gpio in dev

// A udev rule along these lines is recommended, to create symlinks in /dev/gpio:
//
//  SUBSYSTEM=="subsystem", KERNEL=="gpio", ACTION=="add", \
//      RUN+="/bin/mkdir -p /dev/gpio"
//
//  SUBSYSTEM=="gpio", ACTION=="add", TEST=="value", ATTR{label}!="sysfs", \
//      RUN+="/bin/ln -sT '/sys/class/gpio/%k' /dev/gpio/%s{label}"

// from mvduin online at github