diff --git a/soundtrigger/2.1/default/SoundTriggerHw.cpp b/soundtrigger/2.1/default/SoundTriggerHw.cpp
new file mode 100644
index 0000000..246d2bc
--- /dev/null
+++ b/soundtrigger/2.1/default/SoundTriggerHw.cpp
@@ -0,0 +1,194 @@
+/*
+ * 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 "SoundTriggerHw"
+
+#include "SoundTriggerHw.h"
+
+#include <utility>
+
+#include <android/hidl/allocator/1.0/IAllocator.h>
+#include <android/log.h>
+#include <hidlmemory/mapping.h>
+
+using android::hardware::hidl_memory;
+using android::hidl::allocator::V1_0::IAllocator;
+using android::hidl::memory::V1_0::IMemory;
+
+namespace android {
+namespace hardware {
+namespace soundtrigger {
+namespace V2_1 {
+namespace implementation {
+
+namespace {
+
+// Backs up by the vector with the contents of shared memory.
+// It is assumed that the passed hidl_vector is empty, so it's
+// not cleared if the memory is a null object.
+// The caller needs to keep the returned sp<IMemory> as long as
+// the data is needed.
+std::pair<bool, sp<IMemory>> memoryAsVector(const hidl_memory& m, hidl_vec<uint8_t>* vec) {
+    sp<IMemory> memory;
+    if (m.size() == 0) {
+        return std::make_pair(true, memory);
+    }
+    memory = mapMemory(m);
+    if (memory != nullptr) {
+        memory->read();
+        vec->setToExternal(static_cast<uint8_t*>(static_cast<void*>(memory->getPointer())),
+                           memory->getSize());
+        return std::make_pair(true, memory);
+    }
+    ALOGE("%s: Could not map HIDL memory to IMemory", __func__);
+    return std::make_pair(false, memory);
+}
+
+// Moves the data from the vector into allocated shared memory,
+// emptying the vector.
+// It is assumed that the passed hidl_memory is a null object, so it's
+// not reset if the vector is empty.
+// The caller needs to keep the returned sp<IMemory> as long as
+// the data is needed.
+std::pair<bool, sp<IMemory>> moveVectorToMemory(hidl_vec<uint8_t>* v, hidl_memory* mem) {
+    sp<IMemory> memory;
+    if (v->size() == 0) {
+        return std::make_pair(true, memory);
+    }
+    sp<IAllocator> ashmem = IAllocator::getService("ashmem");
+    if (ashmem == 0) {
+        ALOGE("Failed to retrieve ashmem allocator service");
+        return std::make_pair(false, memory);
+    }
+    bool success = false;
+    Return<void> r = ashmem->allocate(v->size(), [&](bool s, const hidl_memory& m) {
+        success = s;
+        if (success) *mem = m;
+    });
+    if (r.isOk() && success) {
+        memory = hardware::mapMemory(*mem);
+        if (memory != 0) {
+            memory->update();
+            memcpy(memory->getPointer(), v->data(), v->size());
+            memory->commit();
+            v->resize(0);
+            return std::make_pair(true, memory);
+        } else {
+            ALOGE("Failed to map allocated ashmem");
+        }
+    } else {
+        ALOGE("Failed to allocate %llu bytes from ashmem", (unsigned long long)v->size());
+    }
+    return std::make_pair(false, memory);
+}
+
+}  // namespace
+
+Return<void> SoundTriggerHw::loadSoundModel_2_1(
+    const V2_1::ISoundTriggerHw::SoundModel& soundModel,
+    const sp<V2_1::ISoundTriggerHwCallback>& callback, int32_t cookie,
+    V2_1::ISoundTriggerHw::loadSoundModel_2_1_cb _hidl_cb) {
+    // It is assumed that legacy data vector is empty, thus making copy is cheap.
