camera2 (v)ndk: Add APIs for pre-allocation of surface buffers.

Clients may need to pre-allocate stream buffers in order to reduce
affects of buffer-allocation time such as frame jank till steady state
capture is reached (eg: for a repeating request).
The SDK already has an api which does this :
CameraCaptureSession.prepare(Surface). We're exposing a similar API to
the ndk/ vndk here.

Bug: 259735869

Test: NdkCameraDeviceTest.java

Change-Id: Iee8559fcebd61a6886f23779a05351b52633f851
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>
diff --git a/camera/ndk/NdkCameraCaptureSession.cpp b/camera/ndk/NdkCameraCaptureSession.cpp
index 65b8837..8a3acf3 100644
--- a/camera/ndk/NdkCameraCaptureSession.cpp
+++ b/camera/ndk/NdkCameraCaptureSession.cpp
@@ -40,6 +40,7 @@
     if (session != nullptr) {
         session->closeByApp();
     }
+
     return;
 }
 
@@ -191,3 +192,42 @@
     }
     return session->updateOutputConfiguration(output);
 }
+EXPORT
+camera_status_t ACameraCaptureSession_setWindowPreparedCallback(
+        ACameraCaptureSession* session, ACameraCaptureSession_prepareCallbacks *cb) {
+    ATRACE_CALL();
+    if (session == nullptr || cb == nullptr) {
+        ALOGE("%s: Error: session %p / callback %p is null", __FUNCTION__, session, cb);
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+
+    if (cb->reserved0 != nullptr || cb->reserved1 != nullptr) {
+         ALOGE("%s: Setting reserved 0 and reserved 1 fields of "
+               "ACameraCaptureSession_prepareCallbacks is currently not supported "
+               " .They must be set to  null", __FUNCTION__);
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+    if (session->isClosed()) {
+        ALOGE("%s: session %p is already closed", __FUNCTION__, session);
+        return ACAMERA_ERROR_SESSION_CLOSED;
+    }
+    session->setWindowPreparedCallback(cb);
+    return ACAMERA_OK;
+}
+
+EXPORT
+camera_status_t ACameraCaptureSession_prepareWindow(
+        ACameraCaptureSession* session,
+        ACameraWindowType *window) {
+    ATRACE_CALL();
+    if (session == nullptr || window == nullptr) {
+        ALOGE("%s: Error: session %p / window %p is null", __FUNCTION__, session, window);
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+
+    if (session->isClosed()) {
+        ALOGE("%s: session %p is already closed", __FUNCTION__, session);
+        return ACAMERA_ERROR_SESSION_CLOSED;
+    }
+    return session->prepare(window);
+}
\ No newline at end of file
diff --git a/camera/ndk/impl/ACameraCaptureSession.cpp b/camera/ndk/impl/ACameraCaptureSession.cpp
index 110d47a..73439c7 100644
--- a/camera/ndk/impl/ACameraCaptureSession.cpp
+++ b/camera/ndk/impl/ACameraCaptureSession.cpp
@@ -146,6 +146,27 @@
     return ret;
 }
 
+camera_status_t ACameraCaptureSession::prepare(ACameraWindowType* window) {
+#ifdef __ANDROID_VNDK__
+    std::shared_ptr<acam::CameraDevice> dev = getDevicePtr();
+#else
+    sp<acam::CameraDevice> dev = getDeviceSp();
+#endif
+    if (dev == nullptr) {
+        ALOGE("Error: Device associated with session %p has been closed!", this);
+        return ACAMERA_ERROR_SESSION_CLOSED;
+    }
+
+    camera_status_t ret;
+    dev->lockDeviceForSessionOps();
+    {
+        Mutex::Autolock _l(mSessionLock);
+        ret = dev->prepareLocked(window);
+    }
+    dev->unlockDevice();
+    return ret;
+}
+
 ACameraDevice*
 ACameraCaptureSession::getDevice() {
     Mutex::Autolock _l(mSessionLock);
diff --git a/camera/ndk/impl/ACameraCaptureSession.h b/camera/ndk/impl/ACameraCaptureSession.h
index cd65e8c..145473b 100644
--- a/camera/ndk/impl/ACameraCaptureSession.h
+++ b/camera/ndk/impl/ACameraCaptureSession.h
@@ -130,6 +130,12 @@
 
     camera_status_t updateOutputConfiguration(ACaptureSessionOutput *output);
 
+    void setWindowPreparedCallback(ACameraCaptureSession_prepareCallbacks *cb) {
+        Mutex::Autolock _l(mSessionLock);
+        mPreparedCb = *cb;
+    }
+    camera_status_t prepare(ACameraWindowType *window);
+
     ACameraDevice* getDevice();
 
   private:
@@ -156,6 +162,7 @@
 
     bool  mIsClosed = false;
     bool  mClosedByApp = false;
+    ACameraCaptureSession_prepareCallbacks mPreparedCb;
     Mutex mSessionLock;
 };
 
diff --git a/camera/ndk/impl/ACameraDevice.cpp b/camera/ndk/impl/ACameraDevice.cpp
index 536055b..b90f276 100644
--- a/camera/ndk/impl/ACameraDevice.cpp
+++ b/camera/ndk/impl/ACameraDevice.cpp
@@ -342,6 +342,58 @@
     return ACAMERA_OK;
 }
 
