We have several pieces of software that make use of the /sys/class/gpio
userspace interface to the GPIO subsystem.
One important prerequisite to being able to use the userspace GPIO
interface is to be able to put the corresponding package pins into GPIO
mode, by modifying the chip's mux settings.
With Fedora 19 on the Pandaboard, we were able to achieve this by poking
around in /sys/kernel/debug/omap_mux. However, when running Fedora 20,
this directory is empty. My assumption is that this functionality has
been subsumed by the pinctrl subsystem in recent kernels.
Unfortunately, there doesn't seem to be any documented userspace API.
I'd greatly appreciate it if someone could give me some pointers about
how to deal with this issue!
Dr Peter Brett <peter(a)peter-b.co.uk>