linux-kernel - Re: [PATCH 1/2] gpio: Add gpio latch driver

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Message-ID: <CACRpkdZboPe5DTkO7HuouAW92cE9NC-dOZ0_zwPTRCOM+pJ8sQ@mail.gmail.com>
Date:   Fri, 26 Aug 2022 15:41:59 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Sascha Hauer <s.hauer@...gutronix.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <brgl@...ev.pl>, kernel@...gutronix.de
Subject: Re: [PATCH 1/2] gpio: Add gpio latch driver

On Thu, Aug 25, 2022 at 11:41 AM Sascha Hauer <s.hauer@...gutronix.de> wrote:

> This driver implements a GPIO multiplexer based on latches connected to
> other GPIOs. A set of data GPIOs is connected to the data input of
> multiple latches. The clock input of each latch is driven by another
> set of GPIOs. With two 8-bit latches 10 GPIOs can be multiplexed into
> 16 GPIOs. GPOs might be a better term as in fact the multiplexed pins
> are output only.
>
> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>

Take a close look at the other forwarding driver:
drivers/gpio/gpio-aggregator.c

Especially (as pointed out by Marco) the sleeping/non-sleeping calls.

There was a lot of discussion around that patch before we got the
forwarding of GPIOs into a nice working shape.

Also get Geert to review this because he knows what you need to
do. :)

Yours,
Linus Walleij