[PATCH 5/6] gpio: ad7768: Add AD7768 GPIO auxiliary driver

[Janani Sunil <janani.sunil@analog.com>]

The AD7768/AD7768-4 ADC exposes 5 general-purpose I/O pins that can be
independently configured as inputs or outputs. Add an auxiliary bus driver
to expose these pins as a GPIO chip, registered by the parent IIO driver.

The driver uses the parent's regmap for register access and delegates
runtime power management to the parent device.

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
 MAINTAINERS                |   1 +
 drivers/gpio/Kconfig       |  10 +++
 drivers/gpio/Makefile      |   1 +
 drivers/gpio/gpio-ad7768.c | 208 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 220 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index dc94e7803a7c..3de7ebcc4ee7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1639,6 +1639,7 @@ L:	linux-iio@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/iio/adc/adi,ad7768.yaml
+F:	drivers/gpio/gpio-ad7768.c
 F:	drivers/iio/adc/ad7768.c
 
 ANALOG DEVICES INC AD7780 DRIVER
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 28cf6d2e83c2..12ebbdb16982 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1796,6 +1796,16 @@ endmenu
 menu "Auxiliary Bus GPIO drivers"
 	depends on AUXILIARY_BUS
 
+config GPIO_AD7768
+	tristate "Analog Devices AD7768 GPIO support"
+	depends on AD7768 && GPIOLIB
+	help
+	  Say yes here to expose the AD7768 utility pins as GPIOs when the
+	  device tree node is marked as a GPIO controller.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called gpio-ad7768.
+
 config GPIO_LTC4283
 	tristate "Analog Devices LTC4283 GPIO support"
 	depends on SENSORS_LTC4283
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 4d0e900402fc..d2921963efc7 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -27,6 +27,7 @@ obj-$(CONFIG_GPIO_104_IDI_48)		+= gpio-104-idi-48.o
 obj-$(CONFIG_GPIO_104_IDIO_16)		+= gpio-104-idio-16.o
 obj-$(CONFIG_GPIO_74X164)		+= gpio-74x164.o
 obj-$(CONFIG_GPIO_74XX_MMIO)		+= gpio-74xx-mmio.o
+obj-$(CONFIG_GPIO_AD7768)		+= gpio-ad7768.o
 obj-$(CONFIG_GPIO_ADNP)			+= gpio-adnp.o
 obj-$(CONFIG_GPIO_ADP5520)		+= gpio-adp5520.o
 obj-$(CONFIG_GPIO_ADP5585)		+= gpio-adp5585.o
diff --git a/drivers/gpio/gpio-ad7768.c b/drivers/gpio/gpio-ad7768.c
new file mode 100644
index 000000000000..c2f01b1abd7c
--- /dev/null
+++ b/drivers/gpio/gpio-ad7768.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Analog Devices AD7768 GPIO auxiliary driver
+ *
+ * Copyright 2026 Analog Devices Inc.
+ */
+
+#include <linux/auxiliary_bus.h>
+#include <linux/cleanup.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+
+#define AD7768_REG_GPIO_CONTROL		0x0E
+#define AD7768_REG_GPIO_WRITE		0x0F
+#define AD7768_REG_GPIO_READ		0x10
+
+#define AD7768_GPIO_UGPIO_ENABLE	BIT(7)
+#define AD7768_GPIO_INPUT		0x00
+#define AD7768_GPIO_OUTPUT(x)		BIT(x)
+
+#define AD7768_NUM_GPIOS		5
+
+struct ad7768_gpio_state {
+	struct device *parent;
+	struct regmap *regmap;
+	struct mutex lock; /* protects regmap accesses */
+	struct gpio_chip gc;
+};
+
+static int ad7768_gpio_direction_input(struct gpio_chip *chip,
+				       unsigned int offset)
+{
+	struct ad7768_gpio_state *st = gpiochip_get_data(chip);
+
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(st->parent, pm);
+	int ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+
+	if (ret)
+		return ret;
+
+	return regmap_update_bits(st->regmap, AD7768_REG_GPIO_CONTROL,
+				  BIT(offset), AD7768_GPIO_INPUT);
+}
+
+static int ad7768_gpio_get_direction(struct gpio_chip *chip,
+				     unsigned int offset)
+{
+	struct ad7768_gpio_state *st = gpiochip_get_data(chip);
+	unsigned int val;
+	int ret;
+
