do we have a generic string-number sysctl mapping library ?

Hi,
I have frequently found myself using sysctls to control some kernel
feature where a string would be a better (and sometimes the only)
option than using a numeric value, yet the internal representation
should be numeric for speed and robustness.
Examples are the kern.timecounter, the default scheduler in dummynet,
and now in netmap the selection between native and emulated mode.
I am sure many of you can come up with other cases.

I wonder if we have some support for that already in the sysctl code,
or i should build a generic one next time i need to do that.

Feel free to criticise the approach and suggest better ones.
Right now i am using sysctls because i have a set of macros
and wrapper functions that let me convert them to sysfs
entries when building kernel code on linux, so I have a
portable solutions.

For the details, I'd like to have a mechanism that requires the
kernel programmer supply a (possibly extensible) table of
supported values, and matching constants to be used within
the kernel. A single declaration should generate entries
to get/set the current value as well as list options.
We can discuss frills (such as wildcards, multiple values,etc).

cheers
luigi