diff --git a/camera/device/3.4/default/ExternalCameraDevice.cpp b/camera/device/3.4/default/ExternalCameraDevice.cpp
index e7361dd..b96f574 100644
--- a/camera/device/3.4/default/ExternalCameraDevice.cpp
+++ b/camera/device/3.4/default/ExternalCameraDevice.cpp
@@ -48,24 +48,31 @@
 } // anonymous namespace
 
 ExternalCameraDevice::ExternalCameraDevice(
-            const std::string& cameraId, const ExternalCameraConfig& cfg) :
+        const std::string& cameraId, const ExternalCameraConfig& cfg) :
         mCameraId(cameraId),
-        mCfg(cfg) {
-
-    status_t ret = initCameraCharacteristics();
-    if (ret != OK) {
-        ALOGE("%s: init camera characteristics failed: errorno %d", __FUNCTION__, ret);
-        mInitFailed = true;
-    }
-}
+        mCfg(cfg) {}
 
 ExternalCameraDevice::~ExternalCameraDevice() {}
 
 bool ExternalCameraDevice::isInitFailed() {
+    Mutex::Autolock _l(mLock);
+    return isInitFailedLocked();
+}
+
+bool ExternalCameraDevice::isInitFailedLocked() {
+    if (!mInitialized) {
+        status_t ret = initCameraCharacteristics();
+        if (ret != OK) {
+            ALOGE("%s: init camera characteristics failed: errorno %d", __FUNCTION__, ret);
+            mInitFailed = true;
+        }
+        mInitialized = true;
+    }
     return mInitFailed;
 }
 
-Return<void> ExternalCameraDevice::getResourceCost(getResourceCost_cb _hidl_cb) {
+Return<void> ExternalCameraDevice::getResourceCost(
+        ICameraDevice::getResourceCost_cb _hidl_cb) {
     CameraResourceCost resCost;
     resCost.resourceCost = 100;
     _hidl_cb(Status::OK, resCost);
@@ -73,11 +80,11 @@
 }
 
 Return<void> ExternalCameraDevice::getCameraCharacteristics(
-        getCameraCharacteristics_cb _hidl_cb) {
+        ICameraDevice::getCameraCharacteristics_cb _hidl_cb) {
     Mutex::Autolock _l(mLock);
     V3_2::CameraMetadata hidlChars;
 
-    if (isInitFailed()) {
+    if (isInitFailedLocked()) {
         _hidl_cb(Status::INTERNAL_ERROR, hidlChars);
         return Void();
     }
@@ -94,7 +101,7 @@
 }
 
 Return<void> ExternalCameraDevice::open(
-        const sp<ICameraDeviceCallback>& callback, open_cb _hidl_cb) {
+        const sp<ICameraDeviceCallback>& callback, ICameraDevice::open_cb _hidl_cb) {
     Status status = Status::OK;
     sp<ExternalCameraDeviceSession> session = nullptr;
 
@@ -143,7 +150,7 @@
         }
     }
 
-    session = new ExternalCameraDeviceSession(
+    session = createSession(
             callback, mCfg, mSupportedFormats, mCroppingType,
             mCameraCharacteristics, mCameraId, std::move(fd));
     if (session == nullptr) {
@@ -479,52 +486,9 @@
     UPDATE(ANDROID_REQUEST_AVAILABLE_RESULT_KEYS, availableResultKeys,
            ARRAY_SIZE(availableResultKeys));
 
-    const int32_t availableCharacteristicsKeys[] = {
-        ANDROID_COLOR_CORRECTION_AVAILABLE_ABERRATION_MODES,
-        ANDROID_CONTROL_AE_AVAILABLE_ANTIBANDING_MODES,
-        ANDROID_CONTROL_AE_AVAILABLE_MODES,
-        ANDROID_CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES,
-        ANDROID_CONTROL_AE_COMPENSATION_RANGE,
-        ANDROID_CONTROL_AE_COMPENSATION_STEP,
-        ANDROID_CONTROL_AE_LOCK_AVAILABLE,
-        ANDROID_CONTROL_AF_AVAILABLE_MODES,
-        ANDROID_CONTROL_AVAILABLE_EFFECTS,
-        ANDROID_CONTROL_AVAILABLE_MODES,
-        ANDROID_CONTROL_AVAILABLE_SCENE_MODES,
-        ANDROID_CONTROL_AVAILABLE_VIDEO_STABILIZATION_MODES,
-        ANDROID_CONTROL_AWB_AVAILABLE_MODES,
-        ANDROID_CONTROL_AWB_LOCK_AVAILABLE,
-        ANDROID_CONTROL_MAX_REGIONS,
-        ANDROID_FLASH_INFO_AVAILABLE,
-        ANDROID_INFO_SUPPORTED_HARDWARE_LEVEL,
-        ANDROID_JPEG_AVAILABLE_THUMBNAIL_SIZES,
-        ANDROID_LENS_FACING,
-        ANDROID_LENS_INFO_AVAILABLE_OPTICAL_STABILIZATION,
-        ANDROID_LENS_INFO_FOCUS_DISTANCE_CALIBRATION,
-        ANDROID_NOISE_REDUCTION_AVAILABLE_NOISE_REDUCTION_MODES,
-        ANDROID_REQUEST_AVAILABLE_CAPABILITIES,
-        ANDROID_REQUEST_MAX_NUM_INPUT_STREAMS,
-        ANDROID_REQUEST_MAX_NUM_OUTPUT_STREAMS,
-        ANDROID_REQUEST_PARTIAL_RESULT_COUNT,
-        ANDROID_REQUEST_PIPELINE_MAX_DEPTH,
-        ANDROID_SCALER_AVAILABLE_MAX_DIGITAL_ZOOM,
-        ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS,
-        ANDROID_SCALER_CROPPING_TYPE,
-        ANDROID_SENSOR_INFO_ACTIVE_ARRAY_SIZE,
-        ANDROID_SENSOR_INFO_MAX_FRAME_DURATION,
-        ANDROID_SENSOR_INFO_PIXEL_ARRAY_SIZE,
-        ANDROID_SENSOR_INFO_PRE_CORRECTION_ACTIVE_ARRAY_SIZE,
-        ANDROID_SENSOR_INFO_TIMESTAMP_SOURCE,
-        ANDROID_SENSOR_ORIENTATION,
-        ANDROID_SHADING_AVAILABLE_MODES,
-        ANDROID_STATISTICS_INFO_AVAILABLE_FACE_DETECT_MODES,
-        ANDROID_STATISTICS_INFO_AVAILABLE_HOT_PIXEL_MAP_MODES,
-        ANDROID_STATISTICS_INFO_AVAILABLE_LENS_SHADING_MAP_MODES,
-        ANDROID_STATISTICS_INFO_MAX_FACE_COUNT,
-        ANDROID_SYNC_MAX_LATENCY};
     UPDATE(ANDROID_REQUEST_AVAILABLE_CHARACTERISTICS_KEYS,
-           availableCharacteristicsKeys,
-           ARRAY_SIZE(availableCharacteristicsKeys));
+           AVAILABLE_CHARACTERISTICS_KEYS_3_4.data(),
+           AVAILABLE_CHARACTERISTICS_KEYS_3_4.size());
 
     return OK;
 }
@@ -931,6 +895,18 @@
     }
 }
 
+sp<ExternalCameraDeviceSession> ExternalCameraDevice::createSession(
+        const sp<ICameraDeviceCallback>& cb,
+        const ExternalCameraConfig& cfg,
+        const std::vector<SupportedV4L2Format>& sortedFormats,
+        const CroppingType& croppingType,
+        const common::V1_0::helper::CameraMetadata& chars,
+        const std::string& cameraId,
+        unique_fd v4l2Fd) {
+    return new ExternalCameraDeviceSession(
+            cb, cfg, sortedFormats, croppingType, chars, cameraId, std::move(v4l2Fd));
+}
+
 }  // namespace implementation
 }  // namespace V3_4
 }  // namespace device
diff --git a/camera/device/3.4/default/ExternalCameraDeviceSession.cpp b/camera/device/3.4/default/ExternalCameraDeviceSession.cpp
index 350f48b..5824be0 100644
--- a/camera/device/3.4/default/ExternalCameraDeviceSession.cpp
+++ b/camera/device/3.4/default/ExternalCameraDeviceSession.cpp
@@ -81,6 +81,8 @@
     return locked;
 }
 
+buffer_handle_t sEmptyBuffer = nullptr;
+
 } // Anonymous namespace
 
 // Static instances
@@ -103,11 +105,8 @@
         mCroppingType(croppingType),
         mCameraId(cameraId),
         mV4l2Fd(std::move(v4l2Fd)),
-        mOutputThread(new OutputThread(this, mCroppingType)),
         mMaxThumbResolution(getMaxThumbResolution()),
-        mMaxJpegResolution(getMaxJpegResolution()) {
-    mInitFail = initialize();
-}
+        mMaxJpegResolution(getMaxJpegResolution()) {}
 
 bool ExternalCameraDeviceSession::initialize() {
     if (mV4l2Fd.get() < 0) {
@@ -142,6 +141,12 @@
             model = card;
         }
     }
+
+    initOutputThread();
+    if (mOutputThread == nullptr) {
+        ALOGE("%s: init OutputThread failed!", __FUNCTION__);
+        return true;
+    }
     mOutputThread->setExifMakeModel(make, model);
 
     status_t status = initDefaultRequests();
@@ -168,6 +173,32 @@
     return false;
 }
 
