compiling ext2fs into a kernel

[DG]

Greetings,

I compiled a kernel from a standard 5.1-RELEASE installation yestreen to
include support for ext2fs, but couldn't find any documentation about what
option to set to include support for ext2fs.  Grepping the handbook and all
files in the .../i386/conf directory did not reveal any references to ext2fs
at all.  I eventually got around it by modifying the Makefile in the modules
directory and successfully compiled a kernel with ext2fs support.

As the kernel is for my gateway machine at home I temporarily don't have
Internet access there, so I did a quick search at work this morning and
found a reference to adding "options EXT2FS" to the config file - probably
the more canonical way of setting options.

My first question is: what documentation is there on the available kernel
options?

My second question (coming from a different open source UNIX-like operating
system background) is: how does one specify to compile a 5.1 feature as a
module as opposed to directly into the kernel, or are all module-capable
features automatically compiled as modules?

tia

Dave