diff --git a/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlBufferTracker.h b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlBufferTracker.h
new file mode 100644
index 0000000..970606c
--- /dev/null
+++ b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlBufferTracker.h
@@ -0,0 +1,119 @@
+/*
+ * Copyright (C) 2021 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_FRAMEWORKS_ML_NN_COMMON_AIDL_BUFFER_TRACKER_H
+#define ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_BUFFER_TRACKER_H
+
+#include <android-base/macros.h>
+#include <android-base/thread_annotations.h>
+
+#include <map>
+#include <memory>
+#include <mutex>
+#include <set>
+#include <stack>
+#include <utility>
+#include <vector>
+
+#include "AidlHalInterfaces.h"
+#include "AidlValidateHal.h"
+
+namespace android::nn {
+
+// This class manages a CPU buffer allocated on heap and provides validation methods.
+class AidlManagedBuffer {
+  public:
+    static std::shared_ptr<AidlManagedBuffer> create(uint32_t size,
+                                                     std::set<AidlHalPreparedModelRole> roles,
+                                                     const Operand& operand);
+
+    // Prefer AidlManagedBuffer::create.
+    AidlManagedBuffer(std::unique_ptr<uint8_t[]> buffer, uint32_t size,
+                      std::set<AidlHalPreparedModelRole> roles, const Operand& operand);
+
+    uint8_t* getPointer() const { return kBuffer.get(); }
+    uint32_t getSize() const { return kSize; }
+
+    // "poolIndex" is the index of this buffer in the request.pools.
+    ErrorStatus validateRequest(uint32_t poolIndex, const Request& request,
+                                const aidl_hal::IPreparedModel* preparedModel) const;
+
+    // "size" is the byte size of the Memory provided to the copyFrom or copyTo method.
+    ErrorStatus validateCopyFrom(const std::vector<uint32_t>& dimensions, uint32_t size) const;
+    ErrorStatus validateCopyTo(uint32_t size) const;
+
+    bool updateDimensions(const std::vector<uint32_t>& dimensions);
+    void setInitialized(bool initialized);
+
+  private:
+    mutable std::mutex mMutex;
+    const std::unique_ptr<uint8_t[]> kBuffer;
+    const uint32_t kSize;
+    const std::set<AidlHalPreparedModelRole> kRoles;
+    const OperandType kOperandType;
+    const std::vector<uint32_t> kInitialDimensions;
+    std::vector<uint32_t> mUpdatedDimensions GUARDED_BY(mMutex);
+    bool mInitialized GUARDED_BY(mMutex) = false;
+};
+
+// Keep track of all AidlManagedBuffers and assign each with a unique token.
+class AidlBufferTracker : public std::enable_shared_from_this<AidlBufferTracker> {
+    DISALLOW_COPY_AND_ASSIGN(AidlBufferTracker);
+
+  public:
+    // A RAII class to help manage the lifetime of the token.
+    // It is only supposed to be constructed in AidlBufferTracker::add.
+    class Token {
+        DISALLOW_COPY_AND_ASSIGN(Token);
+
+      public:
+        Token(uint32_t token, std::shared_ptr<AidlBufferTracker> tracker)
+            : kToken(token), kBufferTracker(std::move(tracker)) {}
+        ~Token() { kBufferTracker->free(kToken); }
+        uint32_t get() const { return kToken; }
+
+      private:
+        const uint32_t kToken;
+        const std::shared_ptr<AidlBufferTracker> kBufferTracker;
+    };
+
+    // The factory of AidlBufferTracker. This ensures that the AidlBufferTracker is always managed
+    // by a shared_ptr.
+    static std::shared_ptr<AidlBufferTracker> create() {
+        return std::make_shared<AidlBufferTracker>();
+    }
+
+    // Prefer AidlBufferTracker::create.
