Re: VGA PCI IO port reservations

From: Jeff Garzik (jgarzik@mandrakesoft.com)
Date: Fri Nov 17 2000 - 12:03:21 EST


Russell King wrote:
> Jeff Garzik writes:
> > If XFree86 not fbdev is using the hardware, you can always have a stub
> > driver that does nothing but reserve the ports. Remember, too, that the
> > ports claimed depend on register settings in the video card and PCI
> > config space..
>
> I wish. Unfortunately, ones of this nature tend to be rather fixed. No amount
> of config space twiddling will move them. However, as someone else pointed out,
> x86 gets around this problem by only allowing IO ports to be allocated in the
> (addr & 0x0300) == 0 range, thereby avoiding the problem.

Dig through the video card docs, even older ISA video cards let you
disable I/O decoding on all but a few ports, and/or relocate the ports
it does use to other areas. Different with every video card, of course,
but most of them can do this to a greater or lesser extent.

        Jeff

-- 
Jeff Garzik             |
Building 1024           | The chief enemy of creativity is "good" sense
MandrakeSoft            |          -- Picasso
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