diff --git a/base/HidlSupport.cpp b/base/HidlSupport.cpp
index 58afa69..f97f216 100644
--- a/base/HidlSupport.cpp
+++ b/base/HidlSupport.cpp
@@ -36,27 +36,28 @@
 }  // namespace details
 
 hidl_handle::hidl_handle() {
-    mHandle = nullptr;
-    mOwnsHandle = false;
+    memset(this, 0, sizeof(*this));
+    // mHandle = nullptr;
+    // mOwnsHandle = false;
 }
 
 hidl_handle::~hidl_handle() {
     freeHandle();
 }
 
-hidl_handle::hidl_handle(const native_handle_t *handle) {
+hidl_handle::hidl_handle(const native_handle_t* handle) : hidl_handle() {
     mHandle = handle;
     mOwnsHandle = false;
 }
 
 // copy constructor.
-hidl_handle::hidl_handle(const hidl_handle &other) {
+hidl_handle::hidl_handle(const hidl_handle& other) : hidl_handle() {
     mOwnsHandle = false;
     *this = other;
 }
 
 // move constructor.
-hidl_handle::hidl_handle(hidl_handle&& other) noexcept {
+hidl_handle::hidl_handle(hidl_handle&& other) noexcept : hidl_handle() {
     mOwnsHandle = false;
     *this = std::move(other);
 }
@@ -137,10 +138,11 @@
 
 static const char *const kEmptyString = "";
 
-hidl_string::hidl_string()
-    : mBuffer(kEmptyString),
-      mSize(0),
-      mOwnsBuffer(false) {
+hidl_string::hidl_string() {
+    memset(this, 0, sizeof(*this));
+    // mSize is zero
+    // mOwnsBuffer is false
+    mBuffer = kEmptyString;
 }
 
 hidl_string::~hidl_string() {
diff --git a/base/include/hidl/HidlInternal.h b/base/include/hidl/HidlInternal.h
index 6377c46..0b80cd4 100644
--- a/base/include/hidl/HidlInternal.h
+++ b/base/include/hidl/HidlInternal.h
@@ -68,6 +68,7 @@
 struct hidl_pointer {
     hidl_pointer()
         : _pad(0) {
+        static_assert(sizeof(*this) == 8, "wrong size");
     }
     hidl_pointer(T* ptr) : hidl_pointer() { mPointer = ptr; }
     hidl_pointer(const hidl_pointer<T>& other) : hidl_pointer() { mPointer = other.mPointer; }
diff --git a/base/include/hidl/HidlSupport.h b/base/include/hidl/HidlSupport.h
index 79dd992..4c133c1 100644
--- a/base/include/hidl/HidlSupport.h
+++ b/base/include/hidl/HidlSupport.h
@@ -328,11 +328,15 @@
 struct hidl_vec {
     using value_type = T;
 
-    hidl_vec()
-        : mBuffer(nullptr),
-          mSize(0),
-          mOwnsBuffer(true) {
+    hidl_vec() {
         static_assert(hidl_vec<T>::kOffsetOfBuffer == 0, "wrong offset");
+
+        memset(this, 0, sizeof(*this));
+        // mSize is 0
+        // mBuffer is nullptr
+
+        // this is for consistency with the original implementation
+        mOwnsBuffer = true;
     }
 
     // Note, does not initialize primitive types.
@@ -342,8 +346,7 @@
         *this = other;
     }
 
-    hidl_vec(hidl_vec<T> &&other) noexcept
-    : mOwnsBuffer(false) {
+    hidl_vec(hidl_vec<T> &&other) noexcept : hidl_vec() {
         *this = std::move(other);
     }
 
@@ -357,7 +360,7 @@
               typename = typename std::enable_if<std::is_convertible<
                   typename std::iterator_traits<InputIterator>::iterator_category,
                   std::input_iterator_tag>::value>::type>
-    hidl_vec(InputIterator first, InputIterator last) : mOwnsBuffer(true) {
+    hidl_vec(InputIterator first, InputIterator last) : hidl_vec() {
         auto size = std::distance(first, last);
         if (size > static_cast<int64_t>(UINT32_MAX)) {
             details::logAlwaysFatal("hidl_vec can't hold more than 2^32 elements.");
@@ -366,7 +369,8 @@
             details::logAlwaysFatal("size can't be negative.");
         }
         mSize = static_cast<uint32_t>(size);
-        mBuffer = new T[mSize];
+        mBuffer = new T[mSize]();
+        mOwnsBuffer = true;
 
         size_t idx = 0;
         for (; first != last; ++first) {
@@ -451,7 +455,7 @@
             delete[] mBuffer;
         }
         mSize = static_cast<uint32_t>(list.size());
-        mBuffer = new T[mSize];
+        mBuffer = new T[mSize]();
         mOwnsBuffer = true;
 