+    AidlBufferTracker() : mTokenToBuffers(1) {}
+
+    std::unique_ptr<Token> add(std::shared_ptr<AidlManagedBuffer> buffer);
+    std::shared_ptr<AidlManagedBuffer> get(uint32_t token) const;
+
+  private:
+    void free(uint32_t token);
+
+    mutable std::mutex mMutex;
+    std::stack<uint32_t, std::vector<uint32_t>> mFreeTokens GUARDED_BY(mMutex);
+
+    // Since the tokens are allocated in a non-sparse way, we use a vector to represent the mapping.
+    // The index of the vector is the token. When the token gets freed, the corresponding entry is
+    // set to nullptr. mTokenToBuffers[0] is always set to nullptr because 0 is an invalid token.
+    std::vector<std::shared_ptr<AidlManagedBuffer>> mTokenToBuffers GUARDED_BY(mMutex);
+};
+
+}  // namespace android::nn
+
+#endif  // ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_BUFFER_TRACKER_H
diff --git a/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlHalInterfaces.h b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlHalInterfaces.h
new file mode 100644
index 0000000..28379bb
--- /dev/null
+++ b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlHalInterfaces.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2021 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_FRAMEWORKS_ML_NN_COMMON_AIDL_HAL_INTERFACES_H
+#define ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_HAL_INTERFACES_H
+
+#include <aidl/android/hardware/neuralnetworks/BnBuffer.h>
+#include <aidl/android/hardware/neuralnetworks/BnBurst.h>
+#include <aidl/android/hardware/neuralnetworks/BnDevice.h>
+#include <aidl/android/hardware/neuralnetworks/BnFencedExecutionCallback.h>
+#include <aidl/android/hardware/neuralnetworks/BnPreparedModel.h>
+#include <aidl/android/hardware/neuralnetworks/BnPreparedModelCallback.h>
+#include <aidl/android/hardware/neuralnetworks/BufferDesc.h>
+#include <aidl/android/hardware/neuralnetworks/BufferRole.h>
+#include <aidl/android/hardware/neuralnetworks/Capabilities.h>
+#include <aidl/android/hardware/neuralnetworks/DataLocation.h>
+#include <aidl/android/hardware/neuralnetworks/DeviceBuffer.h>
+#include <aidl/android/hardware/neuralnetworks/DeviceType.h>
+#include <aidl/android/hardware/neuralnetworks/ErrorStatus.h>
+#include <aidl/android/hardware/neuralnetworks/ExecutionPreference.h>
+#include <aidl/android/hardware/neuralnetworks/Extension.h>
+#include <aidl/android/hardware/neuralnetworks/ExtensionNameAndPrefix.h>
+#include <aidl/android/hardware/neuralnetworks/ExtensionOperandTypeInformation.h>
+#include <aidl/android/hardware/neuralnetworks/FusedActivationFunc.h>
+#include <aidl/android/hardware/neuralnetworks/IBuffer.h>
+#include <aidl/android/hardware/neuralnetworks/IDevice.h>
+#include <aidl/android/hardware/neuralnetworks/IFencedExecutionCallback.h>
+#include <aidl/android/hardware/neuralnetworks/IPreparedModel.h>
+#include <aidl/android/hardware/neuralnetworks/IPreparedModelCallback.h>
+#include <aidl/android/hardware/neuralnetworks/IPreparedModelParcel.h>
+#include <aidl/android/hardware/neuralnetworks/Memory.h>
+#include <aidl/android/hardware/neuralnetworks/Model.h>
+#include <aidl/android/hardware/neuralnetworks/NumberOfCacheFiles.h>
+#include <aidl/android/hardware/neuralnetworks/Operand.h>
+#include <aidl/android/hardware/neuralnetworks/OperandExtraParams.h>
+#include <aidl/android/hardware/neuralnetworks/OperandLifeTime.h>
+#include <aidl/android/hardware/neuralnetworks/OperandPerformance.h>
+#include <aidl/android/hardware/neuralnetworks/OperandType.h>
+#include <aidl/android/hardware/neuralnetworks/Operation.h>
+#include <aidl/android/hardware/neuralnetworks/OperationType.h>
+#include <aidl/android/hardware/neuralnetworks/OutputShape.h>
+#include <aidl/android/hardware/neuralnetworks/PerformanceInfo.h>
+#include <aidl/android/hardware/neuralnetworks/Priority.h>
