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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.server.power;
     18 
     19 import android.util.proto.ProtoOutputStream;
     20 
     21 /**
     22  * Low-level suspend blocker mechanism equivalent to holding a partial wake lock.
     23  *
     24  * This interface is used internally to avoid introducing internal dependencies
     25  * on the high-level wake lock mechanism.
     26  */
     27 interface SuspendBlocker {
     28     /**
     29      * Acquires the suspend blocker.
     30      * Prevents the CPU from going to sleep.
     31      *
     32      * Calls to acquire() nest and must be matched by the same number
     33      * of calls to release().
     34      */
     35     void acquire();
     36 
     37     /**
     38      * Releases the suspend blocker.
     39      * Allows the CPU to go to sleep if no other suspend blockers are held.
     40      *
     41      * It is an error to call release() if the suspend blocker has not been acquired.
     42      * The system may crash.
     43      */
     44     void release();
     45 
     46     void writeToProto(ProtoOutputStream proto, long fieldId);
     47 }
     48