         size_t idx = 0;
@@ -505,7 +509,7 @@
         if (size > UINT32_MAX) {
             details::logAlwaysFatal("hidl_vec can't hold more than 2^32 elements.");
         }
-        T *newBuffer = new T[size];
+        T* newBuffer = new T[size]();
 
         for (size_t i = 0; i < std::min(static_cast<uint32_t>(size), mSize); ++i) {
             newBuffer[i] = mBuffer[i];
@@ -581,7 +585,7 @@
         mSize = static_cast<uint32_t>(size);
         mOwnsBuffer = true;
         if (mSize > 0) {
-            mBuffer = new T[size];
+            mBuffer = new T[size]();
             for (size_t i = 0; i < size; ++i) {
                 mBuffer[i] = data[i];
             }
@@ -851,7 +855,9 @@
 // Version functions
 struct hidl_version {
 public:
-    constexpr hidl_version(uint16_t major, uint16_t minor) : mMajor(major), mMinor(minor) {}
+    constexpr hidl_version(uint16_t major, uint16_t minor) : mMajor(major), mMinor(minor) {
+        static_assert(sizeof(*this) == 4, "wrong size");
+    }
 
     bool operator==(const hidl_version& other) const {
         return (mMajor == other.get_major() && mMinor == other.get_minor());
diff --git a/transport/token/1.0/utils/Android.bp b/transport/token/1.0/utils/Android.bp
index 5a8d51c..cdbdd97 100644
--- a/transport/token/1.0/utils/Android.bp
+++ b/transport/token/1.0/utils/Android.bp
@@ -25,22 +25,16 @@
         "HybridInterface.cpp",
     ],
 
-    header_libs: [
-        "libbinder_headers",
-    ],
-
     shared_libs: [
-        "libutils",
-        "liblog",
-        "libhidlbase",
         "android.hidl.token@1.0",
-    ],
-
-    export_header_lib_headers: [
-        "libbinder_headers",
+        "libbinder",
+        "libhidlbase",
+        "liblog",
+        "libutils",
     ],
 
     export_shared_lib_headers: [
+        "libbinder",
         "libhidlbase",
     ],
 
diff --git a/transport/token/1.0/utils/include/hidl/HybridInterface.h b/transport/token/1.0/utils/include/hidl/HybridInterface.h
index 595c2e3..125d5e8 100644
--- a/transport/token/1.0/utils/include/hidl/HybridInterface.h
+++ b/transport/token/1.0/utils/include/hidl/HybridInterface.h
@@ -23,6 +23,9 @@
 #include <binder/Parcel.h>
 #include <hidl/HidlSupport.h>
 
