kernel device dependency and sys/conf/files format

[Geoffrey C. Speicher]

I'm revisiting the project to determine device dependency in the kernel,
and I've run into a situation where net/if.c requires the ether device,
but no device appears to require net/if.c directly.

sys/conf/files says that net/if.c is "standard", but I have no idea what
that means in terms of building a kernel.  An entry (filename) in that
file can be listed as standard, mandatory, optional, or count.  Mandatory
and optional seem pretty self-explanatory, but can anyone explain the
meaning of standard and count?

I assume that net/if.c can be removed from the build or else it would be
listed as mandatory, but it does appear that an awful lot of things
implicitly depend on it.

Geoff