+bool ExternalCameraDeviceSession::isInitFailed() {
+    Mutex::Autolock _l(mLock);
+    if (!mInitialized) {
+        mInitFail = initialize();
+        mInitialized = true;
+    }
+    return mInitFail;
+}
+
+void ExternalCameraDeviceSession::initOutputThread() {
+    mOutputThread = new OutputThread(this, mCroppingType);
+}
+
+void ExternalCameraDeviceSession::closeOutputThread() {
+    closeOutputThreadImpl();
+}
+
+void ExternalCameraDeviceSession::closeOutputThreadImpl() {
+    if (mOutputThread) {
+        mOutputThread->flush();
+        mOutputThread->requestExit();
+        mOutputThread->join();
+        mOutputThread.clear();
+    }
+}
+
 Status ExternalCameraDeviceSession::initStatus() const {
     Mutex::Autolock _l(mLock);
     Status status = Status::OK;
@@ -181,7 +212,7 @@
 ExternalCameraDeviceSession::~ExternalCameraDeviceSession() {
     if (!isClosed()) {
         ALOGE("ExternalCameraDeviceSession deleted before close!");
-        close();
+        close(/*callerIsDtor*/true);
     }
 }
 
@@ -442,18 +473,23 @@
     return Status::OK;
 }
 
-Return<void> ExternalCameraDeviceSession::close() {
+Return<void> ExternalCameraDeviceSession::close(bool callerIsDtor) {
     Mutex::Autolock _il(mInterfaceLock);
     bool closed = isClosed();
     if (!closed) {
-        mOutputThread->flush();
-        mOutputThread->requestExit();
-        mOutputThread->join();
+        if (callerIsDtor) {
+            closeOutputThreadImpl();
+        } else {
+            closeOutputThread();
+        }
 
         Mutex::Autolock _l(mLock);
         // free all buffers
-        for(auto pair : mStreamMap) {
-            cleanupBuffersLocked(/*Stream ID*/pair.first);
+        {
+            Mutex::Autolock _l(mCbsLock);
+            for(auto pair : mStreamMap) {
+                cleanupBuffersLocked(/*Stream ID*/pair.first);
+            }
         }
         v4l2StreamOffLocked();
         ALOGV("%s: closing V4L2 camera FD %d", __FUNCTION__, mV4l2Fd.get());
@@ -463,10 +499,61 @@
     return Void();
 }
 
-Status ExternalCameraDeviceSession::importRequest(
+Status ExternalCameraDeviceSession::importRequestLocked(
+    const CaptureRequest& request,
+    hidl_vec<buffer_handle_t*>& allBufPtrs,
+    hidl_vec<int>& allFences) {
+    return importRequestLockedImpl(request, allBufPtrs, allFences);
+}
+
+Status ExternalCameraDeviceSession::importBuffer(int32_t streamId,
+        uint64_t bufId, buffer_handle_t buf,
+        /*out*/buffer_handle_t** outBufPtr,
+        bool allowEmptyBuf) {
+    Mutex::Autolock _l(mCbsLock);
+    return importBufferLocked(streamId, bufId, buf, outBufPtr, allowEmptyBuf);
+}
+
+Status ExternalCameraDeviceSession::importBufferLocked(int32_t streamId,
+        uint64_t bufId, buffer_handle_t buf,
+        /*out*/buffer_handle_t** outBufPtr,
+        bool allowEmptyBuf) {
+
+    if (buf == nullptr && bufId == BUFFER_ID_NO_BUFFER) {
+        if (allowEmptyBuf) {
+            *outBufPtr = &sEmptyBuffer;
+            return Status::OK;
+        } else {
+            ALOGE("%s: bufferId %" PRIu64 " has null buffer handle!", __FUNCTION__, bufId);
+            return Status::ILLEGAL_ARGUMENT;
+        }
+    }
+
+    CirculatingBuffers& cbs = mCirculatingBuffers[streamId];
+    if (cbs.count(bufId) == 0) {
+        if (buf == nullptr) {
+            ALOGE("%s: bufferId %" PRIu64 " has null buffer handle!", __FUNCTION__, bufId);
+            return Status::ILLEGAL_ARGUMENT;
+        }
+        // Register a newly seen buffer
+        buffer_handle_t importedBuf = buf;
+        sHandleImporter.importBuffer(importedBuf);
+        if (importedBuf == nullptr) {
+            ALOGE("%s: output buffer for stream %d is invalid!", __FUNCTION__, streamId);
+            return Status::INTERNAL_ERROR;
+        } else {
+            cbs[bufId] = importedBuf;
+        }
+    }
+    *outBufPtr = &cbs[bufId];
+    return Status::OK;
+}
+
+Status ExternalCameraDeviceSession::importRequestLockedImpl(
         const CaptureRequest& request,
         hidl_vec<buffer_handle_t*>& allBufPtrs,
-        hidl_vec<int>& allFences) {
+        hidl_vec<int>& allFences,
+        bool allowEmptyBuf) {
     size_t numOutputBufs = request.outputBuffers.size();
     size_t numBufs = numOutputBufs;
     // Validate all I/O buffers
@@ -485,26 +572,17 @@
         streamIds[i] = request.outputBuffers[i].streamId;
     }
 
-    for (size_t i = 0; i < numBufs; i++) {
-        buffer_handle_t buf = allBufs[i];
-        uint64_t bufId = allBufIds[i];
-        CirculatingBuffers& cbs = mCirculatingBuffers[streamIds[i]];
-        if (cbs.count(bufId) == 0) {
-            if (buf == nullptr) {
-                ALOGE("%s: bufferId %" PRIu64 " has null buffer handle!", __FUNCTION__, bufId);
-                return Status::ILLEGAL_ARGUMENT;
-            }
-            // Register a newly seen buffer
-            buffer_handle_t importedBuf = buf;
-            sHandleImporter.importBuffer(importedBuf);
-            if (importedBuf == nullptr) {
-                ALOGE("%s: output buffer %zu is invalid!", __FUNCTION__, i);
-                return Status::INTERNAL_ERROR;
-            } else {
-                cbs[bufId] = importedBuf;
+    {
+        Mutex::Autolock _l(mCbsLock);
+        for (size_t i = 0; i < numBufs; i++) {
+            Status st = importBufferLocked(
+                    streamIds[i], allBufIds[i], allBufs[i], &allBufPtrs[i],
+                    allowEmptyBuf);
+            if (st != Status::OK) {
+                // Detailed error logs printed in importBuffer
+                return st;
             }
         }
-        allBufPtrs[i] = &cbs[bufId];
     }
 
     // All buffers are imported. Now validate output buffer acquire fences
@@ -652,7 +730,7 @@
         }
     }
 
-    status = importRequest(request, allBufPtrs, allFences);
+    status = importRequestLocked(request, allBufPtrs, allFences);
     if (status != Status::OK) {
         return status;
     }
@@ -775,9 +853,11 @@
         result.outputBuffers[i].bufferId = req->buffers[i].bufferId;
         if (req->buffers[i].fenceTimeout) {
             result.outputBuffers[i].status = BufferStatus::ERROR;
-            native_handle_t* handle = native_handle_create(/*numFds*/1, /*numInts*/0);
-            handle->data[0] = req->buffers[i].acquireFence;
-            result.outputBuffers[i].releaseFence.setTo(handle, /*shouldOwn*/false);
+            if (req->buffers[i].acquireFence > 0) {
+                native_handle_t* handle = native_handle_create(/*numFds*/1, /*numInts*/0);
+                handle->data[0] = req->buffers[i].acquireFence;
+                result.outputBuffers[i].releaseFence.setTo(handle, /*shouldOwn*/false);
+            }
             notifyError(req->frameNumber, req->buffers[i].streamId, ErrorCode::ERROR_BUFFER);
         } else {
             result.outputBuffers[i].status = BufferStatus::OK;
@@ -1747,6 +1827,12 @@
                 (req->frameIn->mFourcc >> 24) & 0xFF);
     }
 
+    int res = requestBufferStart(req->buffers);
+    if (res != 0) {
+        ALOGE("%s: send BufferRequest failed! res %d", __FUNCTION__, res);
+        return onDeviceError("%s: failed to send buffer request!", __FUNCTION__);
+    }
+
     std::unique_lock<std::mutex> lk(mBufferLock);
     // Convert input V4L2 frame to YU12 of the same size
     // TODO: see if we can save some computation by converting to YV12 here
@@ -1755,7 +1841,7 @@
     req->frameIn->map(&inData, &inDataSize);
     // TODO: in some special case maybe we can decode jpg directly to gralloc output?
     ATRACE_BEGIN("MJPGtoI420");
-    int res = libyuv::MJPGToI420(
+    res = libyuv::MJPGToI420(
             inData, inDataSize,
             static_cast<uint8_t*>(mYu12FrameLayout.y),
             mYu12FrameLayout.yStride,
@@ -1779,10 +1865,23 @@
         return true;
     }
 
+    ATRACE_BEGIN("Wait for BufferRequest done");
+    res = waitForBufferRequestDone(&req->buffers);
+    ATRACE_END();
+
+    if (res != 0) {
+        ALOGE("%s: wait for BufferRequest done failed! res %d", __FUNCTION__, res);
+        lk.unlock();
+        return onDeviceError("%s: failed to process buffer request error!", __FUNCTION__);
+    }
+
     ALOGV("%s processing new request", __FUNCTION__);
     const int kSyncWaitTimeoutMs = 500;
     for (auto& halBuf : req->buffers) {
-        if (halBuf.acquireFence != -1) {
+        if (*(halBuf.bufPtr) == nullptr) {
+            ALOGW("%s: buffer for stream %d missing", __FUNCTION__, halBuf.streamId);
+            halBuf.fenceTimeout = true;
+        } else if (halBuf.acquireFence != -1) {
             int ret = sync_wait(halBuf.acquireFence, kSyncWaitTimeoutMs);
             if (ret) {
                 halBuf.fenceTimeout = true;
@@ -2041,7 +2140,7 @@
 }
 
 void ExternalCameraDeviceSession::updateBufferCaches(const hidl_vec<BufferCache>& cachesToRemove) {
-    Mutex::Autolock _l(mLock);
+    Mutex::Autolock _l(mCbsLock);
     for (auto& cache : cachesToRemove) {
         auto cbsIt = mCirculatingBuffers.find(cache.streamId);
         if (cbsIt == mCirculatingBuffers.end()) {
@@ -2494,30 +2593,33 @@
     }
 
