Taking the address assumes that the pin is an object (eg a struct), but it
could be a literal (eg an int). Not taking the address makes this driver
more general for other uses.
genhdr/pins.h is an internal header file that defines all of the pin
objects and it's cleaner to have pin.h include it (where the struct's for
these objects are defined) rather than an explicit include by every user.
Damien George