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[Bug 1209008] Re: [SRU] X doesn't work for video cards with non-KMS drivers on non-seat0 seats
I GOT ENLIGHTENED.
I know what changed since yesterday. I don't have my printer installed
in the multisesat ubuntu, so I'm ocassionally booting into my Debian
install where I have my multiseat setup based on a Xephyr approach,
where both monitors are connected to the two heads of JUST ONE of the
graphics cards. So today the monitor of seat-1 was connected to TWO
cards. Hence seat0 saw two monitors and extended its desktop to both,
and seat-1 also saw one monitor. When I unplugged the reduntant cable,
it all behaves like yesterday: seat-1 wouldn't come back after resume.
That's good and bad news: the good news it that the world still works as
it is supposed, the bad news is that the seat-1 resume problem remains.
I need a break...
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[SRU] X doesn't work for video cards with non-KMS drivers on non-seat0
Status in X.Org X server:
Status in xorg-server package in Ubuntu:
Status in xorg-server source package in Trusty:
* In Xorg-server versions older than 1.16, if Xorg is started as a
non-seat0 X server (i.e. if it was started with "-seat XXXX" option
where "XXXX" != "seat0"), it only probes platform bus for graphics
devices, leaving devices with non-KMS drivers (like NVIDIA proprietary
drivers and old ones like xf86-video-siliconmotion) unreachable.
from lp:~ubuntu-multiseat/xorg-server/trusty-matchseat fixes this.
* systemd-logind has no intrinsic mechanism to assign non-KMS graphics
devices to seats. In this case, one should tag another seat device
(keyboard, USB hub, etc.) in udev as "master-of-seat", and provide a
suitable xorg.conf for that seat. In order to avoid that a given
xorg.conf affects other seats, it should be passed to Xorg via
"-config xorg.conf.custom" option, which requires X server command
line customization support in DM in use (GDM, for example, has no such
Patch "xfree86_add_matchseat_key_to_xorg_conf.patch" from lp:~ubuntu-
multiseat/xorg-server/trusty-matchseat introduces a new MatchSeat key
for xorg.conf sections "Device", "Screen", and "ServerLayout", which
will target a given seat only. Example file
Option "NoLogo" "True"
# This section will only apply for seat-1
* systemd-logind can't handle any VT switching for non-seat0 seats,
but Xorg-server older than 1.16 still opens VT even if it's started as
a non-seat0 X server. This may lead to a race condition between X
servers: if a non-seat0 one is started before a seat0 one, the former
"steals" VTs from the later. If a seat0 X server can't open VTs,
systemd-logind can't activate sessions for seat0, leaving user without
sound or usb input support, for example.
Patch "xfree86_keep_non_seat0_from_touching_vts.patch" from lp
:~ubuntu-multiseat/xorg-server/trusty-matchseat fixes this.
* Set up a multiseat system where your non-seat0 seats use non-KMS
video drivers (you may need to tag another device in udev as "master-
of-seat" in order to achieve it).
* When LightDM/GDM tries to start a Xorg server for your non-seat0
seats, it will end up with the following error: "(EE) No devices
* After applying
xfree86_allow_fallback_to_pci_bus_probe_for_non_seat0.patch, you can
configure your seats in LightDM by setting appropriate "xserver-
config" properties for each seat. However, you can't configure them in
* After applying xfree86_add_matchseat_key_to_xorg_conf.patch,
configure your seats properly and restart LightDM/GDM services (or
reboot your computer) repeatedly. In some iterations, it may happen
that logind can't activate graphical sessions for seat0. If it occurs,
check output of command "ps -FC Xorg" and you'll see that a non-seat0
Xorg server has a lower PID than seat0 one. Moreover, the non-seat0
has opened a TTY, while the seat0 hasn't.
* Very low. All these patches were well tested in xorg-server "trusty"
package available in ppa:ubuntu-multiseat/ppa.
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