RE: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio bindings

["Leonard, Niall" <Niall.Leonard@ncr.com>]

> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Sent: 26 January 2023 12:29
> To: Leonard, Niall <Niall.Leonard@ncr.com>; Linus Walleij
> <linus.walleij@linaro.org>; Bartosz Golaszewski <brgl@bgdev.pl>; Rob
> Herring <robh+dt@kernel.org>; Krzysztof Kozlowski
> <krzysztof.kozlowski+dt@linaro.org>
> Cc: linux-gpio@vger.kernel.org; devicetree@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio
> bindings
> 
> *External Message* - Use caution before opening links or attachments
> 
> On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote:
> > From: Niall Leonard <nl250060@ncr.com>
> 
> Subject: missing "wd,mbl-gpio:" prefix.
> 
> Subject: drop second/last, redundant "bindings". The "dt-bindings"
> prefix is already stating that these are bindings.
> 
> >
> > Added optional "no-input" property
> 
> Missing full stop.
> 
> >
> > Signed-off-by: Niall Leonard <nl250060@ncr.com>
> > ---
> >  Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt
> > b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt
> > index 038c3a6a1f4d..9405f9dad522 100644
> > --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt
> > +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt
> > @@ -18,6 +18,7 @@ Required properties:
> >
> >  Optional properties:
> >  	- no-output: GPIOs are read-only.
> > +	- no-input: GPIOs are write-only. Read is via a shadow register.
> 
> Why this property is needed? Why driver cannot always use shadow
> register?
> 
The shadow register is currently only used during the write operation. It is not available during the read operation. That is essentially the change I have 
submitted.
An alternative approach would have been to develop an entire new gpio driver similar to the 74xx driver, but I felt this approach was better.

> Anyway, please convert the bindings to DT schema first (see writing-schema
> and example-schema).
> Documentation/devicetree/bindings/writing-schema.rst
> 
The bindings for this driver are duplicated in a few files even though they use the same driver.
i.e. wd,mbl-gpio.txt, ni,169445-nand-gpio.txt, brcm,bcm6345-gpio.yaml
I don't know why these multiple bindings exist. It would perhaps make sense to remove these duplicate binding documentation files and replace with a single one for "basic-mmio-gpio". I happened to pick ". wd,mbl-gpio.txt", but I could have just as easily chosen one of the other 2.

What's your view ?

> Best regards,
> Krzysztof