linux-kernel - Re: [net-next: PATCH 00/12] ACPI support for DSA

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Message-ID: <CAPv3WKeeZwNAs06thrYvgXaTPA9KP-9dQZNZsYWx3UXS8LStAQ@mail.gmail.com>
Date:   Tue, 21 Jun 2022 12:46:12 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Andrew Lunn <andrew@...n.ch>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, vivien.didelot@...il.com,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, pabeni@...hat.com,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Grzegorz Bernacki <gjb@...ihalf.com>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@....com>,
        upstream@...ihalf.com, Jon Nettleton <jon@...id-run.com>
Subject: Re: [net-next: PATCH 00/12] ACPI support for DSA

pon., 20 cze 2022 o 20:45 Andrew Lunn <andrew@...n.ch> napisał(a):
>
> > You beat me up to this. I also was about to mention that the problem with such
> > conversions (like this series does) is not in the code. It's simplest part. The
> > problem is bindings and how you get them to be a standard (at least de facto).
>
> De facto is easy. Get it merged. After that, i will simply refuse
> anything else, the same way i and other Maintainers would refuse a
> different DT binding.
>
> If the ACPI committee approve and publish a binding, we will naturally
> accept that as well. So in the end we might have two bindings. But so
> far in this whole ACPI for networking story, i've not heard anybody
> say they are going to submit anything for standardisation. So this
> might be a mute point.
>

I understand your concern and of course it's better to be on a safe
side from the beginning. Based on the hitherto discussion under this
patchset, I would split the question about standardization to 2
orthogonal topics:

1. Relation to the bus and enumeration:
  * As pointed out in another patch some switches can be attached to
    SPI or I2C. In such a case this is simple - SPISerialBus /
I2CSerialBus structures
    in _CRS are included in the ACPI Spec. They allow to comprise more
bus specific
    information and the code in acpi/scan.c marks those child devices
as to be enumerated
    by parent bus.
  * MDIO bus doesn't have its own _CRS macro in the Spec, on the other
hand the _ADR
    seems to be the only object required for proper operation - this
was my base for
    proposed solution in patch 06/12.

2. The device description (unrelated to which bus it is attached)
  * In Linux and other OS's there is a great amount of devices
conforming the guidelines
    and using only the standard device identification/configuration
objects as per [1].
  * Above do not contain custom items and entire information can be obtained by
    existing, generic ACPI accessors - those devices (e.g. NICs,
SD/MMC controllers and
    many others) are not explicitly mentioned in official standards.
  * The question, also related to this DSA case - is the ACPI device()
hierarchical
    structure of this kind a subject for standardization for including
in official ACPI specification?
  * In case not, where to document it? Is Linux' Documentation enough?
    I agree that in the moment of merge it becomes de facto standard ABI and
    it's worth to sort it out.

Rafael, Len, any other ACPI expert - I would appreciate your inputs
and clarification
of the above. Your recommendation would be extremely helpful.

Best regards,
Marcin