why is the device removal message missing with the device file ope

I'm writing and testing a USB device driver on windows 2000.
I hope an application can receive the WM_DEVICECHANGE message of my USB
device.

In my application, I created a window in a thread to receive WM_DEVICECHANGE
message.

With the device file closed, its window procedure can receive such messages
perfectly. Both "DBT_DEVICEARRIVAL" & "DBT_DEVICEREMOVECOMPLETE" can be got.
(------- CASE1)

But the following flow can not work(------- CASE2):
1. I plug-in my usb device

In my application
2. Open the device file via CreateDevice() and get a valid handle
3. Create the window and call RegisterDeviceNotification, do the message
dispatch...

But when I plug-off the usb device, no device change message to reflect the
removal is got. (Neither DBT_DEVICEQUERYREMOVEFAILED nor
DBT_DEVICEREMOVEPENDING).
I only got a WM_DEVICECHANGE message with wParam =7.

Where is the message ??? For a surprise removal, what can I get?

In addition, the wParam value 7 also make me confused. I can't find its
definition in MSDN.

In fact, in CASE1, I got the following device message sequence as I plug-in
and plug-off the usb device:
--on plug-in
device msg param 0x7
device msg param 0x8000 (DBT_DEVICEARRIVAL)
device msg param 0x7

--on plug-off
device msg param 0x7
device msg param 0x8004 (DBT_DEVICEREMOVECOMPLETE)


Would anyone give me some advice? Thanks a lot!

Best Regards
Amanda Lin


This is the value of wParam for different device events (found in MSDN):
DBT_CONFIGCHANGECANCELED 0x19
DBT_CONFIGCHANGED 0x18
DBT_CUSTOMEVENT 0x8006
DBT_DEVICEARRIVAL 0x8000
DBT_DEVICEQUERYREMOVE 0x8001
DBT_DEVICEQUERYREMOVEFAILED 0x8002
DBT_DEVICEREMOVECOMPLETE 0x8004
DBT_DEVICEREMOVEPENDING 0x8003
DBT_DEVICETYPESPECIFIC 0x8005
DBT_QUERYCHANGECONFIG 0x17
DBT_USERDEFINED 0xffff

Best Regards
Amanda Lin

 

I found the value 7 for WM_DEVICECHANGE wParam means "DBT_DEVNODES_CHANGED".
Need the application judge by itself whether a surprise removal occurs?

 

are you registering for notifications on the device interface or on the
device handle itself?

 

Thank you very much, Doron.

You are right. I registered only the device interface notification but no
device handle notification.

So when the usb device is hot-plug-off, my application doesn't recevice any
device handle notification on "DBT_DEVICEREMOVECOMPLETE", nor does it close
the device handle. And therefore my device object is in a delete-pending
state and my application can NOT get the interface notification on
"DBT_DEVICEREMOVECOMPLETE" as a result.

Now I also register the device handle notification after the device file is
opened. (I also must thank fat-boy and Eliyas
....
filter.dbch_devicetype = DBT_DEVTYP_HANDLE;
filter.dbch_handle = my_global.hDevice;
my_global.hHandleNotification = RegisterDeviceNotification(hWnd,
&filter, 0);
....

It can work.
The device handle notification on "DBT_DEVICEREMOVECOMPLETE" comes at
first. I close the device file handle. And then the the device interface
notication on "DBT_DEVICEREMOVECOMPLETE" also comes.


Best Regards
Amanda