+#include <cinttypes>
+#include <variant>
+
 /**
  * Hybrid Interfaces
  * =================
@@ -47,50 +50,130 @@
  *
  * To demonstrate how this is done, here is an example. Suppose `INTERFACE` is
  * `IFoo` and `HALINTERFACE` is `HFoo`. The required steps are:
- * 1. Use DECLARE_HYBRID_META_INTERFACE instead of DECLARE_META_INTERFACE in the
- *    definition of `IFoo`. The usage is
- *        DECLARE_HYBRID_META_INTERFACE(IFoo, HFoo)
- *    inside the body of `IFoo`.
+ * 1. Use `DECLARE_HYBRID_META_INTERFACE` instead of `DECLARE_META_INTERFACE` in
+ *    the declaration of `IFoo`. `DECLARE_HYBRID_META_INTERFACE` takes an
+ *    additional argument that is the hidl interface to be converted into a
+ *    binder interface. Example:
+ *        Change from `DECLARE_META_INTERFACE(Foo)`
+ *                 to `DECLARE_HYBRID_META_INTERFACE(Foo, HFoo)`
  * 2. Create a converter class that derives from
- *    `H2BConverter<HFoo, IFoo, BnFoo>`. Let us call this `H2BFoo`.
+ *    `H2BConverter<HFoo, BnFoo>`. Let us call this `H2BFoo`.
  * 3. Add the following constructor in `H2BFoo` that call the corresponding
  *    constructors in `H2BConverter`:
- *        H2BFoo(const sp<HalInterface>& base) : CBase(base) {}
- *    Note: `CBase = H2BConverter<HFoo, IFoo, BnFoo>` and `HalInterface = HFoo`
- *    are member typedefs of `H2BConverter<HFoo, IFoo, BnFoo>`, so the above
- *    line can be copied into `H2BFoo`.
+ *        `H2BFoo(const sp<HalInterface>& base) : CBase(base) {}`
+ *    Note: `CBase = H2BConverter<HFoo, BnFoo>` and `HalInterface = HFoo` are
+ *    member typedefs of `H2BConverter<HFoo, BnFoo>`, so the above line can be
+ *    copied verbatim into `H2BFoo`.
  * 4. Implement `IFoo` in `H2BFoo` on top of `HFoo`. `H2BConverter` provides a
  *    protected `mBase` of type `sp<HFoo>` that can be used to access the `HFoo`
- *    instance. (There is also a public function named `getHalInterface()` that
- *    returns `mBase`.)
+ *    instance. (There is also a public function named `getBase()` that returns
+ *    `mBase`.)
  * 5. Create a hardware proxy class that derives from
  *    `HpInterface<BpFoo, H2BFoo>`. Name this class `HpFoo`. (This name cannot
  *    deviate. See step 8 below.)
  * 6. Add the following constructor to `HpFoo`:
- *        HpFoo(const sp<IBinder>& base): PBase(base) {}
+ *        `HpFoo(const sp<IBinder>& base): PBase(base) {}`
  *    Note: `PBase` a member typedef of `HpInterface<BpFoo, H2BFoo>` that is
  *    equal to `HpInterface<BpFoo, H2BFoo>` itself, so the above line can be
  *    copied verbatim into `HpFoo`.
- * 7. Delegate all functions in `HpFoo` that come from `IFoo` except
- *    `getHalInterface` to the protected member `mBase`,
- *    which is defined in `HpInterface<BpFoo, H2BFoo>` (hence in `HpFoo`) with
- *    type `IFoo`. (There is also a public function named `getBaseInterface()`
- *    that returns `mBase`.)
- * 8. Replace the existing `IMPLEMENT_META_INTERFACE` for INTERFACE by
- *    `IMPLEMENT_HYBRID_META_INTERFACE`. Note that this macro relies on the
- *    exact naming of `HpFoo`, where `Foo` comes from the interface name `IFoo`.
- *    An example usage is
- *        IMPLEMENT_HYBRID_META_INTERFACE(IFoo, HFoo, "example.interface.foo");
+ * 7. Delegate all functions in `HpFoo` that come from `IFoo` (except those that
+ *    are defined by the macro `DECLARE_HYBRID_META_INTERFACE`) to the protected
+ *    member `mBase`. `mBase` is defined in `HpInterface<BpFoo, H2BFoo>` (hence
+ *    in `HpFoo`) with type `IFoo`. There is also a public function named
+ *    `getBase()` that returns `mBase`.
+ * 8. Replace the existing `IMPLEMENT_META_INTERFACE` for `IFoo` by
+ *    `IMPLEMENT_HYBRID_META_INTERFACE`. This macro assumes that the subclass of
+ *    `HpInterface` for `IFoo` is named `HpFoo`.
  *
- * `GETTOKEN` Template Argument
- * ============================
+ * After the hybrid interface has been put in place properly, it can be used to
+ * do the following tasks:
+ * 1. Create an `IFoo` instance from an `HFoo` by passing `sp<HFoo>` to
+ *    the constructor of `H2BFoo`.
+ * 2. Retrieve an `HFoo` from an `HpFoo` instance by calling
+ *    `HpFoo::getHalInterface<HFoo>()`. This function may return `nullptr` if
