how to deal with the usb modem io control code for windows 98

Hoi,
I’m developing the usb modem driver(in WDM form) for windows 98. It can be
succesfully installed and removed from the system. But when I go to the
HyperTerminal to send at commands, I got a frozen windows(couldn’t type any
words in it).

from the debug session, I found that, in the Dispatch routine, driver
firstly got IRP_MJ_CREATE, so it called Open_Serial function, and execute
successfully.
but it secondly got IRP_MJ_INTERNAL_DEVICE_CONTROL, and I don’t know how to
deal with it, I just implement some Serial-related functions in the
IRP_MJ_DEVICE_CONTROL(it works all right under windows 2000, but under windows
98, it goes to IRP_MJ_INTERNAL_DEVICE_CONTROL).

Is there anything wrong with my IRP_MJ_CREATE handling, or I have to
implement my own functions to deal with IRP_MJ_INTERNAL_DEVICE_CONTROL?

Could anybody share a example on this with me?

best regards

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