Defining Seats

[Daniel Stone]

On Wed, Jul 18, 2007 at 10:22:14PM -0400, ext Chris Tyler wrote:
> On Thu, 2007-07-19 at 02:03 +0300, Daniel Stone wrote:
> > Well, given the extremely limited resources, and huge complexity of all
> > this (you need to have two _completely_ separate X servers in terms of
> > how they interface with clients, but somehow have them completely share
> > the card and its resources -- this amounts to something very close to a
> > server rewrite), it's just not even remotely high on the todo list.
> 
> Plenty of people do this right now using the current Xorg and Xephyr
> servers. Despite the extra overhead of going through two servers for
> every drawing operation, modern GPUs are fast enough that it works well
> for almost every 2D workload.

'Extremely limited resources' in this case means developer resources.
As for GPUs being fast enough to handle it: if you're using Xephyr, then
you have no acceleration.  Xephyr computes a final image and then just
sends that whacking great image to the base server.

> > You need a manual way of configuring it, yes.
> 
> I've been thinking about this more. If you could define both a primary
> server and a secondary server, then GDM could easily manage
> multiseat/single-GPU scenarios:
> 
> - Start one primary X server per graphics card/GPU (Xorg)
> - Start one secondary X server per seat (Xephyr)
> 
> Hot-plugging an additional monitor into an existing graphics card would
> be fairly straightforward: add the monitor to the primary server using
> xrandr, then start an additional secondary server for the new seat. The
> only hard part is figuring out which keyboard and mouse go with each
> seat, but you have that problem with any multiseat configuration.

Right, hence the manual configuration.  Not to mention that, due to
losing all acceleration (2D doesn't seem to be _that_ useful, but losing
video is definitely bad), you need to explicitly select multiseat
somewhere, rather than doing this by default.

Cheers,
Daniel
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