Where to find the implementation of the Android Camera API locking mechanism? -

the camera api use open() , release() calls prevent multiple accesses different apps/processes, kind of want know how underlying mechanism works. example, there mutex share across different processes? can point me right place, did google search can't locate source code.

i linked kitkat source, since it's last version before android.hardware.camera2 introduced.

the lock tried this:

remote()->transact(lock, data, &reply); 

where remote() seems system service. refer answer remote: implementation of remote()

android source code

https://android.googlesource.com/platform/frameworks/base/+/android-4.4.4_r2.0.1/core/java/android/hardware/camera.java:

public native final void lock(); 

https://android.googlesource.com/platform/frameworks/base/+/android-4.4.4_r2.0.1/core/jni/android_hardware_camera.cpp:

static void android_hardware_camera_lock(jnienv *env, jobject thiz) {     alogv("lock");     sp<camera> camera = get_native_camera(env, thiz, null);     if (camera == 0) return;     if (camera->lock() != no_error) {         jnithrowruntimeexception(env, "lock failed");     } } 

https://android.googlesource.com/platform/frameworks/av/+/android-4.4.4_r2.0.1/camera/camera.cpp:

status_t camera::lock() {     sp <icamera> c = mcamera;     if (c == 0) return no_init;     return c->lock(); } 

https://android.googlesource.com/platform/frameworks/av/+/android-4.4.4_r2.0.1/include/camera/icamera.h:

class icamera: public iinterface {     // prevent other processes using icamera interface     virtual status_t        lock() = 0; } 

https://android.googlesource.com/platform/frameworks/av/+/android-4.4.4_r2.0.1/camera/icamera.cpp:

class bpcamera: public bpinterface<icamera> {     virtual status_t lock()     {         parcel data, reply;         data.writeinterfacetoken(icamera::getinterfacedescriptor());         remote()->transact(lock, data, &reply);         return reply.readint32();     } }