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Fri, 20 Feb 2026 09:31:31 -0800 (PST) Received: from lvondent-mobl5 ([72.188.211.115]) by smtp.gmail.com with ESMTPSA id a1e0cc1a2514c-94da8b3eefdsm77864241.9.2026.02.20.09.31.30 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Feb 2026 09:31:30 -0800 (PST) From: Luiz Augusto von Dentz To: linux-bluetooth@vger.kernel.org Subject: [PATCH BlueZ v2 02/12] doc/btmon: Add dedicate sections for timestamp and frame number Date: Fri, 20 Feb 2026 12:31:06 -0500 Message-ID: <20260220173120.3418666-2-luiz.dentz@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260220173120.3418666-1-luiz.dentz@gmail.com> References: <20260220173120.3418666-1-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 This adds sections for how timestamp and frame numbers are generated and explaim the difference between a frame number and a line number. --- doc/btmon.rst | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/doc/btmon.rst b/doc/btmon.rst index e51001921ab1..de05a5fcd6df 100644 --- a/doc/btmon.rst +++ b/doc/btmon.rst @@ -442,6 +442,41 @@ Example of protocol layering in ACL data:: Authentication requirement: Bonding, MITM, SC (0x2d) Max encryption key size: 16 +Timestamp Notes +--------------- + +When reading btsnoop files with ``-t`` or ``-T``, timestamps reflect the +wall-clock time recorded in the btsnoop file. The precision depends on +the source: + +- **Live capture** (``btmon`` monitor channel): Microsecond precision + from the kernel. +- **btsnoop files**: The btsnoop format stores timestamps as + microseconds since epoch, so full microsecond precision is + preserved. Trailing zeros in the display (e.g., ``14:38:46.589000``) + indicate the original capture source had millisecond granularity. + +The default timestamp mode shows seconds elapsed since the first +packet in the trace, which is useful for measuring intervals between +events without needing to know the absolute time. + +Frame Numbers vs Line Numbers +----------------------------- + +btmon assigns sequential **frame numbers** (``#N``) to HCI packets. +These are stable identifiers for specific packets regardless of output +formatting. However, when processing btmon text output with tools like +``grep`` or ``sed``, the relevant unit is **line numbers** in the output +file. The two are unrelated: + +- A single frame may produce many output lines (header + decoded + fields). +- Frame numbers only apply to HCI traffic (``<`` and ``>``). MGMT + (``@``) and system notes (``=``) do not have frame numbers. +- When referencing specific packets, prefer frame numbers (``#487``) + over line numbers, as frame numbers are stable across different + terminal widths and formatting options. + Practical Reading Guide ----------------------- -- 2.52.0