Thanks for your reply. Sorry for the delay, was swamped with other things.
Currently I don't know what to recommend, because I don't understand the other side of the INT 13H/14H, only the OS side.
Well, the other side talks to the hardware, and needs drivers to do so. See src/hw
Surely one can write a serial driver which connects to a remote place using some bluetooth protocol instead of talking to a 16550. That'll be *alot* of work though, you basically have to implement both bluetooth stack and hardware driver.
I expected to assemble, rather than write, such a thing. If not from the Linux source code, then FreeBSD or ReactOS.
If for some reason (what would that be?) no-one has abstracted bluetooth to have a clean interface that I could have trivially reused, then I will put aside my bluetooth dreams and switch to a different technology. How about Wifi? Does that exist in a state usable for my purposes?
Sure. For now, I want PDOS/386 to remain traditional. When I have exhausted everything that is possible via the BIOS, I will consider adding UEFI support.
If you want your firmware provide drivers to you for modern hardware you are in a *much* better position with UEFI.
Well, on some/many/most modern machines there is absolutely no other choice - the BIOS doesn't exist, even as CSM.
There is a bluetooth protocol specification for example, although I'm not sure how common it is to find an actual uefi driver for bluetooth hardware in the firmware. Talking to ethernet using the firmware-provided uefi driver shouldn't be much of a problem though b/c network boot is a rather standard feature.
Ok, maybe in the medium term I should use a hardware device, forget the name, that turns ethernet into Wifi.
So then the problem is reduced to me needing to provide a BOOTX64.EFI that converts INT 14H into UEFI ethernet calls.
But I'd like to transport all of that software, designed for that environment, and change nothing at all, and have it work on a new environment that includes Wifi, bluetooth and maybe ethernet, and maybe infrared, and maybe other things I don't know about, but make sense (at some level) to be accessed via INT 14H.
Well. In the server world it is rather common to provide access to the serial line over the network for system management purposes.
One approach for that is to have a separate management controller (bmc), and the serial port of the machine is linked to the management controller instead of a D9 socket. You can then connect to the bmc to manage the machine, and one of the options available is to get serial console access.
Ok, this would allow me to have a BBS.
But not allow me to have a "virtual modem" so that I can dial out.
Another approach is to have a virtual 16550 provided by the firmware. Accessing the virtual 16550 will trap into SMM mode where the firmware emulates a serial device and allows to access the serial port remotely over the network, roughly comparable to how qemu provides an virtual 16550 to virtual machines.
Ok, but in the case of qemu I have the same issue - at the end of the day I want to drive a modem, so with qemu I can get it to talk to a "virtual modem". If the firmware is providing the serial to network conversion, I also need to stick in a virtual modem there. And that's what I was hoping SeaBIOS would allow me to do.
Note that both approaches work at hardware level not int14h level, because modern operating systems use int14h services in bootloaders only if at all.
My operating system, PDOS/386, may not be considered "modern", even though it is in active development, but I do wish to use INT 14H, as that was the traditional BIOS service provided, and I wish to maintain contact with the original 80386 machines.
I expect a modern environment to have the CPU, memory etc required to support this basic interface.