I'm about to build a small circuit to interface with a Raspberry Pi (Zero W) running OpenWrt. As I understand it, the Pi has programmable pull-up/pull-down internal resistors which can be configured as needed when using the RaspberryPi OS. Given that it is configurable, it gives me some options for the circuit construction, but I'm not seeing this option in OpenWrt.
Here is an example of the GPIO setup, but there doesn't seem to be a file or method described for the option of pull-up vs pull-down.
root@OpenWrt:/sys/class/gpio/gpio516# ls -al
drwxr-xr-x 3 root root 0 May 15 01:51 .
drwxr-xr-x 3 root root 0 May 15 01:51 ..
-rw-r--r-- 1 root root 4096 May 15 01:53 active_low
lrwxrwxrwx 1 root root 0 May 15 01:51 device -> ../../../gpiochip0
-rw-r--r-- 1 root root 4096 May 15 01:51 direction
-rw-r--r-- 1 root root 4096 May 15 01:51 edge
drwxr-xr-x 2 root root 0 May 15 01:51 power
lrwxrwxrwx 1 root root 0 May 15 01:51 subsystem -> ../../../../../../../class/gpio
-rw-r--r-- 1 root root 4096 May 15 01:51 uevent
-rw-r--r-- 1 root root 4096 May 15 01:51 value
Does anyone know if there is a similar option available within OpenWrt on the Pi? If so, how do I set it?