Re: [PATCH v2 2/8] Add Advantech EIO GPIO driver

[Bartosz Golaszewski]

On Tue, 14 Jul 2026 17:54:16 +0200, Ramiro Oliveira
<ramiro.oliveira@xxxxxxxxxxxxx> said:
> This driver controls the GPIO component of the Advantech EIO chip.
>

The subject should be: "gpio: add a driver for the Advantech EIO GPIO
controller"
or similar.

> Signed-off-by: Ramiro Oliveira <ramiro.oliveira@xxxxxxxxxxxxx>
> ---
>  MAINTAINERS             |   7 ++
>  drivers/gpio/Kconfig    |   6 ++
>  drivers/gpio/Makefile   |   1 +
>  drivers/gpio/gpio-eio.c | 252 ++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 266 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 53b5f7412966..a7da47393815 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -609,6 +609,13 @@ S:	Maintained
>  F:	Documentation/scsi/advansys.rst
>  F:	drivers/scsi/advansys.c
>
> +ADVANTECH EIO DRIVER
> +M:	Ramiro Oliveira <ramiro.oliveira@xxxxxxxxxxxxx>
> +S:	Maintained
> +F:	drivers/gpio/gpio-eio.c
> +F:	drivers/mfd/eio_core.c
> +F:	include/linux/mfd/eio.h

Shouldn't this be part of the MFD entry?

> +
>  ADVANTECH SWBTN DRIVER
>  M:	Andrea Ho <Andrea.Ho@xxxxxxxxxxxxxxxx>
>  L:	platform-driver-x86@xxxxxxxxxxxxxxx
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index f03c05288376..696065d77235 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -295,6 +295,12 @@ config GPIO_DWAPB
>  	  Say Y or M here to build support for the Synopsys DesignWare APB
>  	  GPIO block.
>
> +config GPIO_EIO
> +	tristate "Advantech EIO GPIO"
> +	depends on MFD_EIO
> +	help
> +	  Say Y or M to build support for Advantech EIO GPIO block.
> +
>  config GPIO_EIC_SPRD
>  	tristate "Spreadtrum EIC support"
>  	depends on ARCH_SPRD || COMPILE_TEST
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index fa14581e3995..628596705c21 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -64,6 +64,7 @@ obj-$(CONFIG_GPIO_DLN2)			+= gpio-dln2.o
>  obj-$(CONFIG_GPIO_DS4520)		+= gpio-ds4520.o
>  obj-$(CONFIG_GPIO_DWAPB)		+= gpio-dwapb.o
>  obj-$(CONFIG_GPIO_EIC_SPRD)		+= gpio-eic-sprd.o
> +obj-$(CONFIG_GPIO_EIO)			+= gpio-eio.o
>  obj-$(CONFIG_GPIO_ELKHARTLAKE)		+= gpio-elkhartlake.o
>  obj-$(CONFIG_GPIO_EM)			+= gpio-em.o
>  obj-$(CONFIG_GPIO_EN7523)		+= gpio-en7523.o
> diff --git a/drivers/gpio/gpio-eio.c b/drivers/gpio/gpio-eio.c
> new file mode 100644
> index 000000000000..34e1aefd0716
> --- /dev/null
> +++ b/drivers/gpio/gpio-eio.c
> @@ -0,0 +1,252 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * GPIO driver for Advantech EIO Embedded controller.
> + *
> + * Copyright (C) 2025 Advantech Corporation. All rights reserved.
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/gpio/driver.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mfd/eio.h>
> +#include <linux/module.h>
> +
> +#define EIO_GPIO_MAX_PINS	48
> +#define EIO_GPIO_WRITE		0x18
> +#define EIO_GPIO_READ		0x19
> +
> +struct eio_gpio_dev {
> +	u64 avail;
> +	int max;
> +	struct gpio_chip chip;
> +	struct device *dev;
> +};
> +
> +static struct {
> +	int size;
> +	bool write;
> +} ctrl_para[] = {

Please use a common prefix for all symbols. "eio_gpio" like above is fine.

