Static virtual com port

Question

Static virtual com port

Answer 1

First this sounds amazingly close to the discussions on these two questions:

https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/57b24c72-d53b-4f9e-bd89-895edec8003f/filter-driver-to-export-4-com-ports-on-top-a-usb-driver?forum=wdk#57b24c72-d53b-4f9e-bd89-895edec8003f

https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/3fcc0d36-a07f-46f3-bfa4-1f925c08329d/statically-loaded-driver-for-a-pnp-deviceusb?forum=wdk#3fcc0d36-a07f-46f3-bfa4-1f925c08329d

So read them first.  As you will see in those discussions a virtual com-port is a lousy interface for a USB printer device.  Additionally, a static device with a hot-plug (I.E. a USB device) behind it presents a lot of problems.

What is your actual problem?  Is there an application that requires a serial port interface to talk to a printer?   Tell us what the overall design problem you are trying to solve is, and we may be able to give you a good design. 

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Don Burn Windows Driver Consulting Website: http://www.windrvr.com

Answer 2

Well there will not be a good architecture due to the problems mentioned in the previous questions I linked to.   You can start with the virtual serial port sample in the WDK for com port, you will need to modify this since there is going to be some real hardware behind it, so it is likely that a number of the IOCTL's will need more support than the sample gives.  

You are also, going to have to spend a lot of effort handling the interface between the com port and the USB printer.   This is going to require not only dealing with two significantly different interface models, but also the problems of what to do in the serial port when the printer device goes away or comes back.

This is probably possible to do, but this is far from an easy project, and it will take a large amount of development and testing to get to anything one could call a stable set of drivers.

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Don Burn Windows Driver Consulting Website: http://www.windrvr.com