Comment 23 for bug 1209008

Does NOT work for me :-(

I'm still getting the "no screens found" error, which, if I understand correctly, is supposed to be fixed with:
http://bazaar.launchpad.net/~ubuntu-multiseat/xorg-server/trusty-matchseat/revision/287/debian/patches/xfree86_allow_fallback_to_pci_bus_probe_for_non_seat0.patch

$ cat /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu/ trusty-proposed restricted main multiverse universe
deb http://pl.archive.ubuntu.com/ubuntu trusty-updates restricted universe main multiverse
deb http://security.ubuntu.com/ubuntu/ trusty-security restricted universe main multiverse
deb http://pl.archive.ubuntu.com/ubuntu trusty main restricted universe multiverse

$ dpkg -l xserver-xorg-core
...
ii xserver-xorg-core 2:1.15.1-0ubuntu2.6

$ lspci | grep VGA
01:00.0 VGA compatible controller: NVIDIA Corporation G98 [GeForce 8400 GS Rev. 2] (rev a1)
03:00.0 VGA compatible controller: NVIDIA Corporation G86 [Quadro NVS 290] (rev a1)

$ cat /etc/udev/rules.d/99-multiseat.rules
SUBSYSTEM=="drm", KERNEL=="card[0-9]*", ATTRS{vendor}=="0x10de", TAG+="master-of-seat"

TAG=="seat", DEVPATH=="/devices/pci0000:00/0000:00:01.0/0000:01:00.0/*", ENV{ID_SEAT}="seat0", TAG+="seat0"
TAG=="seat", DEVPATH=="/devices/pci0000:00/0000:00:1c.2/0000:03:00.0/*", ENV{ID_SEAT}="seat-1", TAG+="seat-1"

TAG=="seat", SUBSYSTEM=="usb", ATTR{name}=="DELL Dell USB Entry Keyboard", ENV{ID_SEAT}="seat0", TAG+="seat0"
TAG=="seat", SUBSYSTEM=="usb", ATTR{name}=="Logitech USB-PS/2 Optical Mouse", ENV{ID_SEAT}="seat0", TAG+="seat0"

TAG=="seat", SUBSYSTEM=="input", ATTR{name}=="AT Translated Set 2 keyboard", ENV{ID_SEAT}="seat-1", TAG+="seat-1"
TAG=="seat", SUBSYSTEM=="input", ATTR{name}=="ImPS/2 Generic Wheel Mouse", ENV{ID_SEAT}="seat-1", TAG+="seat-1"

$ loginctl list-seats
SEAT
seat0
seat-1

2 seats listed.

$ loginctl show-seat seat0
Id=seat0
ActiveSession=c2
CanMultiSession=yes
CanTTY=yes
CanGraphical=yes
Sessions=c2
IdleHint=no
IdleSinceHint=0
IdleSinceHintMonotonic=0

$ loginctl show-seat seat-1
Id=seat-1
CanMultiSession=no
CanTTY=no
CanGraphical=yes
IdleHint=yes
IdleSinceHint=0
IdleSinceHintMonotonic=0

$ loginctl list-sessions
   SESSION UID USER SEAT
        c2 1000 andrzejtp seat0

1 sessions listed.

$ loginctl seat-status seat0
seat0
        Sessions: *c2
         Devices:
                  /sys/devices/LNXSYSTM:00/LNXPWRBN:00/input/input1
                   input:input1 "Power Button"
                  /sys/devices/LNXSYSTM:00/device:00/PNP0C0C:00/input/input0
                   input:input0 "Power Button"
                  /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card0
                   [MASTER] drm:card0
                  /sys/devices/pci0000:00/0000:00:1a.0/usb3
                   usb:usb3
                  /sys/devices/pci0000:00/0000:00:1a.1/usb4
                   usb:usb4
                  /sys/devices/pci0000:00/0000:00:1a.2/usb5
                   usb:usb5
                  /sys/devices/pci0000:00/0000:00:1a.7/usb1
                   usb:usb1
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0
                   sound:card0 "Intel"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input10
                   input:input10 "HDA Intel Line Out CLFE"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input11
                   input:input11 "HDA Intel Line Out Side"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input12
                   input:input12 "HDA Intel Front Headphone"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input5
                   input:input5 "HDA Intel Rear Mic"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input6
                   input:input6 "HDA Intel Front Mic"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input7
                   input:input7 "HDA Intel Line"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input8
                   input:input8 "HDA Intel Line Out Front"
                  /sys/devices/pci0000:00/0000:00:1b.0/sound/card0/input9
                     input:input9 "HDA Intel Line Out Surround"
                  /sys/devices/pci0000:00/0000:00:1c.4/0000:04:00.0/ata5/host4/target4:0:0/4:0:0:0/block/sr0
                   block:sr0
                  /sys/devices/pci0000:00/0000:00:1c.4/0000:04:00.0/ata5/host4/target4:0:0/4:0:0:0/scsi_generic/sg1
                   scsi_generic:sg1
                  /sys/devices/pci0000:00/0000:00:1c.4/0000:04:00.0/ata5/host4/target4:0:1/4:0:1:0/block/sr1
                   block:sr1
                  /sys/devices/pci0000:00/0000:00:1c.4/0000:04:00.0/ata5/host4/target4:0:1/4:0:1:0/scsi_generic/sg2
                   scsi_generic:sg2
                  /sys/devices/pci0000:00/0000:00:1d.0/usb6
                   usb:usb6
                  /sys/devices/pci0000:00/0000:00:1d.1/usb7
                   usb:usb7
                  /sys/devices/pci0000:00/0000:00:1d.2/usb8
                   usb:usb8
                  /sys/devices/pci0000:00/0000:00:1d.2/usb8/8-1/8-1:1.0/input/input13
                   input:input13 "DELL Dell USB Entry Keyboard"
                  /sys/devices/pci0000:00/0000:00:1d.2/usb8/8-2/8-2:1.0/input/input14
                     input:input14 "Logitech USB-PS/2 Optical Mouse"
                  /sys/devices/pci0000:00/0000:00:1d.7/usb2
                   usb:usb2
                  /sys/devices/pci0000:00/0000:00:1e.0/0000:06:00.0/video4linux/vbi0
                   video4linux:vbi0 "BT878 vbi ( *** UNKNOWN/GENERIC"
                  /sys/devices/pci0000:00/0000:00:1e.0/0000:06:00.0/video4linux/video0
                   video4linux:video0 "BT878 video ( *** UNKNOWN/GENER"
                  /sys/devices/virtual/misc/rfkill
                    misc:rfkill

