First identify the backlight device linked to your panel, thanks to the sysfs:
ls /sys/class/backlight 5a000000.dsi.0
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:
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:
cat /sys/class/backlight/*/max_brightness 255
 Information
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| If the max_brightness value is 1, the backlight can only be switched on and off. If the max_brightness value is above 1, the backlight has several levels on luminosity (pwm-based backlight for instance). |
To get the actual panel backlight value, enter:
cat /sys/class/backlight/*/actual_brightness 32
Use one of the following commands to quickly test the panel backlight:
export bl=/sys/class/backlight/5a000000.dsi.0/brightness export max=/sys/class/backlight/5a000000.dsi.0/max_brightness # switch on/off test (while true; do echo 0 > $bl; sleep 0.5; echo $max > $bl; sleep 0.5; done) # slow 32-step tests (only for pwm-based backlights) (i=0; while true; do i=$(((i+32)%256)); echo $i > $bl; sleep 0.5; done) # fast 1-step test (only for pwm-based backlights) (i=0; while true; do i=$(((i+1)%256)); echo $i > $bl; done)
| Information
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| Be sure the panel is running (power on) before modifying its backlight. |