# mount -t debugfs none /sys/kernel/debug
# cat /sys/kernel/debug/gpio             
[...]
GPIOs 64-95, gpio-2:
 gpio-67  (pin22               ) in  hi
 gpio-68  (PCIE RESET          ) out hi
 gpio-69  (gpio-ir-recv        ) in  hi
 gpio-70  (pin15               ) in  hi
[...]
# echo 67 > /sys/class/gpio/export
# echo out > /sys/class/gpio/gpio67/direction
# cat /sys/kernel/debug/gpio
[...]
GPIOs 64-95, gpio-2:
 gpio-67  (pin22               ) out lo
 gpio-68  (PCIE RESET          ) out hi
 gpio-69  (gpio-ir-recv        ) in  hi
 gpio-70  (pin15               ) in  hi
[...]
# val=1
# while : ; do 
>   echo $val > /sys/class/gpio/gpio67/value
>   echo $val
>   sleep 1
>   val=$((1-$val))
> done
1
0
1
0