linux-kernel - Re: [RFCv2 PATCH 4/4] gpio: add Wiegand GPIO driver

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Date:   Wed, 12 Oct 2022 14:16:08 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Martin Zaťovič <m.zatovic1@...il.com>
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linus.walleij@...aro.org, gregkh@...uxfoundation.org,
        jeffrey.l.hugo@...il.com, andersson@...nel.org,
        Michael.Srba@...nam.cz, saravanak@...gle.com, mani@...nel.org,
        hemantk@...eaurora.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [RFCv2 PATCH 4/4] gpio: add Wiegand GPIO driver

On Wed, Oct 5, 2022 at 4:58 PM Martin Zaťovič <m.zatovic1@...il.com> wrote:
>
> Wiegand GPIO driver uses GPIO lines defined in the devicetree to
> transmit data following the Wiegand protocol.
>
> Signed-off-by: Martin Zaťovič <m.zatovic1@...il.com>
> ---

[snip]

> +
> +DEVICE_ATTR_RW(pulse_len);
> +DEVICE_ATTR_RW(interval_len);
> +DEVICE_ATTR_RW(frame_gap);
> +DEVICE_ATTR_RW(format);
> +DEVICE_ATTR_RW(payload_len);
> +

We don't really allow GPIO drivers to define all kinds of custom
device attributes. Also: this driver does not register a GPIO provider
- rather it's a GPIO consumer.

For what you're trying to achieve: have you tried using libgpiod and
controlling the lines from user-space? If that's too slow, then I'd
say this driver should go somewhere else. Maybe you'd need a whole new
protocol sub-system for that. In any case - this subsystem is not the
right place.

Bartosz

[snip]