Bug#900503: Bug #900503: xbacklight: Packagely solve the case of intel_backlight

[Jens Radloff <plixplox@yahoo.de>]

Hi,

I am using Debian Stretch 9.5 on an Acer Aspire E1-530 laptop. 

Today the backlight brightness of my laptop monitor suddenly got much less 
than 100%, I guess it was suddenly set to about 50% backlight brightness. A 
reboot did not change this unwanted behaviour. 

During every reboot the Grub splash screen was displayed with 100% backlight 
brightness, and after that splash screen disappeared during the boot process, 
these white output lines of the boot process on a black background were first 
displayed with 100% backlight brightness, then they were displayed with much 
less than 100% backlight brightness, I guess with about 50% backlight 
brightness. Then the display manager got started, with a backlight brightness 
much less than 100%, too.

To resolve this issue, I created a /etc/X11/xorg.conf file and inserted the 
following lines in this file, more or less as suggested in message #5 of this 
bug report (see above):

- - -

Section "Device"
    Identifier  "Card0"
    Driver      "intel"
    Option       "Backlight" "intel_backlight"
EndSection

- - -

Note that I do not use the line

    BusID       "PCI:0:2:0"

in the section "Device", as suggested in message #5 of this bug report (see 
above), because I do not know how to find out the BusID of my monitor.

Then I rebooted my machine. The backlight brightness appeared to be still much 
less than 100%. In the meantime I had installed the package xbacklight.

Then I applied

    xbacklight -set 100

, and then the backlight brightness of my monitor was put to 100% again.

Note that the command "xbacklight -set 100" did not work before I created the 
above-mentioned xorg.conf file with the content described above.

Regards,

Jens