The Addons system allows the creation of standalone addon packages, similar to the ports in the kos-ports system.
To install an add-on, simply place the addon directory inside this directory. Addons in this directory are automatically built when KallistiOS is built. Once built, the addon's headers will be available in addons/include and the built libraries in addons/lib. These paths are automatically included in your build flags if you are using the KOS Makefile system. You may disable an addon by creating an unused directory and moving the addons within, or you may uninstall an addon outright by simply deleting its directory.
A few addons are supplied with KallistiOS. These include:
- libkosext2fs: A filesystem driver for the ext2 filesystem
- libkosfat: A filesystem driver for FAT12, FAT16, and FAT32 filesystems, with long name support
- libkosutils: Utilities: Functions for B-spline curve generation, MD5 checksum handling, image handling, network configuration management, and PCX images
- libnavi: A flashROM driver and G2 ATA driver, historically used with Megan Potter's Navi Dreamcast hacking project
- libppp: Point-to-Point Protocol support for modem devices
Although KallistiOS currently only supports the Sega Dreamcast platform, the system is designed to support build quirks for various platforms. Each addon contains a kos directory, which would contain $(KOS_ARCH).cnf files (so, as of now, just dreamcast.cnf). The addon's Makefile contains build instructions to build the addon for KallistiOS, while the dreamcast.cnf contains quirks specific to building for the Dreamcast. If there are no platform-specific build quirks, an empty file named dreamcast.cnf still needs to exist for the build system to recognize that Dreamcast is a valid target platform for the addon.