diff --git a/include/private/performance_hint_private.h b/include/private/performance_hint_private.h
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+/*
+ * 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_PRIVATE_NATIVE_PERFORMANCE_HINT_PRIVATE_H
+#define ANDROID_PRIVATE_NATIVE_PERFORMANCE_HINT_PRIVATE_H
+
+#include <stdint.h>
+
+__BEGIN_DECLS
+
+struct APerformanceHintManager;
+struct APerformanceHintSession;
+
+/**
+ * An opaque type representing a handle to a performance hint manager.
+ * It must be released after use.
+ *
+ * <p>To use:<ul>
+ *    <li>Obtain the performance hint manager instance by calling
+ *        {@link APerformanceHint_getManager} function.</li>
+ *    <li>Create an {@link APerformanceHintSession} with
+ *        {@link APerformanceHint_createSession}.</li>
+ *    <li>Get the preferred update rate in nanoseconds with
+ *        {@link APerformanceHint_getPreferredUpdateRateNanos}.</li>
+ */
+typedef struct APerformanceHintManager APerformanceHintManager;
+
+/**
+ * An opaque type representing a handle to a performance hint session.
+ * A session can only be acquired from a {@link APerformanceHintManager}
+ * with {@link APerformanceHint_getPreferredUpdateRateNanos}. It must be
+ * freed with {@link APerformanceHint_closeSession} after use.
+ *
+ * A Session represents a group of threads with an inter-related workload such that hints for
+ * their performance should be considered as a unit. The threads in a given session should be
+ * long-life and not created or destroyed dynamically.
+ *
+ * <p>Each session is expected to have a periodic workload with a target duration for each
+ * cycle. The cycle duration is likely greater than the target work duration to allow other
+ * parts of the pipeline to run within the available budget. For example, a renderer thread may
+ * work at 60hz in order to produce frames at the display's frame but have a target work
+ * duration of only 6ms.</p>
+ *
+ * <p>After each cycle of work, the client is expected to use
+ * {@link APerformanceHint_reportActualWorkDuration} to report the actual time taken to
+ * complete.</p>
+ *
+ * <p>To use:<ul>
+ *    <li>Update a sessions target duration for each cycle of work
+ *        with  {@link APerformanceHint_updateTargetWorkDuration}.</li>
+ *    <li>Report the actual duration for the last cycle of work with
+ *        {@link APerformanceHint_reportActualWorkDuration}.</li>
+ *    <li>Release the session instance with
+ *        {@link APerformanceHint_closeSession}.</li></ul></p>
+ */
+typedef struct APerformanceHintSession APerformanceHintSession;
+
+/**
+  * Acquire an instance of the performance hint manager.
+  *
+  * @return manager instance on success, nullptr on failure.
+  */
+APerformanceHintManager* APerformanceHint_getManager();
+
+/**
+ * Creates a session for the given set of threads and sets their initial target work
+ * duration.
+ * @param manager The performance hint manager instance.
+ * @param threadIds The list of threads to be associated with this session. They must be part of
+ *     this app's thread group.
+ * @param size the size of threadIds.
+ * @param initialTargetWorkDurationNanos The desired duration in nanoseconds for the new session.
+ *     This must be positive.
+ * @return manager instance on success, nullptr on failure.
+ */
+APerformanceHintSession* APerformanceHint_createSession(APerformanceHintManager* manager,
+                                                        const int32_t* threadIds, size_t size,
+                                                        int64_t initialTargetWorkDurationNanos);
+
+/**
+ * Get preferred update rate information for this device.
+ *
+ * @param manager The performance hint manager instance.
+ * @return the preferred update rate supported by device software.
+ */
+int64_t APerformanceHint_getPreferredUpdateRateNanos(APerformanceHintManager* manager);
+
+/**
+ * Updates this session's target duration for each cycle of work.
+ *
+ * @param session The performance hint session instance to update.
+ * @param targetDurationNanos the new desired duration in nanoseconds. This must be positive.
+ * @return 0 on success
+ *         EINVAL if targetDurationNanos is not positive.
+ *         EPIPE if communication with the system service has failed.
+ */
+int APerformanceHint_updateTargetWorkDuration(APerformanceHintSession* session,
+                                               int64_t targetDurationNanos);
+
+/**
+ * Reports the actual duration for the last cycle of work.
+ *
+ * <p>The system will attempt to adjust the core placement of the threads within the thread
+ * group and/or the frequency of the core on which they are run to bring the actual duration
+ * close to the target duration.</p>
+ *
+ * @param session The performance hint session instance to update.
+ * @param actualDurationNanos how long the thread group took to complete its last task in
+ *     nanoseconds. This must be positive.
+ * @return 0 on success
+ *         EINVAL if actualDurationNanos is not positive.
+ *         EPIPE if communication with the system service has failed.
+ */
+int APerformanceHint_reportActualWorkDuration(APerformanceHintSession* session,
+                                               int64_t actualDurationNanos);
+
+/**
+ * Release the performance hint manager pointer acquired via
+ * {@link APerformanceHint_createSession}.
+ *
+ * @param session The performance hint session instance to release.
+ */
+void APerformanceHint_closeSession(APerformanceHintSession* session);
+
+/**
+ * For testing only.
+ */
+void APerformanceHint_setIHintManagerForTesting(void* iManager);
+
+__END_DECLS
+
+#endif // ANDROID_PRIVATE_NATIVE_PERFORMANCE_HINT_PRIVATE_H