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(st->parent, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(st->regmap, AD7768_REG_GPIO_CONTROL, &val);
+	if (ret)
+		return ret;
+
+	return !!(val & BIT(offset)) ? GPIO_LINE_DIRECTION_OUT :
+				       GPIO_LINE_DIRECTION_IN;
+}
+
+static int ad7768_gpio_direction_output(struct gpio_chip *chip,
+					unsigned int offset, int value)
+{
+	struct ad7768_gpio_state *st = gpiochip_get_data(chip);
+	int ret;
+
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(st->parent, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&st->lock);
+
+	ret = regmap_update_bits(st->regmap, AD7768_REG_GPIO_CONTROL,
+				 BIT(offset), AD7768_GPIO_OUTPUT(offset));
+	if (ret)
+		return ret;
+
+	return regmap_update_bits(st->regmap, AD7768_REG_GPIO_WRITE,
+				  BIT(offset), value << offset);
+}
+
+static int ad7768_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct ad7768_gpio_state *st = gpiochip_get_data(chip);
+	unsigned int val;
+	int ret;
+
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(st->parent, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&st->lock);
+
+	ret = regmap_read(st->regmap, AD7768_REG_GPIO_CONTROL, &val);
+	if (ret)
+		return ret;
+
+	if (val & BIT(offset))
+		ret = regmap_read(st->regmap, AD7768_REG_GPIO_WRITE, &val);
+	else
+		ret = regmap_read(st->regmap, AD7768_REG_GPIO_READ, &val);
+	if (ret)
+		return ret;
+
+	return !!(val & BIT(offset));
+}
+
+static int ad7768_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			   int value)
+{
+	struct ad7768_gpio_state *st = gpiochip_get_data(chip);
+	unsigned int val;
+	int ret;
+
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(st->parent, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
+
+	guard(mutex)(&st->lock);
+
+	ret = regmap_read(st->regmap, AD7768_REG_GPIO_CONTROL, &val);
+	if (ret)
+		return ret;
+
+	if (!(val & BIT(offset)))
+		return 0;
+
+	return regmap_update_bits(st->regmap, AD7768_REG_GPIO_WRITE,
+				  BIT(offset), value << offset);
+}
+
+static int ad7768_gpio_probe(struct auxiliary_device *adev,
+			     const struct auxiliary_device_id *id)
+{
+	struct device *dev = &adev->dev;
+	const char *label = dev_get_platdata(dev);
+	struct ad7768_gpio_state *st;
+	struct gpio_chip *gc;
+	int ret;
+
+	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
+	if (!st)
+		return -ENOMEM;
+
+	st->parent = dev->parent;
+	st->regmap = dev_get_regmap(dev->parent, NULL);
+
+	ret = devm_mutex_init(dev, &st->lock);
+	if (ret)
+		return ret;
+
+	ret = pm_runtime_resume_and_get(st->parent);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_update_bits(st->regmap, AD7768_REG_GPIO_CONTROL,
+				 AD7768_GPIO_UGPIO_ENABLE,
+				 AD7768_GPIO_UGPIO_ENABLE);
+
+	pm_runtime_mark_last_busy(st->parent);
+	pm_runtime_put_autosuspend(st->parent);
+
+	if (ret < 0)
+		return ret;
+
+	gc = &st->gc;
+	gc->label = label;
+	gc->base = -1;
+	gc->ngpio = AD7768_NUM_GPIOS;
+	gc->parent = dev;
+	gc->owner = THIS_MODULE;
+	gc->can_sleep = true;
+	gc->get_direction = ad7768_gpio_get_direction;
+	gc->direction_input = ad7768_gpio_direction_input;
+	gc->direction_output = ad7768_gpio_direction_output;
+	gc->get = ad7768_gpio_get;
+	gc->set = ad7768_gpio_set;
+
+	return devm_gpiochip_add_data(dev, &st->gc, st);
+}
+
+static const struct auxiliary_device_id ad7768_gpio_ids[] = {
+	{ .name = "ad7768.gpio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(auxiliary, ad7768_gpio_ids);
+
+static struct auxiliary_driver ad7768_gpio_driver = {
+	.probe = ad7768_gpio_probe,
+	.id_table = ad7768_gpio_ids,
+};
+module_auxiliary_driver(ad7768_gpio_driver);
+
+MODULE_AUTHOR("Janani Sunil <janani.sunil@analog.com>");
+MODULE_DESCRIPTION("Analog Devices AD7768 GPIO auxiliary driver");
+MODULE_LICENSE("GPL");

-- 
2.43.0