Both LBA and CHS coordinates are now working for the primary disk on the
primary bus.
Failure modes I ran into:
- ATA ports are 16-bit values. Using instructions with 8-bit immediates
will yield strange results. (I had to debug this twice because I missed
poll-ata-primary-bus-primary-drive-regular-status-word the first time
around.)
Mu's toolchain has been found out here. bootstrap has good
errors but doesn't support the instructions I need in boot.subx. The
self-hosted phases support the instructions but provide no error-checking.
Might be worth starting to add error-checking as I encounter the need.
In this case, a vote for validating metadata sizes even if we don't
validate that instructions pass in the right metadata sizes.
- Can't poll readiness first thing. Maybe we need to always select the
drive first.
- Reading 8-bit values from a 16-bit port (data port 0x1f0) returns garbage.
Reading 32-bit values however works totally fine; go figure. (Maybe
it won't work on real hardware?)
https://forum.osdev.org/viewtopic.php?t=36415
- Passing in a 0 segment will never return data.
Kartik K. Agaram