[SeaBIOS] BEV and bootorder

[Steve Goodrich]

I'm working towards a goal of having specific devices be bootable, and
*only* those devices.  For example, if my bootorder file specifies SATA
drive 3, I do not want it to try SATA drives 0, 1, and 2, nor any other HDD
or floppy that it finds.

My first question is: how do I do this?

If that can't be answered, can someone explain to me the relationship
between the bootorder file and the BEV (Boot Execution Vector) configured in
boot.c?

Thanks!
    -- Steve G.