diff --git a/health/utils/libhealth2impl/Health.cpp b/health/utils/libhealth2impl/Health.cpp
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+++ b/health/utils/libhealth2impl/Health.cpp
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+/*
+ * 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.
+ */
+
+#include <health2impl/Health.h>
+
+#include <functional>
+#include <string_view>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android/hardware/health/1.0/types.h>
+#include <android/hardware/health/2.0/IHealthInfoCallback.h>
+#include <android/hardware/health/2.0/types.h>
+#include <android/hardware/health/2.1/IHealthInfoCallback.h>
+#include <hal_conversion.h>
+#include <healthd/healthd.h>
+#include <hidl/HidlTransportSupport.h>
+#include <hwbinder/IPCThreadState.h>
+
+#include <health2impl/Callback.h>
+#include <health2impl/HalHealthLoop.h>
+
+using android::hardware::health::V1_0::BatteryStatus;
+using android::hardware::health::V1_0::toString;
+using android::hardware::health::V1_0::hal_conversion::convertFromHealthInfo;
+using android::hardware::health::V1_0::hal_conversion::convertToHealthConfig;
+using android::hardware::health::V1_0::hal_conversion::convertToHealthInfo;
+using android::hardware::health::V2_0::Result;
+using android::hardware::health::V2_1::IHealth;
+
+using ScreenOn = decltype(healthd_config::screen_on);
+
+namespace android {
+namespace hardware {
+namespace health {
+namespace V2_1 {
+namespace implementation {
+
+/*
+// If you need to call healthd_board_init, construct the Health instance with
+// the healthd_config after calling healthd_board_init:
+struct healthd_config* init_config(struct healthd_config* config) {
+    healthd_board_init(config);
+    return config;
+}
+class MyHealth : public Health {
+    MyHealth(struct healthd_config* config) :
+        Health(init_config(config)) {}
+};
+*/
+
+Health::Health(std::unique_ptr<healthd_config>&& config) : healthd_config_(std::move(config)) {
+    battery_monitor_.init(healthd_config_.get());
+}
+
+//
+// Callbacks are not supported by the passthrough implementation.
+//
+
+Return<Result> Health::registerCallback(const sp<V2_0::IHealthInfoCallback>&) {
+    return Result::NOT_SUPPORTED;
+}
+
+Return<Result> Health::unregisterCallback(const sp<V2_0::IHealthInfoCallback>&) {
+    return Result::NOT_SUPPORTED;
+}
+
+Return<Result> Health::update() {
+    Result result = Result::UNKNOWN;
+    getHealthInfo_2_1([&](auto res, const auto& /* health_info */) {
+        result = res;
+        if (res != Result::SUCCESS) {
+            LOG(ERROR) << "Cannot call getHealthInfo_2_1: " << toString(res);
+            return;
+        }
+
+        battery_monitor_.logValues();
+    });
+    return result;
+}
+
+//
+// Getters.
+//
+
+template <typename T>
+static Return<void> GetProperty(BatteryMonitor* monitor, int id, T defaultValue,
+                                const std::function<void(Result, T)>& callback) {
+    struct BatteryProperty prop;
+    T ret = defaultValue;
+    Result result = Result::SUCCESS;
+    status_t err = monitor->getProperty(static_cast<int>(id), &prop);
+    if (err != OK) {
+        LOG(DEBUG) << "getProperty(" << id << ")"
+                   << " fails: (" << err << ") " << strerror(-err);
+    } else {
+        ret = static_cast<T>(prop.valueInt64);
+    }
+    switch (err) {
+        case OK:
+            result = Result::SUCCESS;
+            break;
+        case NAME_NOT_FOUND:
+            result = Result::NOT_SUPPORTED;
+            break;
+        default:
+            result = Result::UNKNOWN;
+            break;
+    }
+    callback(result, static_cast<T>(ret));
+    return Void();
+}
+
+Return<void> Health::getChargeCounter(getChargeCounter_cb _hidl_cb) {
+    return GetProperty<int32_t>(&battery_monitor_, BATTERY_PROP_CHARGE_COUNTER, 0, _hidl_cb);
+}
+
+Return<void> Health::getCurrentNow(getCurrentNow_cb _hidl_cb) {
+    return GetProperty<int32_t>(&battery_monitor_, BATTERY_PROP_CURRENT_NOW, 0, _hidl_cb);
+}
+
+Return<void> Health::getCurrentAverage(getCurrentAverage_cb _hidl_cb) {
+    return GetProperty<int32_t>(&battery_monitor_, BATTERY_PROP_CURRENT_AVG, 0, _hidl_cb);
+}
+
+Return<void> Health::getCapacity(getCapacity_cb _hidl_cb) {
+    return GetProperty<int32_t>(&battery_monitor_, BATTERY_PROP_CAPACITY, 0, _hidl_cb);
+}
+
+Return<void> Health::getEnergyCounter(getEnergyCounter_cb _hidl_cb) {
+    return GetProperty<int64_t>(&battery_monitor_, BATTERY_PROP_ENERGY_COUNTER, 0, _hidl_cb);
+}
+
+Return<void> Health::getChargeStatus(getChargeStatus_cb _hidl_cb) {
+    return GetProperty(&battery_monitor_, BATTERY_PROP_BATTERY_STATUS, BatteryStatus::UNKNOWN,
+                       _hidl_cb);
+}
+
+Return<void> Health::getStorageInfo(getStorageInfo_cb _hidl_cb) {
+    // This implementation does not support StorageInfo. An implementation may extend this
+    // class and override this function to support storage info.