+#include <aidl/android/hardware/neuralnetworks/Request.h>
+#include <aidl/android/hardware/neuralnetworks/RequestArgument.h>
+#include <aidl/android/hardware/neuralnetworks/RequestMemoryPool.h>
+#include <aidl/android/hardware/neuralnetworks/Subgraph.h>
+#include <aidl/android/hardware/neuralnetworks/SymmPerChannelQuantParams.h>
+#include <aidl/android/hardware/neuralnetworks/Timing.h>
+
+namespace android::nn {
+
+namespace aidl_hal = ::aidl::android::hardware::neuralnetworks;
+
+inline constexpr aidl_hal::Priority kDefaultPriorityAidl = aidl_hal::Priority::MEDIUM;
+
+}  // namespace android::nn
+
+#endif  // ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_HAL_INTERFACES_H
diff --git a/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlHalUtils.h b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlHalUtils.h
new file mode 100644
index 0000000..af2b387
--- /dev/null
+++ b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlHalUtils.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2021 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_FRAMEWORKS_ML_NN_COMMON_AIDL_HAL_UTILS_H
+#define ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_HAL_UTILS_H
+
+#include <vector>
+
+#include "AidlHalInterfaces.h"
+
+namespace android {
+namespace nn {
+
+// Return a vector with one entry for each non-extension OperandType except
+// SUBGRAPH, set to the specified PerformanceInfo value.  The vector will be
+// sorted by OperandType.
+//
+// Control flow (OperandType::SUBGRAPH) operation performance is specified
+// separately using Capabilities::ifPerformance and
+// Capabilities::whilePerformance.
+std::vector<aidl_hal::OperandPerformance> nonExtensionOperandPerformance(
+        aidl_hal::PerformanceInfo perf);
+
+// Update the vector entry corresponding to the specified OperandType with the
+// specified PerformanceInfo value.  The vector must already have an entry for
+// that OperandType, and must be sorted by OperandType.
+void update(std::vector<aidl_hal::OperandPerformance>* operandPerformance,
+            aidl_hal::OperandType type, aidl_hal::PerformanceInfo perf);
+
+// Returns true if an operand type is an extension type.
+bool isExtensionOperandType(aidl_hal::OperandType type);
+
+// Returns true if an operand type is a scalar type.
+bool isNonExtensionScalar(aidl_hal::OperandType type);
+
+}  // namespace nn
+}  // namespace android
+
+#endif  // ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_HAL_UTILS_H
diff --git a/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlValidateHal.h b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlValidateHal.h
new file mode 100644
index 0000000..0354631
--- /dev/null
+++ b/neuralnetworks/aidl/utils/include/nnapi/hal/aidl/AidlValidateHal.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2021 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_FRAMEWORKS_ML_NN_COMMON_AIDL_VALIDATE_HAL_H
+#define ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_VALIDATE_HAL_H
+
+#include <memory>
+#include <set>
+#include <tuple>
+#include <vector>
+
+#include "AidlHalInterfaces.h"
+#include "nnapi/TypeUtils.h"
+#include "nnapi/Validation.h"
+
+namespace android {
+namespace nn {
+
+using AidlHalPreparedModelRole = std::tuple<const aidl_hal::IPreparedModel*, IOType, uint32_t>;
+
+bool validateMemoryDesc(
+        const aidl_hal::BufferDesc& desc,
+        const std::vector<std::shared_ptr<aidl_hal::IPreparedModel>>& preparedModels,
+        const std::vector<aidl_hal::BufferRole>& inputRoles,
+        const std::vector<aidl_hal::BufferRole>& outputRoles,
+        std::function<const aidl_hal::Model*(const std::shared_ptr<aidl_hal::IPreparedModel>&)>
+                getModel,
+        std::set<AidlHalPreparedModelRole>* preparedModelRoles, aidl_hal::Operand* combinedOperand);
+
+}  // namespace nn
+}  // namespace android
+