+ *    the `HpFoo` object is not backed by `HFoo`. The template parameter is
+ *    required because `HpFoo` in fact may be backed by multiple H2B converter
+ *    classes.
  *
- * Following the instructions above, `H2BConverter` and `HpInterface` would use
- * `transact()` to send over tokens, with `code` (the first argument of
- * `transact()`) equal to `DEFAULT_GET_HAL_TOKEN_TRANSACTION_CODE`. If this
- * value clashes with other values already in use in the `Bp` class, it can be
- * changed by supplying the last optional template argument to `H2BConverter`
- * and `HpInterface`.
+ * Multiple H2B Converters
+ * =======================
+ *
+ * Because the system may support multiple versions of hidl interfaces for the
+ * same object, one binder interface may correspond to multiple H2B converters.
+ * The hybrid interface is designed to handle this as
+ * well---`DECLARE_HYBRID_META_INTERFACE` and `HpInterface` can take a variable
+ * number of arguments.
+ *
+ * As a concrete example, suppose `IFoo` is a binder interface that corresponds
+ * to two hidl interfaces `HFoo1` and `HFoo2`. That means `HpFoo`, the hybrid
+ * interface presenting `IFoo`, may be backed by `HFoo1` or `HFoo2`. This is
+ * achievable by
+ *
+ *   - Replacing `DECLARE_META_INTERFACE(Foo)` by
+ *     `DECLARE_HYBRID_META_INTERFACE(Foo, HFoo1, HFoo2)` in the declaration of
+ *     `IFoo`.
+ *   - Creating `H2BFoo1` as a subclass of `H2BConverter<HFoo1, BnFoo>`;
+ *   - Creating `H2BFoo2` as a subclass of `H2BConverter<HFoo2, BnFoo>`; and
+ *   - Creating `HpFoo` as a subclass of `HpInterface<BpFoo, H2BFoo1, H2BFoo2>`.
+ *
+ * It is important that `HFoo1` and `HFoo2` are different hidl interfaces. [The
+ * actual requirement is that for each pair `<HFoo, IFoo>`, there can be only
+ * one subclass of `H2BConverter<HFoo, BnFoo>`.]
+ *
+ * As mentioned in the previous section, `HpFoo::getHalInterface` requires a
+ * template argument because it must be able to return different hidl
+ * interface types based on which hidl interface is being used. The user of
+ * `HpFoo` can query the type of the underlying hidl interface by calling
+ * `HpFoo::getHalIndex()`. The return value is a 1-based index into the list of
+ * all the supported hidl interfaces. In the example with 2 hidl interfaces
+ * `HFoo1` and `HFoo2`, index 1 corresponds to `HFoo1` and index 2 corresponds
+ * to `HFoo2`. A typical code block that accesses the underlying hidl interface
+ * of would look like this:
+ *
+ * void someFunction(const sp<IFoo> &foo) {
+ *
+ *     switch (foo->getHalIndex()) {
+ *     case 1: {
+ *             sp<HFoo1> hFoo1 = foo->getHalInterface<HFoo1>();
+ *             ...
+ *             break;
+ *         }
+ *     case 2: {
+ *             sp<HFoo2> hFoo2 = foo->getHalInterface<HFoo2>();
+ *             ...
+ *             break;
+ *         }
+ *     default: // Not backed by a hidl interface.
+ *              // Alternatively, "case 0:" can be used.
+ *     }
+ *
+ * }
+ *
+ * Error State
+ * ===========
+ *
+ * A corrupted transaction may cause an `HpInterface` to be in an error state.
+ * This could cause `getHalInterface<ExpectedHalInterface>()` to return
+ * `nullptr` even though `getHalIndex()` returns a non-zero index and
+ * `ExpectedHalInterface` is the corresponding hidl interface. It is therefore
+ * recommended that a null check be performed on the return value of
+ * `getHalInterface` before using it.
+ *
+ * DECLARE_HYBRID_META_INTERFACE_WITH_CODE
+ * =======================================
+ *
+ * `H2BConverter` and `HpInterface` use `transact()` to send over tokens with
+ * the transaction code (the first argument of `transact()`) equal to `_GHT`,
+ * which is defined as a global constant named
+ * `DEFAULT_GET_HAL_TOKEN_TRANSACTION_CODE`.
+ *
+ * In the rare occasion that this value clashes with other values already used
+ * by the `Bp` class and modifying the `Bp` class is difficult, the
+ * "GET_HAL_TOKEN" transaction code can be changed to a different value simply
+ * by replacing `DECLARE_HYBRID_META_INTERFACE` with
+ * `DECLARE_HYBRID_META_INTERFACE_WITH_CODE` in the declaration of the base
+ * interface and supplying the new transaction code in the first argument of
+ * this macro.
  *
  */
 
