Incidentally, I’ve been looking into open alternatives to BIOS the last couple of days due to the fact that very few desktop systems’ BIOSes support setting a hard disk password. This seemed to me like the perfect niche for the free DIY solutions: something that BIOS/mobo manufacturers most likely will not fix due to limitedness of the target market, where said market consists of die hard nerds like me who like weird things such as (gasp!) encrypting their data.
I was disappointed to find that, although Coreboot should work on my setup, none of the open source payload solutions seem to support ATA security either.
So I ended up patching my BIOS with another proprietary blob to achieve what I wanted.
(Was there a point to this? Maybe just that the open solutions that are out there are not only limited in compatibility but, even when compatible, still not the end-all to limits imposed by a proprietary BIOS. Of course, they do have the benefit of being more easily modifiable, so if you know your low-level languages, you can build a custom solution yourself. I just wish I was that competent.)