+#endif  // ANDROID_FRAMEWORKS_ML_NN_COMMON_AIDL_VALIDATE_HAL_H
diff --git a/neuralnetworks/aidl/utils/src/AidlBufferTracker.cpp b/neuralnetworks/aidl/utils/src/AidlBufferTracker.cpp
new file mode 100644
index 0000000..15d0810
--- /dev/null
+++ b/neuralnetworks/aidl/utils/src/AidlBufferTracker.cpp
@@ -0,0 +1,227 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include "AidlBufferTracker.h"
+
+#include <android-base/macros.h>
+
+#include <memory>
+#include <mutex>
+#include <set>
+#include <stack>
+#include <utility>
+#include <vector>
+
+#include "AidlHalInterfaces.h"
+#include "nnapi/TypeUtils.h"
+
+namespace android::nn {
+
+std::shared_ptr<AidlManagedBuffer> AidlManagedBuffer::create(
+        uint32_t size, std::set<AidlHalPreparedModelRole> roles, const Operand& operand) {
+    std::unique_ptr<uint8_t[]> buffer(new (std::nothrow) uint8_t[size]);
+    if (buffer == nullptr) {
+        return nullptr;
+    }
+    if (isExtension(operand.type)) {
+        LOG(ERROR) << "AidlManagedBuffer cannot handle extension operands.";
+        return nullptr;
+    }
+    return std::make_shared<AidlManagedBuffer>(std::move(buffer), size, std::move(roles), operand);
+}
+
+AidlManagedBuffer::AidlManagedBuffer(std::unique_ptr<uint8_t[]> buffer, uint32_t size,
+                                     std::set<AidlHalPreparedModelRole> roles,
+                                     const Operand& operand)
+    : kBuffer(std::move(buffer)),
+      kSize(size),
+      kRoles(std::move(roles)),
+      kOperandType(operand.type),
+      kInitialDimensions(operand.dimensions),
+      mUpdatedDimensions(operand.dimensions) {
+    CHECK(!isExtension(kOperandType));
+}
+
+ErrorStatus AidlManagedBuffer::validateRequest(
+        uint32_t poolIndex, const Request& request,
+        const aidl_hal::IPreparedModel* preparedModel) const {
+    CHECK_LT(poolIndex, request.pools.size());
+    CHECK(std::holds_alternative<Request::MemoryDomainToken>(request.pools[poolIndex]));
+    std::lock_guard<std::mutex> guard(mMutex);
+
+    bool usedAsInput = false, usedAsOutput = false;
+    for (uint32_t i = 0; i < request.inputs.size(); i++) {
+        if (request.inputs[i].lifetime != Request::Argument::LifeTime::POOL) continue;
+        if (request.inputs[i].location.poolIndex != poolIndex) continue;
+        // Validate if the input role is specified during allocation.
+        if (kRoles.count({preparedModel, IOType::INPUT, i}) == 0) {
+            LOG(ERROR) << "AidlManagedBuffer::validateRequest -- invalid buffer role.";
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+        if (!mInitialized) {
+            LOG(ERROR)
+                    << "AidlManagedBuffer::validateRequest -- using uninitialized buffer as input "
+                       "request.";
+            return ErrorStatus::GENERAL_FAILURE;
+        }
+        auto combined = combineDimensions(mUpdatedDimensions, request.inputs[i].dimensions);
+        if (!combined.has_value()) {
+            LOG(ERROR) << "AidlManagedBuffer::validateRequest -- incompatible dimensions ("
+                       << toString(mUpdatedDimensions) << " vs "
+                       << toString(request.inputs[i].dimensions) << ")";
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+        usedAsInput = true;
+    }
+    for (uint32_t i = 0; i < request.outputs.size(); i++) {
+        if (request.outputs[i].lifetime != Request::Argument::LifeTime::POOL) continue;
+        if (request.outputs[i].location.poolIndex != poolIndex) continue;
+        if (usedAsInput || usedAsOutput) {
+            LOG(ERROR) << "AidlManagedBuffer::validateRequest -- using the same device memory for "
+                          "input/output or multiple outputs";
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+        // Validate if the output role is specified during allocation.
