per-device sysctls

[M. Warner Losh]

In message: <xzphdxdk690.fsf at dwp.des.no>
            des at des.no (Dag-Erling Smørgrav) writes:
: Robert Watson <rwatson at freebsd.org> writes:
: > Having a unified and managed namespace for device sysctls sounds like a
: > generally good idea to me, as more and more devices require some of
: > another tweaking.  Have you had any thoughts on how to name sysctls and
: > kernel environment variables on a per-driver basis, rather than a
: > per-device basis?  I.e., fxp and some other device drivers have
: > configuration settings that affect all instances of devices, rather than
: > specific instances.
: 
: It should be easy to add a per-devclass_t or per-driver_t sysctl
: context and tree.  These things are disgustingly easy to create; the
: only hard part is figuring out when and where to create them.

You'd need to have devclass as well as dev trees, but that's easy to
do.  We have hw.tsc.<driver>.<stat> sysctls for all the drivers at
work, and it would be nice to have a more general framework to put
stuff like that into.

It would be nice if there was some kind of tie-in to tunables as well,
since many drivers have tunables that are global, but might want to be
less global.

Warner