How to modify the panel backlight

First identify the backlight device linked to your panel, thanks to the sysfs:

Board $> ls /sys/class/backlight

In the above example, there is a single entry named "5a000000.dsi.0", which is replaced by "*" in the below command.

To adjust the panel backlight, enter the following command:

Board $> echo 32 > /sys/class/backlight/*/brightness    # set the dsi panel backlight to the value 32

Note: Only values between 0 and max_brightness must be used.

To get the maximum panel backlight value, enter:

Board $> cat /sys/class/backlight/*/max_brightness

To get the actual panel backlight value, enter:

Board $> cat /sys/class/backlight/*/actual_brightness

Use one of the following commands to quickly test the panel backlight:

Board $> export bl=/sys/class/backlight/5a000000.dsi.0/brightness

Board $> # switch on/off test
Board $> (while true; do echo 0 > $bl; sleep 0.5; echo 255 > $bl; sleep 0.5; done)

Board $> # slow 32-step tests
Board $> (i=0; while true; do i=$(((i+32)%256)); echo $i > $bl; sleep 0.5; done)

Board $> # fast 1-step test
Board $> (i=0; while true; do i=$(((i+1)%256)); echo $i > $bl; done)