FASTIO WITH WFASTIO$ AND SUPPORT .DLL

DISCLAIMER: This sample code is for your information only. Do not attempt to use this code on your equipment without first inspecting the source code and making sure it does what you want. This code is supplied as is without warranty or liability of any kind.

WFASTIO$
I needed a fast way of being able to do fastio to I/O ports, to access a data acquisiton card. I saw the article from EDM/2 detailing the fastio driver. This seemed to be the ticket. But, I needed to change the functionality of the driver to meet the specfic needs of my D/A card. I did not have cl or MASM and could not get them because they are not availible any more. I wanted to be able to use what I had (WATCOM) to be able to make the changes to the driver. The first step was then to port the fastio driver to WATCOM. That is what I did.

With this driver you can access any I/O port you want very quickly. It does so buy calling a r3->r0 call gate which is returned to the application by the device driver. The call gate goes directly to the ring 0 code and executes the in/out instructions; therefore there is no need for a ring 2 IOPL segment. The driver call gate is faster than the standard IOPL r3->r2 call gate. For one there is no stack to copy the iolib passes data in registers. For more details see Holger's Article from EDM which explains the driver (one page back).

Why wouldn't the code work as it was? Well there are two reasons. 1) MASM and WASM are not exactly the same, parts of the assembler source were reqirued to be changed so that they would be compatible with WATCOM. 2) The default calling conventions for WATCOM are different than those for MICORSOFT so the header detailing the prototyping was changed to make WATCOM adhere to C calling conventions. See IOLIB.H for more details on the syntax of the pragma statements.

The code should be complete. What is included are the files for the device driver itself, actually modified from the hello world files, the proper ASM files with all the changes needed for WASM, and an example which uses the driver and reads from the VGA registers on your video card.

Be sure your compile using STACK CALLING CONVENTIONS (page 9 of compiler options) or the example will not work. If you need to change this option you should get a unresolved external error when compiling the code.

ARTICLE
Understanding the fastio$ driver part of an article from EDM

WIOLIBDLL- SUPPORT FOR WFASTIO$
Hello, and welcome. Before using this software there are a few things you should understand. This software should be used to access those devices which you would like to use but do not need to write a device driver for i.e. things like Data Acquisition cards. Be forewarned, that the I/O method used in this package does not have any checks. Having no restriction means that you can write to any port you want including video cards, sound cards etc. Wherever possible you should try to use the OS/2 system API calls to access the above device's. I am not responsible for damage or crashes to the users system as a result of these actions.

This package requires you to first load the WFASTIO$ device driver. For best results, put iolibdll.dll in C:\os2\dll. This way you only need one copy of it. Then link in the lib, and include the header with your application and you can call any of the functions in the dll to access your device.

If you have any questions or suggestions for this package, please feel free to e-mail me alger@avenger.mri.psu.edu. As far as compilers to use it with all should work, and I myself have used it with both Watcom and VAC++.