Android耳机拔插事件流程

Android所有的input设备都会在/dev/input目录下生成对应的设备节点，一旦有任何输入事件产生，便会将事件写到这些节点下，同时对于外部输入设备（鼠标键盘等）的插拔还会引起这些节点的创建和删除
使用adb 命令可以查看当前手机插入的耳机状态,命令为:adb shell cat /sys/class/switch/h2w/state

---

驱动层input事件传递

耳机拔插属于switch类型的按键消息，对于驱动层面，会先到InputDispatcher.cpp中处理

void InputDispatcher::notifySwitch(const NotifySwitchArgs* args) {
#if DEBUG_INBOUND_EVENT_DETAILS
    ALOGD("notifySwitch - eventTime=%lld, policyFlags=0x%x, switchValues=0x%08x, switchMask=0x%08x",
            args->eventTime, args->policyFlags,
            args->switchValues, args->switchMask);
#endif

    uint32_t policyFlags = args->policyFlags;
    policyFlags |= POLICY_FLAG_TRUSTED;
    mPolicy->notifySwitch(args->eventTime,
            args->switchValues, args->switchMask, policyFlags);
}

上述mPolicy就是NativeInputManager，在com_android_server_input_InputManagerService.cpp中定义的NativeInputManager

class NativeInputManager : public virtual RefBase,
    public virtual InputReaderPolicyInterface,
    public virtual InputDispatcherPolicyInterface,
    public virtual PointerControllerPolicyInterface {
    ....


    ....
    /* --- InputDispatcherPolicyInterface implementation --- */

    virtual void notifySwitch(nsecs_t when, uint32_t switchValues, uint32_t switchMask,
            uint32_t policyFlags);
    virtual void notifyConfigurationChanged(nsecs_t when);
    virtual void interceptKeyBeforeQueueing(const KeyEvent* keyEvent, uint32_t& policyFlags);

}

所以上述的调用，会在 com_android_server_input_InputManagerService.cpp中继续处理

void NativeInputManager::notifySwitch(nsecs_t when,
        uint32_t switchValues, uint32_t switchMask, uint32_t /* policyFlags */) {
#if DEBUG_INPUT_DISPATCHER_POLICY
    ALOGD("notifySwitch - when=%lld, switchValues=0x%08x, switchMask=0x%08x, policyFlags=0x%x",
            when, switchValues, switchMask, policyFlags);
#endif
    ATRACE_CALL();

    JNIEnv* env = jniEnv();

    env->CallVoidMethod(mServiceObj, gServiceClassInfo.notifySwitch,
            when, switchValues, switchMask);
    checkAndClearExceptionFromCallback(env, "notifySwitch");
}

可以看到，上述直接通过CallVoidMethod调用java代码，其中gServiceClassInfo.notifySwitch对应的就是InputManagerService#notifySwitch方法

InputManagerService处理switch事件

InputManagerService#notifySwitch

// Native callback.
private void notifySwitch(long whenNanos, int switchValues, int switchMask) {
        if (DEBUG) {
            Slog.d(TAG, "notifySwitch: values=" + Integer.toHexString(switchValues)
                    + ", mask=" + Integer.toHexString(switchMask));
        }
        ....

        if (mUseDevInputEventForAudioJack && (switchMask & SW_JACK_BITS) != 0) {
            mWiredAccessoryCallbacks.notifyWiredAccessoryChanged(whenNanos, switchValues,
                    switchMask);
        }
    ....