     Mutex::Autolock _l(mLock);
-    // Add new streams
-    for (const auto& stream : config.streams) {
-        if (mStreamMap.count(stream.id) == 0) {
-            mStreamMap[stream.id] = stream;
-            mCirculatingBuffers.emplace(stream.id, CirculatingBuffers{});
-        }
-    }
-
-    // Cleanup removed streams
-    for(auto it = mStreamMap.begin(); it != mStreamMap.end();) {
-        int id = it->first;
-        bool found = false;
+    {
+        Mutex::Autolock _l(mCbsLock);
+        // Add new streams
         for (const auto& stream : config.streams) {
-            if (id == stream.id) {
-                found = true;
-                break;
+            if (mStreamMap.count(stream.id) == 0) {
+                mStreamMap[stream.id] = stream;
+                mCirculatingBuffers.emplace(stream.id, CirculatingBuffers{});
             }
         }
-        if (!found) {
-            // Unmap all buffers of deleted stream
-            cleanupBuffersLocked(id);
-            it = mStreamMap.erase(it);
-        } else {
-            ++it;
+
+        // Cleanup removed streams
+        for(auto it = mStreamMap.begin(); it != mStreamMap.end();) {
+            int id = it->first;
+            bool found = false;
+            for (const auto& stream : config.streams) {
+                if (id == stream.id) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                // Unmap all buffers of deleted stream
+                cleanupBuffersLocked(id);
+                it = mStreamMap.erase(it);
+            } else {
+                ++it;
+            }
         }
     }
 
diff --git a/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDeviceSession.h b/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDeviceSession.h
index 6e56596..cabeaa4 100644
--- a/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDeviceSession.h
+++ b/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDeviceSession.h
@@ -97,7 +97,7 @@
     // Call by CameraDevice to dump active device states
     void dumpState(const native_handle_t*);
     // Caller must use this method to check if CameraDeviceSession ctor failed
-    bool isInitFailed() { return mInitFail; }
+    bool isInitFailed();
     bool isClosed();
 
     // Retrieve the HIDL interface, split into its own class to avoid inheritance issues when
@@ -134,7 +134,7 @@
             ICameraDeviceSession::processCaptureRequest_cb);
 
     Return<Status> flush();
-    Return<void> close();
+    Return<void> close(bool callerIsDtor = false);
 
     Return<void> configureStreams_3_3(
             const V3_2::StreamConfiguration&,
@@ -170,10 +170,17 @@
         std::vector<HalStreamBuffer> buffers;
     };
 
+    static const uint64_t BUFFER_ID_NO_BUFFER = 0;
+
     Status constructDefaultRequestSettingsRaw(RequestTemplate type,
             V3_2::CameraMetadata *outMetadata);
 
     bool initialize();
+    // To init/close different version of output thread
+    virtual void initOutputThread();
+    virtual void closeOutputThread();
+    void closeOutputThreadImpl();
+
     Status initStatus() const;
     status_t initDefaultRequests();
     status_t fillCaptureResult(common::V1_0::helper::CameraMetadata& md, nsecs_t timestamp);
@@ -195,10 +202,28 @@
     bool isSupported(const Stream&);
 
     // Validate and import request's output buffers and acquire fence
-    Status importRequest(
+    virtual Status importRequestLocked(
             const CaptureRequest& request,
             hidl_vec<buffer_handle_t*>& allBufPtrs,
             hidl_vec<int>& allFences);
+
+    Status importRequestLockedImpl(
+            const CaptureRequest& request,
+            hidl_vec<buffer_handle_t*>& allBufPtrs,
+            hidl_vec<int>& allFences,
+            // Optional argument for ICameraDeviceSession@3.5 impl
+            bool allowEmptyBuf = false);
+
+    Status importBuffer(int32_t streamId,
+            uint64_t bufId, buffer_handle_t buf,
+            /*out*/buffer_handle_t** outBufPtr,
+            bool allowEmptyBuf);
+
+    Status importBufferLocked(int32_t streamId,
+            uint64_t bufId, buffer_handle_t buf,
+            /*out*/buffer_handle_t** outBufPtr,
+            bool allowEmptyBuf);
+
     static void cleanupInflightFences(
             hidl_vec<int>& allFences, size_t numFences);
     void cleanupBuffersLocked(int id);
@@ -224,7 +249,7 @@
     class OutputThread : public android::Thread {
     public:
         OutputThread(wp<ExternalCameraDeviceSession> parent, CroppingType);
-        ~OutputThread();
+        virtual ~OutputThread();
 
         Status allocateIntermediateBuffers(
                 const Size& v4lSize, const Size& thumbSize,
@@ -236,7 +261,14 @@
         virtual bool threadLoop() override;
 
         void setExifMakeModel(const std::string& make, const std::string& model);
-    private:
+
+    protected:
+        // Methods to request output buffer in parallel
+        // No-op for device@3.4. Implemented in device@3.5
+        virtual int requestBufferStart(const std::vector<HalStreamBuffer>&) { return 0; }
+        virtual int waitForBufferRequestDone(
+                /*out*/std::vector<HalStreamBuffer>*) { return 0; }
+
         static const uint32_t FLEX_YUV_GENERIC = static_cast<uint32_t>('F') |
                 static_cast<uint32_t>('L') << 8 | static_cast<uint32_t>('E') << 16 |
                 static_cast<uint32_t>('X') << 24;
@@ -319,6 +351,7 @@
     //    - init failed
     //    - camera disconnected
     bool mClosed = false;
+    bool mInitialized = false;
     bool mInitFail = false;
     bool mFirstRequest = false;
     common::V1_0::helper::CameraMetadata mLatestReqSetting;
@@ -351,6 +384,8 @@
     typedef std::unordered_map<uint64_t, buffer_handle_t> CirculatingBuffers;
     // Stream ID -> circulating buffers map
     std::map<int, CirculatingBuffers> mCirculatingBuffers;
+    // Protect mCirculatingBuffers, must not lock mLock after acquiring this lock
+    mutable Mutex mCbsLock;
 
     std::mutex mAfTriggerLock; // protect mAfTrigger
     bool mAfTrigger = false;
diff --git a/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDevice_3_4.h b/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDevice_3_4.h
index ff0cfb3..719a3ed 100644
--- a/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDevice_3_4.h
+++ b/camera/device/3.4/default/include/ext_device_v3_4_impl/ExternalCameraDevice_3_4.h
@@ -25,6 +25,8 @@
 #include <hidl/MQDescriptor.h>
 #include "ExternalCameraDeviceSession.h"
 
+#include <vector>
+
 namespace android {
 namespace hardware {
 namespace camera {
@@ -49,7 +51,7 @@
 /*
  * The camera device HAL implementation is opened lazily (via the open call)
  */
-struct ExternalCameraDevice : public ICameraDevice {
+struct ExternalCameraDevice : public virtual RefBase {
 
     // Called by external camera provider HAL.
     // Provider HAL must ensure the uniqueness of CameraDevice object per cameraId, or there could
@@ -57,33 +59,54 @@
     // to keep track of all CameraDevice objects in order to notify CameraDevice when the underlying
     // camera is detached.
     ExternalCameraDevice(const std::string& cameraId, const ExternalCameraConfig& cfg);
-    ~ExternalCameraDevice();
+    virtual ~ExternalCameraDevice();
+
+    // Retrieve the HIDL interface, split into its own class to avoid inheritance issues when
+    // dealing with minor version revs and simultaneous implementation and interface inheritance
+    virtual sp<ICameraDevice> getInterface() {
+        return new TrampolineDeviceInterface_3_4(this);
+    }
 
     // Caller must use this method to check if CameraDevice ctor failed
     bool isInitFailed();
+    bool isInitFailedLocked();
 
     /* Methods from ::android::hardware::camera::device::V3_2::ICameraDevice follow. */
     // The following method can be called without opening the actual camera device
-    Return<void> getResourceCost(getResourceCost_cb _hidl_cb) override;
+    Return<void> getResourceCost(ICameraDevice::getResourceCost_cb _hidl_cb);
 
-    Return<void> getCameraCharacteristics(getCameraCharacteristics_cb _hidl_cb) override;
+    Return<void> getCameraCharacteristics(
+            ICameraDevice::getCameraCharacteristics_cb _hidl_cb);
 
-    Return<Status> setTorchMode(TorchMode) override;
+    Return<Status> setTorchMode(TorchMode);
 
     // Open the device HAL and also return a default capture session
-    Return<void> open(const sp<ICameraDeviceCallback>&, open_cb) override;
+    Return<void> open(const sp<ICameraDeviceCallback>&, ICameraDevice::open_cb);
 
     // Forward the dump call to the opened session, or do nothing
-    Return<void> dumpState(const ::android::hardware::hidl_handle&) override;
+    Return<void> dumpState(const ::android::hardware::hidl_handle&);
     /* End of Methods from ::android::hardware::camera::device::V3_2::ICameraDevice */
 
 protected:
+    // Overridden by child implementations for returning different versions of
+    // ExternalCameraDeviceSession
+    virtual sp<ExternalCameraDeviceSession> createSession(
+            const sp<ICameraDeviceCallback>&,
+            const ExternalCameraConfig& cfg,
+            const std::vector<SupportedV4L2Format>& sortedFormats,
+            const CroppingType& croppingType,
+            const common::V1_0::helper::CameraMetadata& chars,
+            const std::string& cameraId,
+            unique_fd v4l2Fd);
+
     // Init supported w/h/format/fps in mSupportedFormats. Caller still owns fd
     void initSupportedFormatsLocked(int fd);
 
