I have a small embedded system that I am working on that needs to be able to reduce its brightness for power saving reasons. The screen is connected by LVDS with separate Inverter Power Output connection providing the backlights power. The system is running Debian 3.2.68.
I have tried several approaches to this such as
xbacklight but the folder
/sys/class/backlight is empty so it fails with
No outputs have backlight property. Also when I search for any other folders containing "backlight" I go almost nothing back.
$sudo find / -type d -iname \*backlight\* /lib/modules/3.2.0-4-686-pae/kernel/drivers/video/backlight /sys/class/backlight /usr/share/doc/xbacklight
When I run xrandr with no parameters to detect displays I get the following.
$xrandr xrandr: Failed to get size of gamma for output default Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x768 default connected 1024x768+0+0 0mm x 0mm 1024x768 0.0*
I have tried updating and rebuilding my kernel as well as trying different parameters for
acpi_backlight= in my
menu.lst file. Any ideas on what to try from here or other ways to reduce the brightness are greatly appreciated!
Update 11/16: I have tried wiping the drive and starting over with a different distribution (Tiny Core Linux) with Xorg-7.7 in place of Xversa. The result is the same as with Debian where there is
No outputs have backlight property for
xbacklight. This leads me to think the issue is related to the board and its interaction with the monitor? The board is a Advantech MIO-5721 and the monitor is Mitsubishi Electric AA084XE01. They are connected by LVDS for the video and a Inverter Power Output for the backlights power.