}

上述方法调用有一个mWiredAccessoryCallbacks回调，耳机拔插事件，需要从开机以后就实时监听，所以不想到，mWiredAccessoryCallbacks回调的设置是和系统服务启动时机一样，在SystemServer中可以看到它的身影，在startOtherServices中，如下：

try {
                // Listen for wired headset changes
                inputManager.setWiredAccessoryCallbacks(
                        new WiredAccessoryManager(context, inputManager));
} catch (Throwable e) {
     reportWtf("starting WiredAccessoryManager", e);
}

上述mWiredAccessoryCallbacks回调其实是WiredAccessoryManager类型对象，继续分析WiredAccessoryManager#notifyWiredAccessoryChanged

@Override
    public void notifyWiredAccessoryChanged(long whenNanos, int switchValues, int switchMask) {
        if (LOG) Slog.v(TAG, "notifyWiredAccessoryChanged: when=" + whenNanos
                + " bits=" + switchCodeToString(switchValues, switchMask)
                + " mask=" + Integer.toHexString(switchMask));

        synchronized (mLock) {
            int headset;
            mSwitchValues = (mSwitchValues & ~switchMask) | switchValues;
            switch (mSwitchValues &
                (SW_HEADPHONE_INSERT_BIT | SW_MICROPHONE_INSERT_BIT | SW_LINEOUT_INSERT_BIT)) {
                case 0:
                    headset = 0;
                    break;
                // 不带mic的耳机
                case SW_HEADPHONE_INSERT_BIT:
                    headset = BIT_HEADSET_NO_MIC;
                    break;

                case SW_LINEOUT_INSERT_BIT:
                    headset = BIT_LINEOUT;
                    break;

                case SW_HEADPHONE_INSERT_BIT | SW_MICROPHONE_INSERT_BIT:
                    headset = BIT_HEADSET;
                    break;
        // 带mic的耳机
                case SW_MICROPHONE_INSERT_BIT:
                    headset = BIT_HEADSET;
                    break;

                default:
                    headset = 0;
                    break;
            }

            updateLocked(NAME_H2W,
                (mHeadsetState & ~(BIT_HEADSET | BIT_HEADSET_NO_MIC | BIT_LINEOUT)) | headset);
        }
    }

上述流程，主要先获取headset的类型，最终会跳到updateLocked方法，用来检查当前模式是否发生变化

private void updateLocked(String newName, int newState) {
        ....
        Log.i(TAG, "MSG_NEW_DEVICE_STATE");
        Message msg = mHandler.obtainMessage(MSG_NEW_DEVICE_STATE, headsetState,
                mHeadsetState, "");
        mHandler.sendMessage(msg);

        mHeadsetState = headsetState;
}

发送 消息交给mHandler处理

private final Handler mHandler = new Handler(Looper.myLooper(), null, true) {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_NEW_DEVICE_STATE:
                    setDevicesState(msg.arg1, msg.arg2, (String)msg.obj);
                    mWakeLock.release();
                    break;
                case MSG_SYSTEM_READY:
                    onSystemReady();
                    mWakeLock.release();
                    break;
            }
        }
};

private void setDevicesState(
            int headsetState, int prevHeadsetState, String headsetName) {
        synchronized (mLock) {
            int allHeadsets = SUPPORTED_HEADSETS;
            for (int curHeadset = 1; allHeadsets != 0; curHeadset <<= 1) {
                if ((curHeadset & allHeadsets) != 0) {
                    setDeviceStateLocked(curHeadset, headsetState, prevHeadsetState, headsetName);
                    allHeadsets &= ~curHeadset;
                }
            }
        }
}

private void setDeviceStateLocked(int headset,
            int headsetState, int prevHeadsetState, String headsetName) {
        if ((headsetState & headset) != (prevHeadsetState & headset)) {
            ....

            if (LOG) {
                Slog.v(TAG, "headsetName: " + headsetName +
                        (state == 1 ? " connected" : " disconnected"));
            }

            if (outDevice != 0) {
              mAudioManager.setWiredDeviceConnectionState(outDevice, state, "", headsetName);
            }
            if (inDevice != 0) {
              mAudioManager.setWiredDeviceConnectionState(inDevice, state, "", headsetName);
            }
        }
}

