There are many external CD-ROM and disk devices that connect through
your computer's parallel port. Most of them are actually IDE devices
using a parallel port IDE adapter. This option enables the PARIDE
subsystem which contains drivers for many of these external drives.
Read Documentation/blockdev/paride.txt for more information.

If you have said Y to the "Parallel-port support" configuration
option, you may share a single port between your printer and other
parallel port devices. Answer Y to build PARIDE support into your
kernel, or M if you would like to build it as a loadable module. If
your parallel port support is in a loadable module, you must build
PARIDE as a module. If you built PARIDE support into your kernel,
you may still build the individual protocol modules and high-level
drivers as loadable modules. If you build this support as a module,
it will be called paride.

To use the PARIDE support, you must say Y or M here and also to at
least one high-level driver (e.g. "Parallel port IDE disks",
"Parallel port ATAPI CD-ROMs", "Parallel port ATAPI disks" etc.) and
to at least one protocol driver (e.g. "ATEN EH-100 protocol",
"MicroSolutions backpack protocol", "DataStor Commuter protocol"
etc.).

source code:

drivers/block/paride/paride.c