@@ -106,23 +189,19 @@
 bool createHalToken(const sp<HInterface>& interface, HalToken* token);
 bool deleteHalToken(const HalToken& token);
 
-template <
-        typename HINTERFACE,
-        typename INTERFACE,
-        typename BNINTERFACE,
-        uint32_t GETTOKEN = DEFAULT_GET_HAL_TOKEN_TRANSACTION_CODE>
+template <typename HINTERFACE,
+          typename BNINTERFACE>
 class H2BConverter : public BNINTERFACE {
 public:
-    typedef H2BConverter<HINTERFACE, INTERFACE, BNINTERFACE, GETTOKEN> CBase; // Converter Base
-    typedef INTERFACE BaseInterface;
+    typedef H2BConverter<HINTERFACE, BNINTERFACE> CBase; // Converter Base
+    typedef typename BNINTERFACE::BaseInterface BaseInterface;
     typedef HINTERFACE HalInterface;
-    static constexpr uint32_t GET_HAL_TOKEN = GETTOKEN;
+    typedef typename BaseInterface::HalVariant HalVariant;
+    using BaseInterface::sGetHalTokenTransactionCode;
 
-    H2BConverter(const sp<HalInterface>& base) : mBase(base) {}
+    H2BConverter(const sp<HalInterface>& base) : mBase{base} {}
     virtual status_t onTransact(uint32_t code,
             const Parcel& data, Parcel* reply, uint32_t flags = 0);
-    virtual sp<HalInterface> getHalInterface() { return mBase; }
-    HalInterface* getBaseInterface() { return mBase.get(); }
     virtual status_t linkToDeath(
             const sp<IBinder::DeathRecipient>& recipient,
             void* cookie = nullptr,
@@ -132,9 +211,13 @@
             void* cookie = nullptr,
             uint32_t flags = 0,
             wp<IBinder::DeathRecipient>* outRecipient = nullptr);
+    virtual HalVariant getHalVariant() const override { return { mBase }; }
+    HalInterface* getBase() { return mBase.get(); }
 
 protected:
     sp<HalInterface> mBase;
+
+private:
     struct Obituary : public hardware::hidl_death_recipient {
         wp<IBinder::DeathRecipient> recipient;
         void* cookie;
@@ -168,78 +251,174 @@
     };
     std::mutex mObituariesLock;
     std::vector<sp<Obituary> > mObituaries;
+
+    template <size_t Index = std::variant_size_v<HalVariant> - 1>
+    static constexpr size_t _findIndex() {
+        if constexpr (Index == 0) {
+            return Index;
+        } else if constexpr (
+                std::is_same_v<
+                    std::variant_alternative_t<Index, HalVariant>,
+                    sp<HalInterface>>) {
+            return Index;
+        } else {
+            return _findIndex<Index - 1>();
+        }
+    }
+
+    static constexpr size_t sHalIndex = _findIndex<>();
+    static_assert(sHalIndex != 0,
+                  "H2BConverter from an unrecognized HAL interface.");
 };
 
-template <
-        typename BPINTERFACE,
-        typename CONVERTER,
-        uint32_t GETTOKEN = DEFAULT_GET_HAL_TOKEN_TRANSACTION_CODE>
+template <typename BPINTERFACE, typename CONVERTER, typename... CONVERTERS>
 class HpInterface : public CONVERTER::BaseInterface {
 public:
-    typedef HpInterface<BPINTERFACE, CONVERTER, GETTOKEN> PBase; // Proxy Base
+    typedef HpInterface<BPINTERFACE, CONVERTER, CONVERTERS...> PBase; // Proxy Base
     typedef typename CONVERTER::BaseInterface BaseInterface;
-    typedef typename CONVERTER::HalInterface HalInterface;
-    static constexpr uint32_t GET_HAL_TOKEN = GETTOKEN;
+    typedef typename BaseInterface::HalVariant HalVariant;
+    using BaseInterface::sGetHalTokenTransactionCode;
 
     explicit HpInterface(const sp<IBinder>& impl);
-    virtual sp<HalInterface> getHalInterface() { return mHal; }
-    BaseInterface* getBaseInterface() { return mBase.get(); }
+    BaseInterface* getBase() { return mBase.get(); }
+    virtual HalVariant getHalVariant() const override { return mHalVariant; }
 
 protected:
-    IBinder* mImpl;
+    IBinder* mBpBinder;
     sp<BPINTERFACE> mBp;
     sp<BaseInterface> mBase;
-    sp<HalInterface> mHal;
-    IBinder* onAsBinder() override { return mImpl; }
+    HalVariant mHalVariant;
+    bool mHasConverter{false};
+    IBinder* onAsBinder() override { return mBpBinder; }
+
+private:
+    typedef std::variant<std::monostate,
+            CONVERTER, CONVERTERS...> _ConverterVar;
+    typedef std::variant<std::monostate,
+            typename CONVERTER::HalInterface,
+            typename CONVERTERS::HalInterface...> _ConverterHalVar;
+    typedef std::variant<std::monostate,
+            sp<typename CONVERTER::HalInterface>,
+            sp<typename CONVERTERS::HalInterface>...> _ConverterHalPointerVar;
+
+    static_assert(std::is_same_v<_ConverterHalPointerVar, HalVariant>,
+                  "Converter classes do not match HAL interfaces.");
+
+    template <size_t Index = std::variant_size_v<HalVariant> - 1>
+    bool _castFromHalBaseAndConvert(size_t halIndex,
+                                    const sp<HInterface>& halBase) {
+        if constexpr (Index == 0) {
+            return false;
+        } else {
+            if (halIndex != Index) {
+                return _castFromHalBaseAndConvert<Index - 1>(halIndex, halBase);
+            }
+            typedef std::variant_alternative_t<Index, _ConverterHalVar>
+                    HalInterface;
+            sp<HalInterface> halInterface = HalInterface::castFrom(halBase);
+            mHalVariant.template emplace<Index>(halInterface);
+            if (!halInterface) {
+                return false;
+            }
+            if (mHasConverter) {
+                typedef std::variant_alternative_t<Index, _ConverterVar>
+                        Converter;
+                sp<Converter> converter = new Converter(halInterface);
+                if (converter) {
+                    mBase = converter;
+                } else {
+                    ALOGW("HpInterface: Failed to create an H2B converter -- "
+                          "index = %zu.", Index);
+                }
+            }
+            return true;
+        }
+    }
+
+    bool castFromHalBaseAndConvert(size_t halIndex,
+                                   const sp<HInterface>& halBase) {
+        if (!_castFromHalBaseAndConvert<>(halIndex, halBase)) {
+            return false;
+        }
+        return true;
+    }
+
 };
 
