android 4.2之后，因为adb 的控制，统一使用了persist.sys.usb.config 来控制，于是对应的设置点也改到了frameworks/base/service/...../usb/UsbDeviceManager.java 中，您也可以看到类似的代码如：
public  UsbHandler(Looper looper) {
        // persist.sys.usb.config should never be unset.  But if it is, set it to "adb"
        // so we have a chance of debugging what happened.
         mDefaultFunctions = SystemProperties.get("persist.sys.usb.config", "adb");
        // 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;
        String state = FileUtils.readTextFile(new File(STATE_PATH), 0, null).trim();
        updateState(state);
        mAdbEnabled = containsFunction(mCurrentFunctions, UsbManager.USB_FUNCTION_ADB);

public void  systemReady() {
 // make sure the ADB_ENABLED setting value matches the current state
    Settings.Secure.putInt(mContentResolver, Settings.Secure.ADB_ENABLED, mAdbEnabled ? 1 : 0);
 
而这个persist.sys.usb.config 中adb 的配置是在alps/build/tools/post_process_props.py 中根据ro.debuggable = 1 or 0 来设置，1 就是开启adb, 0 即关闭adb debug. 而这个ro.debuggable 也是在alps/build/core/main.mk 中设置，和2.3 修改类似