touch-packages team mailing list archive

[Laércio de Sousa <lbsousajr@xxxxxxxxx>]

Well... Now I can tell the whole story:

1. Following http://www.freedesktop.org/wiki/Software/systemd/writing-
display-managers/ , LightDM gains automatic multiseat support in release
1.11.7. This support improves a bit in release 1.11.8, which now watches
on changes in property "CanGraphical" of logind seats. LightDM only
spawns a greeter on a seat that has property "CanGraphical=yes".

2. Reading systemd-logind source code, I've found that a requisite to a
logind seat gain property "CanGraphical=yes" is attaching a device
tagged in udev as "master-of-seat" to it.

3. systemd-logind ships a default set of udev rules that tags any
framebuffer devices (/dev/fb*) as "master-of-seat", which is OK for all
KMS-compliant video drivers like Intel, Nouveau (open-source driver for
NVIDIA graphics devices) and Radeon (open-source driver for AMD graphics
devices).

4. However, NVIDIA or AMD proprietary drivers don't expose kernel
framebuffer devices, so they need their own udev rule to tag another
kernel device they expose as "master-of-seat" (in @elfy example, we tag
kernel device /dev/dri/card0):

SUBSYSTEM=="drm", KERNEL=="card[0-9]*", ATTRS{vendor}=="0x10de", TAG
+="master-of-seat"

5. Without this custom udev rule, seat0 will change his property
"CanGraphical" from "no" to "yes", so LightDM fails to spawn a greeter
on it.

I don't believe that systemd developers will accept to ship this udev
rule in upstream releases, because they only support open-source
drivers.

The right thing to do right now is reporting a bug to NVIDIA proprietary
driver's Ubuntu package maintainers, asking them to ship a suitable udev
rule like the one above. There's nothing to do with lightdm in this
case.

-- 
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to lightdm in Ubuntu.
https://bugs.launchpad.net/bugs/1365336

Title:
  Lightdm update=No desktop

Status in “lightdm” package in Ubuntu:
  Confirmed

Bug description:
  Update to lightdm from 1.11.7-0ubuntu1 to 1.11.8-0ubuntu1 leaves me
  with no desktop on normal boot.

  Machine boots directly to tty1.

  Logged in at tty1 and then startx leads to a desktop that requires
  password to start properly and with themes unapplied.

  Password required to reboot machine.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.10
  Package: lightdm 1.11.8-0ubuntu1
  ProcVersionSignature: Ubuntu 3.16.0-12.18-generic 3.16.1
  Uname: Linux 3.16.0-12-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.14.7-0ubuntu1
  Architecture: amd64
  CurrentDesktop: XFCE
  Date: Thu Sep  4 08:20:14 2014
  InstallationDate: Installed on 2014-07-17 (48 days ago)
  InstallationMedia: Xubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140717)
  SourcePackage: lightdm
  UpgradeStatus: No upgrade log present (probably fresh install)

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