Subject: Re: i386 + aperture + 1.6Q
To: Perry E. Metzger <>
From: Greywolf <>
List: current-users
Date: 03/28/2003 11:28:16
Thus spake Perry E. Metzger ("PEM> ") sometime Today...

PEM> Consider, for example, that all such cards have DMA controllers on
PEM> board -- DMA controllers which can be programmed to move bits into and
PEM> out of arbitrary portions of memory.

Oh, icky.  I was completely unaware of this!  Thank you for the edification.

However, since the DMA controllers can be programmed, what if it was
set up that only the kernel could get to the DMA, and thus could,
at that point, dictate where the DMA was going to happen?  Or would we
completely lose graphic acceleration at this point?

I'm sorry, I'm not trying to be dense here, but I'm just thinking that
there MUST be a way to make it so that all the other niceties of a raised
securelevel (the immutable files, etc.) can still be maintained while
permitting X to work.  Can't something be worked into the agp/wsdisplay
driver somehow?

I realise that building a card-specific driver into the kernel is likely
to be unpopular, if it is even possible (I know that nSidia, among others,
is really stubborn about allowing other non-Washingtonian operating
systems to make use of its features), but it crossed my mind...

I know.  It's gross and very Linux-like, and I'm not terribly fond
of it either.  I'm grasping at straws.

NetBSD is much like a tipi:  No windows, no gates, and an apache inside.