quoted

+static void ad7768_fill_scale_tbl(struct iio_dev *dev)
+{
+	struct ad7768_state *st = iio_priv(dev);
+	const struct iio_scan_type *scan_type;
+	int val, val2, tmp0, tmp1, i;
+	struct u64_fract fract;
+	unsigned long n, d;
+	u64 tmp2;
+
+	scan_type = iio_get_current_scan_type(dev, &dev->channels[0]);  

Is it usual patter in IIO? Otherwise it can be written as

	scan_type = iio_get_current_scan_type(dev, dev->channels);

From a semantic / readability point of view I'd keep it referencing
the first element.  We are querying the scan type of one specific
channel, rather than the array that is behind dev->channels.

quoted

+	if (scan_type->sign == 's')
+		val2 = scan_type->realbits - 1;
+	else
+		val2 = scan_type->realbits;