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Wed, 09 Sep 2026 11:28:59 -0700 (PDT) Received: from lvondent-mobl5 ([72.188.211.115]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5c81c506f31sm5399388e0c.11.2026.09.09.11.28.58 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2026 11:28:58 -0700 (PDT) From: Luiz Augusto von Dentz To: linux-bluetooth@vger.kernel.org Subject: [PATCH BlueZ v1 10/10] doc/btmon: Document the protocol request references Date: Wed, 9 Sep 2026 14:28:40 -0400 Message-ID: <20260909182840.1289776-11-luiz.dentz@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909182840.1289776-1-luiz.dentz@gmail.com> References: <20260909182840.1289776-1-luiz.dentz@gmail.com> Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Luiz Augusto von Dentz Describe the request references shown on L2CAP, ATT, SDP, AVDTP and AVCTP responses, and what pairs the two halves of a transaction in each of them. The model drafted the text, which the author reviewed against the actual output. Assisted-by: opencode:claude-opus-5 --- doc/btmon.rst | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/doc/btmon.rst b/doc/btmon.rst index 80c8a8947caf..a08a6afa43f4 100644 --- a/doc/btmon.rst +++ b/doc/btmon.rst @@ -275,6 +275,53 @@ once and still resolve correctly. A ``Command Status`` reporting an error means the completing event will never arrive, and the command is dropped rather than left to match a later unrelated event. +Protocols Above HCI +------------------- + +The protocols carried over ACL pair their requests and responses through an +identifier of their own, and their responses carry the same reference:: + + L2CAP: Connection Request (0x02) ident 1 len 4 + L2CAP: Connection Response (0x03) ident 1 len 8 #2 (1.000 msec) + ATT: Read By Group Type Request (0x10) len 6 + ATT: Error Response (0x01) len 4 #6 (45.500 msec) + SDP: Service Search Request (0x02) tid 5 len 8 + SDP: Service Search Response (0x03) tid 5 len 5 #8 (12.400 msec) + AVCTP Control: Command: type 0x00 label 7 PID 0x110e + AVCTP Control: Response: type 0x00 label 7 PID 0x110e #12 (23.100 msec) + +What pairs the two halves differs by protocol: + +.. list-table:: + :header-rows: 1 + :widths: 15 20 65 + + * - Protocol + - Paired by + - Notes + * - L2CAP + - ``ident`` + - Responses are the request code plus one. A Command Reject + may answer any request. + * - ATT + - Opcode + - Responses are the request opcode plus one. Only one request + may be outstanding on a bearer. An Error Response names the + request it rejects. An indication is paired with its + confirmation. + * - SDP + - ``tid`` + - Responses are the request PDU plus one. An Error Response + may answer any request. + * - AVDTP + - ``label`` + - A command is answered by a response accept or reject. + * - AVCTP + - ``label`` + - A command is answered by a response. + +SMP is not tracked, as its exchange has no transaction identifier. + **LE Meta Events** contain a subevent type:: > HCI Event: LE Meta Event (0x3e) plen 31 #487 [hci0] 12:36:18.974201 -- 2.55.0