Is there any Difference in Sending IOCTL's to Internal and External Modem

Hi,
I have to use modem in my driver, so I take the handle of the port
to which the modem is installed.
Then I allocate IRP’s taking care of the stack requirements of the
lower device to which I am about to pass this IRP. I Fill the next Stack
location with MajorFunction, Minor function, and other parameters depending
on the MajorFunction.
This method works fine when I use an external modem, But when I try
this with my internal modem all the IRP’s that I allocated are returned with
status 0xC0000001 which is STATUS_UNSUCCESSFUL.

Can anyone help out with what difference does it make when I use my
internal modem. my internal modem is a PCI modem and it uses a virtual port
COM3 or COM4.

Thanks in anticipation of your help.

Regards
sanjeev


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