android usb相关知识总结

转载请注明出处：http://blog.csdn.net/droyon/article/details/45098027

1、android背景介绍

UsbService，在系统启动时创建，在该文件中，和usb状态息息相关的操作类是UsbDeviceManager，大部分的usb以及adb相关的逻辑，在这个类中做处理。UsbDeviceManager中，我们需要关注三部分内容。一、配置文件。二、private final UEventObserver mUEventObserver = new UEventObserver() ，接受UEvent事件。三、UsbHandler。

其中配置文件，保存当前usb状态。UEventObserver接受usb事件，push给UsbHandler来处理。UsbHandler是用来处理Usb事件的关键类。

2、Usb默认状态从哪里获取，当前的默认状态又是什么？

Usb的当前状态保存在mCurrentFunctions成员变量中，该变量在UsbHandler的构造中进行初始化。

mDefaultFunctions = SystemProperties.get("persist.sys.usb.config", "adb");                // Check if USB mode needs to be overridden depending on OEM specific bootmode.                mDefaultFunctions = processOemUsbOverride(mDefaultFunctions);                // sanity check the sys.usb.config system property                // this may be necessary if we crashed while switching USB configurations                String config = SystemProperties.get("sys.usb.config", "none");                if (!config.equals(mDefaultFunctions)) {                    Slog.w(TAG, "resetting config to persistent property: " + mDefaultFunctions);                    SystemProperties.set("sys.usb.config", mDefaultFunctions);                }                mCurrentFunctions = mDefaultFunctions;

3、插入usb时，弹出adb以及Notification通知的大体流程是什么？

插入usb时，我们的UEventObserver会收到信息，最终push给UsbHandler。

UEvent信息：

04-17 14:20:03.352 V/UsbDeviceManager(  759): USB UEVENT: {USB_STATE=DISCONNECTED, SUBSYSTEM=android_usb, SEQNUM=7528, ACTION=change, DEVPATH=/devices/virtual/android_usb/android0}

然后执行UsbHandler的updateState方法。

private final UEventObserver mUEventObserver = new UEventObserver() {        @Override        public void onUEvent(UEventObserver.UEvent event) {            if (DEBUG) Slog.v(TAG, "USB UEVENT: " + event.toString());            String state = event.get("USB_STATE");            String accessory = event.get("ACCESSORY");            if (state != null) {                mHandler.updateState(state);            } else if ("START".equals(accessory)) {                if (DEBUG) Slog.d(TAG, "got accessory start");                startAccessoryMode();            }        }    };

updateState方法：更新mConnection状态。

public void updateState(String state) {            int connected, configured;            if ("DISCONNECTED".equals(state)) {                connected = 0;                configured = 0;            } else if ("CONNECTED".equals(state)) {                connected = 1;                configured = 0;            } else if ("CONFIGURED".equals(state)) {                connected = 1;                configured = 1;            } else {                Slog.e(TAG, "unknown state " + state);                return;            }            removeMessages(MSG_UPDATE_STATE);            Message msg = Message.obtain(this, MSG_UPDATE_STATE);            msg.arg1 = connected;            msg.arg2 = configured;            // debounce disconnects to avoid problems bringing up USB tethering            sendMessageDelayed(msg, (connected == 0) ? UPDATE_DELAY : 0);        }

最后在UsbHandler中进行更新状态，进而弹出adb以及usb的Notification

case MSG_UPDATE_STATE:                    mConnected = (msg.arg1 == 1);                    mConfigured = (msg.arg2 == 1);                    updateUsbNotification();                    updateAdbNotification();                    if (containsFunction(mCurrentFunctions,                            UsbManager.USB_FUNCTION_ACCESSORY)) {                        updateCurrentAccessory();                    } else if (!mConnected) {                        // restore defaults when USB is disconnected                        setEnabledFunctions(mDefaultFunctions, false);                    }                    if (mBootCompleted) {                        updateUsbState();                        updateAudioSourceFunction();                    }                    break;

