Virtual Serial port with UMDF / WriteFile Error when using FILE_FLAG_OVERLAPPED

NTDEV
1

Hi,

When I use CreateFile with FILE_FLAG_OVERLAPPED flag, and try to write to my driver using WriteFile, it returns an error although my driver received the data just fine.

When not using FILE_FLAG_OVERLAPPED everything is ok.

same happens with the virtual serial port example comes with winDDK 7000.0

any suggestions ??

thanks

2

What was the win32 error? Did you pass a valid OVERLAPPED with a valid hEvent handle?

d

Sent from my phone with no t9, all spilling mistakes are not intentional.

-----Original Message-----
From: xxxxx@gmail.com
Sent: Sunday, May 17, 2009 3:55 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Virtual Serial port with UMDF / WriteFile Error when using FILE_FLAG_OVERLAPPED

Hi,

When I use CreateFile with FILE_FLAG_OVERLAPPED flag, and try to write to my driver using WriteFile, it returns an error although my driver received the data just fine.

When not using FILE_FLAG_OVERLAPPED everything is ok.

same happens with the virtual serial port example comes with winDDK 7000.0

any suggestions ??

thanks

—
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3

the error is :

ERROR_IO_PENDING
997 (0x3E5) Overlapped I/O operation is in progress.

I think I pass a vaild OVERLAPPED, here is they way I create it:

_OVERLAPPED overlp;
overlp.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
overlp.Internal = NULL;
overlp.InternalHigh = NULL;
overlp.Offset =0;
overlp.OffsetHigh =0;
overlp.Pointer=NULL;

4

From:
> the error is :
> ERROR_IO_PENDING
> 997 (0x3E5) Overlapped I/O operation is in progress.

Well, duh! That’s an EXPECTED error. You just need to call
GetOverlappedResult and wait for the operation to finish.

Walter Oney
Consulting and Training
www.oneysoft.com

5

> ERROR_IO_PENDING

997 (0x3E5) Overlapped I/O operation is in progress.

That is normal for overlapped IO and is not an error.

–
Maxim S. Shatskih
Windows DDK MVP
xxxxx@storagecraft.com
http://www.storagecraft.com

6

Note that certain buggy OCX (MSCOMM) may not work with your driver.

7

As do many other virtualization solutions. I considered mentioning that, but the similarities to USB passthrough vs. hardware-level bugs on the USB controllers that might have commonly shipped with 440BX systems are probably a dubious thing to draw conclusions from.

  • S

-----Original Message-----
From: xxxxx@broadcom.com
Sent: Monday, May 18, 2009 17:02
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Virtual Serial port with UMDF / WriteFile Error when using FILE_FLAG_OVERLAPPED

Note that certain buggy OCX (MSCOMM) may not work with your driver.

—
NTDEV is sponsored by OSR

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8

AFAIK, the ocx issues are related to reads, not writes

d

Sent from my phone with no t9, all spilling mistakes are not intentional.

-----Original Message-----
From: xxxxx@broadcom.com
Sent: Monday, May 18, 2009 5:04 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Virtual Serial port with UMDF / WriteFile Error when using FILE_FLAG_OVERLAPPED

Note that certain buggy OCX (MSCOMM) may not work with your driver.

—
NTDEV is sponsored by OSR

For our schedule of WDF, WDM, debugging and other seminars visit:
http://www.osr.com/seminars

To unsubscribe, visit the List Server section of OSR Online at http://www.osronline.com/page.cfm?name=ListServer

9

You guys are right, that is not a problem. I was looking for a reason why .NET’s ports write() function is throwing me timeout, now i see that it is not the reason.

Looking deeper into the BCL, the only difference i see is that .net looks into the OVERLAPPED object and with it determines the number of bytes where written, if the number is 0 it throws the time out.

I was debugging my driver and comparing it to a real COM port, the difference i see is that in OVERLAPPED.Internal my driver puts 0, and the real COM puts 259. Could it be the reason ? I don’t see any other place where it can get the number of byes written to the port(although MSDN says internal means the error code).

any ideas ? thanks …

10

Found the bug !!

in OnWrite() instead of using :

pWdfRequest->Complete(hr);

use:

pWdfRequest->CompleteWithInformation(hr, BytesToWrite);

it should be changed in the exampls too i guess.

thanks for the help !

11

I assume you mean OnWrite in virtualserial\queue.cpp right?

-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of xxxxx@gmail.com
Sent: Monday, May 18, 2009 10:47 PM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Virtual Serial port with UMDF / WriteFile Error when using FILE_FLAG_OVERLAPPED

Found the bug !!

in OnWrite() instead of using :

pWdfRequest->Complete(hr);

use:

pWdfRequest->CompleteWithInformation(hr, BytesToWrite);

it should be changed in the exampls too i guess.

thanks for the help !

NTDEV is sponsored by OSR

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12

Yes exactly.