USB continous reader (KMDF) strange behaviour

Hi,
I am writing an USB KMDF driver.I'm using a Continous Reader to receive data
from the device on an Interrupt or bulk endpoint. The device receives an
interogation packet and sends a response back on the endpoint for which the
reader is set.

All goes well in Windows 7. I have 2 different devices, one is full speed
the other is high speed, both work as expected, I receive the response as
soon as the device gets the interogation packet and sends back the response.

The problem is that the same driver in Windows XP works only for the full
speed device. The high speed one, does not respond , only after 4 "
interogation packets" are snd ( I checked in debuger ,the completion routine
is not called). Any clue why this is happening ? Why the different behaviour
in XP and Windows 7 ?

Any idea how to fix this ? Thank you.

Ada <> wrote:
>
>The problem is that the same driver in Windows XP works only for the full
>speed device. The high speed one, does not respond , only after 4 "
>interogation packets" are snd ( I checked in debuger ,the completion routine
>is not called). Any clue why this is happening ? Why the different behaviour
>in XP and Windows 7 ?
>
>Any idea how to fix this ? Thank you.

Can you post your descriptors? Bulk and interrupt endpoints both need
different descriptors at full speed and high speed.
--
Tim Roberts,
Providenza & Boekelheide, Inc.

I changed the maximum transfer size from 4K to 1K and now it works in XP also. Strange, as the device packets are smaller anyway ( about 40 bytes). Same driver, same device works in Windows 7 with 4K transfer size also.