setting pull-down bias on userspace GPIO in embedded linux

[davegravy]

It seems the pins on this SBC default to pull-up, which I need to change. I spent a while modifying the device tree but while it's easy to configure pins that you're binding to a device with a driver (like gpio-keys) it seems impossible to do it for GPIO that you want to use in userspace. I hope I'm wrong and someone knows of a way.

I tried to set bias using gpiod, which involved needing to compile the latest version in order for gpioset to support the --bias parameter. It doesn't throw an error but it also doesn't work. I read some rather negative things about libgpiod in my quest for an answer.

The only success I've had is using busybox devmem to directly write to the memory address that controls the pin config. I feel like direct memory manipulation like this is kind of dangerous but as it stands running this on startup is the only option I see. 

Please let me know if there's a better way you know about.