I've been working on adding an implementation of I/O port trapping to JEMM using the EMM386/QEMM API (INT 2F.4A15). I have it basically working.
I want to clear up some misconceptions, though. As far as the I/O port trapping, MS did a really crummy job of implementing it. Bob Smith of Qualitas found this out as he was implementing it in QEMM. E.g., the MS implementation only supports byte I/O (not Word or DWord), has a very limited number of port traps that it can implement, and doesn't always uninstall the I/O traps correctly. The description in RBIL is incomplete and doesn't even detail the de-installation procedure. Qualitas' implementation fixed the MS problems and expanded its features (but I've never actually seen or tested the Qualitas implementation). I've added even more features in the JEMM implementation. Even though I have it basically working, it's still far from where it needs to be and would really like someone else to take it and finish so I can concentrate on other things. If anybody wants to do it, I'll send you the code I've got so far and try to explain my thinking. One of the main things missing is supporting JLMs (JLOAD needs to be fixed to make it compatible). However, if this is going to be a "fork" of JEMM rather than an "upgrade", fixing JLOAD may not be necessary. The main reason I started working on it was to support my USB drivers, and in particular the ability to virtualize the following kinds of USB devices: Keyboards Mice Joysticks/Game Pads Serial/COM ports Sound Cards Ethernet Cards Parallel ports (maybe -- these aren't as critical as Serial/COM ports) E.g., for an Ethernet card, it's possible to implement a USB Ethernet drive as a simple packet driver, but virtualizing something like an NE2000 at the hardware level opens up many more possibilities for compatibility with older programs. A couple of the things I've added in my JEMM implementation are support for ports below 100h (though each port can only have a single "manager" or "virtualizer") and IRQ virtualization (which requires manipulation of ports 20h and 70h). One thing that I think still definitely needs to be added is DMA virtualization, though I haven't yet worked through the details on how to do that. And, of course, let's not forget the documentation which I haven't even started yet (and which I'm sure most implementers would just slip through the cracks). I've also created a test program to be able to test all the features to make sure they work. The version of JEMM I started with when I did this was 5.79, and I think Japheth has a newer version out and Japheth's latest changes would also need to be incorporated. I also went through and "cleaned up" some of the code to make it look more consistent. Anyway, does anybody else want to take this over and finish it? I know a lot of people want to see it happen (including me), and I think I've got a good start on it. _______________________________________________ Freedos-devel mailing list Freedos-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-devel