+    // Calls into virtual member function. Do not use it in constructor
     status_t initCameraCharacteristics();
     // Init non-device dependent keys
-    status_t initDefaultCharsKeys(::android::hardware::camera::common::V1_0::helper::CameraMetadata*);
+    virtual status_t initDefaultCharsKeys(
+            ::android::hardware::camera::common::V1_0::helper::CameraMetadata*);
     // Init camera control chars keys. Caller still owns fd
     status_t initCameraControlsCharsKeys(int fd,
             ::android::hardware::camera::common::V1_0::helper::CameraMetadata*);
@@ -103,6 +126,7 @@
             /*inout*/std::vector<SupportedV4L2Format>* pFmts);
 
     Mutex mLock;
+    bool mInitialized = false;
     bool mInitFailed = false;
     std::string mCameraId;
     const ExternalCameraConfig& mCfg;
@@ -112,6 +136,84 @@
     wp<ExternalCameraDeviceSession> mSession = nullptr;
 
     ::android::hardware::camera::common::V1_0::helper::CameraMetadata mCameraCharacteristics;
+
+    const std::vector<int32_t> AVAILABLE_CHARACTERISTICS_KEYS_3_4 = {
+        ANDROID_COLOR_CORRECTION_AVAILABLE_ABERRATION_MODES,
+        ANDROID_CONTROL_AE_AVAILABLE_ANTIBANDING_MODES,
+        ANDROID_CONTROL_AE_AVAILABLE_MODES,
+        ANDROID_CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES,
+        ANDROID_CONTROL_AE_COMPENSATION_RANGE,
+        ANDROID_CONTROL_AE_COMPENSATION_STEP,
+        ANDROID_CONTROL_AE_LOCK_AVAILABLE,
+        ANDROID_CONTROL_AF_AVAILABLE_MODES,
+        ANDROID_CONTROL_AVAILABLE_EFFECTS,
+        ANDROID_CONTROL_AVAILABLE_MODES,
+        ANDROID_CONTROL_AVAILABLE_SCENE_MODES,
+        ANDROID_CONTROL_AVAILABLE_VIDEO_STABILIZATION_MODES,
+        ANDROID_CONTROL_AWB_AVAILABLE_MODES,
+        ANDROID_CONTROL_AWB_LOCK_AVAILABLE,
+        ANDROID_CONTROL_MAX_REGIONS,
+        ANDROID_FLASH_INFO_AVAILABLE,
+        ANDROID_INFO_SUPPORTED_HARDWARE_LEVEL,
+        ANDROID_JPEG_AVAILABLE_THUMBNAIL_SIZES,
+        ANDROID_LENS_FACING,
+        ANDROID_LENS_INFO_AVAILABLE_OPTICAL_STABILIZATION,
+        ANDROID_LENS_INFO_FOCUS_DISTANCE_CALIBRATION,
+        ANDROID_NOISE_REDUCTION_AVAILABLE_NOISE_REDUCTION_MODES,
+        ANDROID_REQUEST_AVAILABLE_CAPABILITIES,
+        ANDROID_REQUEST_MAX_NUM_INPUT_STREAMS,
+        ANDROID_REQUEST_MAX_NUM_OUTPUT_STREAMS,
+        ANDROID_REQUEST_PARTIAL_RESULT_COUNT,
+        ANDROID_REQUEST_PIPELINE_MAX_DEPTH,
+        ANDROID_SCALER_AVAILABLE_MAX_DIGITAL_ZOOM,
+        ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS,
+        ANDROID_SCALER_CROPPING_TYPE,
+        ANDROID_SENSOR_INFO_ACTIVE_ARRAY_SIZE,
+        ANDROID_SENSOR_INFO_MAX_FRAME_DURATION,
+        ANDROID_SENSOR_INFO_PIXEL_ARRAY_SIZE,
+        ANDROID_SENSOR_INFO_PRE_CORRECTION_ACTIVE_ARRAY_SIZE,
+        ANDROID_SENSOR_INFO_TIMESTAMP_SOURCE,
+        ANDROID_SENSOR_ORIENTATION,
+        ANDROID_SHADING_AVAILABLE_MODES,
+        ANDROID_STATISTICS_INFO_AVAILABLE_FACE_DETECT_MODES,
+        ANDROID_STATISTICS_INFO_AVAILABLE_HOT_PIXEL_MAP_MODES,
+        ANDROID_STATISTICS_INFO_AVAILABLE_LENS_SHADING_MAP_MODES,
+        ANDROID_STATISTICS_INFO_MAX_FACE_COUNT,
+        ANDROID_SYNC_MAX_LATENCY};
+
+private:
+
+    struct TrampolineDeviceInterface_3_4 : public ICameraDevice {
+        TrampolineDeviceInterface_3_4(sp<ExternalCameraDevice> parent) :
+            mParent(parent) {}
+
+        virtual Return<void> getResourceCost(V3_2::ICameraDevice::getResourceCost_cb _hidl_cb)
+                override {
+            return mParent->getResourceCost(_hidl_cb);
+        }
+
+        virtual Return<void> getCameraCharacteristics(
+                V3_2::ICameraDevice::getCameraCharacteristics_cb _hidl_cb) override {
+            return mParent->getCameraCharacteristics(_hidl_cb);
+        }
+
+        virtual Return<Status> setTorchMode(TorchMode mode) override {
+            return mParent->setTorchMode(mode);
+        }
+
+        virtual Return<void> open(const sp<V3_2::ICameraDeviceCallback>& callback,
+                V3_2::ICameraDevice::open_cb _hidl_cb) override {
+            return mParent->open(callback, _hidl_cb);
+        }
+
+        virtual Return<void> dumpState(const hidl_handle& fd) override {
+            return mParent->dumpState(fd);
+        }
+
+    private:
+        sp<ExternalCameraDevice> mParent;
+    };
+
 };
 
 }  // namespace implementation
diff --git a/camera/device/3.5/default/Android.bp b/camera/device/3.5/default/Android.bp
index 09cf3a4..7a48865 100644
--- a/camera/device/3.5/default/Android.bp
+++ b/camera/device/3.5/default/Android.bp
@@ -20,6 +20,12 @@
     export_include_dirs: ["include/device_v3_5_impl"]
 }
 
