[PATCH v3] iio: temperature: mlx90632: Interface to change object ambient temperature

[Crt Mori <cmo@melexis.com>]

Since object temperature might be different than the sensor temperature
the infrared sensors should provide an interface to inject ambient
temperature. This was in past done via write to ambient temperature
interface (in_temp_ambient_raw), but I think most people did not know
about it. This solution introduces a new iio type of the CALIBAMBIENT
which is hopefully more descriptive and more explicit about the purpose
and capabilities of the sensors.

Signed-off-by: Crt Mori <cmo@melexis.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 Documentation/ABI/testing/sysfs-bus-iio | 8 ++++++++
 drivers/iio/industrialio-core.c         | 1 +
 drivers/iio/temperature/mlx90632.c      | 9 +++++++--
 include/linux/iio/types.h               | 1 +
 4 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 5c62bfb0f3f5..084436a315e2 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1740,3 +1740,11 @@ KernelVersion:	5.5
 Contact:	linux-iio@vger.kernel.org
 Description:
 		One of the following thermocouple types: B, E, J, K, N, R, S, T.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_temp_object_calibambient
+What:		/sys/bus/iio/devices/iio:deviceX/in_tempX_object_calibambient
+KernelVersion:	5.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Calibrated ambient temperature for object temperature
+		calculation in milli degrees Celsius.
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 606d5e61c575..941011502f4d 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -165,6 +165,7 @@ static const char * const iio_chan_info_postfix[] = {
 	[IIO_CHAN_INFO_CALIBEMISSIVITY] = "calibemissivity",
 	[IIO_CHAN_INFO_OVERSAMPLING_RATIO] = "oversampling_ratio",
 	[IIO_CHAN_INFO_THERMOCOUPLE_TYPE] = "thermocouple_type",
+	[IIO_CHAN_INFO_CALIBAMBIENT] = "calibambient",
 };
 
 #if defined(CONFIG_DEBUG_FS)
diff --git a/drivers/iio/temperature/mlx90632.c b/drivers/iio/temperature/mlx90632.c
index 94bca2b2866a..048cafa04455 100644
--- a/drivers/iio/temperature/mlx90632.c
+++ b/drivers/iio/temperature/mlx90632.c
@@ -761,7 +761,9 @@ static int mlx90632_read_raw(struct iio_dev *indio_dev,
 			*val2 = data->emissivity * 1000;
 		}
 		return IIO_VAL_INT_PLUS_MICRO;
-
+	case IIO_CHAN_INFO_CALIBAMBIENT:
+		*val = data->object_ambient_temperature;
+		return IIO_VAL_INT;
 	default:
 		return -EINVAL;
 	}
@@ -781,6 +783,9 @@ static int mlx90632_write_raw(struct iio_dev *indio_dev,
 			return -EINVAL;
 		data->emissivity = val * 1000 + val2 / 1000;
 		return 0;
+	case IIO_CHAN_INFO_CALIBAMBIENT:
+		data->object_ambient_temperature = val;
+		return 0;
 	default:
 		return -EINVAL;
 	}
@@ -798,7 +803,7 @@ static const struct iio_chan_spec mlx90632_channels[] = {
 		.modified = 1,
 		.channel2 = IIO_MOD_TEMP_OBJECT,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
-			BIT(IIO_CHAN_INFO_CALIBEMISSIVITY),
+			BIT(IIO_CHAN_INFO_CALIBEMISSIVITY) | BIT(IIO_CHAN_INFO_CALIBAMBIENT),
 	},
 };
 
diff --git a/include/linux/iio/types.h b/include/linux/iio/types.h
index e6fd3645963c..1e3ed6f55bca 100644
--- a/include/linux/iio/types.h
+++ b/include/linux/iio/types.h
@@ -59,6 +59,7 @@ enum iio_chan_info_enum {
 	IIO_CHAN_INFO_CALIBEMISSIVITY,
 	IIO_CHAN_INFO_OVERSAMPLING_RATIO,
 	IIO_CHAN_INFO_THERMOCOUPLE_TYPE,
+	IIO_CHAN_INFO_CALIBAMBIENT,
 };
 
 #endif /* _IIO_TYPES_H_ */
-- 
2.25.1