games-emulation/dgen-sdl version 1.32 was released in 2013-02-09. It fixes a bug regarding 6-button controllers. I've just renamed the 1.31 ebuild to the new version and it works for me. Currently, both versions on Gentoo's repository (1.30 and 1.31) are broken, they both can't handle 6-button controllers. Please, let's bump 1.32, and let's try to stabilize it soon.
in portage