+cc_library_headers {
+    name: "camera.device@3.5-external-impl_headers",
+    vendor: true,
+    export_include_dirs: ["include/ext_device_v3_5_impl"]
+}
+
 cc_library_shared {
     name: "camera.device@3.5-impl",
     defaults: ["hidl_defaults"],
@@ -52,3 +58,45 @@
     ],
     local_include_dirs: ["include/device_v3_5_impl"],
 }
+
+cc_library_shared {
+    name: "camera.device@3.5-external-impl",
+    defaults: ["hidl_defaults"],
+    proprietary: true,
+    vendor: true,
+    srcs: [
+        "ExternalCameraDevice.cpp",
+        "ExternalCameraDeviceSession.cpp",
+    ],
+    shared_libs: [
+        "libhidlbase",
+        "libhidltransport",
+        "libutils",
+        "libcutils",
+        "camera.device@3.2-impl",
+        "camera.device@3.3-impl",
+        "camera.device@3.4-external-impl",
+        "android.hardware.camera.device@3.2",
+        "android.hardware.camera.device@3.3",
+        "android.hardware.camera.device@3.4",
+        "android.hardware.camera.device@3.5",
+        "android.hardware.camera.provider@2.4",
+        "android.hardware.graphics.mapper@2.0",
+        "liblog",
+        "libhardware",
+        "libcamera_metadata",
+        "libfmq",
+        "libsync",
+        "libyuv",
+        "libjpeg",
+        "libexif",
+        "libtinyxml2"
+    ],
+    static_libs: [
+        "android.hardware.camera.common@1.0-helper",
+    ],
+    local_include_dirs: ["include/ext_device_v3_5_impl"],
+    export_shared_lib_headers: [
+        "libfmq",
+    ],
+}
diff --git a/camera/device/3.5/default/ExternalCameraDevice.cpp b/camera/device/3.5/default/ExternalCameraDevice.cpp
new file mode 100644
index 0000000..e8d14b5
--- /dev/null
+++ b/camera/device/3.5/default/ExternalCameraDevice.cpp
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "ExtCamDev@3.5"
+//#define LOG_NDEBUG 0
+#include <log/log.h>
+
+#include "ExternalCameraDevice_3_5.h"
+
+namespace android {
+namespace hardware {
+namespace camera {
+namespace device {
+namespace V3_5 {
+namespace implementation {
+
+ExternalCameraDevice::ExternalCameraDevice(
+        const std::string& cameraId, const ExternalCameraConfig& cfg) :
+        V3_4::implementation::ExternalCameraDevice(cameraId, cfg) {}
+
+ExternalCameraDevice::~ExternalCameraDevice() {}
+
+Return<void> ExternalCameraDevice::getPhysicalCameraCharacteristics(const hidl_string&,
+        V3_5::ICameraDevice::getPhysicalCameraCharacteristics_cb _hidl_cb) {
+    CameraMetadata cameraCharacteristics;
+    // External camera HAL doesn't support physical camera functions
+    _hidl_cb(Status::ILLEGAL_ARGUMENT, cameraCharacteristics);
+    return Void();
+}
+
+sp<V3_4::implementation::ExternalCameraDeviceSession> ExternalCameraDevice::createSession(
+        const sp<V3_2::ICameraDeviceCallback>& cb,
+        const ExternalCameraConfig& cfg,
+        const std::vector<SupportedV4L2Format>& sortedFormats,
+        const CroppingType& croppingType,
+        const common::V1_0::helper::CameraMetadata& chars,
+        const std::string& cameraId,
+        unique_fd v4l2Fd) {
+    return new ExternalCameraDeviceSession(
+            cb, cfg, sortedFormats, croppingType, chars, cameraId, std::move(v4l2Fd));
+}
+
+#define UPDATE(tag, data, size)                    \
+do {                                               \
+  if (metadata->update((tag), (data), (size))) {   \
+    ALOGE("Update " #tag " failed!");              \
+    return -EINVAL;                                \
+  }                                                \
+} while (0)
+
+status_t ExternalCameraDevice::initDefaultCharsKeys(
+        ::android::hardware::camera::common::V1_0::helper::CameraMetadata* metadata) {
+    status_t res =
+            V3_4::implementation::ExternalCameraDevice::initDefaultCharsKeys(metadata);
+
+    if (res != OK) {
+        return res;
+    }
+
+    const uint8_t bufMgrVer = ANDROID_INFO_SUPPORTED_BUFFER_MANAGEMENT_VERSION_HIDL_DEVICE_3_5;
+    UPDATE(ANDROID_INFO_SUPPORTED_BUFFER_MANAGEMENT_VERSION, &bufMgrVer, 1);
+
+    std::vector<int> availableCharacteristicsKeys = AVAILABLE_CHARACTERISTICS_KEYS_3_4;
+    availableCharacteristicsKeys.reserve(availableCharacteristicsKeys.size() +
+            EXTRA_CHARACTERISTICS_KEYS_3_5.size());
+    for (const auto& key : EXTRA_CHARACTERISTICS_KEYS_3_5) {
+        availableCharacteristicsKeys.push_back(key);
+    }
+    UPDATE(ANDROID_REQUEST_AVAILABLE_CHARACTERISTICS_KEYS,
+           availableCharacteristicsKeys.data(),
+           availableCharacteristicsKeys.size());
+
+    return OK;
+}
+
+#undef UPDATE
+
+}  // namespace implementation
+}  // namespace V3_5
+}  // namespace device
+}  // namespace camera
+}  // namespace hardware
+}  // namespace android
+
diff --git a/camera/device/3.5/default/ExternalCameraDeviceSession.cpp b/camera/device/3.5/default/ExternalCameraDeviceSession.cpp
new file mode 100644
index 0000000..ae7c45e
--- /dev/null
+++ b/camera/device/3.5/default/ExternalCameraDeviceSession.cpp
@@ -0,0 +1,303 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "ExtCamDevSsn@3.5"
+#include <android/log.h>
+
+#include <utils/Trace.h>
+#include "ExternalCameraDeviceSession.h"
+
+namespace android {
+namespace hardware {
+namespace camera {
+namespace device {
+namespace V3_5 {
+namespace implementation {
+
+ExternalCameraDeviceSession::ExternalCameraDeviceSession(
+        const sp<V3_2::ICameraDeviceCallback>& callback,
+        const ExternalCameraConfig& cfg,
+        const std::vector<SupportedV4L2Format>& sortedFormats,
+        const CroppingType& croppingType,
+        const common::V1_0::helper::CameraMetadata& chars,
+        const std::string& cameraId,
+        unique_fd v4l2Fd) :
+        V3_4::implementation::ExternalCameraDeviceSession(
+                callback, cfg, sortedFormats, croppingType, chars, cameraId, std::move(v4l2Fd)) {
+
+    mCallback_3_5 = nullptr;
+
+    auto castResult = V3_5::ICameraDeviceCallback::castFrom(callback);
+    if (castResult.isOk()) {
+        sp<V3_5::ICameraDeviceCallback> callback3_5 = castResult;
+        if (callback3_5 != nullptr) {
+            mCallback_3_5 = callback3_5;
+        }
+    }
+
+    if (mCallback_3_5 != nullptr) {
+        mSupportBufMgr = true;
+    }
+}
+
+ExternalCameraDeviceSession::~ExternalCameraDeviceSession() {
+    closeOutputThreadImpl();
+}
+
+Return<void> ExternalCameraDeviceSession::configureStreams_3_5(
+        const StreamConfiguration& requestedConfiguration,
+        ICameraDeviceSession::configureStreams_3_5_cb _hidl_cb)  {
+    return configureStreams_3_4(requestedConfiguration.v3_4, _hidl_cb);
+}
+
+Return<void> ExternalCameraDeviceSession::signalStreamFlush(
+        const hidl_vec<int32_t>& /*streamIds*/, uint32_t /*streamConfigCounter*/) {
+    return Void();
+}
+
+Status ExternalCameraDeviceSession::importRequestLocked(
+        const CaptureRequest& request,
+        hidl_vec<buffer_handle_t*>& allBufPtrs,
+        hidl_vec<int>& allFences) {
+    if (mSupportBufMgr) {
+        return importRequestLockedImpl(request, allBufPtrs, allFences, /*allowEmptyBuf*/ true);
+    }
+    return importRequestLockedImpl(request, allBufPtrs, allFences, /*allowEmptyBuf*/ false);
+}
+
+
+ExternalCameraDeviceSession::BufferRequestThread::BufferRequestThread(
+        wp<ExternalCameraDeviceSession> parent,
+        sp<V3_5::ICameraDeviceCallback> callbacks) :
+        mParent(parent),
+        mCallbacks(callbacks) {}
+
+int ExternalCameraDeviceSession::BufferRequestThread::requestBufferStart(
+        const std::vector<HalStreamBuffer>& bufReqs) {
+    if (bufReqs.empty()) {
+        ALOGE("%s: bufReqs is empty!", __FUNCTION__);
+        return -1;
+    }
+
+    {
+        std::lock_guard<std::mutex> lk(mLock);
+        if (mRequestingBuffer) {
+            ALOGE("%s: BufferRequestThread does not support more than one concurrent request!",
+                    __FUNCTION__);
+            return -1;
+        }
+
+        mBufferReqs = bufReqs;
+        mRequestingBuffer = true;
+    }
+    mRequestCond.notify_one();
+    return 0;
+}
+
+int ExternalCameraDeviceSession::BufferRequestThread::waitForBufferRequestDone(
+        std::vector<HalStreamBuffer>* outBufReq) {
+    std::unique_lock<std::mutex> lk(mLock);
+    if (!mRequestingBuffer) {
+        ALOGE("%s: no pending buffer request!", __FUNCTION__);
+        return -1;
+    }
+
+    if (mPendingReturnBufferReqs.empty()) {
+        std::chrono::milliseconds timeout = std::chrono::milliseconds(kReqProcTimeoutMs);
+        auto st = mRequestDoneCond.wait_for(lk, timeout);
+        if (st == std::cv_status::timeout) {
+            ALOGE("%s: wait for buffer request finish timeout!", __FUNCTION__);
+            return -1;
+        }
+    }
+    mRequestingBuffer = false;
+    *outBufReq = std::move(mPendingReturnBufferReqs);
+    mPendingReturnBufferReqs.clear();
+    return 0;
+}
+
+void ExternalCameraDeviceSession::BufferRequestThread::waitForNextRequest() {
+    ATRACE_CALL();
+    std::unique_lock<std::mutex> lk(mLock);
+    int waitTimes = 0;
+    while (mBufferReqs.empty()) {
+        if (exitPending()) {
+            return;
+        }
+        std::chrono::milliseconds timeout = std::chrono::milliseconds(kReqWaitTimeoutMs);
+        auto st = mRequestCond.wait_for(lk, timeout);
+        if (st == std::cv_status::timeout) {
+            waitTimes++;
+            if (waitTimes == kReqWaitTimesWarn) {
+                // BufferRequestThread just wait forever for new buffer request
+                // But it will print some periodic warning indicating it's waiting
+                ALOGV("%s: still waiting for new buffer request", __FUNCTION__);
+                waitTimes = 0;
+            }
+        }
+    }
+
+    // Fill in hidl BufferRequest
+    mHalBufferReqs.resize(mBufferReqs.size());
+    for (size_t i = 0; i < mHalBufferReqs.size(); i++) {
+        mHalBufferReqs[i].streamId = mBufferReqs[i].streamId;
+        mHalBufferReqs[i].numBuffersRequested = 1;
+    }
+}
+
+bool ExternalCameraDeviceSession::BufferRequestThread::threadLoop() {
+    waitForNextRequest();
+    if (exitPending()) {
+        return false;
+    }
+
+    ATRACE_BEGIN("HIDL requestStreamBuffers");
+    BufferRequestStatus status;
+    hidl_vec<StreamBufferRet> bufRets;
+    auto err = mCallbacks->requestStreamBuffers(mHalBufferReqs,
+            [&status, &bufRets]
+            (BufferRequestStatus s, const hidl_vec<StreamBufferRet>& rets) {
+                status = s;
+                bufRets = std::move(rets);
+            });
+    ATRACE_END();
+    if (!err.isOk()) {
+        ALOGE("%s: Transaction error: %s", __FUNCTION__, err.description().c_str());
+        return false;
+    }
+
+    std::unique_lock<std::mutex> lk(mLock);
+    if (status == BufferRequestStatus::OK || status == BufferRequestStatus::FAILED_PARTIAL) {
+        if (bufRets.size() != mHalBufferReqs.size()) {
+            ALOGE("%s: expect %zu buffer requests returned, only got %zu",
+                    __FUNCTION__, mHalBufferReqs.size(), bufRets.size());
+            return false;
+        }
+
+        auto parent = mParent.promote();
+        if (parent == nullptr) {
