linux-kernel - Re: [PATCH 1/3] dt-bindings: auxdisplay: hit, hd44780: drop redundant GPIO node

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Date: Mon, 12 Feb 2024 12:58:39 +0100
From: Ralf Schlatterbeck <rsc@...tux.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Miguel Ojeda <ojeda@...nel.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>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH 1/3] dt-bindings: auxdisplay: hit, hd44780: drop
 redundant GPIO node

On Mon, Feb 12, 2024 at 12:25:48PM +0100, Krzysztof Kozlowski wrote:
> 
> Hm, I don't understand how exactly it helps. The GPIO expander has its
> own example and as you pointed below, this is basically the same code,
> except rw and backlight GPIOs.

The hd44780 is a display that is very often used.
By people (like me some time ago) not familiar with the nice io expander
implementation in Linux. The consequence of that is that you'll find
several out-of-tree implementations for this display with i2c out in the
wild. So my thought of documenting this (again) at that location is to
make it easier for people with a hd44780 with the standard i2c interface
to see how it is done in Linux.

So I really think it helps. It would have helped me :-)

Ralf
-- 
Dr. Ralf Schlatterbeck                  Tel:   +43/2243/26465-16
Open Source Consulting                  www:   www.runtux.com
Reichergasse 131, A-3411 Weidling       email: office@...tux.com