Camera2: Add flush support

- On HAL2 devices, fall back to wait until idle
- On HAL3 devices, call HAL flush method

Bug: 9758581
Change-Id: Ie1c570a15f6590a1ee6c271e3b989c48079b468a
diff --git a/services/camera/libcameraservice/device2/Camera2Device.cpp b/services/camera/libcameraservice/device2/Camera2Device.cpp
index 710d0e9..fe2cd77 100644
--- a/services/camera/libcameraservice/device2/Camera2Device.cpp
+++ b/services/camera/libcameraservice/device2/Camera2Device.cpp
@@ -567,6 +567,13 @@
     return res;
 }
 
+status_t Camera2Device::flush() {
+    ATRACE_CALL();
+
+    mRequestQueue.clear();
+    return waitUntilDrained();
+}
+
 /**
  * Camera2Device::MetadataQueue
  */
@@ -591,9 +598,7 @@
 
 Camera2Device::MetadataQueue::~MetadataQueue() {
     ATRACE_CALL();
-    Mutex::Autolock l(mMutex);
-    freeBuffers(mEntries.begin(), mEntries.end());
-    freeBuffers(mStreamSlot.begin(), mStreamSlot.end());
+    clear();
 }
 
 // Connect to camera2 HAL as consumer (input requests/reprocessing)
@@ -784,6 +789,23 @@
     return signalConsumerLocked();
 }
 
+status_t Camera2Device::MetadataQueue::clear()
+{
+    ATRACE_CALL();
+    ALOGV("%s: E", __FUNCTION__);
+
+    Mutex::Autolock l(mMutex);
+
+    // Clear streaming slot
+    freeBuffers(mStreamSlot.begin(), mStreamSlot.end());
+    mStreamSlotCount = 0;
+
+    // Clear request queue
+    freeBuffers(mEntries.begin(), mEntries.end());
+    mCount = 0;
+    return OK;
+}
+
 status_t Camera2Device::MetadataQueue::dump(int fd,
         const Vector<String16>& /*args*/) {
     ATRACE_CALL();