 // ----------------------------------------------------------------------
 
-#define DECLARE_HYBRID_META_INTERFACE(INTERFACE, HAL)                   \
-    static const ::android::String16 descriptor;                        \
-    static ::android::sp<I##INTERFACE> asInterface(                     \
-            const ::android::sp<::android::IBinder>& obj);              \
-    virtual const ::android::String16& getInterfaceDescriptor() const;  \
-    I##INTERFACE();                                                     \
-    virtual ~I##INTERFACE();                                            \
-    virtual sp<HAL> getHalInterface();                                  \
+#define DECLARE_HYBRID_META_INTERFACE(INTERFACE, ...)                     \
+        DECLARE_HYBRID_META_INTERFACE_WITH_CODE(                          \
+            ::android::DEFAULT_GET_HAL_TOKEN_TRANSACTION_CODE,            \
+            INTERFACE, __VA_ARGS__)                                       \
 
 
-#define IMPLEMENT_HYBRID_META_INTERFACE(INTERFACE, HAL, NAME)           \
-    const ::android::String16 I##INTERFACE::descriptor(NAME);           \
-    const ::android::String16&                                          \
-            I##INTERFACE::getInterfaceDescriptor() const {              \
-        return I##INTERFACE::descriptor;                                \
-    }                                                                   \
-    ::android::sp<I##INTERFACE> I##INTERFACE::asInterface(              \
-            const ::android::sp<::android::IBinder>& obj)               \
-    {                                                                   \
-        ::android::sp<I##INTERFACE> intr;                               \
-        if (obj != nullptr) {                                           \
-            intr = static_cast<I##INTERFACE*>(                          \
-                obj->queryLocalInterface(                               \
-                        I##INTERFACE::descriptor).get());               \
-            if (intr == nullptr) {                                      \
-                intr = new Hp##INTERFACE(obj);                          \
-            }                                                           \
-        }                                                               \
-        return intr;                                                    \
-    }                                                                   \
-    I##INTERFACE::I##INTERFACE() { }                                    \
-    I##INTERFACE::~I##INTERFACE() { }                                   \
-    sp<HAL> I##INTERFACE::getHalInterface() { return nullptr; }         \
+#define DECLARE_HYBRID_META_INTERFACE_WITH_CODE(GTKCODE, INTERFACE, ...)  \
+private:                                                                  \
+    typedef ::std::variant<::std::monostate, __VA_ARGS__> _HalVariant;    \
+    template <typename... Types>                                          \
+    using _SpVariant =                                                    \
+            ::std::variant<::std::monostate, ::android::sp<Types>...>;    \
+public:                                                                   \
+    typedef _SpVariant<__VA_ARGS__> HalVariant;                           \
+    virtual HalVariant getHalVariant() const;                             \
+    size_t getHalIndex() const;                                           \
+    template <size_t Index>                                               \
+    using HalInterface = ::std::variant_alternative_t<Index, _HalVariant>;\
+    template <typename HAL>                                               \
+    sp<HAL> getHalInterface() const {                                     \
+        HalVariant halVariant = getHalVariant();                          \
+        const sp<HAL>* hal = std::get_if<sp<HAL>>(&halVariant);           \
+        return hal ? *hal : nullptr;                                      \
+    }                                                                     \
+                                                                          \
+    static const ::android::String16 descriptor;                          \
+    static ::android::sp<I##INTERFACE> asInterface(                       \
+            const ::android::sp<::android::IBinder>& obj);                \
+    virtual const ::android::String16& getInterfaceDescriptor() const;    \
+    I##INTERFACE();                                                       \
+    virtual ~I##INTERFACE();                                              \
+    static constexpr uint32_t sGetHalTokenTransactionCode = GTKCODE;      \
+
+
+#define IMPLEMENT_HYBRID_META_INTERFACE(INTERFACE, NAME)                  \
+    I##INTERFACE::HalVariant I##INTERFACE::getHalVariant() const {        \
+        return HalVariant{std::in_place_index<0>};                        \
+    }                                                                     \
+    size_t I##INTERFACE::getHalIndex() const {                            \
+        return getHalVariant().index();                                   \
+    }                                                                     \
+    constexpr uint32_t I##INTERFACE::sGetHalTokenTransactionCode;         \
+    const ::android::String16 I##INTERFACE::descriptor(NAME);             \
+    const ::android::String16&                                            \
+            I##INTERFACE::getInterfaceDescriptor() const {                \
+        return I##INTERFACE::descriptor;                                  \
+    }                                                                     \
+    ::android::sp<I##INTERFACE> I##INTERFACE::asInterface(                \
+            const ::android::sp<::android::IBinder>& obj)                 \
+    {                                                                     \
+        ::android::sp<I##INTERFACE> intr;                                 \
+        if (obj != nullptr) {                                             \
+            intr = static_cast<I##INTERFACE*>(                            \
+                obj->queryLocalInterface(                                 \
+                        I##INTERFACE::descriptor).get());                 \
+            if (intr == nullptr) {                                        \
+                intr = new Hp##INTERFACE(obj);                            \
+            }                                                             \
+        }                                                                 \
+        return intr;                                                      \
+    }                                                                     \
+    I##INTERFACE::I##INTERFACE() { }                                      \
+    I##INTERFACE::~I##INTERFACE() { }                                     \
 
