[oe] libusbgx functionfs mount

[Belisko Marek]

Hello,

I'm trying to add support for composite gadgets using
configfs/functionfs. I discovered that there already exist recipe for
config/start gadget in libusbgx and libusbx-config. I have run it on
my platform (with added some default scheme) and only issue I see is
that libcomposite should be probed before running gadget-start script.

I'm bit puzzled how to start then my gadget code (e.g. gadget-ffs) and
who will mount functionfs nodes? Are there any other recipes
available? I found useful this [0] but seems to be bit different what
is achieved in current oe.

[0] - https://www.collabora.com/news-and-blog/blog/2019/03/27/modern-usb-gadget-on-linux-and-how-to-integrate-it-with-systemd-part-2/

Thanks a lot.

BR,

marek