ROM file system support

modulename: romfs.ko

configname: CONFIG_ROMFS_FS

Linux Kernel Configuration
└─>File systems
└─>Miscellaneous filesystems
└─>ROM file system support
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
This is a very small read-only file system mainly intended for
initial ram disks of installation disks, but it could be used for
other read-only media as well. Read
<file:Documentation/filesystems/romfs.rst> for details.

To compile this file system support as a module, choose M here: the
module will be called romfs. Note that the file system of your
root partition (the one containing the directory /) cannot be a
module.

If you don't know whether you need it, then you don't need it:
answer N.

source code: