Date: Fri, 23 Oct 1998 11:40:55 -0700 From: Mike Smith <mike@smith.net.au> To: David Dawes <dawes@rf900.physics.usyd.edu.au> Cc: Mike Smith <mike@smith.net.au>, Greg Lehey <grog@lemis.com>, Jason Thorpe <thorpej@nas.nasa.gov>, Nick Hibma <nick.hibma@jrc.it>, FreeBSD hackers mailing list <hackers@FreeBSD.ORG> Subject: Re: multi-user: multiple consoles in FreeBSD Message-ID: <199810231840.LAA00564@dingo.cdrom.com> In-Reply-To: Your message of "Fri, 23 Oct 1998 13:30:06 %2B1000." <19981023133006.D20302@rf900.physics.usyd.edu.au>
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> The PCI spec doesn't provide a device-independent way of remapping the
> VGA compatibility resources. They are not relocatable in the sense of
> normal PCI resources defined through the base address registers. In my
> experience, most PCI BIOSs disable memory and I/O access for secondary
> VGA-compatible cards by clearing the appropriate bits in the PCI command
> register.
Hmm, Ok, I'm obvoiusly out of whack here. This would imply that there's
not an alternate set of mappings that can be enabled to access the same
register sets in any "standard" fashion?
> We (XFree86) are currently grappling with these issues for our multi-head
> support in 4.0. One thing we're hoping to do is multiplex access to
> fixed resources like the VGA-compatiblity registers when needed and when
> they can be disabled but not relocated. If on some OSs the video BIOS
> could be called by the X server, it may help with initialisation issues.
> It might be even better of the OS took care of this at boot time.
Hmm. I'm working around this area at the moment, although Kazu is
definitely the authority on the matter. I presume you're referring to
something like:
- Disable primary VGA compatibility mappings
- Disable primary VGA BIOS mapping
- Foreach non-primary video adapter
- Enable VGA compatibility mappings
- Enable VGA BIOS mapping
- Make BIOS initialisation call(s)
- Disable VGA compatibility mappings
- Disable VGA BIOS mapping
- Ensable primary VGA compatibility mappings
- Ensable primary VGA BIOS mapping
as well as providing some mechanism for nominating which card of the
set should be mapped at any given time?
Any ideas as to whether card BIOSses would respond well to having their
initialisation code called in v86 mode rather than real mode? I think
this sort of approach could be quite viable.
--
\\ Sometimes you're ahead, \\ Mike Smith
\\ sometimes you're behind. \\ mike@smith.net.au
\\ The race is long, and in the \\ msmith@freebsd.org
\\ end it's only with yourself. \\ msmith@cdrom.com
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