linux-kernel - Re: [PATCH 2/2] gpio: gpio-adg1414: New driver

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Date: Tue, 23 Jan 2024 22:50:52 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: "Paller, Kim Seer" <KimSeer.Paller@...log.com>
Cc: Bartosz Golaszewski <brgl@...ev.pl>, 
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-kernel@...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>
Subject: Re: [PATCH 2/2] gpio: gpio-adg1414: New driver

Hi Kim,

On Tue, Jan 23, 2024 at 11:31 AM Paller, Kim Seer
<KimSeer.Paller@...log.com> wrote:

> > Locking here is simple enough that you could use the SPI regmap and
> > get it to do the serialization for you. And then you could possibly
> > reuse the gpio-regmap abstraction and get an even smaller footprint.
>
> I could not seem to figure out how to use the SPI regmap in this case.
> Since the number of daisy-chained devices depends on the length of
> data transferred with continuous transaction, I could not determine
> how to implement that using the SPI regmap. Or maybe I misunderstood
> the statement. However, is it still acceptable to use the current approach?

You just override or wrap with your own read/write callbacks if necessary
by defining a custom static struct regmap_bus.

For example in drivers/gpu/drm/panel/panel-ilitek-ili9322.c
I do this.

It may not save a lot of code in this case but it's still worth it because
we understand what regmap_read/write/update_bits do and reading
and understanding adg1414_set/get cognitively require more from us
as maintainers.

Yours,
Linus Walleij