linux-kernel - Re: [PATCH v5 1/2] gpio: add GPO driver for PCA9570

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Date:   Mon, 6 Jul 2020 15:27:43 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Sungbo Eo <mans0n@...ani.run>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Michael Walle <michael@...le.cc>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v5 1/2] gpio: add GPO driver for PCA9570

On Sun, Jul 5, 2020 at 4:31 PM Sungbo Eo <mans0n@...ani.run> wrote:
>
> NXP PCA9570 is a 4-bit I2C GPO expander without interrupt functionality.
> Its ports are controlled only by a data byte without register address.

Thank you for an update, my comments (besides what Bart has) below.

> Datasheet: https://www.nxp.com/docs/en/data-sheet/PCA9570.pdf
>
> Signed-off-by: Sungbo Eo <mans0n@...ani.run>

No blank line in between.

...

> +#include <linux/gpio/driver.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>

It also needs property.h.

...

> +struct pca9570 {
> +       struct gpio_chip chip;

> +       struct i2c_client *client;

This basically a duplication of reference to a parent device of GPIO chip.
See below.

> +       u8 out;
> +};
> +
> +static int pca9570_read(struct pca9570 *gpio, u8 *value)
> +{

struct i2c_client *client = to_i2c_client(gpio->chip.parent);

> +       int ret;
> +
> +       ret = i2c_smbus_read_byte(gpio->client);
> +       if (ret < 0)
> +               return ret;
> +
> +       *value = ret;
> +       return 0;
> +}

...

> +static const struct i2c_device_id pca9570_id_table[] = {
> +       { "pca9570", 4 },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, pca9570_id_table);
> +
> +static const struct of_device_id pca9570_of_match_table[] = {
> +       { .compatible = "nxp,pca9570", .data = (void *)4 },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, pca9570_of_match_table);

These structures now can be located closer to the end of the driver
(exactly before first use).

...

> +       gpio->chip = template_chip;

I'm not sure why we need an additional structure to just memcpy() to the chip.
But here I have no strong opinion (perhaps the compiler even optimizes this).

-- 
With Best Regards,
Andy Shevchenko