Custom kernels, config(1), and modules

[Andrew Doran <ad%netbsd.org@localhost>]

.kobjs (already compiled kernel modules) can be added to the OBJS list in
the kernel Makefile, and will be built into the system. No other glue is
required. They should work as expected and show up as "builtins" in
modstat's output.

The kernel configuration files have keywords that allow various chunks of
code to be compiled in: file-system, pseudo-device, options, and so on. I
would like to add another keyword: module. It would cause make to chdir to
sys/modules/foo, build the module and link the resulting .kobj into the
kernel.

For components built that way, there would be only one source of information
about how to build (the Makefile under sys/modules). As a side effect,
static configuration through ifdefs would be discouraged because it wouldn't
be of much use if the feature was to be loaded at run time.

Comments?

Thanks,
Andrew