B2 — the 1-in-3 boot-time READ CAPACITY failure, root-caused: the xHCI
library's awaitTransfer claimed ANY unclaimed transfer event as its own
completion. An interrupt-endpoint event whose TRB pointer no longer
matched the armed subscription (an error or stale completion from the
keyboard/mouse polling concurrently with storage bring-up) fell through
and was misread as the bulk transfer's completion — desynchronizing the
mass-storage bulk protocol in controller state that SURVIVED driver
restarts, so every retry failed too. Awaited transfers now match the
event's slot id and endpoint DCI; foreign events are dropped and named.
Twelve consecutive runs of the previously-flaky cases pass; the full
suite is green with none of its old intermittents.
B1 — and when storage does fail transiently, the system now heals
instead of giving up forever: a nonzero exit maps to ExitReason.aborted
(a deliberate FAILURE exit — supervisors restart those with backoff,
unlike a clean .exited), usb-storage exits nonzero when a PRESENT
device fails bring-up, and the fat service no longer blocks its harness
polling for a block device and then dies — it serves immediately
(requests fail politely), retries on a 500 ms timer, and mounts
whenever storage appears, including after a driver restart.
library/runtime/log.zig wires std.log to the tagged ring: the root shim
installs std_options for every binary (programs may override), logFn
formats one line per record and emits it with its level via
debug_write — the payload no longer carries the process's name; the
kernel stamps identity structurally and the serial renderer prints the
'<binary path>: ' prefix, so the transcript keeps its shape.
Migrate every writeLine/logLine/log helper family (init, vfs, fat,
device-manager, acpi, pci-bus, ps2-bus x3, usb-hid x2, usb-storage,
usb-xhci-bus, virtio-gpu — 104 call sites) to std.log.info, dropping
the hand-written prefixes. A leveled record is a complete line by
contract (raw emissions may still build lines from pieces). Test
fixtures and the display/input services keep raw writes for now — their
ring records are attributed by the kernel regardless.
Harness regexes follow the renamed prefixes (usb-hid-keyboard,
discovery) and path-named restart lines.
init writes /mnt/usb/DANOS.LOG at shutdown and then enters S5 — but the write sat in the USB flash controller's write cache and was lost when power was cut, because nothing issued SCSI SYNCHRONIZE CACHE. Invisible in QEMU (its backing file commits immediately); real on hardware. The boot-time flush survived only because the machine kept running afterward and the cache drained on its own.
- block protocol gains a flush op; usb-storage serves it with SYNCHRONIZE CACHE (10); runtime.block gains Device.flush()
- the FAT server tracks whether blocks were written and, on a file close, commits the device cache (durable-on-close — the right default for removable media, and it makes init's existing shutdown close() persist the log before S5, no init/VFS change needed)
- verified the SYNCHRONIZE CACHE actually reaches the driver on each dirty close; usb-storage/fat-mount/mutations/rename/mtime/log-flush all green
Flesh out the xHCI host-controller driver into a full transfer engine and build
the three USB class drivers on top, all verified end to end under QEMU.
- xHCI engine (usb-xhci-library.zig): controller reset, command/event rings with
cycle-bit bookkeeping (gated on a No-Op-command proof), device slots, Address
Device, control transfers, full chapter-9 enumeration, Configure Endpoint, and
interrupt/bulk transfers. Each interface is device_registered with its
(class,subclass,protocol) identity, unique per (port,interface).
- Bus<->class transfer protocol (usb-transfer-protocol.zig + runtime.usb): open /
control / interrupt-subscribe (async report pump on a poll timer) / bulk-by-
physical-address, so sector data never crosses the 256-byte IPC limit.
- USB HID keyboard + mouse (usb-hid/): decode boot-protocol reports and publish
to the input service. A USB usage is already the input protocol's keycode.
- USB mass storage (usb-storage/): Bulk-Only Transport + transparent SCSI,
serving a block device under the new .block service id (block-protocol).
- device-manager matches USB interfaces to class drivers (usbDriverForIdentity).
- usb-abi / usb-ids made importable modules; add HID and mass-storage class
requests, packTriple, and a usb_device DeviceClass.
- Fix test/qemu_test.py on macOS: the QMP unix-socket path was built from the
deep worktree path and exceeded the 104-byte sun_path limit, so QEMU exited
before booting. It now lives under a short temp path.
Tests: usb-report, usb-hid, usb-storage pass under python3 test/qemu_test.py;
host units (usb-abi, usb-ids, hid-report, bulk-only-transport, scsi) green.
Daniel Samson