+camera_status_t CameraDevice::prepareLocked(ACameraWindowType *window) {
+    camera_status_t ret = checkCameraClosedOrErrorLocked();
+    if (ret != ACAMERA_OK) {
+        return ret;
+    }
+
+    if (window == nullptr) {
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+
+    int32_t streamId = -1;
+    for (auto& kvPair : mConfiguredOutputs) {
+        if (window == kvPair.second.first) {
+            streamId = kvPair.first;
+            break;
+        }
+    }
+    if (streamId < 0) {
+        ALOGE("Error: Invalid output configuration");
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+    auto remoteRet = mRemote->prepare(streamId);
+    if (!remoteRet.isOk()) {
+        // TODO:(b/259735869) Do this check for all other binder calls in the
+        // ndk as well.
+        if (remoteRet.exceptionCode() != EX_SERVICE_SPECIFIC) {
+            ALOGE("Camera device %s failed to prepare output window %p: %s", getId(), window,
+                    remoteRet.toString8().string());
+            return ACAMERA_ERROR_UNKNOWN;
+
+        }
+        switch (remoteRet.serviceSpecificErrorCode()) {
+            case hardware::ICameraService::ERROR_INVALID_OPERATION:
+                ALOGE("Camera device %s invalid operation: %s", getId(),
+                        remoteRet.toString8().string());
+                return ACAMERA_ERROR_INVALID_OPERATION;
+                break;
+            case hardware::ICameraService::ERROR_ILLEGAL_ARGUMENT:
+                ALOGE("Camera device %s invalid input argument: %s", getId(),
+                        remoteRet.toString8().string());
+                return ACAMERA_ERROR_INVALID_PARAMETER;
+                break;
+            default:
+                ALOGE("Camera device %s failed to prepare output window %p: %s", getId(), window,
+                        remoteRet.toString8().string());
+                return ACAMERA_ERROR_UNKNOWN;
+        }
+    }
+
+    return ACAMERA_OK;
+}
+
 camera_status_t
 CameraDevice::allocateCaptureRequest(
         const ACaptureRequest* request, /*out*/sp<CaptureRequest>& outReq) {
@@ -919,6 +971,7 @@
         case kWhatCaptureSeqEnd:
         case kWhatCaptureSeqAbort:
         case kWhatCaptureBufferLost:
+        case kWhatPreparedCb:
             ALOGV("%s: Received msg %d", __FUNCTION__, msg->what());
             break;
         case kWhatCleanUpSessions:
@@ -992,6 +1045,7 @@
         case kWhatCaptureSeqEnd:
         case kWhatCaptureSeqAbort:
         case kWhatCaptureBufferLost:
+        case kWhatPreparedCb:
         {
             sp<RefBase> obj;
             found = msg->findObject(kSessionSpKey, &obj);
@@ -1034,6 +1088,26 @@
                     (*onState)(context, session.get());
                     break;
                 }
+                case kWhatPreparedCb:
+                {
+                    ACameraCaptureSession_prepareCallback onWindowPrepared;
+                    found = msg->findPointer(kCallbackFpKey, (void**) &onWindowPrepared);
+                    if (!found) {
+                        ALOGE("%s: Cannot find state callback!", __FUNCTION__);
+                        return;
+                    }
+                    if (onWindowPrepared == nullptr) {
+                        return;
+                    }
+                    ACameraWindowType* anw;
+                    found = msg->findPointer(kAnwKey, (void**) &anw);
+                    if (!found) {
+                        ALOGE("%s: Cannot find ANativeWindow: %d!", __FUNCTION__, __LINE__);
+                        return;
+                    }
+                    (*onWindowPrepared)(context, anw, session.get());
+                    break;
+                }
                 case kWhatCaptureStart:
                 {
                     ACameraCaptureSession_captureCallback_start onStart;
@@ -1729,8 +1803,36 @@
 }
 
 binder::Status
-CameraDevice::ServiceCallback::onPrepared(int) {
-    // Prepare not yet implemented in NDK
+CameraDevice::ServiceCallback::onPrepared(int streamId) {
+    ALOGV("%s: callback for stream id %d", __FUNCTION__, streamId);
+    binder::Status ret = binder::Status::ok();
+    sp<CameraDevice> dev = mDevice.promote();
+    if (dev == nullptr) {
+        return ret; // device has been closed
+    }
+    Mutex::Autolock _l(dev->mDeviceLock);
+    if (dev->isClosed() || dev->mRemote == nullptr) {
+        return ret;
+    }
+    auto it = dev->mConfiguredOutputs.find(streamId);
+    if (it == dev->mConfiguredOutputs.end()) {
+        ALOGE("%s: stream id %d does not exist", __FUNCTION__ , streamId);
+        return ret;
+    }
+    sp<ACameraCaptureSession> session = dev->mCurrentSession.promote();
+    if (session == nullptr) {
+        ALOGE("%s: Session is dead already", __FUNCTION__ );
+        return ret;
+    }
+    // We've found the window corresponding to the surface id.
+    ACameraWindowType *window = it->second.first;
+    sp<AMessage> msg = new AMessage(kWhatPreparedCb, dev->mHandler);
+    msg->setPointer(kContextKey, session->mPreparedCb.context);
+    msg->setPointer(kAnwKey, window);
+    msg->setObject(kSessionSpKey, session);
+    msg->setPointer(kCallbackFpKey, (void *)session->mPreparedCb.onWindowPrepared);
+    dev->postSessionMsgAndCleanup(msg);
+
     return binder::Status::ok();
 }
 
