partition.Volume gains a FilesystemKind signature (today .fat for every probed
volume; S4 adds a real VBR recognizer for exFAT) — the seam filesystems.csv keys
on to choose a service binary. New filesystem-map.zig parses
`/system/configuration/filesystems.csv` (signature, binary) into rules and
match()es a signature to its binary, mirroring the device registry: a signature
no row matches goes unserved, never guessed; slices point into the source
buffer. Three host tests (fat->binary, the binary is data-driven not hardcoded,
malformed rows counted); the test rule buffer is a named fixture size so the
bounds gate stays quiet. The VM's build gains the csv dependency and wires the
filesystem-map test into its package test step. Not yet consumed by the binary —
that lands when the VM loads the tables (step 4).
The storage layer gains its policy home (storage-architecture.md): a new
system/services/volume-manager, spawned by init, that acquires the mass-
storage block channel through the device manager (the same lineage a
filesystem uses), reads block 0, and parses the first volume out of it. The
partition-table walk that lived in the FAT engine moves here, above the
driver where it belongs (partition.zig, host-tested: MBR entry, bare-FAT,
no-signature). Identity is the MBR disk signature + partition index — the
weak rung of the ladder; GPT GUID and FAT serial refine identityOf without
changing shape.
This increment is discovery + probe + log only, additive: the FAT service
still acquires its own volume, so nothing changes for it. Confining each
filesystem to its partition and spawning one per volume (the flip) lands
next, keeping fat working throughout.
Grants + wiring: init.csv spawns it after the device manager; protocol.csv
grants bind volume-manager + open device-manager. Verified: volume-probe
asserts the parse (bare-FAT volume at lba 0), neutral 10/10 across storage,
restart, display, logging, confinement — the volume manager now runs in
every boot and disturbs nothing.
Daniel Samson