netdev - Re: [PATCH 09/10] net: ethernet: ixp4xx: Get port ID from base address

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Date:   Fri, 1 Nov 2019 00:17:46 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Networking <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 09/10] net: ethernet: ixp4xx: Get port ID from base address

On Mon, Oct 21, 2019 at 12:30 PM Arnd Bergmann <arnd@...db.de> wrote:
> On Mon, Oct 21, 2019 at 2:10 AM Linus Walleij <linus.walleij@...aro.org> wrote:
> >
> > The port->id was picked from the platform device .id field,
> > but this is not supposed to be used for passing around
> > random numbers in hardware. Identify the port ID number
> > from the base address instead.
> >
> > Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
>
> I'm not sure this is better, as now the driver hardcodes the physical
> address, and the port->id value is still the same as the pdev->id
> value that all boards still pass.
>
> Is this just meant to avoid setting the port id explicitly in DT?

Yes, because the DT bindings people would not like us to encode
that in DT, as it is a Linuxism.

To DT these are just three networking engines (NPEs) that the
OS can choose to use however it likes.

That they behave differently and that the driver has to cope
with that is due to different firmware being loaded into the
different NPE:s. DT doesn't care about that.

I will mention it in the commit message.

Yours,
Linus Walleij