Backlight

Most drivers use the fbtft backlight support to control backlight.
This is enabled if there is a 'led' gpio present.

These drivers will have backlight power control exposed in the sysfs filesystem.

# Turn off backlight
echo 1 | sudo tee /sys/class/backlight/*/bl_power

# Turn on backlight
echo 0 | sudo tee /sys/class/backlight/*/bl_power

Brightness is currently not supported (need a kernel PWM driver for the Raspberry Pi).

Reference: https://www.kernel.org/doc/Documentation/ABI/stable/sysfs-class-backlight

Also see Console blanking

Backlight control outside of FBTFT

Wiring Pi can be used to dim the backlight.

gpio -g mode 18 pwm 
gpio -g pwm 18 1023