linux-kernel - Re: [PATCH v2 14/15] dt-bindings: auxdisplay: Add Maxim MAX6958/6959

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Date: Thu, 15 Feb 2024 13:26:35 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Robin van der Gracht <robin@...tonic.nl>, Paul Burton <paulburton@...nel.org>
Subject: Re: [PATCH v2 14/15] dt-bindings: auxdisplay: Add Maxim MAX6958/6959

Hi Andy,

On Thu, Feb 15, 2024 at 12:17 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> On Thu, Feb 15, 2024 at 11:57:53AM +0100, Geert Uytterhoeven wrote:
> > On Mon, Feb 12, 2024 at 6:16 PM Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> > > On Mon, Feb 12, 2024 at 07:14:53PM +0200, Andy Shevchenko wrote:
> > > +description:
> > > +  The Maxim MAX6958/6959 7-segment LED display controller provides
> > > +  an I2C interface to up to four 7-segment LED digits. The MAX6959
> > > +  in comparison to MAX6958 has the debounce and interrupt support.
> >
> > IUIC, the primary differentiating factor is that the MAX6959 adds input
> > and GPIO support?  Debounce and interrupt support are merely features
> > of input support.
>
> What should I do here? Rephrase?

    The Maxim MAX6958/6959 7-segment LED display controller provides
    an I2C interface to up to four 7-segment LED digits. The MAX6959
    adds input support.

> > > +  Type of the chip can be autodetected via specific register read,
> > > +  and hence the features may be enabled in the driver at run-time.
> >
> > I don't think you need to read that register, as the users of the
> > features (keypad mapping, interrupts property, ...) also need to be
> > described in DTS (once supported).
>
> So, the idea that if DT describes those we will check the chip ID and
> instantiate what is asked?

Even the check for the chip ID is probably not needed. E.g.
  - If the DTS has an interrupt property, (the future version of)
    the driver sets up the interrupt.
  - If the DTS has a linux,keymap, (the future version of) enables the
    keypad.

> > > +  Given hardware is simple and does not provide any additional pins,
> > > +  such as reset or enable.
> >
> > Does this matter? I.e. is it important to say this in the bindings?
>
> From Krzysztof's review of v1 I understood that it is important to say so
> people wouldn't wonder if HW has support of that which is not implemented
> (yet) or simply has no such pins.

It might be good to mention that in the commit description.
IMHO a list of all possible things that do not exist does not belong in the
bindings.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds