Register an IIO channel to allow reading the temperature using the IIO
interface.

Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
---
 drivers/thermal/thermal-generic-adc.c | 56 +++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/drivers/thermal/thermal-generic-adc.c b/drivers/thermal/thermal-generic-adc.c
index ee3d0aa31406..14aef682e0fb 100644
--- a/drivers/thermal/thermal-generic-adc.c
+++ b/drivers/thermal/thermal-generic-adc.c
@@ -7,6 +7,7 @@
  * Author: Laxman Dewangan <ldewangan@nvidia.com>
  */
 #include <linux/iio/consumer.h>
+#include <linux/iio/iio.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -23,6 +24,10 @@ struct gadc_thermal_info {
 	int nlookup_table;
 };
 
+struct gadc_iio {
+	struct gadc_thermal_info *gti;
+};
+
 static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
 {
 	int temp, temp_hi, temp_lo, adc_hi, adc_lo;
@@ -115,10 +120,44 @@ static int gadc_thermal_read_linear_lookup_table(struct device *dev,
 	return 0;
 }
 
+static int gadc_adc_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct gadc_iio *data = iio_priv(indio_dev);
+	int iio_val;
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		ret = iio_read_channel_processed(data->gti->channel, &iio_val);
+		if (ret < 0)
+			return ret;
+
+		*val = gadc_thermal_adc_to_temp(data->gti, iio_val);
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info gadc_adc_info = {
+	.read_raw = &gadc_adc_read_raw,
+};
+
+static const struct iio_chan_spec gadc_adc_channels[] = {
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+	},
+};
+
 static int gadc_thermal_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct gadc_thermal_info *gti;
+	struct iio_dev *indio_dev;
+	struct gadc_iio *data;
 	int ret;
 
 	if (!dev->of_node) {
@@ -153,6 +192,23 @@ static int gadc_thermal_probe(struct platform_device *pdev)
 
 	devm_thermal_add_hwmon_sysfs(dev, gti->tz_dev);
 
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	data->gti = gti;
+
+	indio_dev->name = pdev->name;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &gadc_adc_info;
+	indio_dev->channels = gadc_adc_channels;
+	indio_dev->num_channels = ARRAY_SIZE(gadc_adc_channels);
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register IIO device\n");
+
 	return 0;
 }
 

-- 
2.51.0

On Fri, 10 Oct 2025 13:22:01 +0200
Luca Weiss <luca.weiss@fairphone.com> wrote:

> Register an IIO channel to allow reading the temperature using the IIO
> interface.
> 
> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
Just one question below.

>  static int gadc_thermal_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
>  	struct gadc_thermal_info *gti;
> +	struct iio_dev *indio_dev;
> +	struct gadc_iio *data;
>  	int ret;
>  
>  	if (!dev->of_node) {
> @@ -153,6 +192,23 @@ static int gadc_thermal_probe(struct platform_device *pdev)
>  
>  	devm_thermal_add_hwmon_sysfs(dev, gti->tz_dev);
>  
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	data->gti = gti;
> +
> +	indio_dev->name = pdev->name;
what does this end up as?

obviously we don't really care what name the user space interface we
aren't using advertises but this should be something part number like.

> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &gadc_adc_info;
> +	indio_dev->channels = gadc_adc_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(gadc_adc_channels);
> +
> +	ret = devm_iio_device_register(dev, indio_dev);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to register IIO device\n");
> +
>  	return 0;
>  }
>  
>