diff --git a/camera/ndk/impl/ACameraDevice.h b/camera/ndk/impl/ACameraDevice.h
index 17988fe..382d6ce 100644
--- a/camera/ndk/impl/ACameraDevice.h
+++ b/camera/ndk/impl/ACameraDevice.h
@@ -151,6 +151,8 @@
 
     camera_status_t updateOutputConfigurationLocked(ACaptureSessionOutput *output);
 
+    camera_status_t prepareLocked(ACameraWindowType *window);
+
     camera_status_t allocateCaptureRequest(
             const ACaptureRequest* request, sp<CaptureRequest>& outReq);
 
@@ -222,7 +224,8 @@
         kWhatLogicalCaptureFail, // onLogicalCameraCaptureFailed
         kWhatCaptureSeqEnd,    // onCaptureSequenceCompleted
         kWhatCaptureSeqAbort,  // onCaptureSequenceAborted
-        kWhatCaptureBufferLost,// onCaptureBufferLost
+        kWhatCaptureBufferLost, // onCaptureBufferLost
+        kWhatPreparedCb, // onWindowPrepared
         // Internal cleanup
         kWhatCleanUpSessions   // Cleanup cached sp<ACameraCaptureSession>
     };
diff --git a/camera/ndk/include/camera/NdkCameraCaptureSession.h b/camera/ndk/include/camera/NdkCameraCaptureSession.h
index b0fd00c..0211d83 100644
--- a/camera/ndk/include/camera/NdkCameraCaptureSession.h
+++ b/camera/ndk/include/camera/NdkCameraCaptureSession.h
@@ -99,6 +99,45 @@
     ACameraCaptureSession_stateCallback onActive;
 } ACameraCaptureSession_stateCallbacks;
 
+/**
+ * The definition of camera capture session onWindowPrepared callback.
+ * @param context The optional app-provided context pointer that was included in
+ *        the {@link ACameraCaptureSession_prepareCallbacks} struct.
+ * @param window The window that {@link ACameraCaptureSession_prepare} was called on.
+ * @param session The camera capture session on which {@link ACameraCaptureSession_prepare} was
+ *                called on.
+ */
+typedef void (*ACameraCaptureSession_prepareCallback)(
+        void *context,
+        ACameraWindowType *window,
+        ACameraCaptureSession *session);
+
+/**
+ * Capture session state callbacks used in {@link ACameraDevice_setPrepareCallbacks}
+ */
+typedef struct ACameraCaptureSession_prepareCallbacks {
+    /// optional application context. This will be passed in the context
+    /// parameter of the {@link onWindowPrepared} callback.
+    void*                               context;
+
+    /**
+     * This callback is called when the buffer pre-allocation for an output window Surface is
+     * complete.
+     * <p>Buffer pre-allocation for an output window is started by
+     * {@link ACameraCaptureSession_prepare}
+     * call. While allocation is underway, the output must not be used in a capture request.
+     * Once this callback is called, the output provided can be used as a target for a
+     * capture request. In case of an error during pre-allocation (such as running out of
+     * suitable-memory), this callback is still invoked after the error is encountered, though some
+     * buffers may not have been successfully pre-allocated </p>
+     */
+    ACameraCaptureSession_prepareCallback onWindowPrepared;
+
+    // Reserved for future callback additions, these must be set to nullptr by the client.
+    ACameraCaptureSession_prepareCallback reserved0;
+    ACameraCaptureSession_prepareCallback reserved1;
+} ACameraCaptureSession_prepareCallbacks;
+
 /// Enum for describing error reason in {@link ACameraCaptureFailure}
 enum {
     /**
@@ -989,6 +1028,89 @@
         int numRequests, ACaptureRequest** requests,
         /*optional*/int* captureSequenceId) __INTRODUCED_IN(33);
 
