UAS (USB Attached SCSI)

An independent clean-room UASP VIP: a host that allocates tags and issues Command Information Units, a separately written device that queues them and may complete OUT OF ORDER, and a passive protocol checker (“uas/, make uas_oss, 23/23 checks). Covers the Command / Read Ready / Write Ready / Sense / Response / Task Management IUs, the tag that identifies a command, the stream that carries its data, and command queuing with out-of-order completion — the thing UAS exists to do and Bulk-Only Transport cannot. Six rules, each pinned by a per-rule mask to its own injected fault. SCOPE: the UAS layer. The USB 3.x bulk-endpoint and stream machinery underneath is vip-usb32 / vip-usb2, SCSI command semantics are an opaque opcode, and BOT is out. The sharpest result is a NEGATIVE one, and it is a different blind spot from the rest of this family: it is in TIME, not in a table. A tag names a SLOT, not a command, and the slot is legitimately reusable the moment its command completes. T9 replays a Sense IU verbatim after its tag has been handed to a new command: the outstanding-tag rule passes (the tag genuinely IS outstanding), the duplicate-tag rule passes (the previous holder genuinely DID complete first), every field is legal and the ordering is legal — and one command’s outcome is attributed to another. A Sense IU carries a tag, not an identity, and no rule can recover one from the other.

Key Features

• Command / Read Ready / Write Ready / Sense / Response / Task Management IUs
• Tag allocation and the tag↔︎stream correspondence for data transfers
• Command queuing with genuine out-of-order completion, each status attributed correctly
• Passive checker, 6 rules, each pinned by a per-rule mask to its own injected fault
• The stale-status-on-a-reused-tag blind spot named and asserted, not papered over

Standards & Compliance

USB-IF USB Attached SCSI Protocol (UASP)

Pairs With

Built to lean against these catalog IPs during integration:

• usb2_dev