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" > /sys/class/backlight/<drivername>/bl_power

# Turn on backlight
echo "0" > /sys/class/backlight/<drivername>/bl_power

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

Reference: http://www.mjmwired.net/kernel/Documentation/ABI/stable/sysfs-class-backlight

Backlight control outside of FBTFT

Wiring Pi can be used to dim the backlight.

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