+/**
+ * Set the callback that is called when the output window for which the client has requested
+ * pre-allocation of buffers through the {@link ACameraCaptureSession_prepareWindow} call has
+ * completed the pre-allocation of buffers.
+ * @param session the ACameraCaptureSession on which ACameraCaptureSession_prepareWindow was called.
+ * @param callbacks the callback to be called when the output window's buffer pre-allocation is
+ *                  complete.
+ * @return <ul><li> {@link ACAMERA_OK} if the method succeeds</li>
+ *         <li>{@link ACAMERA_ERROR_INVALID_PARAMETER} if session or callbacks is
+ *              NULL. Or if the session has not been configured with the window</li>
+ *         <li>{@link ACAMERA_ERROR_SESSION_CLOSED} if the capture session has been closed</li>
+ *         <li>{@link ACAMERA_ERROR_CAMERA_DISCONNECTED} if the camera device is closed</li>
+ *         <li>{@link ACAMERA_ERROR_CAMERA_DEVICE} if the camera device encounters fatal error</li>
+ *         <li>{@link ACAMERA_ERROR_CAMERA_SERVICE} the camera service encounters fatal error</li>
+ *         <li>{@link ACAMERA_ERROR_UNKNOWN} if the method fails for some other reasons</li></ul>
+ */
+camera_status_t ACameraCaptureSession_setWindowPreparedCallback(
+    ACameraCaptureSession* session,
+    ACameraCaptureSession_prepareCallbacks* callbacks) __INTRODUCED_IN(34);
+
+/**
+ *
+ * <p>Pre-allocate all buffers for an output window.</p>
+ *
+ * <p>Normally, the image buffers for a given output window are allocated on-demand,
+ * to minimize startup latency and memory overhead.</p>
+ *
+ * <p>However, in some cases, it may be desirable for the buffers to be allocated before
+ * any requests targeting the window are actually submitted to the device. Large buffers
+ * may take some time to allocate, which can result in delays in submitting requests until
+ * sufficient buffers are allocated to reach steady-state behavior. Such delays can cause
+ * bursts to take longer than desired, or cause skips or stutters in preview output.</p>
+ *
+ * <p>The ACameraCaptureSession_prepare() call can be used to perform this pre-allocation.
+ * It may only be called for a given output window before that window is used as a target for a
+ * request. The number of buffers allocated is the sum of the count needed by the consumer providing
+ * the output window, and the maximum number needed by the camera device to fill its pipeline.
+ * Since this may be a larger number than what is actually required for steady-state operation,
+ * using this call may result in higher memory consumption than the normal on-demand behavior
+ * results in. This method will also delay the time to first output to a given Surface, in exchange
+ * for smoother frame rate once the allocation is complete.</p>
+ *
+ * <p>For example, an application that creates an
+ * {@link AImageReader} with a maxImages argument of 10,
+ * but only uses 3 simultaneous {@link AImage}s at once, would normally only cause those 3 images
+ * to be allocated (plus what is needed by the camera device for smooth operation).  But using
+ * ACameraCaptureSession_prepare() on the {@link AImageReader}'s window will result in all 10
+ * {@link AImage}s being allocated. So applications using this method should take care to request
+ * only the number of buffers actually necessary for their application.</p>
+ *
+ * <p>If the same output window is used in consecutive sessions (without closing the first
+ * session explicitly), then its already-allocated buffers are carried over, and if it was
+ * used as a target of a capture request in the first session, prepare cannot be called on it
+ * in the second session. If it is, {@link ACAMERA_ERROR_INVALID_PARAMETER} will
+ * be returned by the method</p>
+ *
+ * <p>Once allocation is complete, {@link ACameraCaptureSession_prepareCallback#onWindowPrepared}
+ * will be invoked with the output provided to this method. Between the prepare call and the
+ * {@link ACameraCaptureSession_prepareCallback#onWindowPrepared} call,
+ * the output provided to prepare must not be used as a target of a capture qequest submitted
+ * to this session.</p>
+ *
+ * <p>{@link android.hardware.camera2.CameraCharacteristics#INFO_SUPPORTED_HARDWARE_LEVEL_LEGACY LEGACY}
+ * devices cannot pre-allocate output buffers; for those devices,
+ * {@link ACameraCaptureSession_prepareCallback#onWindowPrepared} will be immediately called,
+ * and no pre-allocation is done.</p>
+ *
+ * @param session the {@link ACameraCaptureSession} that needs to prepare output buffers.
+ * @param window the {@link ACameraWindowType} for which the output buffers need to be prepared.
+ *
+ * @return <ul><li>
+ *             {@link ACAMERA_OK} if the method succeeds</li>
+ *         <li>{@link ACAMERA_ERROR_INVALID_PARAMETER} if session/ window or prepareCallbacks is
+ *              NULL. Or if the session has not been configured with the window</li>
+ *         <li>{@link ACAMERA_ERROR_SESSION_CLOSED} if the capture session has been closed</li>
+ *         <li>{@link ACAMERA_ERROR_CAMERA_DISCONNECTED} if the camera device is closed</li>
+ *         <li>{@link ACAMERA_ERROR_CAMERA_DEVICE} if the camera device encounters fatal error</li>
+ *         <li>{@link ACAMERA_ERROR_CAMERA_SERVICE} if the camera service encounters fatal error</li>
+ *         <li>{@link ACAMERA_ERROR_UNKNOWN} if the method fails for some other reasons</li></ul>
+ */
+camera_status_t ACameraCaptureSession_prepareWindow(
+    ACameraCaptureSession* session,
+    ACameraWindowType *window) __INTRODUCED_IN(34);
 __END_DECLS
 