$ loginctl seat-status seat-1
seat-1
         Devices:
                  /sys/devices/pci0000:00/0000:00:1c.2/0000:03:00.0/drm/card1
                   [MASTER] drm:card1
                  /sys/devices/platform/i8042/serio0/input/input2
                   input:input2 "AT Translated Set 2 keyboard"
                  /sys/devices/platform/i8042/serio1/input/input4
                    input:input4 "ImPS/2 Generic Wheel Mouse"

$ lsmod | grep nouveau
$ lsmod | grep nvidia
nvidia 9704610 58
drm 244037 3 nvidia

$ cat /etc/lightdm/lightdm.conf
[LightDM]
logind-load-seats=true
logind-check-graphical=true

# cat /var/log/lightdm/x-1.log

X.Org X Server 1.15.1
Release Date: 2014-04-13
X Protocol Version 11, Revision 0
Build Operating System: Linux 3.2.0-70-generic i686 Ubuntu
Current Operating System: Linux turbo 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:44 UTC 2014 i686
Kernel command line: BOOT_IMAGE=/vmlinuz root=/dev/sda1 nomodeset
Build Date: 10 December 2014 06:16:10PM
xorg-server 2:1.15.1-0ubuntu2.6 (For technical support please see http://www.ubuntu.com/support)
Current version of pixman: 0.30.2
 Before reporting problems, check http://wiki.x.org
 to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
 (++) from command line, (!!) notice, (II) informational,
 (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.1.log", Time: Sat Dec 13 19:25:33 2014
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
Initializing built-in extension Generic Event Extension
Initializing built-in extension SHAPE
Initializing built-in extension MIT-SHM
Initializing built-in extension XInputExtension
Initializing built-in extension XTEST
Initializing built-in extension BIG-REQUESTS
Initializing built-in extension SYNC
Initializing built-in extension XKEYBOARD
Initializing built-in extension XC-MISC
Initializing built-in extension SECURITY
Initializing built-in extension XINERAMA
Initializing built-in extension XFIXES
Initializing built-in extension RENDER
Initializing built-in extension RANDR
Initializing built-in extension COMPOSITE
Initializing built-in extension DAMAGE
Initializing built-in extension MIT-SCREEN-SAVER
Initializing built-in extension DOUBLE-BUFFER
Initializing built-in extension RECORD
Initializing built-in extension DPMS
Initializing built-in extension Present
Initializing built-in extension DRI3
Initializing built-in extension X-Resource
Initializing built-in extension XVideo
Initializing built-in extension XVideo-MotionCompensation
Initializing built-in extension SELinux
Initializing built-in extension XFree86-VidModeExtension
Initializing built-in extension XFree86-DGA
Initializing built-in extension XFree86-DRI
Initializing built-in extension DRI2
Loading extension GLX
(EE)
Fatal server error:
(EE) no screens found(EE)
(EE)
Please consult the The X.Org Foundation support
  at http://wiki.x.org
 for help.
(EE) Please also check the log file at "/var/log/Xorg.1.log" for additional information.
(EE)
(EE) Server terminated with error (1). Closing log file.

On the other hand, if I use nouveau, both seats come up, but once a demanding application (like firefox) is started at seat-1, screen quickly becomes full of garbage and in dmes I can see many lines like:
Dec 13 17:20:28 turbo kernel: [ 2788.000175] nouveau E[ PGRAPH][0000:03:00.0] ch 2 [0x000fb43000 Xorg[21316]] subc 0 class 0x0030 mthd 0x0224 data 0x00000140
Dec 13 17:20:28 turbo kernel: [ 2788.000193] nouveau E[ PGRAPH][0000:03:00.0] ILLEGAL_MTHD.

To conclude this lengthy post: either I have both seats but one unusable (with nouveau), or I have just one seat working properly while the other gets "no screens found" (with nvidia).