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

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Date:   Sun, 24 Jul 2022 09:59:14 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <vladimir.oltean@....com>,
        Andrew Lunn <andrew@...n.ch>
Cc:     "netdev@...r.kernel.org" <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>
Subject: Re: [PATCH net-next] net: dsa: validate that DT nodes of shared ports
 have the properties they need

Le 24/07/2022 à 07:21, Vladimir Oltean a écrit :
> On Sat, Jul 23, 2022 at 08:09:34PM +0200, Andrew Lunn wrote:
>> Hi Vladimir
>>
>> I think this is a first good step.
>>
>>> +static const char * const dsa_switches_skipping_validation[] = {
>>
>> One thing to consider is do we want to go one step further and make
>> this dsa_switches_dont_enforce_validation
>>
>> Meaning always run the validation, and report what is not valid, but
>> don't enforce with an -EINVAL for switches on the list?
> 
> Can do. The question is what are our prospects of eventually getting rid
> of incompletely specified DT blobs. If they're likely to stay around
> forever, maybe printing with dev_err() doesn't sound like such a great
> idea?
> 
> I know what's said in Documentation/devicetree/bindings/net/dsa/marvell.txt
> about not putting a DT blob somewhere where you can't update it, but
> will that be the case for everyone? Florian, I think some bcm_sf2 device
> trees are pretty much permanent, based on some of your past commits?

The Device Tree blob is provided and runtime populated by the 
bootloader, so we can definitively make changes and missing properties 
are always easy to add as long as we can keep a reasonable window of 
time (2 to 3 years seems to be about the right window) for people to 
update their systems. FWIW, all of the bcm_sf2 based systems have had a 
fixed-link property for the CPU port.

> 
>> Maybe it is too early for that, we first need to submit patches to the
>> mainline DT files to fixes those we can?
>>
>> Looking at the mv88e6xxx instances, adding fixed-links should not be
>> too hard. What might be harder is the phy-mode, in particular, what
>> RGMII delay should be specified.
> 
> Since DT blobs and kernels have essentially separate lifetimes, I'm
> thinking it doesn't matter too much if we first fix the mainline DT
> blobs or not; it's not like that would avoid users seeing errors.
> 
> Anyway I'm thinking it would be useful in general to verbally resolve
> some of the incomplete DT descriptions I've pointed out here. This would
> be a good indication whether we can add automatic logic that comes to
> the same resolution at least for all known cases.

Agreed.
-- 
Florian