[PATCH v4 13/14] gpio: ad7768: Add AD7768 GPIO auxiliary driver

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

The AD7768 provides five GPIOs controlled through registers shared
with the parent IIO device. Register an auxiliary gpio-regmap driver
and use the parent device for runtime PM.

The device has separate input-state and output-latch registers. Add a
reg_mask_xlate() callback that checks the line direction and reads the
programmed output latch for output lines while retaining input-state
reads for input lines.

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
 MAINTAINERS                |   1 +
 drivers/gpio/Kconfig       |  12 +++++
 drivers/gpio/Makefile      |   1 +
 drivers/gpio/gpio-ad7768.c | 118 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 132 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..85cb0c82a823 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1796,6 +1796,18 @@ endmenu
 menu "Auxiliary Bus GPIO drivers"
 	depends on AUXILIARY_BUS
 
+config GPIO_AD7768
+	tristate "Analog Devices AD7768 GPIO support"
+	depends on AD7768
+	depends on GPIOLIB
+	select GPIO_REGMAP
+	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..710739e33dff
--- /dev/null
+++ b/drivers/gpio/gpio-ad7768.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Analog Devices AD7768 GPIO auxiliary driver
+ *
+ * Copyright 2026 Analog Devices Inc.
+ */
+
+#include <linux/auxiliary_bus.h>
+#include <linux/bitmap.h>
+#include <linux/bits.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/regmap.h>
+#include <linux/module.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+
+#define AD7768_REG_GPIO_CONTROL		0x0E
+#define   AD7768_GPIO_UGPIO_ENABLE	BIT(7)
+
+#define AD7768_REG_GPIO_WRITE		0x0F
+#define AD7768_REG_GPIO_READ		0x10
+
+#define AD7768_NUM_GPIOS		5
+
+static int ad7768_gpio_init_valid_mask(struct gpio_chip *gc,
+				       unsigned long *valid_mask,
+				       unsigned int ngpios)
+{
+	unsigned long *mask = dev_get_platdata(gc->parent);
+
+	bitmap_copy(valid_mask, mask, ngpios);
+
+	return 0;
+}
+
+static int ad7768_gpio_reg_mask_xlate(struct gpio_regmap *gpio,
+				      unsigned int base, unsigned int offset,
+				      unsigned int *reg, unsigned int *mask)
+{
+	struct regmap *regmap = gpio_regmap_get_drvdata(gpio);
+	int ret;
+
+	*reg = base;
+	*mask = BIT(offset);
+
+	if (base != AD7768_REG_GPIO_READ)
+		return 0;
+
+	/*
+	 * AD7768 has separate input-state and output-latch registers. For an
+	 * output line, report the programmed value from the output latch;
+	 * input lines continue to use the input-state register.
+	 */
+	ret = regmap_test_bits(regmap, AD7768_REG_GPIO_CONTROL, *mask);
+	if (ret < 0)
+		return ret;
+	if (ret)
+		*reg = AD7768_REG_GPIO_WRITE;
+
+	return 0;
+}
+
+static int ad7768_gpio_probe(struct auxiliary_device *adev,
+			     const struct auxiliary_device_id *id)
+{
+	struct device *parent = adev->dev.parent;
+	struct gpio_regmap_config config = {
+		.parent = &adev->dev,
+		.label = dev_name(parent),
+		.ngpio = AD7768_NUM_GPIOS,
+		.reg_dat_base = AD7768_REG_GPIO_READ,
+		.reg_set_base = AD7768_REG_GPIO_WRITE,
+		.reg_dir_out_base = AD7768_REG_GPIO_CONTROL,
+		.pm_dev = parent,
+		.reg_mask_xlate = ad7768_gpio_reg_mask_xlate,
+		.init_valid_mask = ad7768_gpio_init_valid_mask,
+	};
+	struct gpio_regmap *gpio;
+	struct regmap *map;
+	int ret;
+
+	map = dev_get_regmap(parent, NULL);
+	if (!map)
+		return -ENODEV;
+
+	PM_RUNTIME_ACQUIRE_AUTOSUSPEND(parent, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
+
+	ret = regmap_set_bits(map, AD7768_REG_GPIO_CONTROL, AD7768_GPIO_UGPIO_ENABLE);
+	if (ret)
+		return ret;
+
+	config.regmap = map;
+	config.drvdata = map;
+
+	gpio = devm_gpio_regmap_register(&adev->dev, &config);
+	return PTR_ERR_OR_ZERO(gpio);
+}
+
+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