iio:inkern: Add function to read the processed value

Add a function to read a processed value from a channel. The function will first
attempt to read the IIO_CHAN_INFO_PROCESSED attribute. If that fails it will
read the IIO_CHAN_INFO_RAW attribute and convert the result from a raw value to
a processed value.

The patch also introduces a function to convert raw value to a processed value
and exports it, in case a user needs or wants to do the conversion by itself.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
index 62118dd707d7..e875bcf0478f 100644
--- a/include/linux/iio/consumer.h
+++ b/include/linux/iio/consumer.h
@@ -71,6 +71,21 @@ int iio_read_channel_raw(struct iio_channel *chan,
                          int *val);
 
 /**
+ * iio_read_channel_processed() - read processed value from a given channel
+ * @chan:               The channel being queried.
+ * @val:                Value read back.
+ *
+ * Returns an error code or 0.
+ *
+ * This function will read a processed value from a channel. A processed value
+ * means that this value will have the correct unit and not some device internal
+ * representation. If the device does not support reporting a processed value
+ * the function will query the raw value and the channels scale and offset and
+ * do the appropriate transformation.
+ */
+int iio_read_channel_processed(struct iio_channel *chan, int *val);
+
+/**
  * iio_get_channel_type() - get the type of a channel
  * @channel:            The channel being queried.
  * @type:               The type of the channel.
@@ -93,4 +108,27 @@ int iio_get_channel_type(struct iio_channel *channel,
 int iio_read_channel_scale(struct iio_channel *chan, int *val,
                            int *val2);
 
+/**
+ * iio_convert_raw_to_processed() - Converts a raw value to a processed value
+ * @chan:               The channel being queried
+ * @raw:                The raw IIO to convert
+ * @processed:          The result of the conversion
+ * @scale:              Scale factor to apply during the conversion
+ *
+ * Returns an error code or 0.
+ *
+ * This function converts a raw value to processed value for a specific channel.
+ * A raw value is the device internal representation of a sample and the value
+ * returned by iio_read_channel_raw, so the unit of that value is device
+ * depended. A processed value on the other hand is value has a normed unit
+ * according with the IIO specification.
+ *
+ * The scale factor allows to increase the precession of the returned value. For
+ * a scale factor of 1 the function will return the result in the normal IIO
+ * unit for the channel type. E.g. millivolt for voltage channels, if you want
+ * nanovolts instead pass 1000 as the scale factor.
+ */
+int iio_convert_raw_to_processed(struct iio_channel *chan, int raw,
+        int *processed, unsigned int scale);
+
 #endif