linux-kernel - Re: [PATCH RFC v1 1/2] bus: add Wiegand write-only GPIO driver

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Message-ID: <CACRpkdbD1qzJujhq-U0UN0tWam9CaoLvVuAQfafq4XNaEdZ2QA@mail.gmail.com>
Date:   Mon, 22 Aug 2022 09:14:38 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Martin Zaťovič <m.zatovic1@...il.com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        mani@...nel.org, hemantk@...eaurora.org, elder@...aro.org,
        f.fainelli@...il.com, Michael.Srba@...nam.cz,
        jeffrey.l.hugo@...il.com, gregkh@...uxfoundation.org,
        bjorn.andersson@...aro.org, saravanak@...gle.com,
        krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org
Subject: Re: [PATCH RFC v1 1/2] bus: add Wiegand write-only GPIO driver

Hi Martin!

Thanks for your patch!

On Thu, Jul 28, 2022 at 11:17 AM Martin Zaťovič <m.zatovic1@...il.com> wrote:

> Wiegand is a communication protocol that is still widely used
> especially for access control applications. It utilizes two wires to
> transmit data - D0 and D1, the generic names of which are data-lo and
> data-hi.

So the driver provides Wiegand GPIO, if you want to provide
generic Wiegand infrastructure (for other things than GPIO
as well) then that should indeed be in drivers/bus.

However then you should provide an API for random WIegand
drivers, such as the now baked-in GPIO driver, so I think
what you want to achieve is:

1. A wiegand bus transport driver in drives/bus
2. A wiegand abstract API in include/linux/wiegand.h
3. A GPIO driver on top of the wiegand bus in
   drivers/gpio/wiegand-gpio.c that uses <linux/wiegand.h>

How does this sound?

I don't know how a wiegand device driver API would look
but there are several examples in other subsystems and
buses then the wiegand specifics need to be accounted for.

Yours,
Linus Walleij