netdev - Re: [PATCH net v2 1/2] dt-bindings: net: dsa: realtek: cleanup compatible strings

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Date:   Wed, 27 Apr 2022 18:43:31 -0300
From:   Luiz Angelo Daros de Luca <luizluca@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     "open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, krzk+dt@...nel.org,
        Arınç ÜNAL <arinc.unal@...nc9.com>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net v2 1/2] dt-bindings: net: dsa: realtek: cleanup
 compatible strings

> On Mon, Apr 18, 2022 at 08:35:57PM -0300, Luiz Angelo Daros de Luca wrote:
> > Compatible strings are used to help the driver find the chip ID/version
> > register for each chip family. After that, the driver can setup the
> > switch accordingly. Keep only the first supported model for each family
> > as a compatible string and reference other chip models in the
> > description.
>
> The power supplies needing power before you can actually read the ID
> registers are the same for all the variations?
>
> The RTL8366s has a serdes power supply while the RTL8370 does not. Maybe
> that doesn't matter as the PHYs probably don't need power to access
> registers, but I didn't look at more than 2 datasheets. If there's *any*
> differences in power sequencing then you need specific compatibles.

Hi Rob,

I don't believe we would need to deal with any special power sequences
in order to read the switch registers.
Anyway, if we face a situation where we do need to handle a special
device differently, it is always less drastic to add a new compatible
string than to remove one already in use.

Regards,

Luiz