[PATCH v7 16/17] iio: adc: ad7768: Register GPIO auxiliary device

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

Register an auxiliary device when the AD7768 is described as a GPIO
controller. This allows the GPIO driver to share the parent regmap and
runtime power-management state.

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
 drivers/iio/adc/Kconfig  |  1 +
 drivers/iio/adc/ad7768.c | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index c784bee0fd65..dea25315ed20 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -435,6 +435,7 @@ config AD7768
 	tristate "Analog Devices AD7768/AD7768-4 ADC driver"
 	depends on SPI
 	select REGULATOR
+	select AUXILIARY_BUS
 	select IIO_BUFFER
 	select IIO_BACKEND
 	select REGMAP
diff --git a/drivers/iio/adc/ad7768.c b/drivers/iio/adc/ad7768.c
index b854c10467a2..24a963ad2bf4 100644
--- a/drivers/iio/adc/ad7768.c
+++ b/drivers/iio/adc/ad7768.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/array_size.h>
+#include <linux/auxiliary_bus.h>
 #include <linux/bitfield.h>
 #include <linux/bitmap.h>
 #include <linux/bitops.h>
@@ -1265,6 +1266,30 @@ static const struct iio_info ad7768_info = {
 	.update_scan_mode = ad7768_update_scan_mode,
 };
 
+static int ad7768_gpio_adev_init(struct ad7768_state *st)
+{
+	struct device *dev = regmap_get_device(st->regmap);
+	struct spi_device *spi = to_spi_device(dev);
+	struct auxiliary_device *adev;
+	int id;
+
+	if (!device_property_read_bool(dev, "gpio-controller"))
+		return 0;
+
+	/*
+	 * Use the SPI bus number and chip select to derive a stable per-device
+	 * ID.
+	 */
+	id = (spi->controller->bus_num << 8) | spi_get_chipselect(spi, 0);
+	adev = __devm_auxiliary_device_create(dev, KBUILD_MODNAME, "gpio",
+					      NULL, id);
+	if (!adev)
+		return dev_err_probe(dev, -ENODEV,
+				     "Failed to create GPIO auxiliary device\n");
+
+	return 0;
+}
+
 static int ad7768_configure_precharge_buffers(struct iio_dev *indio_dev,
 					      struct ad7768_precharge_config *precharge_cfg)
 {
@@ -1837,6 +1862,10 @@ static int ad7768_probe(struct spi_device *spi)
 		return dev_err_probe(dev, ret,
 				     "Failed to register VCM regulator\n");
 
+	ret = ad7768_gpio_adev_init(st);
+	if (ret)
+		return ret;
+
 	return devm_iio_device_register(dev, indio_dev);
 }
 

-- 
2.43.0