Feature: pluggable block devices #247
Description
I want to be able to add drives via drivers. This means coming up with some mapping between the BIOS and the driver.
So, maybe, these entrypoints:
- get DPH for drive
- read host sector (automatically deblocked)
- write host sector (ditto)
Drive selection is done by allocating a range of 16 device driver IDs, A-P.
The BIOS would have common deblocking code because everything will need that. The easiest would be to hard-code 512-byte sectors, but we do occasionally need something else. Is variable-sized deblocking feasible?
(The BIOS would have a common directory buffer. Let's just ignore the one in the DPH. This would require a trivial BDOS change, making it smaller.)
Performance implications --- host read and write would require traversing the driver list. I don't think this is a problem; the number of cycles is tiny compared to actually touching the hardware.