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docs: P3-A runtime validation — hub chain proven, hub-child gap recorded

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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.
This commit is contained in:
vasilito
2026-07-19 11:17:21 +09:00
parent a8ca01d84b
commit e55e0f186b
2 changed files with 22 additions and 1 deletions
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local/docs/HARDWARE-VALIDATION-MATRIX.md
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| xHCI host controller | ✅ | 🔲 | Interrupt-driven mode proven (test-xhci-irq-qemu.sh); 51-flag quirk table + HCCPARAMS2 gating (P2-A/B); 36-code error recovery (P2-C); not HW-validated |
| EHCI/UHCI/OHCI controllers | 🔲 | 🔲 | Compile clean; runtime enumeration proofs planned (P8-B) |
| USB storage (BOT) | ✅ | 🔲 | usbscsid autospawn + bounded sector readback proven (test-usb-storage-qemu.sh); guest-side write verify open |
| USB hub (non-root) | 🔲 | 🔲 | P3-A enumeration core complete (debounce/reset-wait/U0-wait/wHubDelay, 14 unit tests); runtime hub proof pending (P8-B test-usb-hub-qemu.sh) |
| USB hub (non-root) | ✅ | 🔲 | Hub enumeration chain proven in QEMU (test-usb-hub-qemu.sh): descriptor, EP1 change detection, initial scan, debounce, reset→enable; hub-child device enumeration (kbd→HID) blocked on xhcid TT/debug path |
| **GPU/Display** | | | |
| VESA | ✅ | 🔲 | QEMU framebuffer works |
| virtio-gpu | ✅ | N/A | 2D only, QEMU |
local/docs/USB-IMPLEMENTATION-PLAN.md
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@@ -371,6 +371,27 @@ U1/U2 LPM on hub ports (P7); interrupt-EP usage on USB 3 hubs without one
**Exit met:** complete hub enumeration including power timing, USB 3 hub
handling, and TT accumulation.
**Runtime validation (2026-07-19, `test-usb-hub-qemu.sh` on QEMU
`usb-hub` + `usb-kbd` behind it):** the full usbhubd chain is proven at
runtime — hub descriptor read (8 ports), EP1 interrupt-driven change
detection, initial full port scan, connection debounce, port reset with
completion wait, and port enable all observed in the boot log. The proof
also surfaced and we fixed five latent bugs: the xhcid scheme refused
port-dir opens for unenumerated hub children (attach bootstrap
deadlock), a status-bitmap off-by-one (bit N−1 vs spec's bit N), a
missing initial scan (daemon could block on EP1 before ever polling),
an unbounded EP1 wait (state changes during synchronous waits produce
no new interrupt), and a debounce that could deadlock on a hung
C_PORT_CONNECTION clear (stability is now judged on connection state,
with the change bit cleared post-attach). QEMU's hub stalls
ClearPortFeature on change indicators — handled gracefully by the P2-C
stall recovery (best-effort, no crash). **Remaining gap:** the hub-child
device (usb-kbd) reaches `enabled: true` but does not complete
enumeration to a HID driver — xhcid's hub-child attach path progresses
only at debug level and needs TT/route investigation with debug
logging. Also observed: an intermittent xhcid IRQ-reactor startup race
(one boot showed no reactor start; retry passed).
### P3-B: Hub interrupt-driven change detection ✅ COMPLETE (verified 2026-07-18)
**Reference:** `linux-7.1/drivers/usb/core/hub.c:1000+` `hub_irq()`.