Linux Backlight class digital display backlights

A digital display which has a backlight may have a Linux backlight driver which provides a sysfs API. Typically these are implemented via PWM signals allowing a variable brightness or a GPIO signal allowing a simple on/off.

Mapping A backlight driver to a PWM, GPIO, or other controller is done in the board support file or in the case of more modern kernels such as Ventana in the device-tree. See the backlight node in the ​gw54xx device-tree for example.

To list available backlight controllers:

ls /sys/class/backlight

To see current/available brightness values:

cat /sys/class/backlight/*/brightness # current brightness
cat /sys/class/backlight/*/max_brightness # max brightness

To set brightness (to a value equal or less than max_brightness)

echo 0 > /sys/class/backlight/*/brightness # turn off backlight

References:

• ​GPIO backlight
• ​PWM backlight
• ​sysfs-class-backlight

Other References

Here are some other useful references from our wiki:

• General Purpose I/O (GPIO)
• Pulse-Width-Modulation (PWM)
• GPIO in OpenWrt
• Ventana product family Digital I/O
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