From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B073C433EF for ; Mon, 24 Jan 2022 09:28:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233754AbiAXJ2j (ORCPT ); Mon, 24 Jan 2022 04:28:39 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:26204 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233715AbiAXJ2g (ORCPT ); Mon, 24 Jan 2022 04:28:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643016515; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PU7JbFuDwdFKk/VjKzygUczh9Zjw5LHX5d/gO46ICZ4=; b=VfGViklEVimD6k0TdE77xCrQNDYEnfO6MXn4H8IWAYqMHlW3vwHzwHJXpyjJ003lnx9ceD l47dFaGEr5/rwAPkK1SijzF/pT4CHc1exySixscdsaFy4qF+Tkg08Mms2K4a33Erql1jNg OYis1GtnDCQ+3AkdTReJtM+gua6LUtU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-664-h86HWp00MZiTOBQxiU5KBw-1; Mon, 24 Jan 2022 04:28:29 -0500 X-MC-Unique: h86HWp00MZiTOBQxiU5KBw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6CE8B5108D; Mon, 24 Jan 2022 09:28:27 +0000 (UTC) Received: from localhost (unknown [10.43.135.229]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C25C770D52; Mon, 24 Jan 2022 09:28:24 +0000 (UTC) Date: Mon, 24 Jan 2022 10:28:23 +0100 From: Miroslav Lichvar To: Richard Cochran Cc: Vladimir Oltean , Andrew Lunn , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , David Miller , Grygorii Strashko , Jakub Kicinski , Joakim Zhang , Kurt Kanzenbach , Russell King Subject: Re: [PATCH RFC V1 net-next 3/4] net: Let the active time stamping layer be selectable. Message-ID: References: <20220103232555.19791-4-richardcochran@gmail.com> <20220120164832.xdebp5vykib6h6dp@skbuf> <20220121040508.GA7588@hoboy.vegasvil.org> <20220121145035.z4yv2qsub5mr7ljs@skbuf> <20220121152820.GA15600@hoboy.vegasvil.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220121152820.GA15600@hoboy.vegasvil.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jan 21, 2022 at 07:28:20AM -0800, Richard Cochran wrote: > On Fri, Jan 21, 2022 at 02:50:36PM +0000, Vladimir Oltean wrote: > > So as I mentioned earlier, the use case would be hardware performance > > testing and diagnosing. You may consider that as not that important, but > > this is basically what I had to do for several months, and even wrote > > a program for that, that collects packet timestamps at all possible points. > > This is not possible without making a brand new CMSG to accommodate > time stamps from all the various layers. FWIW, scm_timestamping has three fields and the middle one no longer seems to be used. If a new socket/timestamping option enabled all three (SW, MAC, PHY) timestamps in the cmsg, I think that would be a nice feature. There are applications that receive both SW and HW timestamps in order to fall back to SW when a HW timestamp glitched or is missing. This could be extended to three levels with MAC and PHY timestamps. > That is completely out of scope for this series. > > The only practical use case of this series is to switch from PHY back to MAC. >From an admin point of view, it makes sense to me to have an option to disable PHY timestamps for the whole device if there are issues with it. For debugging and applications, it would be nice to have an option to get all of them at the same time. -- Miroslav Lichvar