+        if (kRoles.count({preparedModel, IOType::OUTPUT, i}) == 0) {
+            LOG(ERROR) << "AidlManagedBuffer::validateRequest -- invalid buffer role.";
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+        auto combined = combineDimensions(kInitialDimensions, request.outputs[i].dimensions);
+        if (!combined.has_value()) {
+            LOG(ERROR) << "AidlManagedBuffer::validateRequest -- incompatible dimensions ("
+                       << toString(kInitialDimensions) << " vs "
+                       << toString(request.outputs[i].dimensions) << ")";
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+        usedAsOutput = true;
+    }
+    return ErrorStatus::NONE;
+}
+
+ErrorStatus AidlManagedBuffer::validateCopyFrom(const std::vector<uint32_t>& dimensions,
+                                                uint32_t size) const {
+    if (size != kSize) {
+        LOG(ERROR) << "AidlManagedBuffer::validateCopyFrom -- invalid memory size: " << kSize
+                   << " vs " << size;
+        return ErrorStatus::INVALID_ARGUMENT;
+    }
+
+    if (isNonExtensionScalar(kOperandType)) {
+        if (!dimensions.empty()) {
+            LOG(ERROR) << "AidlManagedBuffer::validateCopyFrom -- invalid dimensions for scalar "
+                          "operand: "
+                       << toString(dimensions);
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+        return ErrorStatus::NONE;
+    }
+
+    if (dimensions.empty()) {
+        if (tensorHasUnspecifiedDimensions(kOperandType, kInitialDimensions)) {
+            LOG(ERROR) << "AidlManagedBuffer::validateCopyFrom -- the initial dimensions are not "
+                          "fully "
+                          "specified and no dimension update is provided: "
+                       << toString(kInitialDimensions);
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+    } else {
+        if (tensorHasUnspecifiedDimensions(kOperandType, dimensions)) {
+            LOG(ERROR) << "AidlManagedBuffer::validateCopyFrom -- the updated dimensions are not "
+                          "fully "
+                          "specified: "
+                       << toString(dimensions);
+            return ErrorStatus::INVALID_ARGUMENT;
+        }
+    }
+
+    const auto combined = combineDimensions(kInitialDimensions, dimensions);
+    if (!combined.has_value()) {
+        LOG(ERROR) << "AidlManagedBuffer::validateCopyFrom -- incompatible dimensions ("
+                   << toString(kInitialDimensions) << " vs " << toString(dimensions) << ")";
+        return ErrorStatus::INVALID_ARGUMENT;
+    }
+    return ErrorStatus::NONE;
+}
+
+ErrorStatus AidlManagedBuffer::validateCopyTo(uint32_t size) const {
+    if (size != kSize) {
+        LOG(ERROR) << "AidlManagedBuffer::validateCopyTo -- invalid memory size: " << kSize
