XFree under alien systems - the XF86Sup.sys approach and Windows NT

[Federico Bianchi]

On Tue, 5 Oct 1999, Suhaib Siddiqi wrote:

> Jan Rouvillain is studying xf86sup.sys driver and ask 
> programming questions about xf86sup.sys driver.
> I have posted a copy of Holger Veit's e-mail at cygwin-xfree URL,
> or you can access it directly:
> http://sourceware.cygnus.com/cygwin/xfree/xf86sup.html
> 
> You may find Holger e-mail very informative.

It is - and the XF86Sup.sys (whose source I have never seen) is actually
one of the neatest hacks I have ever seen in the OS/2 environment.

I had a discussion thread with Suhaib a couple of months ago about both
the XFree86 port to Win32 and the XF86Sup.sys approach chosen for the OS/2
one. I used (and modified) the files he gave me to work with two generic
drivers available under NT, i.e., PortIO.sys and MapMem.sys (the names are
pretty explainatory: PortIO lets user mode apps perform IN and OUTs to
devices, while MapMem maps a chunk of physical memory into an app virtual
space), but so far my test applications consistently give BSOD on an NT
4.0SP5, S3 equipped machine. I had a similar trouble at the end of 1997
(I had to access SVGA/VESA under the NT VDM/DPMI subsystem), and I found 
it was due to the optimizations the NT display driver used when switching
modes.

While mantaining my doubts over the blind-port approach (Suhaib knows,
should anyone be interested, I will let you know why and what the
alternatives are IMHO), I am therefore planning to write a very simple
"shim" driver to let user mode programs access the VESA VBE 2.0+ protected
mode SPIs, with particular regard to the mode switching functions - even
though I am wondering whether the generic call gate interface might be
enough. As usual, I have very little "predictable" spare time, but I will
let you know of any progress. 

Best regards to you all

	 		Federico Bianchi
			Dipartimento di Storia delle Arti
			Universita` degli Studi di Pisa
			p.zza S.Matteo in Soarta, 2 - 56127 Pisa (Italy)
			tel. +39-050-587111 (cent.), +39-050-587224 (uff.)
			fax. +39-050-580128; e-mail: <f.bianchi@arte.unipi.it>
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