 #endif /* _NDK_CAMERA_CAPTURE_SESSION_H */
diff --git a/camera/ndk/libcamera2ndk.map.txt b/camera/ndk/libcamera2ndk.map.txt
index b3977ff..4c54658 100644
--- a/camera/ndk/libcamera2ndk.map.txt
+++ b/camera/ndk/libcamera2ndk.map.txt
@@ -12,6 +12,8 @@
     ACameraCaptureSession_logicalCamera_setRepeatingRequest; # introduced=29
     ACameraCaptureSession_logicalCamera_setRepeatingRequestV2; # introduced=33
     ACameraCaptureSession_stopRepeating;
+    ACameraCaptureSession_setWindowPreparedCallback; # introduced=34
+    ACameraCaptureSession_prepareWindow; # introduced=34
     ACameraCaptureSession_updateSharedOutput; # introduced=28
     ACameraDevice_close;
     ACameraDevice_createCaptureRequest;
diff --git a/camera/ndk/ndk_vendor/impl/ACameraDevice.cpp b/camera/ndk/ndk_vendor/impl/ACameraDevice.cpp
index 96df7db..87102e4 100644
--- a/camera/ndk/ndk_vendor/impl/ACameraDevice.cpp
+++ b/camera/ndk/ndk_vendor/impl/ACameraDevice.cpp
@@ -340,6 +340,33 @@
     return ACAMERA_OK;
 }
 
+camera_status_t CameraDevice::prepareLocked(ACameraWindowType *window) {
+    camera_status_t ret = checkCameraClosedOrErrorLocked();
+    if (ret != ACAMERA_OK) {
+        return ret;
+    }
+
+    if (window == nullptr) {
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+
+    int32_t streamId = -1;
+    for (auto& kvPair : mConfiguredOutputs) {
+        if (window == kvPair.second.first) {
+            streamId = kvPair.first;
+            break;
+        }
+    }
+    if (streamId < 0) {
+        ALOGE("Error: Invalid output configuration");
+        return ACAMERA_ERROR_INVALID_PARAMETER;
+    }
+
+    auto remoteRet = mRemote->prepare(streamId);
+    CHECK_TRANSACTION_AND_RET(remoteRet, "prepare()")
+    return ACAMERA_OK;
+}
+
 camera_status_t CameraDevice::allocateCaptureRequestLocked(
         const ACaptureRequest* request, /*out*/sp<CaptureRequest> &outReq) {
     sp<CaptureRequest> req(new CaptureRequest());
@@ -929,6 +956,7 @@
         case kWhatCaptureSeqEnd:
         case kWhatCaptureSeqAbort:
         case kWhatCaptureBufferLost:
+        case kWhatPreparedCb:
             ALOGV("%s: Received msg %d", __FUNCTION__, msg->what());
             break;
         case kWhatCleanUpSessions:
@@ -1002,6 +1030,7 @@
         case kWhatCaptureSeqEnd:
         case kWhatCaptureSeqAbort:
         case kWhatCaptureBufferLost:
+        case kWhatPreparedCb:
         {
             sp<RefBase> obj;
             found = msg->findObject(kSessionSpKey, &obj);
@@ -1045,6 +1074,26 @@
                     (*onState)(context, session.get());
                     break;
                 }
+                case kWhatPreparedCb:
+                {
+                    ACameraCaptureSession_prepareCallback onWindowPrepared;
+                    found = msg->findPointer(kCallbackFpKey, (void**) &onWindowPrepared);
+                    if (!found) {
+                        ALOGE("%s: Cannot find state callback!", __FUNCTION__);
+                        return;
+                    }
+                    if (onWindowPrepared == nullptr) {
+                        return;
+                    }
+                    native_handle_t* anw;
+                    found = msg->findPointer(kAnwKey, (void**) &anw);
+                    if (!found) {
+                        ALOGE("%s: Cannot find ANativeWindow: %d!", __FUNCTION__, __LINE__);
+                        return;
+                    }
+                    (*onWindowPrepared)(context, anw, session.get());
+                    break;
+                }
                 case kWhatCaptureStart:
                 {
                     ACameraCaptureSession_captureCallback_start onStart;
@@ -1772,6 +1821,37 @@
     return ScopedAStatus::ok();
 }
 
+ScopedAStatus CameraDevice::ServiceCallback::onPrepared(int32_t streamId) {
+    ALOGV("%s: callback for stream id %d", __FUNCTION__, streamId);
+    std::shared_ptr<CameraDevice> dev = mDevice.lock();
+    if (dev == nullptr) {
+        return ScopedAStatus::ok();
+    }
+    Mutex::Autolock _l(dev->mDeviceLock);
+    if (dev->isClosed() || dev->mRemote == nullptr) {
+        return ScopedAStatus::ok();
+    }
+    auto it = dev->mConfiguredOutputs.find(streamId);
+    if (it == dev->mConfiguredOutputs.end()) {
+        ALOGE("%s: stream id %d does not exist", __FUNCTION__ , streamId);
+        return ScopedAStatus::ok();
+    }
+    sp<ACameraCaptureSession> session = dev->mCurrentSession.promote();
+    if (session == nullptr) {
+        ALOGE("%s: Session is dead already", __FUNCTION__ );
+        return ScopedAStatus::ok();
+    }
+    // We've found the window corresponding to the surface id.
+    const native_handle_t *anw = it->second.first.mWindow;
+    sp<AMessage> msg = new AMessage(kWhatPreparedCb, dev->mHandler);
+    msg->setPointer(kContextKey, session->mPreparedCb.context);
+    msg->setPointer(kAnwKey, (void *)anw);
+    msg->setObject(kSessionSpKey, session);
+    msg->setPointer(kCallbackFpKey, (void *)session->mPreparedCb.onWindowPrepared);
+    dev->postSessionMsgAndCleanup(msg);
+    return ScopedAStatus::ok();
+}
+
 camera_status_t CameraDevice::ServiceCallback::readOneResultMetadata(
         const CaptureMetadataInfo& captureMetadataInfo, ResultMetadataQueue* metadataQueue,
         CameraMetadata* metadata) {
diff --git a/camera/ndk/ndk_vendor/impl/ACameraDevice.h b/camera/ndk/ndk_vendor/impl/ACameraDevice.h
index cad23aa..6e0c772 100644
--- a/camera/ndk/ndk_vendor/impl/ACameraDevice.h
+++ b/camera/ndk/ndk_vendor/impl/ACameraDevice.h
@@ -130,6 +130,7 @@
 
