Bug#776355: gdm3 turns backlight off when multiple monitors are connected, yet puts the login prompt on the darkened monitor

[Olliver Schinagl]

Package: gdm3
Version: 3.14.1-3
Severity: normal

Dear Maintainer,

Whenever I do a cold boot, I see the boot messages on my laptop screen and
monitor in parallel. Whenever GDM starts however, backlight is set to be off.
The secondary monitor still shows the gdm background. The login prompt however
remains on the primary laptop screen and thus cannot be interacted with.

Booting with no external monitors connected works fine.

Additionally, the backlight brightness cannot be adjusted when gdm is active
(but I think this is to be expected due to permissions?).

This on a mid 2013 macbook pro retina,
00:02.0 VGA compatible controller: Intel Corporation Device 0a2e (rev 09)
[    2.598451] fbcon: inteldrmfb (fb0) is primary device
[    3.996610] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
model name: Intel(R) Core(TM) i5-4258U CPU @ 2.40GHz

It does not matter whether the display is connected via hdmi or display-port.



-- System Information:
Debian Release: 8.0
  APT prefers testing-updates
  APT policy: (500, 'testing-updates'), (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, armhf

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gdm3 depends on:
ii  accountsservice                       0.6.37-3+b1
ii  adduser                               3.113+nmu3
ii  dconf-cli                             0.22.0-1
ii  dconf-gsettings-backend               0.22.0-1
ii  debconf [debconf-2.0]                 1.5.55
ii  gir1.2-gdm3                           3.14.1-3
ii  gnome-session [x-session-manager]     3.14.0-2
ii  gnome-session-bin                     3.14.0-2
ii  gnome-settings-daemon                 3.14.2-2
ii  gnome-shell                           3.14.2-3+b1
ii  gnome-terminal [x-terminal-emulator]  3.14.1-1
ii  gsettings-desktop-schemas             3.14.1-1
ii  libaccountsservice0                   0.6.37-3+b1
ii  libaudit1                             1:2.4-1+b1
ii  libc6                                 2.19-13
ii  libcanberra-gtk3-0                    0.30-2.1
ii  libcanberra0                          0.30-2.1
ii  libgdk-pixbuf2.0-0                    2.31.1-2+b1
ii  libgdm1                               3.14.1-3
ii  libglib2.0-0                          2.42.1-1
ii  libglib2.0-bin                        2.42.1-1
ii  libgtk-3-0                            3.14.5-1
ii  libpam-modules                        1.1.8-3.1
ii  libpam-runtime                        1.1.8-3.1
ii  libpam-systemd                        215-8
ii  libpam0g                              1.1.8-3.1
ii  librsvg2-common                       2.40.5-1
ii  libselinux1                           2.3-2
ii  libsystemd0                           215-8
ii  libwrap0                              7.6.q-25
ii  libx11-6                              2:1.6.2-3
ii  libxau6                               1:1.0.8-1
ii  libxdmcp6                             1:1.1.1-1+b1
ii  libxrandr2                            2:1.4.2-1+b1
ii  lsb-base                              4.1+Debian13+nmu1
ii  metacity [x-window-manager]           1:3.14.3-1
ii  mutter [x-window-manager]             3.14.2-1
ii  policykit-1                           0.105-8
ii  terminology [x-terminal-emulator]     0.7.0-1
ii  ucf                                   3.0030
ii  x11-common                            1:7.7+7
ii  x11-xserver-utils                     7.7+3+b1
ii  xterm [x-terminal-emulator]           312-1

Versions of packages gdm3 recommends:
ii  at-spi2-core               2.14.0-1
ii  desktop-base               8.0.2
ii  gnome-icon-theme           3.12.0-1
ii  gnome-icon-theme-symbolic  3.12.0-1
ii  x11-xkb-utils              7.7+1
ii  xserver-xephyr             2:1.16.2.901-1
ii  xserver-xorg               1:7.7+7
ii  zenity                     3.14.0-1

Versions of packages gdm3 suggests:
ii  gnome-orca            3.14.0-2
ii  libpam-gnome-keyring  3.14.0-1+b1

-- debconf information:
* shared/default-x-display-manager: gdm3
  gdm3/daemon_name: /usr/sbin/gdm3