Comment 2 for bug 910536

I noticed that running manually
xrandr --output LVDS1 --set BACKLIGHT 0
makes the screen brightness maximum.

If I boot without acpi=off and run the xrandr-command, nothing happends. None of the Fn-key work either as acpi is on, so I guess the ACPI is broken.

To make the screen as dim as possible, run
xrandr --output LVDS1 --set BACKLIGHT 2948310

Maybe the range should be the other way around, 0 as minimum lightness?

$ xrandr --prop
Screen 0: minimum 320 x 200, current 1366 x 768, maximum 8192 x 8192
LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
 EDID:
  00ffffffffffff000daf991500000000
  07140103802213780a3d9594564f8e28
  26505400000001010101010101010101
  0101010101017a1d56d250001e303c28
  360058c110000018000000fe004e3135
  3642332d4c30420a2020000000fe0043
  4d4f0a202020202020202020000000fe
  004e31353642332d4c30420a20200048
 BACKLIGHT: 1 (0x00000001) range: (0,2948310)
 Backlight: 1 (0x00000001) range: (0,2948310)
 scaling mode: Full aspect
  supported: None Full Center Full aspect
   1366x768 60.0*+
   1360x768 59.8 60.0
   1024x768 60.0
   800x600 60.3 56.2
   640x480 59.9

As a workaround I tried to add
xrandr --output LVDS1 --set BACKLIGHT 0 -display :0
to /etc/rc.local but it does not work (error says cookie mismatch).

A less optimal workaround I added the command to the Gnome session, but LDM starts out dimmed, so the sole user of the laptop has to enter their password blindly (screen is to dark to see almost anything).