+                   << " vs " << size;
+        return ErrorStatus::INVALID_ARGUMENT;
+    }
+    std::lock_guard<std::mutex> guard(mMutex);
+    if (!mInitialized) {
+        LOG(ERROR) << "AidlManagedBuffer::validateCopyTo -- using uninitialized buffer as source.";
+        return ErrorStatus::GENERAL_FAILURE;
+    }
+    return ErrorStatus::NONE;
+}
+
+bool AidlManagedBuffer::updateDimensions(const std::vector<uint32_t>& dimensions) {
+    auto combined = combineDimensions(kInitialDimensions, dimensions);
+    if (!combined.has_value()) {
+        LOG(ERROR) << "AidlManagedBuffer::updateDimensions -- incompatible dimensions ("
+                   << toString(kInitialDimensions) << " vs " << toString(dimensions) << ")";
+        return false;
+    }
+    std::lock_guard<std::mutex> guard(mMutex);
+    mUpdatedDimensions = std::move(combined).value();
+    return true;
+}
+
+void AidlManagedBuffer::setInitialized(bool initialized) {
+    std::lock_guard<std::mutex> guard(mMutex);
+    mInitialized = initialized;
+}
+
+std::unique_ptr<AidlBufferTracker::Token> AidlBufferTracker::add(
+        std::shared_ptr<AidlManagedBuffer> buffer) {
+    if (buffer == nullptr) {
+        return nullptr;
+    }
+    std::lock_guard<std::mutex> guard(mMutex);
+    uint32_t token = 0;
+    if (mFreeTokens.empty()) {
+        token = mTokenToBuffers.size();
+        mTokenToBuffers.push_back(std::move(buffer));
+    } else {
+        token = mFreeTokens.top();
+        mFreeTokens.pop();
+        mTokenToBuffers[token] = std::move(buffer);
+    }
+    VLOG(MEMORY) << "AidlBufferTracker::add -- new token = " << token;
+    return std::make_unique<Token>(token, shared_from_this());
+}
+
+std::shared_ptr<AidlManagedBuffer> AidlBufferTracker::get(uint32_t token) const {
+    std::lock_guard<std::mutex> guard(mMutex);
+    if (mTokenToBuffers.size() <= token || mTokenToBuffers[token] == nullptr) {
+        LOG(ERROR) << "AidlBufferTracker::get -- unknown token " << token;
+        return nullptr;
+    }
+    return mTokenToBuffers[token];
+}
+
+void AidlBufferTracker::free(uint32_t token) {
+    std::lock_guard<std::mutex> guard(mMutex);
+    CHECK_LT(token, mTokenToBuffers.size());
+    CHECK(mTokenToBuffers[token] != nullptr);
+    VLOG(MEMORY) << "AidlBufferTracker::free -- release token = " << token;
+    mTokenToBuffers[token] = nullptr;
+    mFreeTokens.push(token);
+}
+
+}  // namespace android::nn
diff --git a/neuralnetworks/aidl/utils/src/AidlHalUtils.cpp b/neuralnetworks/aidl/utils/src/AidlHalUtils.cpp
new file mode 100644
index 0000000..6fc46ab
--- /dev/null
+++ b/neuralnetworks/aidl/utils/src/AidlHalUtils.cpp
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+// This file contains pre-canonical-types utility code and includes HAL
+// utilities. LegacyUtils.h is the subset of these utilities that do not touch
+// HAL.
