staging:iio:find iio channel from scan index util function

Useful for getting to the channel based on scan mask alone.
Signed-off-by: NJonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/iio.h

@@ -322,6 +322,14 @@ struct iio_dev {
 	int				groupcounter;
 };
 
+/**
+ * iio_find_channel_from_si() - get channel from its scan index
+ * @indio_dev:		device
+ * @si:			scan index to match
+ */
+const struct iio_chan_spec
+*iio_find_channel_from_si(struct iio_dev *indio_dev, int si);
+
 /**
  * iio_device_register() - register a device with the IIO subsystem
  * @indio_dev:		Device structure filled by the device driver

drivers/staging/iio/industrialio-core.c

@@ -89,6 +89,17 @@ static const char * const iio_chan_info_postfix[] = {
 	= "filter_low_pass_3db_frequency",
 };
 
+const struct iio_chan_spec
+*iio_find_channel_from_si(struct iio_dev *indio_dev, int si)
+{
+	int i;
+
+	for (i = 0; i < indio_dev->num_channels; i++)
+		if (indio_dev->channels[i].scan_index == si)
+			return &indio_dev->channels[i];
+	return NULL;
+}
+
 /**
  * struct iio_detected_event_list - list element for events that have occurred
  * @list:		linked list header