From - Thu Sep 25 07:42:39 1997
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From: "Kerry Krieske" <kerry@i3.attmail.com>
Newsgroups: comp.os.ms-windows.programmer.nt.kernel-mode
Subject: Re: Serial Programming on NT
Date: Wed, 24 Sep 1997 11:56:00 -0700
Organization: Transport Logic - www.transport.com
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>If you are asking about interfacing to the SERIAL.SYS driver in NT using
>the layered (is there any other way) approach, I have the same question.  I
>looked into using the ZwXxxx functions to open a handle to the serial
>device and do I/O but had to abandon this approach because I'm not always
>at PASSIVE_LEVEL nor am I always running in the same context.  I typically
>run at DISPATCH_LEVEL in a DPC.
>
>Anyone have any suggestions for me as to how to use SERIAL.SYS from a DPC
>context?  I think I can piece it together eventually but I've never done it
>before so any help would be appreciated.
>
>-Michael

You should open the port with  IoGetDeviceObjectPointer and from then on you
can invoke IoCallDriver with the returned device object and irp's you create
(read/write/ioctl).

Isn't it amazing how much more complicated the source for serial.sys is from
the source for serial.vxd?   Fortunately, it is not that complicated for a
vxd or sys driver to use each of these serial drivers (serial.vxd via vcomm)
in either OS.