+
+#include "AidlHalUtils.h"
+
+#include <android-base/logging.h>
+#include <nnapi/hal/aidl/Conversions.h>
+
+#include <algorithm>
+#include <iterator>
+#include <type_traits>
+#include <vector>
+
+#include "AidlHalInterfaces.h"
+#include "nnapi/TypeUtils.h"
+
+namespace android::nn {
+
+std::vector<aidl_hal::OperandPerformance> nonExtensionOperandPerformance(
+        aidl_hal::PerformanceInfo perf) {
+    static constexpr ndk::enum_range<aidl_hal::OperandType> kOperandTypeRange;
+    std::vector<aidl_hal::OperandPerformance> ret;
+    ret.reserve(std::distance(kOperandTypeRange.begin(), kOperandTypeRange.end()));
+    for (aidl_hal::OperandType type : kOperandTypeRange) {
+        if (type != aidl_hal::OperandType::SUBGRAPH) {
+            ret.push_back(aidl_hal::OperandPerformance{type, perf});
+        }
+    }
+    std::sort(ret.begin(), ret.end(),
+              [](const aidl_hal::OperandPerformance& a, const aidl_hal::OperandPerformance& b) {
+                  return a.type < b.type;
+              });
+
+    return ret;
+}
+
+void update(std::vector<aidl_hal::OperandPerformance>* operandPerformance,
+            aidl_hal::OperandType type, aidl_hal::PerformanceInfo perf) {
+    CHECK(operandPerformance != nullptr);
+    const auto it = std::lower_bound(operandPerformance->begin(), operandPerformance->end(), type,
+                                     [](const aidl_hal::OperandPerformance& perf,
+                                        aidl_hal::OperandType type) { return perf.type < type; });
+    CHECK(it != operandPerformance->end())
+            << toString(type) << " not in operand performance vector";
+    it->info = perf;
+}
+
+bool isExtensionOperandType(aidl_hal::OperandType type) {
+    return isExtension(convert(type).value());
+}
+
+bool isNonExtensionScalar(aidl_hal::OperandType type) {
+    return isNonExtensionScalar(convert(type).value());
+}
+
+}  // namespace android::nn
diff --git a/neuralnetworks/aidl/utils/src/AidlValidateHal.cpp b/neuralnetworks/aidl/utils/src/AidlValidateHal.cpp
new file mode 100644
index 0000000..a1c496a
--- /dev/null
+++ b/neuralnetworks/aidl/utils/src/AidlValidateHal.cpp
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2021 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 "ValidateHal"
+
+#include "AidlValidateHal.h"
+
+#include <android-base/logging.h>
+#include <nnapi/hal/aidl/Conversions.h>
+
+#include <algorithm>
+#include <memory>
+#include <set>
+#include <utility>
+#include <vector>
+
+#include "AidlHalUtils.h"
+#include "nnapi/TypeUtils.h"
+
+namespace android {
+namespace nn {
+
+bool validateMemoryDesc(
+        const aidl_hal::BufferDesc& desc,
+        const std::vector<std::shared_ptr<aidl_hal::IPreparedModel>>& preparedModels,
+        const std::vector<aidl_hal::BufferRole>& inputRoles,
+        const std::vector<aidl_hal::BufferRole>& outputRoles,
+        std::function<const aidl_hal::Model*(const std::shared_ptr<aidl_hal::IPreparedModel>&)>
+                getModel,
+        std::set<AidlHalPreparedModelRole>* preparedModelRoles,
+        aidl_hal::Operand* combinedOperand) {
+    NN_RET_CHECK(!preparedModels.empty());
+    NN_RET_CHECK(!inputRoles.empty() || !outputRoles.empty());
+
+    std::set<AidlHalPreparedModelRole> roles;
+    std::vector<aidl_hal::Operand> operands;
+    operands.reserve(inputRoles.size() + outputRoles.size());
+    for (const auto& role : inputRoles) {
+        NN_RET_CHECK_GE(role.modelIndex, 0);
+        NN_RET_CHECK_LT(static_cast<size_t>(role.modelIndex), preparedModels.size());
+        const auto& preparedModel = preparedModels[role.modelIndex];
+        NN_RET_CHECK(preparedModel != nullptr);
+        const auto* model = getModel(preparedModel);
+        NN_RET_CHECK(model != nullptr);
+        const auto& inputIndexes = model->main.inputIndexes;
+        NN_RET_CHECK_GE(role.ioIndex, 0);