4、可设置的usb类型有哪些？

public static final String USB_FUNCTION_MASS_STORAGE = "mass_storage";    /**     * Name of the adb USB function.     * Used in extras for the {@link #ACTION_USB_STATE} broadcast     *     * {@hide}     */    public static final String USB_FUNCTION_ADB = "adb";    /**     * Name of the RNDIS ethernet USB function.     * Used in extras for the {@link #ACTION_USB_STATE} broadcast     *     * {@hide}     */    public static final String USB_FUNCTION_RNDIS = "rndis";    /**     * Name of the MTP USB function.     * Used in extras for the {@link #ACTION_USB_STATE} broadcast     *     * {@hide}     */    public static final String USB_FUNCTION_MTP = "mtp";    /**     * Name of the PTP USB function.     * Used in extras for the {@link #ACTION_USB_STATE} broadcast     *     * {@hide}     */    public static final String USB_FUNCTION_PTP = "ptp";    /**     * Name of the CHARGING USB function.     * Used in extras for the {@link #ACTION_USB_STATE} broadcast     *     * {@hide}     */    public static final String USB_FUNCTION_CHARGING = "charging";    /**     * Name of the audio source USB function.     * Used in extras for the {@link #ACTION_USB_STATE} broadcast     *     * {@hide}     */    public static final String USB_FUNCTION_AUDIO_SOURCE = "audio_source";    /**     * Name of the Accessory USB function.     * Used in extras for the {@link #ACTION_USB_STATE} broadcast     *     * {@hide}     */    public static final String USB_FUNCTION_ACCESSORY = "accessory";

这些是其定义。其中adb与charging不能同时兼容。

ps:Charging在底层是没有设备文件与之对应的,设定充电模式,会将adb等配置移除.

5、设置usb的流程是什么？

上层能够设定usb类型的类名叫做：UsbSettings，在其中，用户可以设定当前UsbSettings状态为mtp、ptp以及厂商定义的其他usb状态。

在用户操作时，会调用mUsbManager.setCurrentFunction(function, true);

tring function = USB_FUNCTION_DEFAULT;        if (preference == mMtp && mMtp.isChecked()) {            function = UsbManager.USB_FUNCTION_MTP;        } else if (preference == mPtp && mPtp.isChecked()) {            function = UsbManager.USB_FUNCTION_PTP;        } else if (preference == mCharging && mCharging.isChecked()) {            function = UsbManager.USB_FUNCTION_CHARGING;        } else if (preference == mSDCard && mSDCard.isChecked()) {            function = UsbManager.USB_FUNCTION_MASS_STORAGE;        }        operateInprogress = true;        mUsbManager.setCurrentFunction(function, true);        updateToggles(function);

USBManager会继而调用UsbService的setCurrentFunction

UsbService.java

@Override    public void setCurrentFunction(String function, boolean makeDefault) {        mContext.enforceCallingOrSelfPermission(android.Manifest.permission.MANAGE_USB, null);        // If attempt to change USB function while file transfer is restricted, ensure that        // the current function is set to "none", and return.        UserManager userManager = (UserManager) mContext.getSystemService(Context.USER_SERVICE);        if (userManager.hasUserRestriction(UserManager.DISALLOW_USB_FILE_TRANSFER)) {            if (mDeviceManager != null) mDeviceManager.setCurrentFunctions("none", false);            return;        }        if (mDeviceManager != null) {            mDeviceManager.setCurrentFunctions(function, makeDefault);        } else {            throw new IllegalStateException("USB device mode not supported");        }    }

最终还是会调用UsbDeviceManager中的setCurrentFunction。

UsbDeviceManager.java

public void setCurrentFunctions(String functions, boolean makeDefault) {        if (DEBUG) Slog.d(TAG, "setCurrentFunctions(" + functions + ") default: " + makeDefault);        mHandler.sendMessage(MSG_SET_CURRENT_FUNCTIONS, functions, makeDefault);    }