+            ALOGE("%s: session has been disconnected!", __FUNCTION__);
+            return false;
+        }
+
+        hidl_vec<int> importedFences;
+        importedFences.resize(bufRets.size());
+        for (size_t i = 0; i < bufRets.size(); i++) {
+            int streamId = bufRets[i].streamId;
+            switch (bufRets[i].val.getDiscriminator()) {
+                case StreamBuffersVal::hidl_discriminator::error:
+                    continue;
+                case StreamBuffersVal::hidl_discriminator::buffers: {
+                    const hidl_vec<V3_2::StreamBuffer>& hBufs = bufRets[i].val.buffers();
+                    if (hBufs.size() != 1) {
+                        ALOGE("%s: expect 1 buffer returned, got %zu!", __FUNCTION__, hBufs.size());
+                        return false;
+                    }
+                    const V3_2::StreamBuffer& hBuf = hBufs[0];
+
+                    mBufferReqs[i].bufferId = hBuf.bufferId;
+                    // TODO: create a batch import API so we don't need to lock/unlock mCbsLock
+                    // repeatedly?
+                    lk.unlock();
+                    Status s = parent->importBuffer(streamId,
+                            hBuf.bufferId, hBuf.buffer.getNativeHandle(),
+                            /*out*/&mBufferReqs[i].bufPtr,
+                            /*allowEmptyBuf*/false);
+                    lk.lock();
+
+                    if (s != Status::OK) {
+                        ALOGE("%s: stream %d import buffer failed!", __FUNCTION__, streamId);
+                        cleanupInflightFences(importedFences, i - 1);
+                        return false;
+                    }
+                    if (!sHandleImporter.importFence(hBuf.acquireFence,
+                            mBufferReqs[i].acquireFence)) {
+                        ALOGE("%s: stream %d import fence failed!", __FUNCTION__, streamId);
+                        cleanupInflightFences(importedFences, i - 1);
+                        return false;
+                    }
+                    importedFences[i] = mBufferReqs[i].acquireFence;
+                }
+                break;
+                default:
+                    ALOGE("%s: unkown StreamBuffersVal discrimator!", __FUNCTION__);
+                    return false;
+            }
+        }
+    } else {
+        ALOGE("%s: requestStreamBuffers call failed!", __FUNCTION__);
+    }
+
+    mPendingReturnBufferReqs = std::move(mBufferReqs);
+    mBufferReqs.clear();
+
+    lk.unlock();
+    mRequestDoneCond.notify_one();
+    return true;
+}
+
+void ExternalCameraDeviceSession::initOutputThread() {
+    if (mSupportBufMgr) {
+        mBufferRequestThread = new BufferRequestThread(this, mCallback_3_5);
+        mBufferRequestThread->run("ExtCamBufReq", PRIORITY_DISPLAY);
+    }
+    mOutputThread = new OutputThread(this, mCroppingType, mBufferRequestThread);
+}
+
+void ExternalCameraDeviceSession::closeOutputThreadImpl() {
+    if (mBufferRequestThread) {
+        mBufferRequestThread->requestExit();
+        mBufferRequestThread->join();
+        mBufferRequestThread.clear();
+    }
+}
+
+void ExternalCameraDeviceSession::closeOutputThread() {
+    closeOutputThreadImpl();
+    V3_4::implementation::ExternalCameraDeviceSession::closeOutputThread();
+}
+
+ExternalCameraDeviceSession::OutputThread::OutputThread(
+        wp<ExternalCameraDeviceSession> parent,
+        CroppingType ct,
+        sp<BufferRequestThread> bufReqThread) :
+        V3_4::implementation::ExternalCameraDeviceSession::OutputThread(parent, ct),
+        mBufferRequestThread(bufReqThread) {}
+
+ExternalCameraDeviceSession::OutputThread::~OutputThread() {}
+
+int ExternalCameraDeviceSession::OutputThread::requestBufferStart(
+        const std::vector<HalStreamBuffer>& bufs) {
+    if (mBufferRequestThread != nullptr) {
+        return mBufferRequestThread->requestBufferStart(bufs);
+    }
+    return 0;
+}
+
+int ExternalCameraDeviceSession::OutputThread::waitForBufferRequestDone(
+        /*out*/std::vector<HalStreamBuffer>* outBufs) {
+    if (mBufferRequestThread != nullptr) {
+        return mBufferRequestThread->waitForBufferRequestDone(outBufs);
+    }
+    return 0;
+}
+
+} // namespace implementation
+}  // namespace V3_5
+}  // namespace device
+}  // namespace camera
+}  // namespace hardware
+}  // namespace android
diff --git a/camera/device/3.5/default/include/ext_device_v3_5_impl/ExternalCameraDeviceSession.h b/camera/device/3.5/default/include/ext_device_v3_5_impl/ExternalCameraDeviceSession.h
new file mode 100644
index 0000000..4d2d6b7
--- /dev/null
+++ b/camera/device/3.5/default/include/ext_device_v3_5_impl/ExternalCameraDeviceSession.h
@@ -0,0 +1,256 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_HARDWARE_CAMERA_DEVICE_V3_5_EXTCAMERADEVICE3SESSION_H
+#define ANDROID_HARDWARE_CAMERA_DEVICE_V3_5_EXTCAMERADEVICE3SESSION_H
+
+#include <android/hardware/camera/device/3.5/ICameraDeviceCallback.h>
+#include <android/hardware/camera/device/3.5/ICameraDeviceSession.h>
+#include <../../3.4/default/include/ext_device_v3_4_impl/ExternalCameraDeviceSession.h>
+
+namespace android {
+namespace hardware {
+namespace camera {
+namespace device {
+namespace V3_5 {
+namespace implementation {
+
+using ::android::hardware::camera::device::V3_2::BufferCache;
+using ::android::hardware::camera::device::V3_5::BufferRequest;
+using ::android::hardware::camera::device::V3_5::BufferRequestStatus;
+using ::android::hardware::camera::device::V3_2::BufferStatus;
+using ::android::hardware::camera::device::V3_2::CameraMetadata;
+using ::android::hardware::camera::device::V3_2::CaptureRequest;
+using ::android::hardware::camera::device::V3_2::CaptureResult;
+using ::android::hardware::camera::device::V3_2::ErrorCode;
+using ::android::hardware::camera::device::V3_5::ICameraDeviceCallback;
+using ::android::hardware::camera::device::V3_2::MsgType;
+using ::android::hardware::camera::device::V3_2::NotifyMsg;
+using ::android::hardware::camera::device::V3_2::RequestTemplate;
+using ::android::hardware::camera::device::V3_2::Stream;
+using ::android::hardware::camera::device::V3_5::StreamConfiguration;
+using ::android::hardware::camera::device::V3_2::StreamConfigurationMode;
+using ::android::hardware::camera::device::V3_2::StreamRotation;
+using ::android::hardware::camera::device::V3_2::StreamType;
+using ::android::hardware::camera::device::V3_2::DataspaceFlags;
+using ::android::hardware::camera::device::V3_2::CameraBlob;
+using ::android::hardware::camera::device::V3_2::CameraBlobId;
+using ::android::hardware::camera::device::V3_4::HalStreamConfiguration;
+using ::android::hardware::camera::device::V3_5::ICameraDeviceSession;
+using ::android::hardware::camera::common::V1_0::Status;
+using ::android::hardware::camera::common::V1_0::helper::HandleImporter;
+using ::android::hardware::camera::common::V1_0::helper::ExifUtils;
+using ::android::hardware::camera::external::common::ExternalCameraConfig;
+using ::android::hardware::camera::external::common::Size;
+using ::android::hardware::camera::external::common::SizeHasher;
+using ::android::hardware::graphics::common::V1_0::BufferUsage;
+using ::android::hardware::graphics::common::V1_0::Dataspace;
+using ::android::hardware::graphics::common::V1_0::PixelFormat;
+using ::android::hardware::kSynchronizedReadWrite;
+using ::android::hardware::MessageQueue;
+using ::android::hardware::MQDescriptorSync;
+using ::android::hardware::Return;
+using ::android::hardware::Void;
+using ::android::hardware::hidl_vec;
+using ::android::hardware::hidl_string;
+using ::android::sp;
+using ::android::Mutex;
+using ::android::base::unique_fd;
+
+using ::android::hardware::camera::device::V3_4::implementation::SupportedV4L2Format;
+using ::android::hardware::camera::device::V3_4::implementation::CroppingType;
+
+struct ExternalCameraDeviceSession : public V3_4::implementation::ExternalCameraDeviceSession {
+
+    ExternalCameraDeviceSession(const sp<V3_2::ICameraDeviceCallback>&,
+            const ExternalCameraConfig& cfg,
+            const std::vector<SupportedV4L2Format>& sortedFormats,
+            const CroppingType& croppingType,
+            const common::V1_0::helper::CameraMetadata& chars,
+            const std::string& cameraId,
+            unique_fd v4l2Fd);
+    virtual ~ExternalCameraDeviceSession();
+
+    // Retrieve the HIDL interface, split into its own class to avoid inheritance issues when
+    // dealing with minor version revs and simultaneous implementation and interface inheritance
+    virtual sp<V3_4::ICameraDeviceSession> getInterface() override {
+        return new TrampolineSessionInterface_3_5(this);
+    }
+
+protected:
+    // Methods from v3.4 and earlier will trampoline to inherited implementation
+    Return<void> configureStreams_3_5(
+            const StreamConfiguration& requestedConfiguration,
+            ICameraDeviceSession::configureStreams_3_5_cb _hidl_cb);
+
+    Return<void> signalStreamFlush(
+            const hidl_vec<int32_t>& requests,
+            uint32_t streamConfigCounter);
+
+    virtual void initOutputThread() override;
+    virtual void closeOutputThread() override;
+    void closeOutputThreadImpl();
+
+    virtual Status importRequestLocked(
+            const CaptureRequest& request,
+            hidl_vec<buffer_handle_t*>& allBufPtrs,
+            hidl_vec<int>& allFences) override;
+
+    class BufferRequestThread : public android::Thread {
+    public:
+        BufferRequestThread(
+                wp<ExternalCameraDeviceSession> parent,
+                sp<V3_5::ICameraDeviceCallback> callbacks);
+
+        int requestBufferStart(const std::vector<HalStreamBuffer>&);
+        int waitForBufferRequestDone(
+                /*out*/std::vector<HalStreamBuffer>*);
+
+        virtual bool threadLoop() override;
+
+    private:
+        void waitForNextRequest();
+
+        const wp<ExternalCameraDeviceSession> mParent;
+        const sp<V3_5::ICameraDeviceCallback> mCallbacks;
+
+        std::mutex mLock;
+        bool mRequestingBuffer = false;
+
+        std::vector<HalStreamBuffer> mBufferReqs;
+        std::vector<HalStreamBuffer> mPendingReturnBufferReqs;
+        // mHalBufferReqs is not under mLock protection during the HIDL transaction
+        hidl_vec<BufferRequest>      mHalBufferReqs;
+
+        // request buffers takes much less time in steady state, but can take much longer
+        // when requesting 1st buffer from a stream.
+        // TODO: consider a separate timeout for new vs. steady state?
+        // TODO: or make sure framework is warming up the pipeline during configure new stream?
+        static const int kReqProcTimeoutMs = 66;
+
+        static const int kReqWaitTimeoutMs = 33;
+        static const int kReqWaitTimesWarn = 90;  // 33ms * 90 ~= 3 sec
+        std::condition_variable mRequestCond;     // signaled when a new buffer request incoming
+        std::condition_variable mRequestDoneCond; // signaled when a request is done
+    };
+
+    sp<BufferRequestThread> mBufferRequestThread;
+
+    class OutputThread :