         ndk::ScopedAStatus onCaptureStarted(const CaptureResultExtras& in_resultExtras,
                                             int64_t in_timestamp) override;
+        ndk::ScopedAStatus onPrepared(int32_t in_streamId) override;
         ndk::ScopedAStatus onRepeatingRequestError(int64_t in_lastFrameNumber,
                                                    int32_t in_repeatingRequestId) override;
         ndk::ScopedAStatus onResultReceived(const CaptureMetadataInfo& in_result,
@@ -196,6 +197,8 @@
 
     camera_status_t updateOutputConfigurationLocked(ACaptureSessionOutput *output);
 
+    camera_status_t prepareLocked(ACameraWindowType *window);
+
     // Since this writes to ICameraDeviceUser's fmq, clients must take care that:
     //   a) This function is called serially.
     //   b) This function is called in accordance with ICameraDeviceUser.submitRequestList,
@@ -269,7 +272,8 @@
         kWhatLogicalCaptureFail, // onLogicalCameraCaptureFailed
         kWhatCaptureSeqEnd,    // onCaptureSequenceCompleted
         kWhatCaptureSeqAbort,  // onCaptureSequenceAborted
-        kWhatCaptureBufferLost,// onCaptureBufferLost
+        kWhatCaptureBufferLost, // onCaptureBufferLost
+        kWhatPreparedCb, // onPrepared
         // Internal cleanup
         kWhatCleanUpSessions   // Cleanup cached sp<ACameraCaptureSession>
     };
diff --git a/camera/ndk/ndk_vendor/tests/AImageReaderVendorTest.cpp b/camera/ndk/ndk_vendor/tests/AImageReaderVendorTest.cpp
index 3a13a73..e62f7c3 100644
--- a/camera/ndk/ndk_vendor/tests/AImageReaderVendorTest.cpp
+++ b/camera/ndk/ndk_vendor/tests/AImageReaderVendorTest.cpp
@@ -66,7 +66,7 @@
     // Retaining the error code in case the caller needs to analyze it.
     std::variant<int, ConfiguredWindows> initCamera(const native_handle_t* imgReaderAnw,
             const std::vector<PhysicalImgReaderInfo>& physicalImgReaders,
-            bool usePhysicalSettings) {
+            bool usePhysicalSettings, bool prepareWindows = false) {
         ConfiguredWindows configuredWindows;
         if (imgReaderAnw == nullptr) {
             ALOGE("Cannot initialize camera before image reader get initialized.");
@@ -142,7 +142,25 @@
             ALOGE("ACameraDevice_createCaptureSession failed, ret=%d", ret);
             return ret;
         }
-
+        if (prepareWindows) {
+            // Set window prepared callback
+            ACameraCaptureSession_setWindowPreparedCallback(mSession, &mPreparedCb);
+            // Prepare windows
+            for (auto &window : configuredWindows) {
+                ret = ACameraCaptureSession_prepareWindow(mSession, window);
+                if (ret != ACAMERA_OK) {
+                    ALOGE("%s: ACameraCaptureSession_prepareWindow failed", __FUNCTION__);
+                    return ret;
+                }
+                incPendingPrepared(window);
+            }
+            // Some time for the on-PreparedCallbacks
+            usleep(configuredWindows.size() * 100000);
+            // Check that callbacks were received
+            if (!gotAllPreparedCallbacks()) {
+                return -1;
+            }
+        }
         // Create capture request
         if (usePhysicalSettings) {
             ret = ACameraDevice_createCaptureRequest_withPhysicalIds(mDevice,
@@ -277,9 +295,56 @@
 