> +	{ 0x01, false }, { 0x00, false }, { 0x00, false }, { 0x02, false },
> +	{ 0x01, false }, { 0x00, false }, { 0x00, false }, { 0x00, false },
> +	{ 0x00, false }, { 0x00, false }, { 0x00, false }, { 0x00, false },
> +	{ 0x00, false }, { 0x00, false }, { 0x00, false }, { 0x00, false },
> +	{ 0x01, true  }, { 0x01, true  }, { 0x02, true  }, { 0x02, true  },
> +	{ 0x02, false }, { 0x10, false }
> +};
> +
> +enum gpio_ctrl {
> +	EIO_GPIO_STATUS = 0x0,
> +	EIO_GPIO_GROUP_AVAIL = 0x3,
> +	EIO_GPIO_ERROR = 0x04,
> +	EIO_GPIO_PIN_DIR = 0x10,
> +	EIO_GPIO_PIN_LEVEL = 0x11,
> +	EIO_GPIO_GROUP_DIR = 0x12,
> +	EIO_GPIO_GROUP_LEVEL = 0x13,
> +	EIO_GPIO_MAPPING = 0x14,
> +	EIO_GPIO_NAME = 0x15
> +};
> +
> +static struct {
> +	int group;
> +	int port;
> +} group_map[] = {
> +	{ 0, 0 }, { 0, 1 },
> +	{ 1, 0 }, { 1, 1 },
> +	{ 2, 0 }, { 2, 1 },
> +	{ 3, 0 }, { 3, 1 },
> +	{ 3, 2 }, { 3, 3 },
> +	{ 3, 4 }, { 3, 5 },
> +	{ 3, 6 }, { 3, 7 }
> +};
> +
> +static int pmc_write(struct device *mfd_dev, u8 ctrl, u8 dev_id, void *data)
> +{
> +	struct pmc_op op = {
> +		 .cmd       = EIO_GPIO_WRITE,
> +		 .control   = ctrl,
> +		 .device_id = dev_id,
> +		 .payload   = (u8 *)data,
> +	};
> +
> +	if (ctrl >= ARRAY_SIZE(ctrl_para))
> +		return -ENOMEM;
> +
> +	if (!ctrl_para[ctrl].write)
> +		return -EINVAL;
> +
> +	op.size = ctrl_para[ctrl].size;
> +
> +	return eio_core_pmc_operation(mfd_dev, &op);
> +}
> +
> +static int pmc_read(struct device *mfd_dev, u8 ctrl, u8 dev_id, void *data)
> +{
> +	struct pmc_op op = {
> +		 .cmd       = EIO_GPIO_READ,
> +		 .control   = ctrl,
> +		 .device_id = dev_id,
> +		 .payload   = (u8 *)data,
> +	};
> +
> +	if (ctrl > ARRAY_SIZE(ctrl_para))
> +		return -ENOMEM;
> +
> +	op.size = ctrl_para[ctrl].size;
> +
> +	return eio_core_pmc_operation(mfd_dev, &op);
> +}
> +
> +static int get_dir(struct gpio_chip *chip, unsigned int offset)
> +{
> +	u8 dir;
> +	int ret;
> +
> +	ret = pmc_read(chip->parent, EIO_GPIO_PIN_DIR, offset, &dir);
> +	if (ret)
> +		return ret;
> +
> +	return dir ? 0 : 1;
> +}
> +
> +static int dir_input(struct gpio_chip *chip, unsigned int offset)
> +{
> +	u8 dir = 0;
> +
> +	return pmc_write(chip->parent, EIO_GPIO_PIN_DIR, offset, &dir);
> +}
> +
> +static int dir_output(struct gpio_chip *chip, unsigned int offset, int value)
> +{
> +	u8 dir = 1;
> +	u8 val = value;
> +
> +	pmc_write(chip->parent, EIO_GPIO_PIN_DIR, offset, &dir);
> +
> +	return pmc_write(chip->parent, EIO_GPIO_PIN_LEVEL, offset, &val);
> +}
> +
> +static int gpio_get(struct gpio_chip *chip, unsigned int offset)
> +{
> +	u8 level;
> +	int ret;
> +
> +	ret = pmc_read(chip->parent, EIO_GPIO_PIN_LEVEL, offset, &level);
> +	if (ret)
> +		return ret;
> +
> +	return level;
> +}
> +
> +static int gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
> +{
> +	u8 val = value;
> +
> +	return pmc_write(chip->parent, EIO_GPIO_PIN_LEVEL, offset, &val);
> +}
> +
> +static int check_support(struct device *dev)
> +{
> +	u8  data;
> +	int ret;
> +
> +	ret = pmc_read(dev, EIO_GPIO_STATUS, 0, &data);
> +	if (ret)
> +		return ret;
> +
> +	if ((data & 0x01) == 0)
> +		return -EOPNOTSUPP;
> +
> +	return 0;
> +}
> +
> +static int check_pin(struct device *dev, int pin)
> +{
> +	int ret;
> +	int group, bit;

Why not put all ints on the same line? Same elsewhere.

