Re: [PATCH v2 08/20] dt-bindings: serial: samsung: Add google-gs101-uart compatible

[Linus Walleij <linus.walleij@linaro.org>]

On Wed, Oct 11, 2023 at 9:48 AM Greg KH <gregkh@linuxfoundation.org> wrote:

> >        - enum:
> >            - apple,s5l-uart
> >            - axis,artpec8-uart
> > +          - google,gs101-uart
>
> These shouldn't be needed, just declare the device as the same as what
> the chip really is (i.e. a samsung uart), that way no .yaml or kernel
> driver changes are needed at all.

We strive to have these as unique as possible, as it is a hardware
description. It is fine to write drivers in Linux or any other OS just
being aware of a "courser" idea of what UART this is, in this case
would have looked something like this:

    compatible = "google,gs101-uart", "samsung-uart";

And the driver would be able to match to just the latter string
(these are listed in "particularity order").

BUT! The binding authors chose not to go that path, instead they
have one unique compatible string per hardware/integration version,
essentially per-SoC. So in this case it is just:

    compatible = "google,gs101-uart";

It is kind of impossible to fix now as well, because these bindings
are already deployed. So they are like a BIOS: written in stone.

It is possible to add dual compatibles for this *and following*
variants, but I don't know how Krzysztof feels about that, and as
others point out, probably knowledge of the exact SoC is
necessary.

Yours,
Linus Walleij