 
    private:
+    static void onPreparedCb(void* obj, ACameraWindowType *anw, ACameraCaptureSession *session) {
+        CameraHelper* thiz = reinterpret_cast<CameraHelper*>(obj);
+        thiz->handlePrepared(anw, session);
+    }
+    bool gotAllPreparedCallbacks() {
+        std::lock_guard<std::mutex> lock(mMutex);
+        bool ret = (mPendingPreparedCbs.size() == 0);
+        if (!ret) {
+            ALOGE("%s: mPendingPreparedCbs has the following expected callbacks", __FUNCTION__);
+            for (auto pair : mPendingPreparedCbs) {
+                ALOGE("%s: ANW: %p : pending callbacks %d", __FUNCTION__, pair.first, pair.second);
+            }
+        }
+        return ret;
+    }
+
+    void handlePrepared(ACameraWindowType *anw, ACameraCaptureSession *session) {
+        // Reduce the pending prepared count of anw by 1. If count is  0, remove the key.
+        std::lock_guard<std::mutex> lock(mMutex);
+        if (session != mSession) {
+            ALOGE("%s: Received callback for incorrect session ? mSession %p, session %p",
+                    __FUNCTION__, mSession, session);
+            return;
+        }
+        if(mPendingPreparedCbs.find(anw) == mPendingPreparedCbs.end()) {
+            ALOGE("%s: ANW %p was not being prepared at all ?", __FUNCTION__, anw);
+            return;
+        }
+        mPendingPreparedCbs[anw]--;
+        if (mPendingPreparedCbs[anw] == 0) {
+            mPendingPreparedCbs.erase(anw);
+        }
+    }
+    void incPendingPrepared(ACameraWindowType *anw) {
+        std::lock_guard<std::mutex> lock(mMutex);
+        if (!(mPendingPreparedCbs.find(anw) == mPendingPreparedCbs.end())) {
+            mPendingPreparedCbs[anw] = 1;
+            return;
+        }
+        mPendingPreparedCbs[anw]++;
+    }
+
+    // ANW -> pending prepared callbacks
+    std::unordered_map<ACameraWindowType *, int> mPendingPreparedCbs;
     ACameraDevice_StateCallbacks mDeviceCb{this, nullptr, nullptr};
     ACameraCaptureSession_stateCallbacks mSessionCb{ this, nullptr, nullptr, nullptr};
 
+    ACameraCaptureSession_prepareCallbacks mPreparedCb{
+            this, onPreparedCb, /*reserved0*/nullptr, /*reserved1*/nullptr};
+
     const native_handle_t* mImgReaderAnw = nullptr;  // not owned by us.
 
     // Camera device
@@ -628,7 +693,7 @@
     }
 
     bool takePictures(const char* id, uint64_t readerUsage, int readerMaxImages,
-            bool readerAsync, int pictureCount, bool v2 = false) {
+            bool readerAsync, int pictureCount, bool v2 = false, bool prepareSurfaces = false) {
         int ret = 0;
 
         ImageReaderTestCase testCase(
@@ -643,7 +708,7 @@
         CameraHelper cameraHelper(id, mCameraManager);
         std::variant<int, ConfiguredWindows> retInit =
                 cameraHelper.initCamera(testCase.getNativeWindow(), {}/*physicalImageReaders*/,
-                                        false/*usePhysicalSettings*/);
+                                        false/*usePhysicalSettings*/, prepareSurfaces);
         int *retp = std::get_if<int>(&retInit);
         if (retp) {
             ALOGE("Unable to initialize camera helper");
@@ -690,7 +755,7 @@
                     cameraHelper.checkCallbacks(pictureCount, /* printLog= */true);
     }
 
-    bool testTakePicturesNative(const char* id) {
+    bool testTakePicturesNative(const char* id, bool prepareSurfaces) {
         for (auto& readerUsage :
              {AHARDWAREBUFFER_USAGE_CPU_READ_OFTEN}) {
             for (auto& readerMaxImages : {1, 4, 8}) {
@@ -698,7 +763,7 @@
                     for (auto& pictureCount : {1, 4, 8}) {
                         for ( auto & v2 : {true, false}) {
                             if (!takePictures(id, readerUsage, readerMaxImages,
-                                    readerAsync, pictureCount, v2)) {
+                                    readerAsync, pictureCount, v2, prepareSurfaces)) {
                                 ALOGE("Test takePictures failed for test case usage=%" PRIu64
                                       ", maxImages=%d, async=%d, pictureCount=%d",
                                       readerUsage, readerMaxImages, readerAsync, pictureCount);
@@ -878,39 +943,46 @@
 
         ACameraMetadata_free(staticMetadata);
     }
+
+    void testBasicTakePictures(bool prepareSurfaces) {
+        // We always use the first camera.
+        const char* cameraId = mCameraIdList->cameraIds[0];
+        ASSERT_TRUE(cameraId != nullptr);
+
+        ACameraMetadata* staticMetadata = nullptr;
+        camera_status_t ret = ACameraManager_getCameraCharacteristics(
+                mCameraManager, cameraId, &staticMetadata);
+        ASSERT_EQ(ret, ACAMERA_OK);
+        ASSERT_NE(staticMetadata, nullptr);
+
+        bool isBC = isCapabilitySupported(staticMetadata,
+                ACAMERA_REQUEST_AVAILABLE_CAPABILITIES_BACKWARD_COMPATIBLE);
+
+        uint32_t namedTag = 0;
+        // Test that ACameraMetadata_getTagFromName works as expected for public tag
+        // names
+        camera_status_t status = ACameraManager_getTagFromName(mCameraManager, cameraId,
+                "android.control.aeMode", &namedTag);
+
+        ASSERT_EQ(status, ACAMERA_OK);
+        ASSERT_EQ(namedTag, ACAMERA_CONTROL_AE_MODE);
+
+        ACameraMetadata_free(staticMetadata);
+
+        if (!isBC) {
+            ALOGW("Camera does not support BACKWARD_COMPATIBLE.");
+            return;
+        }
+
+        EXPECT_TRUE(testTakePicturesNative(cameraId, prepareSurfaces));
+    }
 };
 
