Are register names and locations under copyright?

[Philipp Klaus Krause <pkk@spth.de>]

SDCC, a free C compiler targeting microcontrollers wants to provide
header files that contain I/O register names and locations for their
targets. The header files are automatically generated from some files
from the hardware vendor (e.g. tables in datasheets or some database).

For some targets, SDCC already has such files (e.g.
https://sourceforge.net/p/sdcc/code/HEAD/tree/trunk/sdcc/device/non-free/include/pic16/pic18f1320.h).

Problem: Hardware vendors want to impose non-free terms on the header
files (via a copyright claim on the files that the headers were
generated from).

Are the register names and locations under copyright? Is the generated
header file under copyright? If yes, who are the owners of the
copyright? Does the situation vary across jurisdictions?

SDCC developers are currently unsure about this. To err on the safe
side, all such headers live in a separate directory called "non-free"
since many years ago. The headers still live in the SDCC repository, are
distributed with tarballs, etc. The Debian package does not currently
include those headers.

Naturally, it would be good for SDCC users, if they could be confident
that they can use those headers in free software and if Debian could
include the headers in the package.

Philipp