Userspace application check for devfs in use?

["Kevin P. Fleming" <kevin@xxxxxxxxxxxxx>]

What is the proper (documented, recommended, whatever) method for a
userspace application to check if the /dev filesystem is coming from devfs
or not? I am modifying a tunneling application to use new-style /dev paths
if devfs is in use, but it needs to know...

Right now I'm just relying on a stat() of /dev/.devfsd returning without an
error if devfs is mounted on /dev, but that may not be optimal (or
future-proof). Any other suggestions?