linux-kernel - Re: [PATCH v2 3/3] dt-bindings: gpio: Add Nuvoton NPCM750 serial I/O expansion interface(SGPIO)

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Date:   Fri, 11 Nov 2022 15:20:02 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Jim Liu <jim.t90615@...il.com>
Cc:     JJLIU0@...oton.com, KWLIU@...oton.com, brgl@...ev.pl,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, openbmc@...ts.ozlabs.org
Subject: Re: [PATCH v2 3/3] dt-bindings: gpio: Add Nuvoton NPCM750 serial I/O
 expansion interface(SGPIO)

On Fri, Nov 11, 2022 at 10:30 AM Jim Liu <jim.t90615@...il.com> wrote:

> -D_out:
> the output data is the serial data needed to connect to hc595 and the
> data will output to hc595 parallel pins.
> you can use dts nout_gpios to create the number of pins.
>
> -D_in
> this pin need to connect to hc165 and get the serial data from hc165.
> you can use dts nin_gpios to create the number of pins.

In the example it seems you enable d_out and d_in for *all* 64
pins, correct? So they are all either input or output.

That in effect turns them into GPIOs, so I don't see the problem
with simply always doing this?

Just that things are configurable doesn't mean we always need
to provide means to configure them.

If you have a use case where the user wants to control this, then
that is another thing. Otherwise just make all pins input and output
and wait for a usecase that needs more control, maybe it will
never appear.

Yours,
Linus Walleij