在内部类UsbHandler中:

case MSG_SET_CURRENT_FUNCTIONS:                    String functions = (String)msg.obj;                    boolean makeDefault = (msg.arg1 == 1);                    setEnabledFunctions(functions, makeDefault);                    break;

setEnabledFunctions方法中:

private void setEnabledFunctions(String functions, boolean makeDefault) {            if (DEBUG) Slog.d(TAG, "setEnabledFunctions " + functions                    + " makeDefault: " + makeDefault);            // Do not update persystent.sys.usb.config if the device is booted up            // with OEM specific mode.            if (functions != null && makeDefault && !needsOemUsbOverride()) {//0,persist.sys.usb.config为usb的默认配置值,makeDefault是说在每次Usb切换时,是否改变默认配置.                if (!UsbManager.USB_FUNCTION_CHARGING.equals(functions)                        && mAdbEnabled) {//1,首先UsbManager是否设定为充电模式,如果是,从当前UsbFuncton中移除adb,否则,为当前UsbFunctions增加adb.                    functions = addFunction(functions, UsbManager.USB_FUNCTION_ADB);                } else {                    functions = removeFunction(functions, UsbManager.USB_FUNCTION_ADB);                }                if (!mDefaultFunctions.equals(functions)) {//2,如果当前模式与当前默认模式不一致                    if (!setUsbConfig("none")) {//3,设定sys.usb.config为none[在由一种usb模式切换为另一种usb模式时,需要先将之前的模式设定为none,因为                                                //init.rc中有如下触发器:on property:persist.sys.usb.config=* setprop sys.usb.config $persist.sys.usb.config]                        Slog.e(TAG, "Failed to disable USB");                        // revert to previous configuration if we fail                        setUsbConfig(mCurrentFunctions);                        return;                    }                    // setting this property will also change the current USB state                    // via a property trigger                    SystemProperties.set("persist.sys.usb.config", functions);//4,设定当前usb 功能配置,同时sys.usb.config也会随着改变,因为触发器的原因.                    if (waitForState(functions)) {                        mCurrentFunctions = functions;                        mDefaultFunctions = functions;                    } else {                        Slog.e(TAG, "Failed to switch persistent USB config to " + functions);                        // revert to previous configuration if we fail                        SystemProperties.set("persist.sys.usb.config", mDefaultFunctions);                    }                }            } else {                if (functions == null) {                    functions = mDefaultFunctions;                }                // Override with bootmode specific usb mode if needed                functions = processOemUsbOverride(functions);                if (!UsbManager.USB_FUNCTION_CHARGING.equals(functions)                        && mAdbEnabled) {//5,首先UsbManager是否设定为充电模式,如果是,从当前UsbFuncton中移除adb,否则,为当前UsbFunctions增加adb.                    functions = addFunction(functions, UsbManager.USB_FUNCTION_ADB);                } else {                    functions = removeFunction(functions, UsbManager.USB_FUNCTION_ADB);                }                if (!mCurrentFunctions.equals(functions)) {//6,当前模式与设定不一致时,设定sys.usb.config,底层会读取该属性,进而启用相应的设备文件节点.                    if (!setUsbConfig("none")) {                        Slog.e(TAG, "Failed to disable USB");                        // revert to previous configuration if we fail                        setUsbConfig(mCurrentFunctions);                        return;                    }                    if (setUsbConfig(functions)) {                        mCurrentFunctions = functions;                    } else {                        Slog.e(TAG, "Failed to switch USB config to " + functions);                        // revert to previous configuration if we fail                        setUsbConfig(mCurrentFunctions);                    }                }            }        }

总结:
1,在usb链接状态时,sys.usb.config与persist.sys.usb.config由于触发器的原因会保持一致.
2,当Usb状态断开时,sys.usb.config由于与persist.sys.usb.config触发器的原因,本应保持一致,但应移除是否含有adb功能配置.
3,充电模式与adb不可同时共存.

