linux-kernel - Re: [PATCH] gpio: add GPO driver for PCA9570

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Message-ID: <CAMpxmJVvU1Q2OHYfqqAMcojniQ6TSK+n5AejddwZ=pArtUWNYg@mail.gmail.com>
Date:   Wed, 24 Jun 2020 14:29:35 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Sungbo Eo <mans0n@...ani.run>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-gpio <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH] gpio: add GPO driver for PCA9570

wt., 23 cze 2020 o 08:05 Sungbo Eo <mans0n@...ani.run> napisał(a):
>
> This patch adds support for the PCA9570 I2C GPO expander.
>
> Signed-off-by: Sungbo Eo <mans0n@...ani.run>

Hi Sungbo, this looks pretty good, but there are some nits listed below.

> ---
> Tested in kernel 5.4 on an ipq40xx platform.
>
> This is my first time submitting a whole driver patch, and I'm not really familiar with this PCA expander series.
> Please let me know how I can improve this patch further. (Do I also need to document the DT compatible string?)
>

Yes, you should send a separate patch to DT maintainers with DT
binding document (preferably in YAML). Please see
Documentations/devicetree/bindings for more info.

> FYI there's an unmerged patch for this chip.
> http://driverdev.linuxdriverproject.org/pipermail/driverdev-devel/2017-May/105602.html
> I don't have PCA9571 either so I didn't add support for it.
> ---
>  drivers/gpio/Kconfig        |   8 ++
>  drivers/gpio/Makefile       |   1 +
>  drivers/gpio/gpio-pca9570.c | 159 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 168 insertions(+)
>  create mode 100644 drivers/gpio/gpio-pca9570.c
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index c6b5c65c8405..d10dcb81b841 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -962,6 +962,14 @@ config GPIO_PCA953X_IRQ
>           Say yes here to enable the pca953x to be used as an interrupt
>           controller. It requires the driver to be built in the kernel.
>
> +config GPIO_PCA9570
> +       tristate "PCA9570 4-Bit I2C GPO expander"
> +       help
> +         Say yes here to enable the GPO driver for the NXP PCA9570 chip.
> +
> +         To compile this driver as a module, choose M here: the module will
> +         be called gpio-pca9570.
> +
>  config GPIO_PCF857X
>         tristate "PCF857x, PCA{85,96}7x, and MAX732[89] I2C GPIO expanders"
>         select GPIOLIB_IRQCHIP
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index 1e4894e0bf0f..33cb40c28a61 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -110,6 +110,7 @@ obj-$(CONFIG_GPIO_OCTEON)           += gpio-octeon.o
>  obj-$(CONFIG_GPIO_OMAP)                        += gpio-omap.o
>  obj-$(CONFIG_GPIO_PALMAS)              += gpio-palmas.o
>  obj-$(CONFIG_GPIO_PCA953X)             += gpio-pca953x.o
> +obj-$(CONFIG_GPIO_PCA9570)             += gpio-pca9570.o
>  obj-$(CONFIG_GPIO_PCF857X)             += gpio-pcf857x.o
>  obj-$(CONFIG_GPIO_PCH)                 += gpio-pch.o
>  obj-$(CONFIG_GPIO_PCIE_IDIO_24)                += gpio-pcie-idio-24.o
> diff --git a/drivers/gpio/gpio-pca9570.c b/drivers/gpio/gpio-pca9570.c
> new file mode 100644
> index 000000000000..9ed01554f5df
> --- /dev/null
> +++ b/drivers/gpio/gpio-pca9570.c
> @@ -0,0 +1,159 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Driver for PCA9570 I2C GPO expander
> + *
> + * Copyright (C) 2020 Sungbo Eo <mans0n@...ani.run>
> + *
> + * Based on gpio-tpic2810.c
> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
> + *     Andrew F. Davis <afd@...com>
> + */
> +
> +#include <linux/gpio/driver.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +
> +/**
> + * struct pca9570 - GPIO driver data
> + * @chip: GPIO controller chip
> + * @client: I2C device pointer
> + * @buffer: Buffer for device register
> + * @lock: Protects write sequences
> + */
> +struct pca9570 {
> +       struct gpio_chip chip;
> +       struct i2c_client *client;
> +       u8 buffer;
> +       struct mutex lock;
> +};
> +
> +static void pca9570_set(struct gpio_chip *chip, unsigned offset, int value);
> +

Please just move this function here instead of declaring it and
implementing it later.

[snip!]

> +
> +static int pca9570_probe(struct i2c_client *client,
> +                        const struct i2c_device_id *id)
> +{
> +       struct pca9570 *gpio;
> +       int ret;
> +
> +       gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);
> +       if (!gpio)
> +               return -ENOMEM;
> +
> +       i2c_set_clientdata(client, gpio);
> +
> +       gpio->chip = template_chip;
> +       gpio->chip.parent = &client->dev;
> +
> +       gpio->client = client;
> +
> +       mutex_init(&gpio->lock);
> +
> +       ret = gpiochip_add_data(&gpio->chip, gpio);

Why not devm_gpiochip_add_data()? You could drop the remove callback.

> +       if (ret < 0) {
> +               dev_err(&client->dev, "Unable to register gpiochip\n");
> +               return ret;
> +       }
> +
> +       return 0;
> +}
> +
> +static int pca9570_remove(struct i2c_client *client)
> +{
> +       struct pca9570 *gpio = i2c_get_clientdata(client);
> +
> +       gpiochip_remove(&gpio->chip);
> +
> +       return 0;
> +}
> +

[snip!]

Bartosz