Here is what I learned the last days:
The information that can be found in the windows registry is read by the virtual device driver VPENDC.VXD during startup. Among other things, you can find there some binary stuff called "hardwareinfo" and "peninfo". The structure of these things are explained at
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wmeother/pen_0bhs.asp
As I have no windows at my Point 510, I looked at the Point 510 of a friend and got these values (from "hardwareinfo"): COM 4, IRQ 15, PORT 0x2e8
I tried these on my device by calling "setserial /dev/ttyS3 uart 8250 irq 15 port 0x2e8", adjusting the XF86Config to use the passive pen driver from www.linuxslate.org with /dev/ttyS3 and then starting XWindows. It didn't work 
Perhaps someone could do the same and check whether it *really* is not working, or if I just did something wrong...?
Btw: I am not sure, but as far as I know, it should be possible to check the serial settings under linux by a simple "cat /dev/ttySn" (I currently get "input/output error" all the time). Is this right? If so, I wouldn't need to alter XF86Config and start X for every test... ?
Today, I tried to reengineer the VPENDC.VXD. As far as I know, this should be the place where Point 510 specific stuff can be found, if there is any. I already got far enough to think that I need some C-Headers to understand the constants that are used. I heard rumors that these headers were part of a Windows 95 DDK Beta and were removed in the final version. ( Strange, you find infos about them at the MSDN pages ). The headers are definitly not part of the Windows98 DDK. Anyone out there who knows more about it?
Probably, I will reinstall windows on my Point 510 and try to patch the VPENDC.VXD to log some information about what is actually going on. Not sure about that, though ( I've already put by far to much time into this little old thing...)
Any ideas?
Regards,
Norbert
P.S.: The MSDN is definitly worth a visit if you want to know what is going on in the windows pen driver.
