Subject: Re: Status of i810 agp X support?
To: Jonathan Stone <jonathan@DSG.Stanford.EDU>
From: Thor Lancelot Simon <>
List: tech-security
Date: 08/12/2000 19:33:41
  by with SMTP; 12 Aug 2000 23:33:42 -0000
	by (Postfix) with ESMTP
	id C963D30EDD; Sat, 12 Aug 2000 19:33:41 -0400 (EDT)
Date: Sat, 12 Aug 2000 19:33:41 -0400
From: Thor Lancelot Simon <>
To: Jonathan Stone <jonathan@DSG.Stanford.EDU>
Subject: Re: Status of i810 agp X support?
Message-ID: <>
References: <> <>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.4i
In-Reply-To: <>; from jonathan@DSG.Stanford.EDU on Sat, Aug 12, 2000 at 12:21:42PM -0700

On Sat, Aug 12, 2000 at 12:21:42PM -0700, Jonathan Stone wrote:
> In message <>IWAMOTO Toshihiro writes
> >At Thu, 10 Aug 2000 18:15:42 -0700,
> >The PCI bus probing code is ugly (the definition of pci_softc was
> >copied from the kernel source) and should be fixed, but I think that
> >there should be no real problem with importing.
> I was wondering if someone wanted to redo it completely (Jason?)
> and integrate it as a non-modular device.

It's noteworthy that this device could be somewhat problematic.  The i810,
like most AGP video chipsets, has a DMA engine that can be programmed to
go to and from arbitrary bus addresses.  Having a device driver that
made the i810 "work" without regard to securelevel would essentially
bypass the entire securelevel mechanism.

Similarly, we don't have general-purpose AGP GART manipulation code in
our kernel, like Linux does.  This is a lose because it keeps us from
using DMA to get commands and data (e.g. textures) on and off the 3D
accellerators supported by MesaGLX -- this is why our MesaGLX modules
are much, much slower than the Linux ones.  But it's pretty hard to see
how this *could* be made to work without either moving all of the GL
support into the kernel or discarding the securelevel guarantees

Upshot: to do this kind of thing without ditching XFree, it needs to
"work" *only* when securelevel < 1.  If you're going to implement a
device to support the i810 or AGP GART in general, please keep this
in mind.