This is an ebuild for OMFS 0.7.6, the filesystem used by the Rio Karma. It works fine for me on an x86. Note that I didn't write this, it's just a version-bumped copy of one attached to bug 74316, written by Frank Zschockelt. Reproducible: Always Steps to Reproduce:
Created attachment 145747 [details] OMFS 0.7.6 ebuild
There hasn't been a new release of OMFS since version 0.8.0 in July 2008, which is hardly surprising given Rio Karma stopped being available in retail 3 years prior to that. I would hazard a guess that the answer to this is obvious, just in case though - is there still user interest in adding this to Portage?