 // ----------------------------------------------------------------------
 
-template <
-        typename HINTERFACE,
-        typename INTERFACE,
-        typename BNINTERFACE,
-        uint32_t GETTOKEN>
-status_t H2BConverter<HINTERFACE, INTERFACE, BNINTERFACE, GETTOKEN>::
+template <typename HINTERFACE,
+          typename BNINTERFACE>
+status_t H2BConverter<HINTERFACE, BNINTERFACE>::
         onTransact(
         uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags) {
-    if (code == GET_HAL_TOKEN) {
+    if (code == sGetHalTokenTransactionCode) {
         if (!data.enforceInterface(BaseInterface::getInterfaceDescriptor())) {
             return BAD_TYPE;
         }
@@ -247,27 +426,35 @@
         HalToken token;
         bool result;
         result = createHalToken(mBase, &token);
+        // Write whether a HAL token is present.
+        reply->writeBool(result);
         if (!result) {
             ALOGE("H2BConverter: Failed to create HAL token.");
+            return NO_ERROR;
         }
-        reply->writeBool(result);
+
+        // Write the HAL token.
         reply->writeByteArray(token.size(), token.data());
+
+        // Write the HAL index.
+        reply->writeUint32(static_cast<uint32_t>(sHalIndex));
+
+        // Write a flag indicating that a converter needs to be created.
+        reply->writeBool(true);
+
         return NO_ERROR;
     }
     return BNINTERFACE::onTransact(code, data, reply, flags);
 }
 
-template <
-        typename HINTERFACE,
-        typename INTERFACE,
-        typename BNINTERFACE,
-        uint32_t GETTOKEN>
-status_t H2BConverter<HINTERFACE, INTERFACE, BNINTERFACE, GETTOKEN>::
-        linkToDeath(
+template <typename HINTERFACE,
+          typename BNINTERFACE>
+status_t H2BConverter<HINTERFACE, BNINTERFACE>::linkToDeath(
         const sp<IBinder::DeathRecipient>& recipient,
         void* cookie, uint32_t flags) {
-    LOG_ALWAYS_FATAL_IF(recipient == nullptr,
-            "linkToDeath(): recipient must be non-nullptr");
+    LOG_ALWAYS_FATAL_IF(
+            recipient == nullptr,
+            "linkToDeath(): recipient must not be null.");
     {
         std::lock_guard<std::mutex> lock(mObituariesLock);
         mObituaries.push_back(new Obituary(recipient, cookie, flags, this));
@@ -278,13 +465,9 @@
     return NO_ERROR;
 }
 
-template <
-        typename HINTERFACE,
-        typename INTERFACE,
-        typename BNINTERFACE,
-        uint32_t GETTOKEN>
-status_t H2BConverter<HINTERFACE, INTERFACE, BNINTERFACE, GETTOKEN>::
-        unlinkToDeath(
+template <typename HINTERFACE,
+          typename BNINTERFACE>
+status_t H2BConverter<HINTERFACE, BNINTERFACE>::unlinkToDeath(
         const wp<IBinder::DeathRecipient>& recipient,
         void* cookie, uint32_t flags,
         wp<IBinder::DeathRecipient>* outRecipient) {
@@ -304,37 +487,70 @@
     return NAME_NOT_FOUND;
 }
 
