RFC: Correct location for SUBsystem-wide options ?

[Luigi Rizzo]

Hi,
in the process of deciding where to put the kernel option for NETMAP,
i have looked at the current practice, and i see a bit of confusion
on how things are done.

Looking at the comment at the top of sys/conf/options we have
* opt_foo.h             for options affecting a single source file foo.[cs]
* opt_some_name.h       for option SOME_NAME affecting only a few files.
  <GAP_HERE>            for options affecting many but not all files
                        (e.g. all network interfaces) 
* opt_global.h          for system-wide options

So, we have no standard place for options affecting all network
interfaces, which are exactly the thing i am looking at, and I
see all possible varieties in our sys/conf/options:

INET, INET6     go into their own headers (opt_inet.h and opt_inet6.h)
                In my view these are system wide in the sense that 
                INET support may use some specific code also in
                device drivers, e.g. all the checksum and tcp offloading
                support

DEVICE_POLLING  goes into opt_device_polling.h
NETGRAPH        goes into opt_netgraph.h

ALTQ, VIMAGE    go into opt_global.h
                (note that internal ALTQ_* options are in opt_altq.h)


Missing a specific header opt_network.h, in my opinion the correct
approach is the one used for ALTQ and VIMAGE: they properly go
into opt_global.h, and we should move there also INET, INET6,
DEVICE_POLLING and NETGRAPH (and DEV_NETMAP).

This way we reduce the clutter in all the if_*.c files, and
also avoid the risk that one of these files forgets to include
a required opt_something.h

In any case, it is not my intention to modify the status quo,
but at least add a proper suggestion in sys/conf/options
to deal with these cases.

Comments ?

	cheers
	luigi