上述mAudioManager会跨进程通信，最终调用到AudioService#setWiredDeviceConnectionState

AudioService传递switch事件

public void setWiredDeviceConnectionState(int type, int state, String address, String name,
            String caller) {
        synchronized (mConnectedDevices) {
            if (DEBUG_DEVICES) {
                Slog.i(TAG, "setWiredDeviceConnectionState(" + state + " nm: " + name + " addr:"
                        + address + ")");
            }
            int delay = checkSendBecomingNoisyIntent(type, state, AudioSystem.DEVICE_NONE);
            queueMsgUnderWakeLock(mAudioHandler,
                    MSG_SET_WIRED_DEVICE_CONNECTION_STATE,
                    0 /* arg1 unused */,
                    0 /* arg2 unused */,
                    new WiredDeviceConnectionState(type, state, address, name, caller),
                    delay);
        }
}

private void queueMsgUnderWakeLock(Handler handler, int msg,
            int arg1, int arg2, Object obj, int delay) {
        final long ident = Binder.clearCallingIdentity();
        // Always acquire the wake lock as AudioService because it is released by the
        // message handler.
        mAudioEventWakeLock.acquire();
        Binder.restoreCallingIdentity(ident);
        sendMsg(handler, msg, SENDMSG_QUEUE, arg1, arg2, obj, delay);
    }

上述msg对应的是MSG_SET_WIRED_DEVICE_CONNECTION_STATE消息，该消息在AudioService$AudioHandler处理

case MSG_SET_WIRED_DEVICE_CONNECTION_STATE:
                    {   WiredDeviceConnectionState connectState =
                            (WiredDeviceConnectionState)msg.obj;
                        mWiredDevLogger.log(new WiredDevConnectEvent(connectState));
                        onSetWiredDeviceConnectionState(connectState.mType, connectState.mState,
                                connectState.mAddress, connectState.mName, connectState.mCaller);
                        mAudioEventWakeLock.release();
                    }
                    break;

private void onSetWiredDeviceConnectionState(int device, int state, String address,
            String deviceName, String caller) {
        if (DEBUG_DEVICES) {
            Slog.i(TAG, "onSetWiredDeviceConnectionState(dev:" + Integer.toHexString(device)
                    + " state:" + Integer.toHexString(state)
                    + " address:" + address
                    + " deviceName:" + deviceName
                    + " caller: " + caller + ");");
        }

        synchronized (mConnectedDevices) {
            if ((state == 0) && ((device & DEVICE_OVERRIDE_A2DP_ROUTE_ON_PLUG) != 0)) {
                setBluetoothA2dpOnInt(true, "onSetWiredDeviceConnectionState state 0");
            }

            if (!handleDeviceConnection(state == 1, device, address, deviceName)) {
                // change of connection state failed, bailout
                return;
            }
            if (state != 0) {
                if ((device & DEVICE_OVERRIDE_A2DP_ROUTE_ON_PLUG) != 0) {
                    setBluetoothA2dpOnInt(false, "onSetWiredDeviceConnectionState state not 0");
                }
                if ((device & mSafeMediaVolumeDevices) != 0) {
                    sendMsg(mAudioHandler,
                            MSG_CHECK_MUSIC_ACTIVE,
                            SENDMSG_REPLACE,
                            0,
                            0,
                            caller,
                            MUSIC_ACTIVE_POLL_PERIOD_MS);
                }
                // Television devices without CEC service apply software volume on HDMI output
                if (isPlatformTelevision() && ((device & AudioSystem.DEVICE_OUT_HDMI) != 0)) {
                    mFixedVolumeDevices |= AudioSystem.DEVICE_OUT_HDMI;
                    checkAllFixedVolumeDevices();
                    if (mHdmiManager != null) {
                        synchronized (mHdmiManager) {
                            if (mHdmiPlaybackClient != null) {
                                mHdmiCecSink = false;
                                mHdmiPlaybackClient.queryDisplayStatus(mHdmiDisplayStatusCallback);
                            }
                        }
                    }
                }
            } else {
                if (isPlatformTelevision() && ((device & AudioSystem.DEVICE_OUT_HDMI) != 0)) {
                    if (mHdmiManager != null) {
                        synchronized (mHdmiManager) {
                            mHdmiCecSink = false;
                        }
                    }
                }
            }
            sendDeviceConnectionIntent(device, state, address, deviceName);
            updateAudioRoutes(device, state);
        }
    }

