In some email I received from Nathan J. Williams, sie wrote:
> <darrenr@reed.wattle.id.au> (Darren Reed) writes:
> 
> > I don't think I've been very clear here.  The idea is to have a "standard"
> > function that would deal with all "int" (say) types of data in the sysctl
> > tree.  That would deal with min/max properties.
> > 
> > For others, where you want to confine it to being in lots of 1000 or it
> > must always increase, a separate function would be called to "verify" that
> > the new value is acceptable.
> 
> This feels like the Solaris kernel mechanisim for ndd(1), which isn't
> a bad thing. The drivers call a function to put variables into the
> namespace, with a string name, a cookie, and read/write
> callbacks. There are also a standard set of callbacks for reading and
> writing unconstrained basic data types (int, char, maybe string).

This is where I snatched this idea (min/max/default) from.

Darren