+        NN_RET_CHECK_LT(static_cast<size_t>(role.ioIndex), inputIndexes.size());
+        NN_RET_CHECK_GT(role.probability, 0.0f);
+        NN_RET_CHECK_LE(role.probability, 1.0f);
+        const auto [it, success] = roles.emplace(preparedModel.get(), IOType::INPUT, role.ioIndex);
+        NN_RET_CHECK(success);
+        operands.push_back(model->main.operands[inputIndexes[role.ioIndex]]);
+    }
+    for (const auto& role : outputRoles) {
+        NN_RET_CHECK_GE(role.modelIndex, 0);
+        NN_RET_CHECK_LT(static_cast<size_t>(role.modelIndex), preparedModels.size());
+        const auto& preparedModel = preparedModels[role.modelIndex];
+        NN_RET_CHECK(preparedModel != nullptr);
+        const auto* model = getModel(preparedModel);
+        NN_RET_CHECK(model != nullptr);
+        const auto& outputIndexes = model->main.outputIndexes;
+        NN_RET_CHECK_GE(role.ioIndex, 0);
+        NN_RET_CHECK_LT(static_cast<size_t>(role.ioIndex), outputIndexes.size());
+        NN_RET_CHECK_GT(role.probability, 0.0f);
+        NN_RET_CHECK_LE(role.probability, 1.0f);
+        const auto [it, success] = roles.emplace(preparedModel.get(), IOType::OUTPUT, role.ioIndex);
+        NN_RET_CHECK(success);
+        operands.push_back(model->main.operands[outputIndexes[role.ioIndex]]);
+    }
+
+    CHECK(!operands.empty());
+    const auto opType = operands[0].type;
+    const auto canonicalOperandType = convert(opType);
+    NN_RET_CHECK(canonicalOperandType.has_value()) << canonicalOperandType.error().message;
+    const bool isExtensionOperand = isExtension(canonicalOperandType.value());
+
+    auto maybeDimensions = toUnsigned(desc.dimensions);
+    NN_RET_CHECK(maybeDimensions.has_value()) << maybeDimensions.error().message;
+    std::vector<uint32_t> dimensions = std::move(maybeDimensions).value();
+
+    for (const auto& operand : operands) {
+        NN_RET_CHECK(operand.type == operands[0].type)
+                << toString(operand.type) << " vs " << toString(operands[0].type);
+        NN_RET_CHECK_EQ(operand.scale, operands[0].scale);
+        NN_RET_CHECK_EQ(operand.zeroPoint, operands[0].zeroPoint);
+        // NOTE: validateMemoryDesc cannot validate extra parameters for extension operand type.
+        if (!isExtensionOperand) {
+            const auto& lhsExtraParams = operand.extraParams;
+            const auto& rhsExtraParams = operands[0].extraParams;
+            NN_RET_CHECK(lhsExtraParams == rhsExtraParams)
+                    << (lhsExtraParams.has_value() ? lhsExtraParams.value().toString()
+                                                   : "std::nullopt")
+                    << " vs "
+                    << (rhsExtraParams.has_value() ? rhsExtraParams.value().toString()
+                                                   : "std::nullopt");
+        }
+        const auto maybeRhsDimensions = toUnsigned(operand.dimensions);
+        NN_RET_CHECK(maybeRhsDimensions.has_value()) << maybeRhsDimensions.error().message;
+        const auto combined = combineDimensions(dimensions, maybeRhsDimensions.value());
+        NN_RET_CHECK(combined.has_value());
+        dimensions = combined.value();
+    }
+
+    // NOTE: validateMemoryDesc cannot validate scalar dimensions with extension operand type.
+    if (!isExtensionOperand) {
+        NN_RET_CHECK(!isNonExtensionScalar(opType) || dimensions.empty())
+                << "invalid dimensions with scalar operand type.";
+    }
+
+    if (preparedModelRoles != nullptr) {
+        *preparedModelRoles = std::move(roles);
+    }
+    if (combinedOperand != nullptr) {
+        *combinedOperand = operands[0];
+        // No need to check that values fit int32_t here, since the original values are obtained
+        // from int32_t.
+        combinedOperand->dimensions = aidl_hal::utils::toSigned(dimensions).value();
+    }
+    return true;
+}
+
+}  // namespace nn
+}  // namespace android