Udev rule for gpios for non root access

[tllim]

Using armbian bionic mainline kernel on A64-v1.1 board
Linux pine64 4.19.38-sunxi64 #5.83 SMP Fri May 3 21:02:31 CEST 2019 aarch64 aarch64 aarch64 GNU/Linux

Need to allow non-root access to gpio pins (i.e. gpio group with access to export and unexport etc) via udev.  I've done this successfully before on an RPI but no matter what I try the gpio group and permissions are not set.   Maybe it's something specific to Pine64 so asking here.  

here is one version of rules I've tried.   using udevadm I've confirmed the file is read and loaded but the changes are not made

Code:

SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'find -L /sys/class/gpio/ -maxdepth 2 -exec chown root:gpio {} \; -exec chmod 770 {} \; || true'"

Any suggestions?  Anyone have a successful udev rules for this board?  If so please share

Hopefully this article helps: http://synfare.com/599N105E/hwdocs/pine64/index.html