+    V2_0::ISoundTriggerHw::SoundModel soundModel_2_0(soundModel.header);
+    auto result = memoryAsVector(soundModel.data, &soundModel_2_0.data);
+    if (result.first) {
+        sp<SoundModelClient> client =
+            new SoundModelClient_2_1(nextUniqueModelId(), cookie, callback);
+        _hidl_cb(doLoadSoundModel(soundModel_2_0, client), client->getId());
+        return Void();
+    }
+    _hidl_cb(-ENOMEM, 0);
+    return Void();
+}
+
+Return<void> SoundTriggerHw::loadPhraseSoundModel_2_1(
+    const V2_1::ISoundTriggerHw::PhraseSoundModel& soundModel,
+    const sp<V2_1::ISoundTriggerHwCallback>& callback, int32_t cookie,
+    V2_1::ISoundTriggerHw::loadPhraseSoundModel_2_1_cb _hidl_cb) {
+    V2_0::ISoundTriggerHw::PhraseSoundModel soundModel_2_0;
+    // It is assumed that legacy data vector is empty, thus making copy is cheap.
+    soundModel_2_0.common = soundModel.common.header;
+    // Avoid copying phrases data.
+    soundModel_2_0.phrases.setToExternal(
+        const_cast<V2_0::ISoundTriggerHw::Phrase*>(soundModel.phrases.data()),
+        soundModel.phrases.size());
+    auto result = memoryAsVector(soundModel.common.data, &soundModel_2_0.common.data);
+    if (result.first) {
+        sp<SoundModelClient> client =
+            new SoundModelClient_2_1(nextUniqueModelId(), cookie, callback);
+        _hidl_cb(doLoadSoundModel((const V2_0::ISoundTriggerHw::SoundModel&)soundModel_2_0, client),
+                 client->getId());
+        return Void();
+    }
+    _hidl_cb(-ENOMEM, 0);
+    return Void();
+}
+
+Return<int32_t> SoundTriggerHw::startRecognition_2_1(
+    int32_t modelHandle, const V2_1::ISoundTriggerHw::RecognitionConfig& config) {
+    // It is assumed that legacy data vector is empty, thus making copy is cheap.
+    V2_0::ISoundTriggerHw::RecognitionConfig config_2_0(config.header);
+    auto result = memoryAsVector(config.data, &config_2_0.data);
+    return result.first ? startRecognition(modelHandle, config_2_0) : Return<int32_t>(-ENOMEM);
+}
+
+void SoundTriggerHw::SoundModelClient_2_1::recognitionCallback(
+    struct sound_trigger_recognition_event* halEvent) {
+    if (halEvent->type == SOUND_MODEL_TYPE_KEYPHRASE) {
+        V2_0::ISoundTriggerHwCallback::PhraseRecognitionEvent event_2_0;
+        convertPhaseRecognitionEventFromHal(
+            &event_2_0, reinterpret_cast<sound_trigger_phrase_recognition_event*>(halEvent));
+        event_2_0.common.model = mId;
+        V2_1::ISoundTriggerHwCallback::PhraseRecognitionEvent event;
+        event.phraseExtras.setToExternal(event_2_0.phraseExtras.data(),
+                                         event_2_0.phraseExtras.size());
+        auto result = moveVectorToMemory(&event_2_0.common.data, &event.common.data);
+        if (result.first) {
+            // The data vector is now empty, thus copying is cheap.
+            event.common.header = event_2_0.common;
+            mCallback->phraseRecognitionCallback_2_1(event, mCookie);
+        }
+    } else {
+        V2_1::ISoundTriggerHwCallback::RecognitionEvent event;
+        convertRecognitionEventFromHal(&event.header, halEvent);
+        event.header.model = mId;
+        auto result = moveVectorToMemory(&event.header.data, &event.data);
+        if (result.first) {
+            mCallback->recognitionCallback_2_1(event, mCookie);
+        }
+    }
+}
+
+void SoundTriggerHw::SoundModelClient_2_1::soundModelCallback(
+    struct sound_trigger_model_event* halEvent) {
+    V2_1::ISoundTriggerHwCallback::ModelEvent event;
+    convertSoundModelEventFromHal(&event.header, halEvent);
+    event.header.model = mId;
+    auto result = moveVectorToMemory(&event.header.data, &event.data);
+    if (result.first) {
+        mCallback->soundModelCallback_2_1(event, mCookie);
+    }
+}
+
+ISoundTriggerHw* HIDL_FETCH_ISoundTriggerHw(const char* /* name */) {
+    return (new SoundTriggerHw())->getInterface();
+}
+
+}  // namespace implementation
+}  // namespace V2_1
+}  // namespace soundtrigger
+}  // namespace hardware
+}  // namespace android