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SubjectRFC - sysctl or module parameters.

There are so many ways to feed configuration parameters into the
kernel these days.
There is sysctl. There is sysfs. And there are module paramters.
(procfs? who said procfs? I certainly didn't).

I have a module - let's call it 'lockd'.
I want to make it configurable - say to be able to identify
peers by IP address (as it currently does) or host name
(good for multi homed peers, if you trust them).

And I want Jo Sysadmin to be able to set some simple configuration
setting somewhere and have it 'just work'.

Options:
- I could make it a module parameter: use_hostnames, and tell
Jo to put
options lockd use_hostnames=yes
in /etc/modprobe.d/lockd if that is what (s)he wants.
But that won't work if the module is compiled in (will it?).

- I could make a sysctl /proc/sys/fs/nfs/nsm_use_hostnames
at tell Jo to put
fs.nfs.nsm_use_hostnames=1
if /etc/sysctl.conf if desired.
But that wouldn't work if lockd is a module that is loaded
after "/usr/sbin/sysctl -p" has been run.

- I could do both and tell Jo to make both changes, just in case,
but that is rather ugly, though that is what we currently do
for nlm_udpport, nlm_tcpport, nlm_timeout, nlm_grace_period.

It occurs to me that since we have /sys/module/X/parameters,
it wouldn't be too hard to have some functionality, possibly
in modprobe, that looked for all the 'options' lines in
modprobe config files, checked to see if the modules was loaded,
and then imposed those options that could be imposed.

Thus we could just have a module option, just add module config
information to /etc/modprobe.d and run
modprobe --apply-option-to-active-modules
at the same time as "sysctl -p" and it would all 'just work'
whether the module were compiled in to not.

Is that a reasonable idea?

(I'll probably add both a sysctl and a mod param for my current
problem, but I'd love it if there were a better approach
possible in the future).

Thanks,
NeilBrown
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