-template <typename BPINTERFACE, typename CONVERTER, uint32_t GETTOKEN>
-HpInterface<BPINTERFACE, CONVERTER, GETTOKEN>::HpInterface(
-        const sp<IBinder>& impl) :
-    mImpl(impl.get()),
-    mBp(new BPINTERFACE(impl)) {
+template <typename BPINTERFACE, typename CONVERTER, typename... CONVERTERS>
+HpInterface<BPINTERFACE, CONVERTER, CONVERTERS...>::HpInterface(
+        const sp<IBinder>& impl)
+      : mBpBinder{impl.get()},
+        mBp{new BPINTERFACE(impl)} {
     mBase = mBp;
-    if (mImpl->remoteBinder() == nullptr) {
+    if (!mBpBinder->remoteBinder()) {
         return;
     }
     Parcel data, reply;
     data.writeInterfaceToken(BaseInterface::getInterfaceDescriptor());
-    if (mImpl->transact(GET_HAL_TOKEN, data, &reply) == NO_ERROR) {
-        bool tokenCreated = reply.readBool();
+    if (mBpBinder->transact(sGetHalTokenTransactionCode,
+                            data, &reply) == NO_ERROR) {
+        // Read whether a HAL token is present.
+        bool tokenCreated;
+        if (reply.readBool(&tokenCreated) != OK) {
+            ALOGW("HpInterface: Corrupted parcel from GET_HAL_TOKEN "
+                  "(tokenCreated).");
+        }
 
+        if (!tokenCreated) {
+            ALOGW("HpInterface: No HAL token was created.");
+            return;
+        }
+
+        // Read the HAL token.
         std::vector<uint8_t> tokenVector;
-        reply.readByteVector(&tokenVector);
-        HalToken token = HalToken(tokenVector);
+        if (reply.readByteVector(&tokenVector) != OK) {
+            ALOGW("HpInterface: Corrupted parcel from GET_HAL_TOKEN "
+                  "(halToken).");
+            return;
+        }
 
-        if (tokenCreated) {
-            sp<HInterface> hBase = retrieveHalInterface(token);
-            if (hBase != nullptr) {
-                mHal = HalInterface::castFrom(hBase);
-                if (mHal != nullptr) {
-                    mBase = new CONVERTER(mHal);
-                } else {
-                    ALOGE("HpInterface: Wrong interface type.");
-                }
-            } else {
-                ALOGE("HpInterface: Invalid HAL token.");
-            }
-            deleteHalToken(token);
+        // Retrieve the HAL interface from the token.
+        HalToken token{tokenVector};
+        sp<HInterface> halBase = retrieveHalInterface(token);
+        deleteHalToken(token);
+
+        if (!halBase) {
+            ALOGW("HpInterface: Failed to retrieve HAL interface.");
+            return;
+        }
+
+        uint32_t halIndex;
+        // Read the hal index.
+        if (reply.readUint32(&halIndex) != OK) {
+            ALOGW("HpInterface: Corrupted parcel from GET_HAL_TOKEN "
+                  "(halIndex).");
+            return;
+        }
+
+        // Read the converter flag.
+        if (reply.readBool(&mHasConverter) != OK) {
+            ALOGW("HpInterface: Corrupted parcel from GET_HAL_TOKEN "
+                  "(hasConverter).");
+            return;
+        }
+
+        // Call castFrom from the right HAL interface and create a converter if
+        // needed.
+        if (!castFromHalBaseAndConvert(static_cast<size_t>(halIndex),
+                                       halBase)) {
+            ALOGW("HpInterface: Failed to cast to the correct HAL interface -- "
+                  "HAL index = %" PRIu32 ".", halIndex);
         }
     }
 }
diff --git a/vintfdata/Android.mk b/vintfdata/Android.mk
index ffe361f..7a30668 100644
--- a/vintfdata/Android.mk
+++ b/vintfdata/Android.mk
@@ -23,10 +23,6 @@
 # installed on product partition.
 
 FRAMEWORK_MANIFEST_INPUT_FILES := $(LOCAL_PATH)/manifest.xml
-# TODO(b/110487738): replace with vintf_fragment
-ifdef USE_VR_FLINGER
-  FRAMEWORK_MANIFEST_INPUT_FILES += $(LOCAL_PATH)/manifest_vr_hwc.xml
-endif
 ifdef DEVICE_FRAMEWORK_MANIFEST_FILE
   FRAMEWORK_MANIFEST_INPUT_FILES += $(DEVICE_FRAMEWORK_MANIFEST_FILE)
 endif
diff --git a/vintfdata/manifest_vr_hwc.xml b/vintfdata/manifest_vr_hwc.xml
deleted file mode 100644
index 1068cac..0000000
--- a/vintfdata/manifest_vr_hwc.xml
+++ /dev/null
@@ -1,11 +0,0 @@
-<manifest version="1.0" type="framework">
-    <hal>
-      <name>android.hardware.graphics.composer</name>
-      <transport>hwbinder</transport>
-      <version>2.1</version>
-      <interface>
-          <name>IComposer</name>
-          <instance>vr</instance>
-      </interface>
-    </hal>
-</manifest>