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SubjectRe: short display with 2.1.132-ac3, matroxfb and XF86_SVGA 3.3.3
>>>>> "Linus" == Linus Torvalds <> writes:

Linus> For X servers where the mode switching works even together with
Linus> CONFIG_FB (and yes, there are tons of people that seem to use
Linus> CONFIG_FB together with some accelerated servers already), I
Linus> would think we _want_ to use those accelerated X servers -
Linus> possibly with a caveat that they aren't guaranteed to work. But
Linus> the mentality that "if you have CONFIG_FB you have to use
Linus> XF86_FBdev" must go, imho. Jes, do you understand?

In some cases it will work and in some it is damn hard to make it
work. I am by no way an X expert, I just hacked up a an acceleration
module (from the NetBSD in fact) to work on the NCR chip I have on my
video card).

Geert gave me an example earlier today as to why, let me try to quote
it from memory: One problem is that some X servers (like the Mach64
one) reads memory clock settings from the BIOS on the card instead of
reading them from the registers. The frame buffer driver does not
necessarily use the same settings as in the BIOS and in this case you
may see unpredictable results when running the X server.

What else some X servers will read from board BIOSes is beyond me but
there is a potential danger here. I strongly support the idea of
making the general X server FB aware, whether we refer to it as the
new SVGA server, the FBDev server or something else I expect it to be
the same thing.

Linus> I already applied a documentation patch by Jes from to
Linus> 2.2.0pre4 saying that CONFIG_FB is not necessarily a good idea
Linus> if you can avoid it. But Jes, if you continue to say that if
Linus> you run CONFIG_FB you _cannot_ run any other X server, then I
Linus> will just change the config option to something like
Linus> CONFIG_SCREEN_SLOW_X and change the documentation to match to
Linus> make _sure_ nobody ever does it even by mistake.

I do not say you cannot, I do say there may be problems and therefore
people are lucky if it works - it is not guaranteed to work as in the
example with the Mach64 server.


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