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

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Date: Mon, 12 Feb 2024 12:25:48 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: 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>,
 Ralf Schlatterbeck <rsc@...tux.com>
Subject: Re: [PATCH 1/3] dt-bindings: auxdisplay: hit,hd44780: drop redundant
 GPIO node

On 12/02/2024 09:41, Geert Uytterhoeven wrote:
> Thanks for your patch!
> 
>> --- a/Documentation/devicetree/bindings/auxdisplay/hit,hd44780.yaml
>> +++ b/Documentation/devicetree/bindings/auxdisplay/hit,hd44780.yaml
>> @@ -99,17 +99,7 @@ examples:
>>      };
>>    - |
>>      #include <dt-bindings/gpio/gpio.h>
>> -    i2c {
>> -            #address-cells = <1>;
>> -            #size-cells = <0>;
>>
>> -            pcf8574: pcf8574@27 {
>> -                    compatible = "nxp,pcf8574";
>> -                    reg = <0x27>;
>> -                    gpio-controller;
>> -                    #gpio-cells = <2>;
>> -            };
>> -    };
> 
> This part was added delberately in commit c784e46c8445635a ("auxdisplay:
> Add I2C gpio expander example"), to aid makers who are not DT experts.
> Note that there are no other examples of this popular wiring scheme
> in upstream DTS.

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.


> 
>>      hd44780 {
>>              compatible = "hit,hd44780";
>>              display-height-chars = <2>;
> 
> If you do want to insist on removing the i2c GPIO expander part,
> I think this node should be removed too, as it is almost identical
> to the first example.
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 

Best regards,
Krzysztof