multiseat

[Daniel Stone]

On Thu, Jul 28, 2005 at 10:44:32AM -0700, Jesse Barnes wrote:
> On Thursday, July 28, 2005 7:52 am, Adam Jackson wrote:
> > The arbitration idea is lovely but it assumes that the card gives a
> > damn when you tell it not to decode the VGA space, and there are many
> > video cards that will stick their fingers in their ears and go LA LA
> > LA I CAN'T HEAR YOU when you try.  You could assert that those cards
> > are broken, but that's sort of the point: hardware is broken and will
> > actively defeat attempts to be used in a multiseat setup.
> 
> As a result, I think it's reasonable to limit multiseat setups to a sane 
> subset of cards that X supports.  If a card needs the VGA registers to 
> be enabled during runtime for use by the driver, it seems especially 
> broken to me.

Right.  Unfortunately, this is particularly the case with old drivers
for old cards that no-one cares about anymore, which also happens to be
the cheapest way to fly.  And often, the motivator for multiseat setups
is to reduce cost.  Finding new cards x4 (i.e. one AGP and three PCI) is
surprisingly non-trivial.  I set out with a mandate to get three PCI
GeForces (any generation), and wandered around Melbourne's swap meets,
which have the cheapest kit, and often second-hand.  $230 later, I had
my three cards.

Now, I can eBay old PCI cards (Tseng, ARK, Mach64s, whatever), for
cheap.  But it's eBaying recent PCI cards (which are rare as hen's teeth
because AGP really rocks, right?) is also non-trivial.

So, in an ideal world the drivers would be fixed.  But in reality we're
kind of limiting ourselves to pre-made setups like the HP 441 here.

> Other than that though, VGA registers should only need to be available 
> for card posting--once that's done, VGA stuff shouldn't happen at all, 
> right?  Can we do things like screen blanking without it though?

Right.  But getting them past the POST can be the difficult bit. :)