+    _hidl_cb(Result::NOT_SUPPORTED, {});
+    return Void();
+}
+
+Return<void> Health::getDiskStats(getDiskStats_cb _hidl_cb) {
+    // This implementation does not support DiskStats. An implementation may extend this
+    // class and override this function to support disk stats.
+    _hidl_cb(Result::NOT_SUPPORTED, {});
+    return Void();
+}
+
+template <typename T, typename Method>
+static inline void GetHealthInfoField(Health* service, Method func, T* out) {
+    *out = T{};
+    std::invoke(func, service, [out](Result result, const T& value) {
+        if (result == Result::SUCCESS) *out = value;
+    });
+}
+
+Return<void> Health::getHealthInfo(getHealthInfo_cb _hidl_cb) {
+    return getHealthInfo_2_1(
+            [&](auto res, const auto& health_info) { _hidl_cb(res, health_info.legacy); });
+}
+
+Return<void> Health::getHealthInfo_2_1(getHealthInfo_2_1_cb _hidl_cb) {
+    battery_monitor_.updateValues();
+
+    HealthInfo health_info = battery_monitor_.getHealthInfo_2_1();
+
+    // Fill in storage infos; these aren't retrieved by BatteryMonitor.
+    GetHealthInfoField(this, &Health::getStorageInfo, &health_info.legacy.storageInfos);
+    GetHealthInfoField(this, &Health::getDiskStats, &health_info.legacy.diskStats);
+
+    // A subclass may want to update health info struct before returning it.
+    UpdateHealthInfo(&health_info);
+
+    _hidl_cb(Result::SUCCESS, health_info);
+    return Void();
+}
+
+Return<void> Health::debug(const hidl_handle& handle, const hidl_vec<hidl_string>&) {
+    if (handle == nullptr || handle->numFds == 0) {
+        return Void();
+    }
+
+    int fd = handle->data[0];
+    battery_monitor_.dumpState(fd);
+    getHealthInfo_2_1([fd](auto res, const auto& info) {
+        android::base::WriteStringToFd("\ngetHealthInfo -> ", fd);
+        if (res == Result::SUCCESS) {
+            android::base::WriteStringToFd(toString(info), fd);
+        } else {
+            android::base::WriteStringToFd(toString(res), fd);
+        }
+        android::base::WriteStringToFd("\n", fd);
+    });
+
+    fsync(fd);
+    return Void();
+}
+
+Return<void> Health::getHealthConfig(getHealthConfig_cb _hidl_cb) {
+    HealthConfig config = {};
+    convertToHealthConfig(healthd_config_.get(), config.battery);
+    config.bootMinCap = static_cast<int32_t>(healthd_config_->boot_min_cap);
+
+    _hidl_cb(Result::SUCCESS, config);
+    return Void();
+}
+
+Return<void> Health::shouldKeepScreenOn(shouldKeepScreenOn_cb _hidl_cb) {
+    if (!healthd_config_->screen_on) {
+        _hidl_cb(Result::NOT_SUPPORTED, true);
+        return Void();
+    }
+
+    Result returned_result = Result::UNKNOWN;
+    bool screen_on = true;
+    getHealthInfo_2_1([&](auto res, const auto& health_info) {
+        returned_result = res;
+        if (returned_result != Result::SUCCESS) return;
+
+        struct BatteryProperties props = {};
+        V1_0::hal_conversion::convertFromHealthInfo(health_info.legacy.legacy, &props);
+        screen_on = healthd_config_->screen_on(&props);
+    });
+    _hidl_cb(returned_result, screen_on);
+    return Void();
+}
+
+//
+// Subclass helpers / overrides
+//
+
+void Health::UpdateHealthInfo(HealthInfo* /* health_info */) {
+    /*
+        // Sample code for a subclass to implement this:
+        // If you need to modify values (e.g. batteryChargeTimeToFullNowSeconds), do it here.
+        health_info->batteryChargeTimeToFullNowSeconds = calculate_charge_time_seconds();
+
+        // If you need to call healthd_board_battery_update:
+        struct BatteryProperties props;
+        convertFromHealthInfo(health_info.legacy.legacy, &props);
+        healthd_board_battery_update(&props);
+        convertToHealthInfo(&props, health_info.legacy.legacy);
+    */
+}
+
+}  // namespace implementation
+}  // namespace V2_1
+}  // namespace health
+}  // namespace hardware
+}  // namespace android