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 X-Spam-Level: X-Spam-Status: No, score=-7.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B234C64E7B for ; Wed, 2 Dec 2020 17:55:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E276E221FB for ; Wed, 2 Dec 2020 17:55:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727744AbgLBRzL (ORCPT ); Wed, 2 Dec 2020 12:55:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726485AbgLBRzK (ORCPT ); Wed, 2 Dec 2020 12:55:10 -0500 Received: from mail-ot1-x341.google.com (mail-ot1-x341.google.com [IPv6:2607:f8b0:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 000C5C0613D4 for ; Wed, 2 Dec 2020 09:54:29 -0800 (PST) Received: by mail-ot1-x341.google.com with SMTP id y24so2450564otk.3 for ; Wed, 02 Dec 2020 09:54:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=XKXDSwzwN3DvDbrQ1CTHSLUB3du6MYM5ojk411EZVbU=; b=CZjUd2guM5b9M/zv1S/4YP9kviqicyFdedMYvVVXXYBhDaC9WiQsNNiYxKqBOmVxJY rKVxf8H9gOT8WxoJoeORf0/ee6T8/d1tGidqFT28GkOORF+LwOyxnhxp3Dla9XGOVg97 Uz0MD5YCkP6/Vz475DGnNAGGe70OG9xjRpjRk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=XKXDSwzwN3DvDbrQ1CTHSLUB3du6MYM5ojk411EZVbU=; b=rpXSoLQGgOjPH+X1OMPk4co0AHHaqrbNUxf/FalMCVsBrlZrSlBWNqJwl+bm8VwK0W /SWSJW1PBnSed2dTcmdmT2REMpGVGlBJPFN9LGfKSppBXyZw5NFgNStYzD9+eZLSBi4J 3xRn5jFbNwG5VDWaruUozJ7rk+LVBz446IlEhNZeJPkAifBob/XNNwG7g5RZmD41x3KV lsiIAnuGfs1Gk5vJvBdgPhqQZuubBc47FIOTDOc6Vymk/AHcgK7VRoTmsOJrdrJ+35Xx AXyeCZJyhxUcLT2UV5le+GUtu4vbRacgqZ0zdKhZ0kVTqKyJfz1TS2YAw7QD1qolDtN6 41rQ== X-Gm-Message-State: AOAM533cO2iUHIgakkU6pE70S8NTjXYL/cAAhFyYAK2YgyXZDxRTv5H6 jpJywBKBKwf4qq49+KNLH3p5kOIGcK4qvPctvpvxVmULEaeF0Q== X-Google-Smtp-Source: ABdhPJzeobTHIJ8r3s9hjQetVecQT1Q0Vcf+2v7FAb6gSFva90CUBWdHZrZAye21M5UQThz2Fj0GZ1AIcWLs4H3k4pA= X-Received: by 2002:a9d:5904:: with SMTP id t4mr2783212oth.109.1606931667897; Wed, 02 Dec 2020 09:54:27 -0800 (PST) MIME-Version: 1.0 References: <20201010154119.3537085-1-idosch@idosch.org> <20201010154119.3537085-2-idosch@idosch.org> <20201123094026.GF3055@nanopsycho.orion> <20201130171428.GJ3055@nanopsycho.orion> <20201201112250.GK3055@nanopsycho.orion> <20201202100922.GM3055@nanopsycho.orion> In-Reply-To: <20201202100922.GM3055@nanopsycho.orion> From: Edwin Peer Date: Wed, 2 Dec 2020 09:53:51 -0800 Message-ID: Subject: Re: [PATCH net-next 1/6] ethtool: Extend link modes settings uAPI with lanes To: Jiri Pirko Cc: Ido Schimmel , netdev , "David S . Miller" , Jakub Kicinski , Jiri Pirko , Danielle Ratson , Andrew Lunn , f.fainelli@gmail.com, Michal Kubecek , mlxsw , Ido Schimmel Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="00000000000058880e05b57eefe6" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --00000000000058880e05b57eefe6 Content-Type: text/plain; charset="UTF-8" On Wed, Dec 2, 2020 at 2:09 AM Jiri Pirko wrote: > >I'm not suggesting the port split be dynamic at all. I'm suggesting that if > >the admin wants or needs to force PAM4 on a port that would otherwise > >be able to achieve the given speed using more lanes with NRZ, then the > >admin should split the port, so that it has fewer lanes, in order to make > >that intent clear (or otherwise configure the port to have fewer lanes > >attached, if you really don't want to or can't create the additional split > >port). > > Okay, I see your point now. The thing is, the port split/unsplit causes > a great distubance. Meaning, the netdevs all of the port > disappear/reappear. Now consider following example: I guess that's a detail of the present implementation and/or device capabilities (I'm not particularly familiar), but presumably it is at least possible, in principle, to modify a device's port config without taking down the netdev. That said, after spending more time thinking about this, I'm coming around to the idea of being able to explicitly set encoding (not lanes) via ethtool. And, in this context, by encoding, I technically mean line code signalling, not symbol encoding. Although it does for today's link modes, the number of lanes does not generally imply signalling mode. In future we may have PAM8 signalling and then the present proposal of deriving the signalling mode for a given speed from the lane count falls down. We should be specifying signalling mode via ethtool instead of lanes. Alternatively, we need to be specifying the fully defined link mode. But, doing so is fraught with other issues, including how to represent it in the interface and the fact that the user doesn't necessarily want to specify physical media in these cases, something that is implied by the full link mode definition. 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