附:log文件:
1,由ptp切换模式至mtp模式log信息:
07-15 20:34:56.862 D/UsbDeviceManager( 761): setEnabledFunctions - functions: mtp
07-15 20:34:56.862 D/UsbDeviceManager( 761): setEnabledFunctions - mDefaultFunctions: ptp,adb
07-15 20:34:56.862 D/UsbDeviceManager( 761): setEnabledFunctions - mCurrentFunctions: ptp,adb
07-15 20:34:56.862 D/UsbDeviceManager( 761): setEnabledFunctions - mSettingFunction: ptp,adb
07-15 20:34:56.862 D/UsbDeviceManager( 761): Add adb into mtp
07-15 20:34:56.862 D/UsbDeviceManager( 761): sys.usb.acm_idx=,mAcmPortIdx=
07-15 20:34:56.867 D/UsbDeviceManager( 761): setEnabledFunctions - functions: mtp,adb
07-15 20:34:56.868 D/UsbDeviceManager( 761): setUsbConfig(none)
07-15 20:34:56.868 D/UsbDeviceManager( 761): setUsbConfig - config: none
07-15 20:34:56.976 D/UsbDeviceManager( 761): handleMessage - MSG_SET_CURRENT_FUNCTION - functions: mtp
07-15 20:34:57.241 V/UsbDeviceManager( 761): USB UEVENT: {USB_STATE=DISCONNECTED, SUBSYSTEM=android_usb, SEQNUM=2751, ACTION=change, DEVPATH=/devices/virtual/android_usb/android0}
07-15 20:34:57.242 D/UsbDeviceManager( 761): mUEventObserver - onUEvent - state: DISCONNECTED
07-15 20:34:57.242 D/UsbDeviceManager( 761): updateState - DISCONNECTED
07-15 20:34:57.242 D/UsbDeviceManager( 761): updateState - RNDIS_UPDATE_DELAY DISCONNECTED mSettingFunction: mtp
07-15 20:34:57.331 V/UsbDeviceManager( 761): USB UEVENT: {USB_STATE=CONNECTED, SUBSYSTEM=android_usb, SEQNUM=2756, ACTION=change, DEVPATH=/devices/virtual/android_usb/android0}
07-15 20:34:57.331 D/UsbDeviceManager( 761): mUEventObserver - onUEvent - state: CONNECTED
07-15 20:34:57.331 D/UsbDeviceManager( 761): updateState - CONNECTED
07-15 20:34:57.331 D/UsbDeviceManager( 761): updateState - RNDIS_UPDATE_DELAY CONNECTED mSettingFunction: mtp
07-15 20:34:57.332 W/UsbDeviceManager( 761): handleMessage - 0
07-15 20:34:57.332 D/UsbDeviceManager( 761): updateUsbNotification - mNotificationManager: android.app.NotificationManager@230489b9
07-15 20:34:57.332 D/UsbDeviceManager( 761): updateUsbNotification - mUseUsbNotification: true
07-15 20:34:57.332 W/UsbDeviceManager( 761): updateUsbNotification - mConnected: true
07-15 20:34:57.332 W/UsbDeviceManager( 761): updateUsbNotification - mCurrentFunctions: mtp,adb
07-15 20:34:57.332 D/UsbDeviceManager( 761): updateUsbNotification - containsFunction: USB_FUNCTION_MTP
07-15 20:34:57.332 D/UsbDeviceManager( 761): UsbDeviceManager updateUsbNotification mConnected is:true,mBootCompleted is:true,mUsbNotificationId is:17040616,id is:17040615,mCurrentFunctions is:mtp,adb,mDefaultFunctions is:mtp,adb
07-15 20:34:57.334 V/UsbDeviceManager( 761): USB UEVENT: {USB_STATE=CONFIGURED, SUBSYSTEM=android_usb, SEQNUM=2757, ACTION=change, DEVPATH=/devices/virtual/android_usb/android0}
07-15 20:34:57.334 D/UsbDeviceManager( 761): mUEventObserver - onUEvent - state: CONFIGURED
07-15 20:34:57.334 D/UsbDeviceManager( 761): updateState - CONFIGURED
07-15 20:34:57.334 D/UsbDeviceManager( 761): updateState - RNDIS_UPDATE_DELAY CONFIGURED mSettingFunction: mtp
07-15 20:34:57.340 D/UsbDeviceManager( 761): UsbDeviceManager updateUsbNotification mConnected is:true,mBootCompleted is:true,show is:true,setupWized is:true,isInCall is:false
