linux-kernel - Re: [PATCH v2 1/2] gpio: add GPO driver for PCA9570

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Message-ID: <CAHp75VeeqvR=0caAmYW5fhMP0p25Xn2hmhhDLU9dZopwQ69HXQ@mail.gmail.com>
Date:   Thu, 25 Jun 2020 11:59:11 +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>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] gpio: add GPO driver for PCA9570

On Thu, Jun 25, 2020 at 10:59 AM Sungbo Eo <mans0n@...ani.run> wrote:
>
> NXP PCA9570 is 4-bit I2C GPO expander without interrupt functionality.
> Its ports are controlled only by a data byte without register address.
>
> As there is no other driver similar enough to be adapted for it, a new
> driver is introduced here.

Thanks for an update. I'll look at them later, so please defer the
next version a bit (perhaps for one week).
My comments below.

...

> +static void pca9570_set_mask_bits(struct gpio_chip *chip, u8 mask, u8 bits)
> +{
> +       struct pca9570 *gpio = gpiochip_get_data(chip);
> +       u8 buffer;
> +       int err;
> +
> +       mutex_lock(&gpio->lock);

> +       buffer = gpio->buffer & ~mask;
> +       buffer |= (mask & bits);

Usual pattern is to put this on one line

       buffer = (gpio->buffer & ~mask) | (bits & mask);

> +       err = i2c_smbus_write_byte(gpio->client, buffer);

> +       if (!err)
> +               gpio->buffer = buffer;

I'm not sure I understand why this is under lock.

> +
> +       mutex_unlock(&gpio->lock);

Can't you simple do it here like

if (err)
  return;

... = buffer;

?

> +}

...

> +static int pca9570_probe(struct i2c_client *client,
> +                        const struct i2c_device_id *id)

Can't you use ->probe_new() instead?

> +{
> +       struct pca9570 *gpio;
> +       int ret;
> +
> +       gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);
> +       if (!gpio)
> +               return -ENOMEM;
> +

> +       i2c_set_clientdata(client, gpio);

Either move this before return 0; or...

> +       gpio->chip = template_chip;
> +       gpio->chip.parent = &client->dev;
> +
> +       gpio->client = client;
> +
> +       mutex_init(&gpio->lock);
> +
> +       ret = devm_gpiochip_add_data(&client->dev, &gpio->chip, gpio);

> +       if (ret < 0) {

(What is the meaning of ' < 0' ?

> +               dev_err(&client->dev, "Unable to register gpiochip\n");
> +               return ret;
> +       }
> +
> +       return 0;

...simple return devm_...(...);

> +}

-- 
With Best Regards,
Andy Shevchenko