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

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Date:   Mon, 29 Aug 2022 16:21:35 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH 1/2] gpio: Add gpio latch driver

Hi Marco,

On Fri, Aug 26, 2022 at 07:53:07AM +0200, Marco Felsch wrote:
> Hi Sascha,
> 
> nice patche, please see inline.
> 
> On 22-08-25, Sascha Hauer 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.
> > 

[snip]

> > +
> > +static void __gpio_latch_set(struct gpio_latch_priv *priv, unsigned int offset, int val)
> > +{
> > +	int latch = offset / priv->n_pins;
> > +	int i;
> > +
> > +	if (val)
> > +		priv->shadow[latch] |= BIT(offset % priv->n_pins);
> > +	else
> > +		priv->shadow[latch] &= ~BIT(offset % priv->n_pins);
> > +
> > +	for (i = 0; i < priv->n_pins; i++)
> > +		gpiod_set_value(priv->data_gpios->desc[i], priv->shadow[latch] & BIT(i));
> > +
> > +	gpiod_set_value(priv->clk_gpios->desc[latch], 1);
> > +	gpiod_set_value(priv->clk_gpios->desc[latch], 0);
> 
> Your have two access function for _can_sleep and "can not sleep" but
> here you don't resepect it.

I thought the gpio framework would pick the right implementation
automatically. Apparently it doesn't. Will fix in v2.

Sascha

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