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docs(wiki): printer USB transport + open-question for the provisioning

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New concepts/printer-usb-transport.md (the seam, usblp char device,
reachability-only status, threat model). open-questions #14: confirm the
on-site printer is USB and bake the usblp + udev write-access rule into the
appliance image (provisioning, not app code; unverified on hardware). Updated
rongta-printer.md (USB transport note), index.md, log.md.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V
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Julian Çuni
2026-06-24 20:32:24 +02:00
parent 793b8d83ee
commit 6d7682ab4a
5 changed files with 130 additions and 1 deletions
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wiki/decisions/open-questions.md
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@@ -95,3 +95,15 @@ procurement. (See [[parking-system-architecture]] §10.)
vs. serve-degraded — lean **serve-degraded + loud alarm** (fail-open on exit still governs;
refusing to boot could strand a lane). Software-only, independent of the TPM/[[atecc608]] hardware.
See [[append-only-event-chain]].
14. **Printer USB transport — confirm the on-site printer + bake the provisioning.** _(Recorded
2026-06-24; the transport code is built — see [[printer-usb-transport]].)_ The ESC/POS drivers
now drive **TCP (port 9100) OR local USB (`/dev/usb/lp0`)** behind one render layer, selectable
per device. **Open:** is the actual booth printer USB or network? (The site's verified units are
*networked* — Cashino `10.0.10.9`, Rongta `10.0.10.10` — so USB may be unused here; the original
BOM listed "Epson TM / Citizen (USB **or** network)", so a future site may need it.) If USB is
used, the **appliance image** must (a) load/keep the **`usblp`** kernel module bound to the
printer (CUPS can claim the interface first), and (b) ship a **udev rule** giving the non-root
server process write access to `/dev/usb/lp*`. Both are [[appliance-provisioning]] steps, **not
app code**, and are **unverified on hardware**. Close this once the printer transport per site is
fixed and (if USB) the udev/usblp rule is in the image and a real USB print is verified. Relates
to #1 (lane topology / image standardization). See [[printer-usb-transport]], [[rongta-printer]].