Now that I have SD card access working, I find myself in a position where I must now consider how to invoke BIOS services from programs developed long after BIOS itself has been compiled. I don't want to have to resort to using the CPU's ECALL or EBREAK instructions (or any trap, for that matter), because this both consumes an opcode that should really be used by a proper operating system, and because it would require that I renovate the linkage approach I have between the assembly language bootstrap and the C code. Jump-tables or entry-point vectors are ideal for the needs of the BIOS; since I am working primarily in C at the moment, it seems reasonable that invoking services through a C-accessible mechanism is the best solution (otherwise, I'd have to write yet more assembly language stubs/proxies). I knew just where to look; I decided to go back a decade, and excavate my old code from my GCOM project, my own clean-room clone of Component Object Model.
I'm happy to announce that I've managed to port a reasonable subset of GCOM into the firmware. As the proof of concept, I only implemented console output functions
Vertigo
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