On Fri, 12 Dec 2025 17:40:53 +0100, Ramiro Oliveira
[off-list ref] said:

Instead of churning MAINTAINERS in every patch of the series, I suggest you
add a separate patch adding the full entry at the end.

Don't include this, it's a legacy header as per one of the first lines in this
file.

+#include <linux/gpio/driver.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/eio.h>
+#include <linux/module.h>
+
+#define GPIO_MAX_PINS	48
+#define GPIO_WRITE	0x18
+#define GPIO_READ	0x19
+
+struct eio_gpio_dev {
+	u64 avail;
+	int max;
+	struct gpio_chip chip;
+	struct device *dev;
+};
+
+struct {
+	int size;
+	bool write;
+} ctrl_para[] = {
+	{ 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 }
+};

This should be static.

+
+enum {
+	GPIO_STATUS	 = 0,
+	GPIO_GROUP_AVAIL = 3,
+	GPIO_ERROR	 = 0x04,
+	GPIO_PIN_DIR	 = 0x10,
+	GPIO_PIN_LEVEL	 = 0x11,
+	GPIO_GROUP_DIR	 = 0x12,
+	GPIO_GROUP_LEVEL = 0x13,
+	GPIO_MAPPING	 = 0x14,
+	GPIO_NAME	 = 0x15
+} gpio_ctrl;

Do enum gpio_ctrl {. But also use a common prefix for all symbols in
this driver.

+
+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 timeout;
+module_param(timeout, int, 0444);
+MODULE_PARM_DESC(timeout, "Set PMC command timeout value.\n");
+
+static int pmc_write(struct device *mfd_dev, u8 ctrl, u8 dev_id, void *data)
+{
+	struct pmc_op op = {
+		 .cmd       = GPIO_WRITE,
+		 .control   = ctrl,
+		 .device_id = dev_id,
+		 .payload   = (u8 *)data,
+		 .timeout   = timeout,
+	};
+
+	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       = GPIO_READ,
+		 .control   = ctrl,
+		 .device_id = dev_id,
+		 .payload   = (u8 *)data,
+		 .timeout   = timeout,
+	};
+
+	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, 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, 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, GPIO_PIN_DIR, offset, &dir);
+
+	return pmc_write(chip->parent, 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, 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;
+
+	pmc_write(chip->parent, GPIO_PIN_LEVEL, offset, &val);
+
+	return 0;
+}
+
+static int check_support(struct device *dev)
+{
+	u8  data;
+	int ret;
+
+	ret = pmc_read(dev, 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;
+	u16 data;
+
+	/* Get pin mapping */
+	ret = pmc_read(dev, 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, 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;
+	int i;

Keep these on the same line.

+	char str[GPIO_MAX_PINS + 1];
+
+	memset(str, 0x30, sizeof(str));
+
+	ret = check_support(mfd);
+	if (ret) {
+		dev_err(eio_gpio->dev, "GPIO not supported (%d)\n", ret);

return dev_err_probe()

+		return ret;
+	}
+
+	eio_gpio->avail = 0;
+
+	for (i = 0 ; i <  GPIO_MAX_PINS ; i++) {
+		ret = check_pin(mfd, i);
+		if (ret)
+			continue;
+
+		eio_gpio->avail |= BIT(i);
+		eio_gpio->max = i + 1;
+		str[GPIO_MAX_PINS - i] = '1';
+	}
+
+	dev_info(eio_gpio->dev, "GPIO pins=%s\n", str);
+

No need to print anything here.

+	return eio_gpio->max ? 0 : -EOPNOTSUPP;
+}
+
+static const struct gpio_chip eio_gpio_chip = {
+	.label	 	  = KBUILD_MODNAME,
+	.owner		  = THIS_MODULE,
+	.direction_input  = dir_input,
+	.get		  = gpio_get,
+	.direction_output = dir_output,
+	.set		  = gpio_set,
+	.get_direction	  = get_dir,
+	.base		  = -1,
+	.can_sleep	  = true,
+};

Instead of having an unnecessary copy of the chip in .rodata, just use compound
literals when initiating it in probe().

+
+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) {
+		dev_err(dev, "Error contact eio_core\n");
+		return -ENODEV;
+	}

return dev_err_probe()

+
+	eio_gpio = devm_kzalloc(dev, sizeof(*eio_gpio), GFP_KERNEL);

This can fail, please check the return value.

+	eio_gpio->dev = dev;
+
+	if (gpio_init(dev->parent, eio_gpio))
+		return -EIO;
+
+	eio_gpio->chip	   = eio_gpio_chip;

Don't use tabs like that please. Just stick to single spaces.

+	eio_gpio->chip.parent = dev->parent;
+	eio_gpio->chip.ngpio  = eio_gpio->max;
+
+	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 [off-list ref]");
+MODULE_AUTHOR("Ramiro Oliveira [off-list ref]");
+MODULE_DESCRIPTION("GPIO driver for Advantech EIO embedded controller");
+MODULE_LICENSE("GPL");

--
2.43.0