+            public V3_4::implementation::ExternalCameraDeviceSession::OutputThread {
+    public:
+        // TODO: pass buffer request thread to OutputThread ctor
+        OutputThread(wp<ExternalCameraDeviceSession> parent, CroppingType,
+                sp<BufferRequestThread> bufReqThread);
+        virtual ~OutputThread();
+
+    protected:
+        // Methods to request output buffer in parallel
+        virtual int requestBufferStart(const std::vector<HalStreamBuffer>&) override;
+        virtual int waitForBufferRequestDone(
+                /*out*/std::vector<HalStreamBuffer>*) override;
+
+        const sp<BufferRequestThread> mBufferRequestThread;
+    };
+
+    sp<V3_5::ICameraDeviceCallback> mCallback_3_5;
+    bool mSupportBufMgr;
+
+private:
+
+    struct TrampolineSessionInterface_3_5 : public ICameraDeviceSession {
+        TrampolineSessionInterface_3_5(sp<ExternalCameraDeviceSession> parent) :
+                mParent(parent) {}
+
+        virtual Return<void> constructDefaultRequestSettings(
+                RequestTemplate type,
+                V3_3::ICameraDeviceSession::constructDefaultRequestSettings_cb _hidl_cb) override {
+            return mParent->constructDefaultRequestSettings(type, _hidl_cb);
+        }
+
+        virtual Return<void> configureStreams(
+                const V3_2::StreamConfiguration& requestedConfiguration,
+                V3_3::ICameraDeviceSession::configureStreams_cb _hidl_cb) override {
+            return mParent->configureStreams(requestedConfiguration, _hidl_cb);
+        }
+
+        virtual Return<void> processCaptureRequest(const hidl_vec<V3_2::CaptureRequest>& requests,
+                const hidl_vec<V3_2::BufferCache>& cachesToRemove,
+                V3_3::ICameraDeviceSession::processCaptureRequest_cb _hidl_cb) override {
+            return mParent->processCaptureRequest(requests, cachesToRemove, _hidl_cb);
+        }
+
+        virtual Return<void> getCaptureRequestMetadataQueue(
+                V3_3::ICameraDeviceSession::getCaptureRequestMetadataQueue_cb _hidl_cb) override  {
+            return mParent->getCaptureRequestMetadataQueue(_hidl_cb);
+        }
+
+        virtual Return<void> getCaptureResultMetadataQueue(
+                V3_3::ICameraDeviceSession::getCaptureResultMetadataQueue_cb _hidl_cb) override  {
+            return mParent->getCaptureResultMetadataQueue(_hidl_cb);
+        }
+
+        virtual Return<Status> flush() override {
+            return mParent->flush();
+        }
+
+        virtual Return<void> close() override {
+            return mParent->close();
+        }
+
+        virtual Return<void> configureStreams_3_3(
+                const V3_2::StreamConfiguration& requestedConfiguration,
+                configureStreams_3_3_cb _hidl_cb) override {
+            return mParent->configureStreams_3_3(requestedConfiguration, _hidl_cb);
+        }
+
+        virtual Return<void> configureStreams_3_4(
+                const V3_4::StreamConfiguration& requestedConfiguration,
+                configureStreams_3_4_cb _hidl_cb) override {
+            return mParent->configureStreams_3_4(requestedConfiguration, _hidl_cb);
+        }
+
+        virtual Return<void> processCaptureRequest_3_4(const hidl_vec<V3_4::CaptureRequest>& requests,
+                const hidl_vec<V3_2::BufferCache>& cachesToRemove,
+                ICameraDeviceSession::processCaptureRequest_3_4_cb _hidl_cb) override {
+            return mParent->processCaptureRequest_3_4(requests, cachesToRemove, _hidl_cb);
+        }
+
+        virtual Return<void> configureStreams_3_5(
+                const StreamConfiguration& requestedConfiguration,
+                configureStreams_3_5_cb _hidl_cb) override {
+            return mParent->configureStreams_3_5(requestedConfiguration, _hidl_cb);
+        }
+
+        virtual Return<void> signalStreamFlush(
+                const hidl_vec<int32_t>& requests,
+                uint32_t streamConfigCounter) override {
+            return mParent->signalStreamFlush(requests, streamConfigCounter);
+        }
+
+    private:
+        sp<ExternalCameraDeviceSession> mParent;
+    };
+};
+
+}  // namespace implementation
+}  // namespace V3_5
+}  // namespace device
+}  // namespace camera
+}  // namespace hardware
+}  // namespace android
+
+#endif  // ANDROID_HARDWARE_CAMERA_DEVICE_V3_5_EXTCAMERADEVICE3SESSION_H
diff --git a/camera/device/3.5/default/include/ext_device_v3_5_impl/ExternalCameraDevice_3_5.h b/camera/device/3.5/default/include/ext_device_v3_5_impl/ExternalCameraDevice_3_5.h
new file mode 100644
index 0000000..7db86dc
--- /dev/null
+++ b/camera/device/3.5/default/include/ext_device_v3_5_impl/ExternalCameraDevice_3_5.h
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_HARDWARE_CAMERA_DEVICE_V3_5_EXTCAMERADEVICE_H
+#define ANDROID_HARDWARE_CAMERA_DEVICE_V3_5_EXTCAMERADEVICE_H
+
+#include "utils/Mutex.h"
+#include "CameraMetadata.h"
+
+#include <android/hardware/camera/device/3.5/ICameraDevice.h>
+#include <android/hardware/camera/device/3.5/ICameraDeviceCallback.h>
+#include <hidl/Status.h>
+#include <hidl/MQDescriptor.h>
+#include "ExternalCameraDeviceSession.h"
+#include <../../../../3.4/default/include/ext_device_v3_4_impl/ExternalCameraDevice_3_4.h>
+
+namespace android {
+namespace hardware {
+namespace camera {
+namespace device {
+namespace V3_5 {
+namespace implementation {
+
+using namespace ::android::hardware::camera::device;
+using ::android::hardware::camera::device::V3_5::ICameraDevice;
+using ::android::hardware::camera::common::V1_0::CameraResourceCost;
+using ::android::hardware::camera::common::V1_0::TorchMode;
+using ::android::hardware::camera::common::V1_0::Status;
+using ::android::hardware::camera::external::common::ExternalCameraConfig;
+using ::android::hardware::camera::external::common::Size;
+using ::android::hardware::Return;
+using ::android::hardware::Void;
+using ::android::hardware::hidl_vec;
+using ::android::hardware::hidl_string;
+using ::android::sp;
+
+/*
+ * The camera device HAL implementation is opened lazily (via the open call)
+ */
+struct ExternalCameraDevice : public V3_4::implementation::ExternalCameraDevice {
+
+    // Called by external camera provider HAL.
+    // Provider HAL must ensure the uniqueness of CameraDevice object per cameraId, or there could
+    // be multiple CameraDevice trying to access the same physical camera.  Also, provider will have
+    // to keep track of all CameraDevice objects in order to notify CameraDevice when the underlying
+    // camera is detached.
+    ExternalCameraDevice(const std::string& cameraId, const ExternalCameraConfig& cfg);
+    virtual ~ExternalCameraDevice();
+
+    virtual sp<V3_2::ICameraDevice> getInterface() override {
+        return new TrampolineDeviceInterface_3_5(this);
+    }
+
+    Return<void> getPhysicalCameraCharacteristics(const hidl_string& physicalCameraId,
+            V3_5::ICameraDevice::getPhysicalCameraCharacteristics_cb _hidl_cb);
+
+protected:
+    virtual sp<V3_4::implementation::ExternalCameraDeviceSession> createSession(
+            const sp<V3_2::ICameraDeviceCallback>&,
+            const ExternalCameraConfig& cfg,
+            const std::vector<SupportedV4L2Format>& sortedFormats,
+            const CroppingType& croppingType,
+            const common::V1_0::helper::CameraMetadata& chars,
+            const std::string& cameraId,
+            unique_fd v4l2Fd) override;
+
+    virtual status_t initDefaultCharsKeys(
+            ::android::hardware::camera::common::V1_0::helper::CameraMetadata*) override;
+
+    const std::vector<int32_t> EXTRA_CHARACTERISTICS_KEYS_3_5 = {
+        ANDROID_INFO_SUPPORTED_BUFFER_MANAGEMENT_VERSION
+    };
+
+private:
+    struct TrampolineDeviceInterface_3_5 : public ICameraDevice {
+        TrampolineDeviceInterface_3_5(sp<ExternalCameraDevice> parent) :
+            mParent(parent) {}
+
+        virtual Return<void> getResourceCost(V3_2::ICameraDevice::getResourceCost_cb _hidl_cb)
+                override {
+            return mParent->getResourceCost(_hidl_cb);
+        }
+
+        virtual Return<void> getCameraCharacteristics(
+                V3_2::ICameraDevice::getCameraCharacteristics_cb _hidl_cb) override {
+            return mParent->getCameraCharacteristics(_hidl_cb);
+        }
+
+        virtual Return<Status> setTorchMode(TorchMode mode) override {
+            return mParent->setTorchMode(mode);
+        }
+
+        virtual Return<void> open(const sp<V3_2::ICameraDeviceCallback>& callback,
+                V3_2::ICameraDevice::open_cb _hidl_cb) override {
+            return mParent->open(callback, _hidl_cb);
+        }
+
+        virtual Return<void> dumpState(const hidl_handle& fd) override {
+            return mParent->dumpState(fd);
+        }
+
+        virtual Return<void> getPhysicalCameraCharacteristics(const hidl_string& physicalCameraId,
+                V3_5::ICameraDevice::getPhysicalCameraCharacteristics_cb _hidl_cb) override {
+            return mParent->getPhysicalCameraCharacteristics(physicalCameraId, _hidl_cb);
+        }
+    private:
+        sp<ExternalCameraDevice> mParent;
+    };
+};
+
+}  // namespace implementation
+}  // namespace V3_5
+}  // namespace device
+}  // namespace camera
+}  // namespace hardware
+}  // namespace android
+
+#endif  // ANDROID_HARDWARE_CAMERA_DEVICE_V3_5_EXTCAMERADEVICE_H
diff --git a/camera/provider/2.4/default/Android.bp b/camera/provider/2.4/default/Android.bp
index de02d78..167954c 100644
--- a/camera/provider/2.4/default/Android.bp
+++ b/camera/provider/2.4/default/Android.bp
@@ -21,6 +21,7 @@
         "camera.device@3.4-impl",
         "camera.device@3.5-impl",
         "camera.device@3.4-external-impl",
+        "camera.device@3.5-external-impl",
         "android.hardware.camera.provider@2.4",
         "android.hardware.camera.common@1.0",
         "android.hardware.graphics.mapper@2.0",
@@ -34,7 +35,8 @@
     header_libs: [
         "camera.device@3.4-impl_headers",
         "camera.device@3.5-impl_headers",
-        "camera.device@3.4-external-impl_headers"
+        "camera.device@3.4-external-impl_headers",
+        "camera.device@3.5-external-impl_headers"
     ],
     static_libs: [
         "android.hardware.camera.common@1.0-helper",
@@ -107,6 +109,8 @@
         "android.hardware.camera.device@1.0",
         "android.hardware.camera.device@3.2",
         "android.hardware.camera.device@3.3",
+        "android.hardware.camera.device@3.4",
+        "android.hardware.camera.device@3.5",
         "android.hardware.camera.provider@2.4",
         "android.hardware.camera.common@1.0",
     ],
diff --git a/camera/provider/2.4/default/ExternalCameraProvider.cpp b/camera/provider/2.4/default/ExternalCameraProvider.cpp
index 1cec0e5..604df5c 100644
--- a/camera/provider/2.4/default/ExternalCameraProvider.cpp
+++ b/camera/provider/2.4/default/ExternalCameraProvider.cpp
@@ -24,6 +24,8 @@
 #include <linux/videodev2.h>
 #include "ExternalCameraProvider.h"
 #include "ExternalCameraDevice_3_4.h"
+#include "ExternalCameraDevice_3_5.h"
+#include <cutils/properties.h>
 
