How to root or GPIO access on custom android-based development board

Question

I have this development board Open-Q 820

It is running an Android 7.0 based on some sources from CodeAurora (that seem based on AOSP sources). Seems it uses proprietary bootloader that can not be changed. I need to access GPIO (/system/class/gpio) from my android app to control an external device. Problem is I can not do this from android app - seems only root can access this files. I can call "adb root" command from PC and then call from "adb shell" something like

echo 0 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio0/direction
echo 1 > /sys/class/gpio/gpio0/value

and it is working. But I need to do the same from my android app. I know how to access terminal and su from android app. I just dont know how to root custom device. I tried to install SuperSU.apk app and its corresponding su native app manually. It starts and says it need to update su binaries. After installing binaries and reboot the system then it becomes broken - infinite android logo. If I not install binaries update then SuperSU can grant permissions to my app but actully app still can not use su (I dont know why - I use this library inside my app: https://github.com/Chrisplus/RootManager ). And after reboot SuperSU not working longer. So may be you know some SuperSU alternatives (Knigroot not working too) or steps how to correctly install some superuser management app. Or may be I can use su directly (I tried but my app has not rights to access /system/xbin/su). Or may be I can make /sys/class/gpio accessible by android apps somehow (I tried chmod 777 on it - not works). May be some SElinux rights, but I have no experience with this.

Thank you

Answer 1

Magisk helped me. Since it is have option to patch custom boot image. I used this option and now root access works.