linux-kernel - Re: [PATCH v3 08/15] pinctrl: keembay: use a dedicated structure for the pinfunction description

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Message-ID: <CAMRc=MeEo6p=6Tp5kORi9y5tGNJKrzh0kq7tpe_E=5TasMjgbg@mail.gmail.com>
Date: Tue, 29 Jul 2025 11:23:54 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, Alexey Klimov <alexey.klimov@...aro.org>, 
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	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Paul Cercueil <paul@...pouillou.net>, Kees Cook <kees@...nel.org>, 
	Andy Shevchenko <andy@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	David Hildenbrand <david@...hat.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
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	Sascha Hauer <s.hauer@...gutronix.de>, Tony Lindgren <tony@...mide.com>, 
	Haojian Zhuang <haojian.zhuang@...aro.org>, Geert Uytterhoeven <geert+renesas@...der.be>, 
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	linux-omap@...r.kernel.org, linux-renesas-soc@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v3 08/15] pinctrl: keembay: use a dedicated structure for
 the pinfunction description

On Thu, Jul 24, 2025 at 1:11 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Thu, Jul 24, 2025 at 11:25 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> >
> > struct function_desc is a wrapper around struct pinfunction with an
> > additional void *data pointer. We're working towards reducing the usage
> > of struct function_desc in pinctrl drivers - they should only be created
> > by pinmux core and accessed by drivers using
> > pinmux_generic_get_function().
>
> Any link to the discussion and perhaps an updated in-kernel
> documentation and/or TODO?
>

The discussions happened under v1 and v2 of this series. The "reducing
the usage ..." part refers to the need to avoid memory duplication of
struct pinfunction really but it's a prerequisite.

> > This driver uses the data pointer so in
> > order to stop using struct function_desc, we need to provide an
> > alternative that also wraps the mux mode which is passed to pinctrl core
> > as user data.
>
> ...
>
> > +struct keembay_pinfunction {
> > +       struct pinfunction func;
> > +       u8 mux_mode;
> > +};
>
> My gut's feeling that this type of construction will be in tons of the
> drivers, perhaps better to provide an alternative like
> struct pinfunction_with_mode {
>   ...

Nah, literally only this one so far. And I bet we could rework it to
avoid it altogether. Your proposal is too specific IMO. Let's cross
that bridge when (if) we get there.

> };
>
> Or even with variadic arguments... (just saying)
>

Oh please no. :)

Bartosz