 namespace android {
 namespace hardware {
@@ -62,6 +64,21 @@
         mCfg(ExternalCameraConfig::loadFromCfg()),
         mHotPlugThread(this) {
     mHotPlugThread.run("ExtCamHotPlug", PRIORITY_BACKGROUND);
+
+    mPreferredHal3MinorVersion =
+        property_get_int32("ro.vendor.camera.external.hal3TrebleMinorVersion", 4);
+    ALOGV("Preferred HAL 3 minor version is %d", mPreferredHal3MinorVersion);
+    switch(mPreferredHal3MinorVersion) {
+        case 4:
+        case 5:
+            // OK
+            break;
+        default:
+            ALOGW("Unknown minor camera device HAL version %d in property "
+                    "'camera.external.hal3TrebleMinorVersion', defaulting to 4",
+                    mPreferredHal3MinorVersion);
+            mPreferredHal3MinorVersion = 4;
+    }
 }
 
 ExternalCameraProvider::~ExternalCameraProvider() {
@@ -136,20 +153,43 @@
         return Void();
     }
 
-    ALOGV("Constructing v3.4 external camera device");
-    sp<device::V3_2::ICameraDevice> device;
-    sp<device::V3_4::implementation::ExternalCameraDevice> deviceImpl =
-            new device::V3_4::implementation::ExternalCameraDevice(
+    sp<device::V3_4::implementation::ExternalCameraDevice> deviceImpl;
+    switch (mPreferredHal3MinorVersion) {
+        case 4: {
+            ALOGV("Constructing v3.4 external camera device");
+            deviceImpl = new device::V3_4::implementation::ExternalCameraDevice(
                     cameraId, mCfg);
+            break;
+        }
+        case 5: {
+            ALOGV("Constructing v3.5 external camera device");
+            deviceImpl = new device::V3_5::implementation::ExternalCameraDevice(
+                    cameraId, mCfg);
+            break;
+        }
+        default:
+            ALOGE("%s: Unknown HAL minor version %d!", __FUNCTION__, mPreferredHal3MinorVersion);
+            _hidl_cb(Status::INTERNAL_ERROR, nullptr);
+            return Void();
+    }
+
     if (deviceImpl == nullptr || deviceImpl->isInitFailed()) {
         ALOGE("%s: camera device %s init failed!", __FUNCTION__, cameraId.c_str());
-        device = nullptr;
         _hidl_cb(Status::INTERNAL_ERROR, nullptr);
         return Void();
     }
-    device = deviceImpl;
 
-    _hidl_cb (Status::OK, device);
+    IF_ALOGV() {
+        deviceImpl->getInterface()->interfaceChain([](
+            ::android::hardware::hidl_vec<::android::hardware::hidl_string> interfaceChain) {
+                ALOGV("Device interface chain:");
+                for (auto iface : interfaceChain) {
+                    ALOGV("  %s", iface.c_str());
+                }
+            });
+    }
+
+    _hidl_cb (Status::OK, deviceImpl->getInterface());
 
     return Void();
 }
@@ -157,7 +197,12 @@
 void ExternalCameraProvider::addExternalCamera(const char* devName) {
     ALOGI("ExtCam: adding %s to External Camera HAL!", devName);
     Mutex::Autolock _l(mLock);
-    std::string deviceName = std::string("device@3.4/external/") + devName;
+    std::string deviceName;
+    if (mPreferredHal3MinorVersion == 5) {
+        deviceName = std::string("device@3.5/external/") + devName;
+    } else {
+        deviceName = std::string("device@3.4/external/") + devName;
+    }
     mCameraStatusMap[deviceName] = CameraDeviceStatus::PRESENT;
     if (mCallbacks != nullptr) {
         mCallbacks->cameraDeviceStatusChange(deviceName, CameraDeviceStatus::PRESENT);
@@ -199,7 +244,12 @@
 
 void ExternalCameraProvider::deviceRemoved(const char* devName) {
     Mutex::Autolock _l(mLock);
-    std::string deviceName = std::string("device@3.4/external/") + devName;
+    std::string deviceName;
+    if (mPreferredHal3MinorVersion == 5) {
+        deviceName = std::string("device@3.5/external/") + devName;
+    } else {
+        deviceName = std::string("device@3.4/external/") + devName;
+    }
     if (mCameraStatusMap.find(deviceName) != mCameraStatusMap.end()) {
         mCameraStatusMap.erase(deviceName);
         if (mCallbacks != nullptr) {
diff --git a/camera/provider/2.4/default/ExternalCameraProvider.h b/camera/provider/2.4/default/ExternalCameraProvider.h
index c83cc70..a69cf8b 100644
--- a/camera/provider/2.4/default/ExternalCameraProvider.h
+++ b/camera/provider/2.4/default/ExternalCameraProvider.h
@@ -95,6 +95,7 @@
     std::unordered_map<std::string, CameraDeviceStatus> mCameraStatusMap; // camera id -> status
     const ExternalCameraConfig mCfg;
     HotplugThread mHotPlugThread;
+    int mPreferredHal3MinorVersion;
 };