From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miroslav Lichvar Subject: Re: [Intel-wired-lan] [RFC v2 net-next 01/10] net: Add a new socket option for a future transmit time. Date: Tue, 13 Feb 2018 10:56:52 +0100 Message-ID: <20180213095652.GA11459@localhost> References: <20180117230621.26074-1-jesus.sanchez-palencia@intel.com> <20180117230621.26074-2-jesus.sanchez-palencia@intel.com> <20180118084227.GL1175@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, john.stultz@linaro.org, Richard Cochran , jiri@resnulli.us, ivan.briano@intel.com, richardcochran@gmail.com, henrik@austad.us, jhs@mojatatu.com, levi.pearson@harman.com, intel-wired-lan@lists.osuosl.org, xiyou.wangcong@gmail.com, tglx@linutronix.de, anna-maria@linutronix.de To: Jesus Sanchez-Palencia Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50676 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934267AbeBMJ45 (ORCPT ); Tue, 13 Feb 2018 04:56:57 -0500 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Feb 12, 2018 at 02:39:06PM -0800, Jesus Sanchez-Palencia wrote: > On 01/18/2018 12:42 AM, Miroslav Lichvar wrote: > > Please keep in mind that the PHCs and the system clock don't have to > > be synchronized to each other. If I understand the rest of the series > > correctly, there is an assumption that the PHCs are keeping time in > > TAI and CLOCK_TAI can be used as a fallback. > > Just to double-check, imagine that I've configured the qdisc for > SW best-effort and with clockid CLOCK_REALTIME. When it receives a > packet with the clockid of a /dev/ptpX, the qdisc should just drop that > packet, right? Yes, I think it should drop it. The kernel does not know the offset between the two clocks (they don't even have to be synchronized), so it cannot convert a PHC-based TX time to the system time. -- Miroslav Lichvar