netdev - Re: [PATCH v2 net-next 4/4] net: dsa: validate that DT nodes of shared ports have the properties they need

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Date:   Fri, 29 Jul 2022 14:24:23 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, Marcin Wojtas <mw@...ihalf.com>
Cc:     Vladimir Oltean <vladimir.oltean@....com>,
        netdev <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Christian Marangi <ansuelsmth@...il.com>,
        John Crispin <john@...ozen.org>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Mans Rullgard <mans@...sr.com>,
        Arun Ramadoss <arun.ramadoss@...rochip.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        George McCollister <george.mccollister@...il.com>,
        DENG Qingfang <dqfext@...il.com>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Aleksander Jan Bajkowski <olek2@...pl>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Luiz Angelo Daros de Luca <luizluca@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Pawel Dembicki <paweldembicki@...il.com>,
        Clément Léger <clement.leger@...tlin.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Marek Behún <kabel@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>
Subject: Re: [PATCH v2 net-next 4/4] net: dsa: validate that DT nodes of
 shared ports have the properties they need

On 7/29/22 14:17, Andrew Lunn wrote:
>> What I propose is to enforce more strictly an update of DT description
>> with a specified timeline, abandoning 'camps' idea and driver-specific
>> contents in the generic code.
> 
> Regressions are the problem. We are supposed to be backwards
> compatible with older DT blobs. If we now say old DT blobs are
> invalid, and refuse to probe, we cause a regression.
> 
> For some of the in kernel DT files using the mv88e6xxx i can make a
> good guess at what the missing properties are. However, i'm bound to
> guess wrong at some point, and cause a regression. So we could change
> just those we can test. But at some point, the other blobs are going
> to fail the enforces checks and cause a regression anyway.
> 
> And what about out of tree blobs? Probably OpenWRT have some. Do we
> want to cause them to regress?

No, we do not want that, which is why Vladimir's approach IMHO is reasonable in that it acknowledges mistakes or shortcomings of the past into the present, and expects the future to be corrected and not repeat those same mistakes. The deprectiation window idea is all well and good in premise, however with such a large user base, I am not sure it is going to go very far unfortunately, nor that it will hinder our ability to have a more maintainable DSA framework TBH.

BTW, OpenWrt does not typically ship DT blobs that stay frozen, all of the kernel, DTBs, root filesystem, and sometimes a recent u-boot copy will be updated at the same time because very rarely do the existing boot loader satisfy modern requirements (PSCI, etc.).
-- 
Florian