> +	u16 data;
> +
> +	/* Get pin mapping */
> +	ret = pmc_read(dev, EIO_GPIO_MAPPING, pin, &data);
> +	if (ret)
> +		return ret;
> +
> +	if ((data & 0xFF) > ARRAY_SIZE(group_map))
> +		return -EINVAL;
> +
> +	group = group_map[data & 0xFF].group;
> +	bit   = data >> 8;
> +
> +	/* Check mapped pin */
> +	ret = pmc_read(dev, EIO_GPIO_GROUP_AVAIL, group, &data);
> +	if (ret)
> +		return ret;
> +
> +	return data & BIT(bit) ? 0 : -EOPNOTSUPP;
> +}
> +
> +static int gpio_init(struct device *mfd, struct eio_gpio_dev *eio_gpio)
> +{
> +	int ret, i;
> +
> +	ret = check_support(mfd);
> +	if (ret)

This warrants an -ENODEV. We don't want to retry probe here, do we?

> +		return dev_err_probe(eio_gpio->dev, ret, "GPIO not supported\n");
> +
> +	eio_gpio->avail = 0;
> +
> +	for (i = 0 ; i < EIO_GPIO_MAX_PINS ; i++) {
> +		ret = check_pin(mfd, i);
> +		if (ret)
> +			continue;
> +
> +		eio_gpio->avail |= BIT(i);
> +		eio_gpio->max = i + 1;
> +	}
> +
> +	return eio_gpio->max ? 0 : -EOPNOTSUPP;
> +}
> +
> +static int gpio_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct eio_gpio_dev *eio_gpio;
> +	struct eio_dev *eio_dev = dev_get_drvdata(dev->parent);
> +
> +	if (!eio_dev)
> +		return dev_err_probe(dev, -ENODEV, "Error contact eio_core\n");

-ENODEV is used for silently bailing out of probe and telling the driver core
to not defer. Basically it means: this device cannot be enabled on this system
or is not present at all. This means: don't use dev_err_probe() and don't emit
any logs. Just return -ENODEV.

Though it makes me think - can this even happen at all? MFD cells won't get
created if parent's probe() failed.

> +
> +	eio_gpio = devm_kzalloc(dev, sizeof(*eio_gpio), GFP_KERNEL);
> +	if (!eio_gpio)
> +		return -ENOMEM;
> +
> +	eio_gpio->dev = dev;
> +
> +	if (gpio_init(dev->parent, eio_gpio))

Can you use the ret = gpio_init() pattern for consistency with the rest of the
code?

> +		return -EIO;
> +
> +	eio_gpio->chip.parent = dev->parent;
> +	eio_gpio->chip.ngpio = eio_gpio->max;
> +	eio_gpio->chip.label = KBUILD_MODNAME;
> +	eio_gpio->chip.owner = THIS_MODULE;
> +	eio_gpio->chip.direction_input = dir_input;
> +	eio_gpio->chip.get = gpio_get;
> +	eio_gpio->chip.direction_output = dir_output;
> +	eio_gpio->chip.set = gpio_set;
> +	eio_gpio->chip.get_direction = get_dir;
> +	eio_gpio->chip.base = -1;
> +	eio_gpio->chip.can_sleep = true;
> +
> +	return devm_gpiochip_add_data(dev, &eio_gpio->chip, eio_gpio);
> +}
> +
> +static struct platform_driver gpio_driver = {
> +	.probe  = gpio_probe,
> +	.driver = { .name = KBUILD_MODNAME, },
> +};
> +
> +module_platform_driver(gpio_driver);
> +
> +MODULE_AUTHOR("Wenkai Chung <wenkai.chung@xxxxxxxxxxxxxxxx>");
> +MODULE_AUTHOR("Ramiro Oliveira <ramiro.oliveira@xxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("GPIO driver for Advantech EIO embedded controller");
> +MODULE_LICENSE("GPL");
>
> --
> 2.43.0
>
>

Bart