关于在android系统移植中usb的连接问题
近来在研究系统移植，出现了这样一个情况：连接usb线，usb Debugging connect(usb调试)显示正确，但是通知栏却没有出现usb连接的图标，statusBar也没有弹出连接usb的提示，故对此情况做出分析，找出原因所在。接下来的内容是记录自己寻找解决问题的整个过程。
这是log打印信息所示
显示ums连接失败
首先从usb连接模式讲起，usb连接时，有两种模式，一种是AC模式（充电），另一种是usb模式（usb_storage connect和usb Debugging connect），具体的判断在之前的一篇日志里有说明，在这里不提，因为在sys文件系统里我找到了我的对应的两个文件
/sys/class/power_supply/ac/online 显示值为0；
/sys/class/power_supply/usb/online 显示值为1；
由此可以判断，内核判断正确，此错误不是出在内核上，问题应该在frame框架层接受参数出错
接下来就重点于frame框架层的问题寻找。
记于2012/11/16日
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查阅相关资料，和源代码，找到usb连接的相关类：
在系统级APK-SystemUI.apk 下的usb文件夹内找到以下类：
StorageNotification.java
UsbStorageActivity.java
这是另个正常的log信息：省略号为其他log信息，
--------- beginning of /dev/log/system
I/Vold ( 1245): Vold 2.1 (the revenge) firing up
D/Vold ( 1245): Volume sdcard state changing -1 (Initializing) -> 0 (No-Media)
D/Vold ( 1245): Volume sdcard state changing 0 (No-Media) -> 2 (Pending)
D/Vold ( 1245): Volume sdcard state changing 2 (Pending) -> 1 (Idle-Unmounted)
W/Vold ( 1245): Ignoring unknown switch 'msm_hsusb_peripheral'
W/Vold ( 1245): Ignoring unknown switch 'msm_hsusb_peripheral'
.............
I/SystemServer( 1327): USB Service
I/UsbService( 1327): This kernel does not have USB configuration switch support
I/UsbService( 1327): Trying legacy USB configuration switch support
W/UsbService( 1327): This kernel does not have USB composite class support
D/UsbService( 1327): diag contains non-numeric data
............
D/VoldCmdListener( 1245): share status ums
D/StorageNotification( 1453): Startup with UMS connection false (media state unmounted)
I/StorageNotification( 1453): UMS connection changed to true (media state unmounted)
现在遇到的问题就是最后一句，错误的log信息为UMS connection changed to false（media state unmounted）
这句话的log信息出自StorageNotification.java中的onUsbMassStorageConnectionChangedAsync方法中
private void onUsbMassStorageConnectionChangedAsync(boolean connected) {
mUmsAvailable = connected;
String st = Environment.getExternalStorageState();
Slog.i(TAG, String.format("UMS connection changed to %s (media state %s)", connected, st));
Slog.v(TAG, String.format("UMS connection changed to %s (media state %s)", connected, st));
source code
updateUsbMassStorageNotification(connected);
}
最后调用了一个updateUsbMassStorageNotification()方法来传递参数connected（available或者unavailable）void updateUsbMassStorageNotification(boolean available) {
if (available) {
Intent intent = new Intent();
intent.setClass(mContext,com.android.systemui.usb.UsbStorageActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
PendingIntent pi =PendingIntent.getActivity(mContext, 0, intent, 0);
setUsbStorageNotification(
com.android.internal.R.string.usb_storage_notification_title,
com.android.internal.R.string.usb_storage_notification_message,
com.android.internal.R.drawable.stat_sys_data_usb,
false, true, pi);
} else {
setUsbStorageNotification(0, 0, 0,false, false, null);
}
}
从上边的update方法我们可以看出只要传递的connected参数为available时，将更新状态栏的信息，出现usb连接的title，而connected的参数是从哪传来的呢？接下来我们再看一段log信息：
usb未连接
10-1116:51:19.714: DEBUG/Vold(70): USB disconnected
10-1116:51:19.714: DEBUG/Vold(70): Share method ums now unavailable
10-1116:51:19.734: INFO/StorageNotification(177): UMS connection changed to false(media state removed)
10-1116:51:19.734: VERBOSE/StorageNotification(177): UMS connection changed to false(media state removed)
10-1116:51:19.734: VERBOSE/StorageNotification(177): --------- beginning of/dev/log/main
10-1116:51:20.820: DEBUG/Tethering(112): InitialState.processMessage what=4
10-1116:51:20.820: DEBUG/Tethering(112): sendTetherStateChangedBroadcast 0, 0, 0
usb已连接
10-1116:51:30.101: DEBUG/Vold(70): USB connected
10-1116:51:30.101: DEBUG/Vold(70): Share method ums now available
10-1116:51:30.132: VERBOSE/Environment(177): getExternalStorageState()
10-1116:51:30.140: INFO/StorageNotification(177): UMS connection changed to true(media state removed)
10-1116:51:30.140: VERBOSE/StorageNotification(177): UMS connection changed to true(media state removed)
10-1116:51:30.156: DEBUG/Tethering(112): sendTetherStateChangedBroadcast 1, 0, 0
10-1116:51:30.156: DEBUG/Tethering(112): interfaceAdded :usb0
从这段log里我们可以看到available这个参数是从vold底层传上来的未完待续。。。
记于2012/11/19日
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