目录
[2.1 binder溯源](#2.1 binder溯源)
这几天撸了android11 aosp闪光灯源码，本着前人栽树后人乘凉的原则，有志于android系统开发的新同学们提供一盏明灯，照亮你们前行。
本人撸代码风格，喜欢从app撸到kernel，启航出发。
一、APP层源码分析
下拉状态栏，可见"手电筒"快捷开关，点击后开启手电筒，UI见下图，
这部分代码，在目录：frameworks/base/packages/SystemUI/src/com/android/systemui/qs/tiles/FlashlightTile.java，点击按钮回调，
protected void handleClick() {
if (ActivityManager.isUserAMonkey()) {
return;
}
boolean newState = !mState.value;
refreshState(newState);
//点击"手电筒"核心核数
mFlashlightController.setFlashlight(newState);
}通过 mFlashlightController.setFlashlight(newState)走到文件
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/policy/FlashlightControllerImpl.java，
public void setFlashlight(boolean enabled) {
boolean pendingError = false;
synchronized (this) {
if (mCameraId == null) return;
if (mFlashlightEnabled != enabled) {
mFlashlightEnabled = enabled;
try {
//核心调用
mCameraManager.setTorchMode(mCameraId, enabled);
} catch (CameraAccessException e) {
Log.e(TAG, "Couldn't set torch mode", e);
mFlashlightEnabled = false;
pendingError = true;
}
}
}
dispatchModeChanged(mFlashlightEnabled);
if (pendingError) {
dispatchError();
}
}通过mCameraManager.setTorchMode(mCameraId, enabled)走到frameworks/base/core/java/android/hardware/camera2/CameraManager.java，
public void setTorchMode(@NonNull String cameraId, boolean enabled)
throws CameraAccessException {
if (CameraManagerGlobal.sCameraServiceDisabled) {
throw new IllegalArgumentException("No cameras available on device");
}
CameraManagerGlobal.get().setTorchMode(cameraId, enabled);
}CameraManagerGlobal.get().setTorchMode(cameraId, enabled)走到，
public void setTorchMode(String cameraId, boolean enabled) throws CameraAccessException {
synchronized(mLock) {
if (cameraId == null) {
throw new IllegalArgumentException("cameraId was null");
}
ICameraService cameraService = getCameraService();
if (cameraService == null) {
throw new CameraAccessException(CameraAccessException.CAMERA_DISCONNECTED,
"Camera service is currently unavailable");
}
try {
cameraService.setTorchMode(cameraId, enabled, mTorchClientBinder);
} catch(ServiceSpecificException e) {
throwAsPublicException(e);
} catch (RemoteException e) {
throw new CameraAccessException(CameraAccessException.CAMERA_DISCONNECTED,
"Camera service is currently unavailable");
}
}
} ICameraService cameraService = getCameraService();看到这句是不是很熟悉，android获取系统服务，跨进程调用。只是和我们app开发常用的 不同，这里直接拿到camera服务的proxy。对下面这行代码不理解的，可以学习下android binder机制，本质就是拿到camera服务的proxyICameraService cameraService = ICameraService.Stub.asInterface(cameraServiceBinder);原来操作"手电筒"的不是单独模块，而是通过camera模块来控制的，666。
二，framework层代码分析
2.1 binder溯源
由第一部分分析可知，"手电筒"通过cameraservice来操作，结合binder知识，可以在ICameraService.aidl接口定义中找到，
void setTorchMode(String cameraId, boolean enabled, IBinder clientBinder);aidl文件会自动生成java文件，再通过jni调用到cpp文件，最终在ICameraService.cpp中实现了client的调用，
::android::binder::Status BpCameraService::setTorchMode(const ::android::String16& cameraId, bool enabled, const ::android::sp<::android::IBinder>& clientBinder) {
::android::Parcel _aidl_data;
::android::Parcel _aidl_reply;
::android::status_t _aidl_ret_status = ::android::OK;
