Error 8020: Error Reading Comm Device

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Hi All,

I have developed a USB-Serial driver. For this i have used KMDF
osrusbfx2 and serial samples.

I m using RS232-analyzer application for testing. This can be
downloaded at http://www.232analyzer.com/CommFront-Downloads.htm. I
have attached a loopback connector to the NULL modem cable and used
this applcation for sending/receiving ascii data. I get the error
Number 8020 and message that followed is "Error reading comm device".
I have debugged the driver and i see that driver is able to write and
then read the data. But the application does not receive the data. I
googled the intertet for the error and found the following url.
http://support.microsoft.com/default.aspx?scid=kb;en-us;318784.

The resolution mentioned is "A serial driver should return SUCCESS
synchronously for all read requests that can be immediately fulfilled
with data that is currently present".

My question is the serial EvtIoRead is a void callback function, so
how can i make it to return SUCCESS?

One other thing i observed is i have replaced the serial inbox drivers
with the serial sample provided in KMDF. I have built the serial
sample and replaced it. The same error occurs with standard COM port
as well. This error does not happen with WDM serial driver.

Is this a bug in KMDF serial sample driver?

All above tests are done in Windows XP 32 bit OS.

All your suggestions are appreciable.

Thanks in Advance.

Regards,
madhukar
.

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