEvents(sensors_event_t const* buffer, size_t count,
sensors_event_t* scratch,
SensorEventConnection const * const * mapFlushEventsToConnections = NULL);
bool hasSensor(int32_t handle) const;
bool hasAnySensor() const;
bool hasOneShotSensors() const;
bool addSensor(int32_t handle);
bool removeSensor(int32_t handle);
void setFirstFlushPending(int32_t handle, bool value);
void dump(String8& result);
bool needsWakeLock();
void resetWakeLockRefCount();
String8 getPackageName() const;
uid_t getUid() const { return mUid; }
};
参考:
深入浅出 - Android系统移植与平台开发（十四） - Sensor HAL框架分析之四
SensorService启动分析