::android::binder::Status _aidl_status;
_aidl_ret_status = _aidl_data.writeInterfaceToken(getInterfaceDescriptor());
if (((_aidl_ret_status) != (::android::OK))) {
goto _aidl_error;
}
_aidl_ret_status = _aidl_data.writeString16(cameraId);
if (((_aidl_ret_status) != (::android::OK))) {
goto _aidl_error;
}
_aidl_ret_status = _aidl_data.writeBool(enabled);
if (((_aidl_ret_status) != (::android::OK))) {
goto _aidl_error;
}
_aidl_ret_status = _aidl_data.writeStrongBinder(clientBinder);
if (((_aidl_ret_status) != (::android::OK))) {
goto _aidl_error;
}
_aidl_ret_status = remote()->transact(::android::IBinder::FIRST_CALL_TRANSACTION + 15 /* setTorchMode */, _aidl_data, &_aidl_reply);
if (UNLIKELY(_aidl_ret_status == ::android::UNKNOWN_TRANSACTION && ICameraService::getDefaultImpl())) {
return ICameraService::getDefaultImpl()->setTorchMode(cameraId, enabled, clientBinder);
}
if (((_aidl_ret_status) != (::android::OK))) {
goto _aidl_error;
}
_aidl_ret_status = _aidl_status.readFromParcel(_aidl_reply);
if (((_aidl_ret_status) != (::android::OK))) {
goto _aidl_error;
}
if (!_aidl_status.isOk()) {
return _aidl_status;
}
_aidl_error:
_aidl_status.setFromStatusT(_aidl_ret_status);
return _aidl_status;
}通过remote()->transact()发起IPC请求，事务码FIRST_CALL_TRANSACTION + 15对应setTorchMode方法，数据通过_aidl_dataParcel传递，执行到CameraService.cpp文件，
Status CameraService::setTorchMode(const String16& cameraId, bool enabled,
const sp<IBinder>& clientBinder) {
Mutex::Autolock lock(mServiceLock);
ATRACE_CALL();
if (enabled && clientBinder == nullptr) {
ALOGE("%s: torch client binder is NULL", __FUNCTION__);
return STATUS_ERROR(ERROR_ILLEGAL_ARGUMENT,
"Torch client Binder is null");
}
String8 id = String8(cameraId.string());
int uid = CameraThreadState::getCallingUid();
if (shouldRejectSystemCameraConnection(id)) {
return STATUS_ERROR_FMT(ERROR_ILLEGAL_ARGUMENT, "Unable to set torch mode"
" for system only device %s: ", id.string());
}
// verify id is valid.
auto state = getCameraState(id);
if (state == nullptr) {
ALOGE("%s: camera id is invalid %s", __FUNCTION__, id.string());
return STATUS_ERROR_FMT(ERROR_ILLEGAL_ARGUMENT,
"Camera ID \"%s\" is a not valid camera ID", id.string());
}
StatusInternal cameraStatus = state->getStatus();
if (cameraStatus != StatusInternal::PRESENT &&
cameraStatus != StatusInternal::NOT_AVAILABLE) {
ALOGE("%s: camera id is invalid %s, status %d", __FUNCTION__, id.string(), (int)cameraStatus);
return STATUS_ERROR_FMT(ERROR_ILLEGAL_ARGUMENT,
"Camera ID \"%s\" is a not valid camera ID", id.string());
}
{
Mutex::Autolock al(mTorchStatusMutex);
TorchModeStatus status;
status_t err = getTorchStatusLocked(id, &status);
if (err != OK) {
if (err == NAME_NOT_FOUND) {
return STATUS_ERROR_FMT(ERROR_ILLEGAL_ARGUMENT,
"Camera \"%s\" does not have a flash unit", id.string());
}
ALOGE("%s: getting current torch status failed for camera %s",
__FUNCTION__, id.string());
return STATUS_ERROR_FMT(ERROR_INVALID_OPERATION,
"Error updating torch status for camera \"%s\": %s (%d)", id.string(),
strerror(-err), err);
}
if (status == TorchModeStatus::NOT_AVAILABLE) {
