Re: VGA and pci_enable_device (was Re: Linux 2.4.0test1-ac6)

From: Jeff Garzik (jgarzik@mandrakesoft.com)
Date: Tue May 30 2000 - 20:35:04 EST


James Simmons wrote:
>
> > In practise, very few fbdev drivers support multi-head, so an
> > fbdev-correct hardware setup should never have this conflict occur.
> > However users who don't know this will get bitten if they stick two PCI
> > VGA cards into the computer, and try to get both going with fbdev
> > drivers.
>
> I have had this problem. I found I have to run a x86 bios emulator to get
> a second card going.

A much better solution is to duplicate the VGA BIOS init logic, POSTing
the card itself. Much smaller than an x86 emulator in the code, much
faster, and much safer. This is what matroxfb does. I have code to do
this for some nVidia chips (for use in rivafb), but it is known buggy
code at present..

> > The correct solution is to implement PCI VGA region sharing, a la
> > XFree4's resource access control (RAC). Until fbdev gets that, problems
> > related to sharing the VGA region will continue to crop up.
>
> Which files in the X server tree have this code? I like to take a look at
> this code.

hw/xfree86/rac/*

        Jeff

-- 
Jeff Garzik              | Liberty is always dangerous, but
Building 1024            | it is the safest thing we have.
MandrakeSoft, Inc.       |      -- Harry Emerson Fosdick

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