USB-IMPLEMENTATION-PLAN.md P3-A: record the 2026-07-19 QEMU runtime
validation (test-usb-hub-qemu.sh) — full usbhubd chain proven
(descriptor, EP1 change detection, initial scan, debounce, reset to
port-enable), the five latent bugs it surfaced and that were fixed
(scheme attach bootstrap, bitmap off-by-one, missing initial scan,
unbounded EP1 wait, debounce clear deadlock), QEMU's ClearPortFeature
stall handled gracefully by P2-C recovery, and the remaining gap:
hub-child device enumeration (usb-kbd to HID driver) blocked on
xhcid's hub-child attach path (debug-level; TT/route investigation)
plus an intermittent xhcid IRQ-reactor startup race.
HARDWARE-VALIDATION-MATRIX.md: hub row to QEMU-validated for the
enumeration chain, with the hub-child gap noted.
vasilito
e55e0f186b