if (cameraStatus == StatusInternal::NOT_AVAILABLE) {
ALOGE("%s: torch mode of camera %s is not available because "
"camera is in use", __FUNCTION__, id.string());
return STATUS_ERROR_FMT(ERROR_CAMERA_IN_USE,
"Torch for camera \"%s\" is not available due to an existing camera user",
id.string());
} else {
ALOGE("%s: torch mode of camera %s is not available due to "
"insufficient resources", __FUNCTION__, id.string());
return STATUS_ERROR_FMT(ERROR_MAX_CAMERAS_IN_USE,
"Torch for camera \"%s\" is not available due to insufficient resources",
id.string());
}
}
}
{
// Update UID map - this is used in the torch status changed callbacks, so must be done
// before setTorchMode
Mutex::Autolock al(mTorchUidMapMutex);
if (mTorchUidMap.find(id) == mTorchUidMap.end()) {
mTorchUidMap[id].first = uid;
mTorchUidMap[id].second = uid;
} else {
// Set the pending UID
mTorchUidMap[id].first = uid;
}
}
status_t err = mFlashlight->setTorchMode(id, enabled);
if (err != OK) {
int32_t errorCode;
String8 msg;
switch (err) {
case -ENOSYS:
msg = String8::format("Camera \"%s\" has no flashlight",
id.string());
errorCode = ERROR_ILLEGAL_ARGUMENT;
break;
default:
msg = String8::format(
"Setting torch mode of camera \"%s\" to %d failed: %s (%d)",
id.string(), enabled, strerror(-err), err);
errorCode = ERROR_INVALID_OPERATION;
}
ALOGE("%s: %s", __FUNCTION__, msg.string());
return STATUS_ERROR(errorCode, msg.string());
}
{
// update the link to client's death
Mutex::Autolock al(mTorchClientMapMutex);
ssize_t index = mTorchClientMap.indexOfKey(id);
if (enabled) {
if (index == NAME_NOT_FOUND) {
mTorchClientMap.add(id, clientBinder);
} else {
mTorchClientMap.valueAt(index)->unlinkToDeath(this);
mTorchClientMap.replaceValueAt(index, clientBinder);
}
clientBinder->linkToDeath(this);
} else if (index != NAME_NOT_FOUND) {
mTorchClientMap.valueAt(index)->unlinkToDeath(this);
}
}
int clientPid = CameraThreadState::getCallingPid();
const char *id_cstr = id.c_str();
const char *torchState = enabled ? "on" : "off";
ALOGI("Torch for camera id %s turned %s for client PID %d", id_cstr, torchState, clientPid);
logTorchEvent(id_cstr, torchState , clientPid);
return Status::ok();
}其中，关键句status_t err = mFlashlight->setTorchMode(id, enabled)；再由hal层交互可知，
最终通过CameraProviderManager查询HAL实现的setTorchMode()接口来控制device。
status_t CameraProviderManager::setTorchMode(const std::string &id, bool enabled) {
std::lock_guard<std::mutex> lock(mInterfaceMutex);
auto deviceInfo = findDeviceInfoLocked(id);
if (deviceInfo == nullptr) return NAME_NOT_FOUND;
// Pass the camera ID to start interface so that it will save it to the map of ICameraProviders
// that are currently in use.
sp<ProviderInfo> parentProvider = deviceInfo->mParentProvider.promote();
if (parentProvider == nullptr) {
return DEAD_OBJECT;
}
const sp<provider::V2_4::ICameraProvider> interface = parentProvider->startProviderInterface();
if (interface == nullptr) {
return DEAD_OBJECT;
}
saveRef(DeviceMode::TORCH, deviceInfo->mId, interface);
return deviceInfo->setTorchMode(enabled);
}最终，通过deviceInfo->setTorchMode(enabled)来实现对硬件的操作。