diff --git a/gnss/2.1/default/Gnss.h b/gnss/2.1/default/Gnss.h
new file mode 100644
index 0000000..a61f71c
--- /dev/null
+++ b/gnss/2.1/default/Gnss.h
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+
+#pragma once
+
+#include <android/hardware/gnss/2.1/IGnss.h>
+#include <hidl/MQDescriptor.h>
+#include <hidl/Status.h>
+#include <atomic>
+#include <mutex>
+#include <thread>
+
+namespace android {
+namespace hardware {
+namespace gnss {
+namespace V2_1 {
+
+using GnssSvInfo = IGnssCallback::GnssSvInfo;
+
+namespace implementation {
+
+struct Gnss : public IGnss {
+    Gnss();
+    ~Gnss();
+    // Methods from V1_0::IGnss follow.
+    Return<bool> setCallback(const sp<V1_0::IGnssCallback>& callback) override;
+    Return<bool> start() override;
+    Return<bool> stop() override;
+    Return<void> cleanup() override;
+    Return<bool> injectTime(int64_t timeMs, int64_t timeReferenceMs,
+                            int32_t uncertaintyMs) override;
+    Return<bool> injectLocation(double latitudeDegrees, double longitudeDegrees,
+                                float accuracyMeters) override;
+    Return<void> deleteAidingData(V1_0::IGnss::GnssAidingData aidingDataFlags) override;
+    Return<bool> setPositionMode(V1_0::IGnss::GnssPositionMode mode,
+                                 V1_0::IGnss::GnssPositionRecurrence recurrence,
+                                 uint32_t minIntervalMs, uint32_t preferredAccuracyMeters,
+                                 uint32_t preferredTimeMs) override;
+    Return<sp<V1_0::IAGnssRil>> getExtensionAGnssRil() override;
+    Return<sp<V1_0::IGnssGeofencing>> getExtensionGnssGeofencing() override;
+    Return<sp<V1_0::IAGnss>> getExtensionAGnss() override;
+    Return<sp<V1_0::IGnssNi>> getExtensionGnssNi() override;
+    Return<sp<V1_0::IGnssMeasurement>> getExtensionGnssMeasurement() override;
+    Return<sp<V1_0::IGnssNavigationMessage>> getExtensionGnssNavigationMessage() override;
+    Return<sp<V1_0::IGnssXtra>> getExtensionXtra() override;
+    Return<sp<V1_0::IGnssConfiguration>> getExtensionGnssConfiguration() override;
+    Return<sp<V1_0::IGnssDebug>> getExtensionGnssDebug() override;
+    Return<sp<V1_0::IGnssBatching>> getExtensionGnssBatching() override;
+
+    // Methods from V1_1::IGnss follow.
+    Return<bool> setCallback_1_1(const sp<V1_1::IGnssCallback>& callback) override;
+    Return<bool> setPositionMode_1_1(V1_0::IGnss::GnssPositionMode mode,
+                                     V1_0::IGnss::GnssPositionRecurrence recurrence,
+                                     uint32_t minIntervalMs, uint32_t preferredAccuracyMeters,
+                                     uint32_t preferredTimeMs, bool lowPowerMode) override;
+    Return<sp<V1_1::IGnssConfiguration>> getExtensionGnssConfiguration_1_1() override;
+    Return<sp<V1_1::IGnssMeasurement>> getExtensionGnssMeasurement_1_1() override;
+    Return<bool> injectBestLocation(const V1_0::GnssLocation& location) override;
+
+    // Methods from V2_0::IGnss follow.
+    Return<bool> setCallback_2_0(const sp<V2_0::IGnssCallback>& callback) override;
+    Return<sp<V2_0::IGnssConfiguration>> getExtensionGnssConfiguration_2_0() override;
+    Return<sp<V2_0::IGnssDebug>> getExtensionGnssDebug_2_0() override;
+    Return<sp<V2_0::IAGnss>> getExtensionAGnss_2_0() override;
+    Return<sp<V2_0::IAGnssRil>> getExtensionAGnssRil_2_0() override;
+    Return<sp<V2_0::IGnssMeasurement>> getExtensionGnssMeasurement_2_0() override;
+    Return<sp<measurement_corrections::V1_0::IMeasurementCorrections>>
+    getExtensionMeasurementCorrections() override;
+    Return<sp<visibility_control::V1_0::IGnssVisibilityControl>> getExtensionVisibilityControl()
+            override;
+    Return<sp<V2_0::IGnssBatching>> getExtensionGnssBatching_2_0() override;
+    Return<bool> injectBestLocation_2_0(const V2_0::GnssLocation& location) override;
+
+    // Methods from V2_1::IGnss follow.
+    Return<bool> setCallback_2_1(const sp<V2_1::IGnssCallback>& callback) override;
+    Return<sp<V2_1::IGnssMeasurement>> getExtensionGnssMeasurement_2_1() override;
+
+  private:
+    void reportLocation(const V2_0::GnssLocation&) const;
+    void reportSvStatus(const hidl_vec<GnssSvInfo>&) const;
+
+    static sp<V2_1::IGnssCallback> sGnssCallback_2_1;
+    std::atomic<long> mMinIntervalMs;
+    std::atomic<bool> mIsActive;
+    std::thread mThread;
+    mutable std::mutex mMutex;
+};
+
+}  // namespace implementation
+}  // namespace V2_1
+}  // namespace gnss
+}  // namespace hardware
+}  // namespace android