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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48046fba46dsm4783255e9.0.2026.01.21.09.33.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Jan 2026 09:33:12 -0800 (PST) Date: Wed, 21 Jan 2026 09:33:07 -0800 From: Stephen Hemminger To: spinler@cesnet.cz Cc: dev@dpdk.org Subject: Re: [PATCH v4 3/6] net/nfb: update timestamp calculation to meaningful value Message-ID: <20260121093307.299c84f0@phoenix.local> In-Reply-To: <20260121170120.268553-4-spinler@cesnet.cz> References: <20260115140134.235877-1-spinler@cesnet.cz> <20260121170120.268553-1-spinler@cesnet.cz> <20260121170120.268553-4-spinler@cesnet.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Wed, 21 Jan 2026 18:01:17 +0100 spinler@cesnet.cz wrote: > From: Martin Spinler > > The resulting timestamp wasn't monotonically increasing value. > > Now the timestamp is value in nanoseconds (Unix epoch). > > Unfortunately there's currently no safe mechanism in nfb-framework > to get ticks from hardware to implement read_clock function. > > Signed-off-by: Martin Spinler > --- > doc/guides/nics/nfb.rst | 6 ++---- > drivers/net/nfb/nfb_rx.h | 13 +++++++------ > 2 files changed, 9 insertions(+), 10 deletions(-) The patch is ok as far as it goes. But the best practice in DPDK for drivers doing timestamps is for the driver to only put a timestamp on if timestamp offload flag was set when configuring that device. For the case of multiple devices that means that one device may have timestamp and other not. Also any driver that supports receive timestamp must provide a read_clock operation. Otherwise the application has no way of knowing what units the timestamp is in. I added that to the AI review script so new drivers will get rejected with out it. I suspect that in this drivers case it is only used in systems where: - only single instance of device is possible - your application is just assuming a common unit like nanosecond.