07-15 20:34:57.342 D/UsbDeviceManager( 761): broadcasting Intent { act=android.hardware.usb.action.USB_STATE flg=0x20000000 (has extras) } connected: true configured: false
07-15 20:34:57.347 W/UsbDeviceManager( 761): sys.usb.mtpConnect = mtpConnection
07-15 20:34:57.347 D/UsbDeviceManager( 761): sys.usb.acm_idx=
07-15 20:34:57.347 D/UsbDeviceManager( 761): handleMessage mConnected:true,mConfigured:false, mHwDisconnected:false
07-15 20:34:57.347 W/UsbDeviceManager( 761): handleMessage - 0
07-15 20:34:57.347 D/UsbDeviceManager( 761): updateUsbNotification - mNotificationManager: android.app.NotificationManager@230489b9
07-15 20:34:57.347 D/UsbDeviceManager( 761): updateUsbNotification - mUseUsbNotification: true
07-15 20:34:57.347 W/UsbDeviceManager( 761): updateUsbNotification - mConnected: true
07-15 20:34:57.347 W/UsbDeviceManager( 761): updateUsbNotification - mCurrentFunctions: mtp,adb
07-15 20:34:57.347 D/UsbDeviceManager( 761): updateUsbNotification - containsFunction: USB_FUNCTION_MTP
07-15 20:34:57.347 D/UsbDeviceManager( 761): UsbDeviceManager updateUsbNotification mConnected is:true,mBootCompleted is:true,mUsbNotificationId is:17040615,id is:17040615,mCurrentFunctions is:mtp,adb,mDefaultFunctions is:mtp,adb
07-15 20:34:57.348 D/UsbDeviceManager( 761): broadcasting Intent { act=android.hardware.usb.action.USB_STATE flg=0x20000000 (has extras) } connected: true configured: true
07-15 20:34:57.381 W/UsbDeviceManager( 761): sys.usb.mtpConnect = mtpConnection
07-15 20:34:57.381 D/UsbDeviceManager( 761): sys.usb.acm_idx=
07-15 20:34:57.381 D/UsbDeviceManager( 761): handleMessage mConnected:true,mConfigured:true, mHwDisconnected:false
2,由ptp切换为仅充电模式:
07-15 21:18:34.226 D/UsbDeviceManager( 753): setEnabledFunctions - functions: charging
07-15 21:18:34.226 D/UsbDeviceManager( 753): setEnabledFunctions - mDefaultFunctions: ptp,adb
07-15 21:18:34.226 D/UsbDeviceManager( 753): setEnabledFunctions - mCurrentFunctions: adb
07-15 21:18:34.226 D/UsbDeviceManager( 753): setEnabledFunctions - mSettingFunction: ptp
07-15 21:18:34.226 D/UsbDeviceManager( 753): sys.usb.acm_idx=,mAcmPortIdx=
07-15 21:18:34.232 D/UsbDeviceManager( 753): setEnabledFunctions - functions: charging
07-15 21:18:34.232 D/UsbDeviceManager( 753): setUsbConfig(none)
07-15 21:18:34.232 D/UsbDeviceManager( 753): setUsbConfig - config: none
07-15 21:18:48.838 D/UsbDeviceManager( 753): handleMessage - MSG_SET_CURRENT_FUNCTION - functions: ptp
07-15 21:18:49.344 D/UsbDeviceManager( 753): onReceive - BATTERY_CHANGED - mPlugType: 2, mSettingUsbCharging: false, mConnected: false, mSettingUsbBicr: false
07-15 21:18:49.425 V/UsbDeviceManager( 753): USB UEVENT: {USB_STATE=CONNECTED, SUBSYSTEM=android_usb, SEQNUM=2327, ACTION=change, DEVPATH=/devices/virtual/android_usb/android0}
07-15 21:18:49.426 D/UsbDeviceManager( 753): mUEventObserver - onUEvent - state: CONNECTED
07-15 21:18:49.426 D/UsbDeviceManager( 753): updateState - CONNECTED
07-15 21:18:49.426 D/UsbDeviceManager( 753): updateState - RNDIS_UPDATE_DELAY CONNECTED mSettingFunction: ptp
07-15 21:18:49.427 W/UsbDeviceManager( 753): handleMessage - 0
