Re: short display with 2.1.132-ac3, matroxfb and XF86_SVGA 3.3.3

Geert Uytterhoeven (geert@geert.cs.kuleuven.ac.be)
Sun, 3 Jan 1999 16:37:05 +0100 (MET)

On Sat, 2 Jan 1999, Linus Torvalds wrote:
> On Sat, 2 Jan 1999, Geert Uytterhoeven wrote:
> > The main difference between an accelerated frame buffer device based X server
> > and a `classical' X server is that video mode programming and colormap
> > updates are now handled by the kernel. The X server still has to take care of
> > acceleration engine setup and accelerated operations. If there's a clean
> > separation between these two functionalities (video mode programming vs.
> > acceleration), this is a question of some `if (use_fbdev)' statements.
>
> Yes, this is the kind of approach I was after. Not a new X server, but
> rather a straightforward extension to existing ones.
>
> The video mode programming issue is already black magic, and totally
> separate from actually drawing stuff on the screen. I can't for the life
> of me imagine that there would ever be an excuse to make a completely new
> X server just because the mode programming changed.

In theory its separated, but X servers do are complex things. I don't know
whether you ever read X server code, but I did.

> That's like separating the S3 X server into ten different X servers
> depending on which clock chip is on the board. That would just be silly
> and stupid, wouldn't it? But it's really almost exactly the same issue:
> the fact that the kernel handles mode switching could just be considered
> "a software clock chip" kind of thing. No?

Right! Finally we're getting at the same wavelength :-)

But for the 3.x line, XFree86 has many different accelerated X servers, each
with their own screen init functions. The current accelerated XF68_FBDev is
experimental, and we did it the way we did because that was the only way it
made sense to us (at that time, 4.x is not finished). Don't forget that the
`normal' XFree86 doesn't have any acceleration support for the NCR77C32BLT nor
for the IMS Twin Turbo. We borrowed XFree86 accel code for the ATI Mach64 only.

For the 4.x line, things can and should be done The Right Way (I hope).

Greetings,

Geert

--
Geert Uytterhoeven                     Geert.Uytterhoeven@cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}  http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium




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