最后就是通过 ActivityManager发送ACTION_HEADSET_PLUG广播

private void sendDeviceConnectionIntent(int device, int state, String address,
            String deviceName) {
        if (DEBUG_DEVICES) {
            Slog.i(TAG, "sendDeviceConnectionIntent(dev:0x" + Integer.toHexString(device) +
                    " state:0x" + Integer.toHexString(state) + " address:" + address +
                    " name:" + deviceName + ");");
        }
        Intent intent = new Intent();

        if (device == AudioSystem.DEVICE_OUT_WIRED_HEADSET) {
            intent.setAction(Intent.ACTION_HEADSET_PLUG);
            intent.putExtra("microphone", 1);
        } else if (device == AudioSystem.DEVICE_OUT_WIRED_HEADPHONE ||
                   device == AudioSystem.DEVICE_OUT_LINE) {
            intent.setAction(Intent.ACTION_HEADSET_PLUG);
            intent.putExtra("microphone",  0);
        } else if (device == AudioSystem.DEVICE_OUT_USB_HEADSET) {
            intent.setAction(Intent.ACTION_HEADSET_PLUG);
            intent.putExtra("microphone",
                    AudioSystem.getDeviceConnectionState(AudioSystem.DEVICE_IN_USB_HEADSET, "")
                        == AudioSystem.DEVICE_STATE_AVAILABLE ? 1 : 0);
        } else if (device == AudioSystem.DEVICE_IN_USB_HEADSET) {
            if (AudioSystem.getDeviceConnectionState(AudioSystem.DEVICE_OUT_USB_HEADSET, "")
                    == AudioSystem.DEVICE_STATE_AVAILABLE) {
                intent.setAction(Intent.ACTION_HEADSET_PLUG);
                intent.putExtra("microphone", 1);
            } else {
                // do not send ACTION_HEADSET_PLUG when only the input side is seen as changing
                return;
            }
        } else if (device == AudioSystem.DEVICE_OUT_HDMI ||
                device == AudioSystem.DEVICE_OUT_HDMI_ARC) {
            configureHdmiPlugIntent(intent, state);
        }

        if (intent.getAction() == null) {
            return;
        }

        intent.putExtra(CONNECT_INTENT_KEY_STATE, state);
        intent.putExtra(CONNECT_INTENT_KEY_ADDRESS, address);
        intent.putExtra(CONNECT_INTENT_KEY_PORT_NAME, deviceName);

        intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);

        final long ident = Binder.clearCallingIdentity();
        try {
            ActivityManager.broadcastStickyIntent(intent, UserHandle.USER_ALL);  //向上层发送广播
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
 }

可以看到，上述在AudioService中发送广播，并不是通过Context上下文来发送的，而是直接通过AMS#broadcastIntent,其实Context最终也会通过AMS去发送广播的

应用处理广播

上述分析得到，当耳机拔插状态发生变化时候，会在fwk中发送广播

ACTION_HEADSET_PLUG = android.media.AudioManager.ACTION_HEADSET_PLUG;

应用只需要注册该广播，在做具体的操作即可

switch流程总结

上述笔记比较杂乱，下面简单对调用流程zuoxia

• InputDispatcher.cpp #notifySwitch
• com_android_server_input_InputManagerService.cpp # notifySwitch
• InputManagerService#notifySwitch

• WiredAccessoryManager#notifyWiredAccessoryChanged
  ….

• AudioService#setWiredDeviceConnectionState

• AudioService#sendDeviceConnectionIntent
• ActivityManager#broadcastStickyIntent