+
+
 TEST_F(AImageReaderVendorTest, CreateWindowNativeHandle) {
-    // We always use the first camera.
-    const char* cameraId = mCameraIdList->cameraIds[0];
-    ASSERT_TRUE(cameraId != nullptr);
-
-    ACameraMetadata* staticMetadata = nullptr;
-    camera_status_t ret = ACameraManager_getCameraCharacteristics(
-            mCameraManager, cameraId, &staticMetadata);
-    ASSERT_EQ(ret, ACAMERA_OK);
-    ASSERT_NE(staticMetadata, nullptr);
-
-    bool isBC = isCapabilitySupported(staticMetadata,
-            ACAMERA_REQUEST_AVAILABLE_CAPABILITIES_BACKWARD_COMPATIBLE);
-
-    uint32_t namedTag = 0;
-    // Test that ACameraMetadata_getTagFromName works as expected for public tag
-    // names
-    camera_status_t status = ACameraManager_getTagFromName(mCameraManager, cameraId,
-            "android.control.aeMode", &namedTag);
-
-    ASSERT_EQ(status, ACAMERA_OK);
-    ASSERT_EQ(namedTag, ACAMERA_CONTROL_AE_MODE);
-
-    ACameraMetadata_free(staticMetadata);
-
-    if (!isBC) {
-        ALOGW("Camera does not support BACKWARD_COMPATIBLE.");
-        return;
-    }
-
-    EXPECT_TRUE(testTakePicturesNative(cameraId));
+    testBasicTakePictures(/*prepareSurfaces*/ false);
+    testBasicTakePictures(/*prepareSurfaces*/ true);
 }
 
 TEST_F(AImageReaderVendorTest, LogicalCameraPhysicalStream) {
diff --git a/services/camera/libcameraservice/aidl/AidlCameraDeviceCallbacks.cpp b/services/camera/libcameraservice/aidl/AidlCameraDeviceCallbacks.cpp
index 4c6d6f6..e648a36 100644
--- a/services/camera/libcameraservice/aidl/AidlCameraDeviceCallbacks.cpp
+++ b/services/camera/libcameraservice/aidl/AidlCameraDeviceCallbacks.cpp
@@ -178,8 +178,9 @@
     return binder::Status::ok();
 }
 
-binder::Status AidlCameraDeviceCallbacks::onPrepared(int32_t) {
-    // not implemented
+binder::Status AidlCameraDeviceCallbacks::onPrepared(int32_t streamId) {
+    auto ret = mBase->onPrepared(streamId);
+    LOG_STATUS_ERROR_IF_NOT_OK(ret, "onPrepared")
     return binder::Status::ok();
 }
 
@@ -191,6 +192,7 @@
     LOG_STATUS_ERROR_IF_NOT_OK(ret, "onRepeatingRequestError")
     return binder::Status::ok();
 }
+
 binder::Status AidlCameraDeviceCallbacks::onRequestQueueEmpty() {
     // not implemented
     return binder::Status::ok();
diff --git a/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.cpp b/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.cpp
index d9ec0b6..b9f1224 100644
--- a/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.cpp
+++ b/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.cpp
@@ -56,6 +56,7 @@
       mDeviceRemote(deviceRemote) {
     mInitSuccess = initDevice();
 }
+
 bool AidlCameraDeviceUser::initDevice() {
     // TODO: Get request and result metadata queue size from a system property.
     int32_t reqFMQSize = CAMERA_REQUEST_METADATA_QUEUE_SIZE;
@@ -95,6 +96,11 @@
     return ScopedAStatus::ok();
 }
 
+ndk::ScopedAStatus AidlCameraDeviceUser::prepare(int32_t in_streamId) {
+    UStatus ret = mDeviceRemote->prepare(in_streamId);
+    return fromUStatus(ret);
+}
+
 ndk::ScopedAStatus AidlCameraDeviceUser::submitRequestList(
         const std::vector<SCaptureRequest>& in_requestList, bool in_isRepeating,
         SSubmitInfo* _aidl_return) {
diff --git a/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.h b/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.h
index 41a3f43..afff197 100644
--- a/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.h
+++ b/services/camera/libcameraservice/aidl/AidlCameraDeviceUser.h
@@ -84,6 +84,7 @@
             MQDescriptor<int8_t, SynchronizedReadWrite>* _aidl_return) override;
     ndk::ScopedAStatus isSessionConfigurationSupported(
             const SSessionConfiguration& in_sessionConfiguration, bool* _aidl_return) override;
+    ndk::ScopedAStatus prepare(int32_t in_streamId) override;
     ndk::ScopedAStatus submitRequestList(const std::vector<SCaptureRequest>& in_requestList,
                                          bool in_isRepeating, SSubmitInfo* _aidl_return) override;
     ndk::ScopedAStatus updateOutputConfiguration(