07-15 21:18:49.427 D/UsbDeviceManager( 753): updateUsbNotification - mNotificationManager: android.app.NotificationManager@2f18b8c
07-15 21:18:49.427 D/UsbDeviceManager( 753): updateUsbNotification - mUseUsbNotification: true
07-15 21:18:49.427 W/UsbDeviceManager( 753): updateUsbNotification - mConnected: true
07-15 21:18:49.428 W/UsbDeviceManager( 753): updateUsbNotification - mCurrentFunctions: ptp,adb
07-15 21:18:49.428 D/UsbDeviceManager( 753): updateUsbNotification - containsFunction: USB_FUNCTION_PTP
07-15 21:18:49.428 D/UsbDeviceManager( 753): UsbDeviceManager updateUsbNotification mConnected is:true,mBootCompleted is:true,mUsbNotificationId is:134545580,id is:17040616,mCurrentFunctions is:ptp,adb,mDefaultFunctions is:ptp,adb
07-15 21:18:49.435 V/UsbDeviceManager( 753): USB UEVENT: {USB_STATE=CONFIGURED, SUBSYSTEM=android_usb, SEQNUM=2328, ACTION=change, DEVPATH=/devices/virtual/android_usb/android0}
07-15 21:18:49.436 D/UsbDeviceManager( 753): mUEventObserver - onUEvent - state: CONFIGURED
07-15 21:18:49.436 D/UsbDeviceManager( 753): updateState - CONFIGURED
07-15 21:18:49.436 D/UsbDeviceManager( 753): updateState - RNDIS_UPDATE_DELAY CONFIGURED mSettingFunction: ptp
07-15 21:18:49.449 D/UsbDeviceManager( 753): UsbDeviceManager updateUsbNotification mConnected is:true,mBootCompleted is:true,show is:true,setupWized is:true,isInCall is:false
07-15 21:18:49.453 D/UsbDeviceManager( 753): broadcasting Intent { act=android.hardware.usb.action.USB_STATE flg=0x20000000 (has extras) } connected: true configured: false
07-15 21:18:49.486 D/UsbDeviceManager( 753): onReceive - BATTERY_CHANGED - mPlugType: 2, mSettingUsbCharging: false, mConnected: true, mSettingUsbBicr: false
07-15 21:18:49.495 W/UsbDeviceManager( 753): sys.usb.mtpConnect = ptpConnection
07-15 21:18:49.496 D/UsbDeviceManager( 753): sys.usb.acm_idx=
07-15 21:18:49.496 D/UsbDeviceManager( 753): handleMessage mConnected:true,mConfigured:false, mHwDisconnected:false
07-15 21:18:49.497 W/UsbDeviceManager( 753): handleMessage - 0
07-15 21:18:49.498 D/UsbDeviceManager( 753): updateUsbNotification - mNotificationManager: android.app.NotificationManager@2f18b8c
07-15 21:18:49.498 D/UsbDeviceManager( 753): updateUsbNotification - mUseUsbNotification: true
07-15 21:18:49.498 W/UsbDeviceManager( 753): updateUsbNotification - mConnected: true
07-15 21:18:49.498 W/UsbDeviceManager( 753): updateUsbNotification - mCurrentFunctions: ptp,adb
07-15 21:18:49.498 D/UsbDeviceManager( 753): updateUsbNotification - containsFunction: USB_FUNCTION_PTP
07-15 21:18:49.498 D/UsbDeviceManager( 753): UsbDeviceManager updateUsbNotification mConnected is:true,mBootCompleted is:true,mUsbNotificationId is:17040616,id is:17040616,mCurrentFunctions is:ptp,adb,mDefaultFunctions is:ptp,adb
07-15 21:18:49.499 D/UsbDeviceManager( 753): broadcasting Intent { act=android.hardware.usb.action.USB_STATE flg=0x20000000 (has extras) } connected: true configured: true
07-15 21:18:49.513 W/UsbDeviceManager( 753): sys.usb.mtpConnect = ptpConnection
07-15 21:18:49.513 D/UsbDeviceManager( 753): sys.usb.acm_idx=
07-15 21:18:49.513 D/UsbDeviceManager( 753): handleMessage mConnected:true,mConfigured:true, mHwDisconnected:false

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