frameworks_base/services/java/com/android/server/HeadsetObserver.java

/*
 * Copyright (C) 2008 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.
 */

package com.android.server;

import android.app.ActivityManagerNative;
import android.content.Context;
import android.content.Intent;
import android.os.Handler;
import android.os.Message;
import android.os.PowerManager;
import android.os.PowerManager.WakeLock;
import android.os.UEventObserver;
import android.util.Log;
import android.media.AudioManager;

import java.io.FileReader;
import java.io.FileNotFoundException;

/**
 * <p>HeadsetObserver monitors for a wired headset.
 */
class HeadsetObserver extends UEventObserver {
    private static final String TAG = HeadsetObserver.class.getSimpleName();
    private static final boolean LOG = false;

    private static final String HEADSET_UEVENT_MATCH = "DEVPATH=/devices/virtual/switch/h2w";
    private static final String HEADSET_STATE_PATH = "/sys/class/switch/h2w/state";
    private static final String HEADSET_NAME_PATH = "/sys/class/switch/h2w/name";

    private static final int BIT_HEADSET = (1 << 0);
    private static final int BIT_HEADSET_NO_MIC = (1 << 1);
    private static final int SUPPORTED_HEADSETS = (BIT_HEADSET|BIT_HEADSET_NO_MIC);
    private static final int HEADSETS_WITH_MIC = BIT_HEADSET;

    private int mHeadsetState;
    private int mPrevHeadsetState;
    private String mHeadsetName;
    private boolean mPendingIntent;

    private final Context mContext;
    private final WakeLock mWakeLock;  // held while there is a pending route change

    public HeadsetObserver(Context context) {
        mContext = context;
        PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
        mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "HeadsetObserver");
        mWakeLock.setReferenceCounted(false);

        startObserving(HEADSET_UEVENT_MATCH);

        init();  // set initial status
    }

    @Override
    public void onUEvent(UEventObserver.UEvent event) {
        if (LOG) Log.v(TAG, "Headset UEVENT: " + event.toString());

        try {
            update(event.get("SWITCH_NAME"), Integer.parseInt(event.get("SWITCH_STATE")));
        } catch (NumberFormatException e) {
            Log.e(TAG, "Could not parse switch state from event " + event);
        }
    }

    private synchronized final void init() {
        char[] buffer = new char[1024];

        String newName = mHeadsetName;
        int newState = mHeadsetState;
        mPrevHeadsetState = mHeadsetState;
        try {
            FileReader file = new FileReader(HEADSET_STATE_PATH);
            int len = file.read(buffer, 0, 1024);
            newState = Integer.valueOf((new String(buffer, 0, len)).trim());

            file = new FileReader(HEADSET_NAME_PATH);
            len = file.read(buffer, 0, 1024);
            newName = new String(buffer, 0, len).trim();

        } catch (FileNotFoundException e) {
            Log.w(TAG, "This kernel does not have wired headset support");
        } catch (Exception e) {
            Log.e(TAG, "" , e);
        }

        update(newName, newState);
    }

    private synchronized final void update(String newName, int newState) {
        // Retain only relevant bits
        int headsetState = newState & SUPPORTED_HEADSETS;
        int newOrOld = headsetState | mHeadsetState;
        // reject all suspect transitions: only accept state changes from:
        // - a: 0 heaset to 1 headset
        // - b: 1 headset to 0 headset
        if (mHeadsetState == headsetState || ((newOrOld & (newOrOld - 1)) != 0)) {
            return;
        }

        mHeadsetName = newName;
        mPrevHeadsetState = mHeadsetState;
        mHeadsetState = headsetState;
        mPendingIntent = true;

        if (headsetState == 0) {
            Intent intent = new Intent(AudioManager.ACTION_AUDIO_BECOMING_NOISY);
            mContext.sendBroadcast(intent);

            // It can take hundreds of ms flush the audio pipeline after
            // apps pause audio playback, but audio route changes are
            // immediate, so delay the route change by 1000ms.
            // This could be improved once the audio sub-system provides an
            // interface to clear the audio pipeline.
            mWakeLock.acquire();
            mHandler.sendEmptyMessageDelayed(0, 1000);
        } else {
            sendIntents();
            mPendingIntent = false;
        }
    }

    private synchronized final void sendIntents() {
        int allHeadsets = SUPPORTED_HEADSETS;
        for (int curHeadset = 1; allHeadsets != 0; curHeadset <<= 1) {
            if ((curHeadset & allHeadsets) != 0) {
                sendIntent(curHeadset);
                allHeadsets &= ~curHeadset;
            }
        }
    }

    private final void sendIntent(int headset) {
        if ((mHeadsetState & headset) != (mPrevHeadsetState & headset)) {
            //  Pack up the values and broadcast them to everyone
            Intent intent = new Intent(Intent.ACTION_HEADSET_PLUG);
            intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
            int state = 0;
            int microphone = 0;

            if ((headset & HEADSETS_WITH_MIC) != 0) {
                microphone = 1;
            }
            if ((mHeadsetState & headset) != 0) {
                state = 1;
            }
            intent.putExtra("state", state);
            intent.putExtra("name", mHeadsetName);
            intent.putExtra("microphone", microphone);

            if (LOG) Log.v(TAG, "Intent.ACTION_HEADSET_PLUG: state: "+state+" name: "+mHeadsetName+" mic: "+microphone);
            // TODO: Should we require a permission?
            ActivityManagerNative.broadcastStickyIntent(intent, null);
        }
    }

    private final Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            if (mPendingIntent) {
                sendIntents();
                mPendingIntent = false;
            }
            mWakeLock.release();
        }
    };

}