diff --git a/phosphor-regulators/src/sensors.hpp b/phosphor-regulators/src/sensors.hpp
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+/**
+ * Copyright © 2021 IBM Corporation
+ *
+ * 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 "services.hpp"
+
+#include <string>
+
+namespace phosphor::power::regulators
+{
+
+/**
+ * Voltage regulator sensor type.
+ */
+enum class SensorType
+{
+    /**
+     * Output current.
+     */
+    iout,
+
+    /**
+     * Highest output current.
+     */
+    iout_peak,
+
+    /**
+     * Lowest output current.
+     */
+    iout_valley,
+
+    /**
+     * Output power.
+     */
+    pout,
+
+    /**
+     * Temperature.
+     */
+    temperature,
+
+    /**
+     * Highest temperature.
+     */
+    temperature_peak,
+
+    /**
+     * Output voltage.
+     */
+    vout,
+
+    /**
+     * Highest output voltage.
+     */
+    vout_peak,
+
+    /**
+     * Lowest output voltage.
+     */
+    vout_valley
+};
+
+/**
+ * @namespace sensors
+ *
+ * Contains utility functions related to voltage regulator sensors.
+ */
+namespace sensors
+{
+
+/**
+ * Returns the name of the specified SensorType.
+ *
+ * The returned string will exactly match the enumerator name, such as
+ * "temperature_peak".
+ *
+ * @param type sensor type
+ * @return sensor type name
+ */
+std::string toString(SensorType type)
+{
+    std::string name{};
+    switch (type)
+    {
+        case SensorType::iout:
+            name = "iout";
+            break;
+        case SensorType::iout_peak:
+            name = "iout_peak";
+            break;
+        case SensorType::iout_valley:
+            name = "iout_valley";
+            break;
+        case SensorType::pout:
+            name = "pout";
+            break;
+        case SensorType::temperature:
+            name = "temperature";
+            break;
+        case SensorType::temperature_peak:
+            name = "temperature_peak";
+            break;
+        case SensorType::vout:
+            name = "vout";
+            break;
+        case SensorType::vout_peak:
+            name = "vout_peak";
+            break;
+        case SensorType::vout_valley:
+            name = "vout_valley";
+            break;
+    }
+    return name;
+}
+
+} // namespace sensors
+
+/**
+ * @class Sensors
+ *
+ * Abstract base class for a service that maintains a list of voltage regulator
+ * sensors.
+ *
+ * This service makes the voltage regulator sensors available to other BMC
+ * applications.  For example, the Redfish support obtains sensor data from this
+ * service.
+ *
+ * Each voltage rail in the system may provide multiple types of sensor data,
+ * such as temperature, output voltage, and output current (see SensorType).  A
+ * sensor tracks one of these data types for a voltage rail.
+ *
+ * Voltage regulator sensors are typically read frequently based on a timer.
+ * Reading all the sensors once is called a monitoring cycle.  The application
+ * will loop through all voltage rails, reading all supported sensor types for
+ * each rail.  During a monitoring cycle, the following sensor service methods
+ * should be called in the specified order:
+ * - startCycle() // At the start of a sensor monitoring cycle
+ * - startRail()  // Before reading all the sensors for one rail
+ * - setValue()   // To set the value of one sensor for the current rail
+ * - endRail()    // After reading all the sensors for one rail
+ * - endCycle()   // At the end of a sensor monitoring cycle
+ *
+ * This service can be enabled or disabled.  It is typically enabled when the
+ * system is powered on and voltage regulators begin producing output.  It is
+ * typically disabled when the system is powered off.  It can also be
+ * temporarily disabled if other BMC applications need to communicate with the
+ * voltage regulator devices.  When the service is disabled, the sensors still
+ * exist but are in an inactive state since their values are not being updated.
+ */
+class Sensors
+{
+  public:
+    // Specify which compiler-generated methods we want
+    Sensors() = default;
+    Sensors(const Sensors&) = delete;
+    Sensors(Sensors&&) = delete;
+    Sensors& operator=(const Sensors&) = delete;
+    Sensors& operator=(Sensors&&) = delete;
+    virtual ~Sensors() = default;
+
+    /**
+     * Enable the sensors service.
+     *
+     * While the service is enabled, the sensors that it provides will be in an
+     * active state.  This indicates that their value is being updated
+     * periodically.
+     *
+     * @param services system services
+     */
+    virtual void enable(Services& services) = 0;
+
+    /**
+     * Notify the sensors service that the current sensor monitoring cycle has
+     * ended.
+     *
+     * @param services system services
+     */
+    virtual void endCycle(Services& services) = 0;
+
+    /**
+     * Notify the sensors service that sensor monitoring has ended for the
+     * current voltage rail.
+     *
+     * @param errorOccurred specifies whether an error occurred while trying to
+     *                      read all the sensors for the current rail
+     * @param services system services
+     */
+    virtual void endRail(bool errorOccurred, Services& services) = 0;
+
+    /**
+     * Disable the sensors service.
+     *
+     * While the service is disabled, the sensors that it provides will be in an
+     * inactive state.  This indicates that their value is not being updated.
+     *
+     * @param services system services
+     */
+    virtual void disable(Services& services) = 0;
+
+    /**
+     * Sets the value of one sensor for the current voltage rail.
+     *
+     * @param type sensor type
+     * @param value sensor value
+     * @param services system services
+     */
+    virtual void setValue(SensorType type, double value,
+                          Services& services) = 0;
+
+    /**
+     * Notify the sensors service that a sensor monitoring cycle is starting.
+     *
+     * @param services system services
+     */
+    virtual void startCycle(Services& services) = 0;
+
+    /**
+     * Notify the sensors service that sensor monitoring is starting for the
+     * specified voltage rail.
+     *
+     * Calls to setValue() will update sensors for this rail.
+     *
+     * @param rail unique rail ID
+     * @param deviceInventoryPath D-Bus inventory path of the voltage regulator
+     *                            device that produces the rail
+     * @param chassisInventoryPath D-Bus inventory path of the chassis that
+     *                             contains the voltage regulator device
+     * @param services system services
+     */
+    virtual void startRail(const std::string& rail,
+                           const std::string& deviceInventoryPath,
+                           const std::string& chassisInventoryPath,
+                           Services& services) = 0;
+};
+
+} // namespace phosphor::power::regulators