Comment 38 for bug 976124

> Also tried to start x:
> sudo X -core -config xorg-seat1.conf -sharevts :1 -auth
> /var/run/lightdm/root/:1 -nolisten tcp -novtswitch -seat seat1
> X server dosn't start - Fatal server error: (EE) no screens
> found(EE)
>
> After that:
> sudo X -core -config xorg-seat1.conf -sharevts :1 -auth
> /var/run/lightdm/root/:1 -nolisten tcp -novtswitch -seat seat0
> X server started, I was able open gedit on second seat screen from
> terminal (DISPLAY=:1 gedit)

Except for no keyboard and no mouse, your udevadm output looks OK.
That's unexpected, because this really sounds like a udev rules issue
to me (X finds the card when it's looking for seat0 cards, but not
when it's looking for seat1 cards).

It could be an X problem. I just noticed that you're running saucy
(or at least X from saucy). I've never tried saucy; I'm currently
running xserver-xorg-core from the xorg-edgers PPA on raring. I know
there have been some changes with hardware detection between 1.13.3
and 1.14.2 (specifically with nVidia cards; see bug #1190546), so
maybe X is to blame.

You can try the following, but I doubt they will help:

  * tag the video cards with 'master-of-seat' (see
    <http://www.freedesktop.org/wiki/Software/systemd/multiseat/>):

TAG=="seat", DEVPATH=="/devices/pci0000:00/0000:00:01.0/0000:01:00.0/*", TAG+="master-of-seat"
TAG=="seat", DEVPATH=="/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/*", TAG+="master-of-seat"

  * relax your multiseat rules to include the HDMI audio on the video
    card in seat1:

TAG=="seat", DEVPATH=="/devices/pci0000:00/0000:00:1c.0/*", ENV{ID_SEAT}="seat1", TAG+="seat1"

Unfortunately, the following might be your best options for figuring
this out:

  * downgrade X to the raring build in xorg-edgers
  * switch to non-proprietary nVidia drivers