iio: inkern: add iio_write_channel_raw

Introduce API for easy in-kernel setting of DAC values.
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/inkern.c

@@ -631,3 +631,28 @@ int iio_get_channel_type(struct iio_channel *chan, enum iio_chan_type *type)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(iio_get_channel_type);
+
+static int iio_channel_write(struct iio_channel *chan, int val, int val2,
+			     enum iio_chan_info_enum info)
+{
+	return chan->indio_dev->info->write_raw(chan->indio_dev,
+						chan->channel, val, val2, info);
+}
+
+int iio_write_channel_raw(struct iio_channel *chan, int val)
+{
+	int ret;
+
+	mutex_lock(&chan->indio_dev->info_exist_lock);
+	if (chan->indio_dev->info == NULL) {
+		ret = -ENODEV;
+		goto err_unlock;
+	}
+
+	ret = iio_channel_write(chan, val, 0, IIO_CHAN_INFO_RAW);
+err_unlock:
+	mutex_unlock(&chan->indio_dev->info_exist_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_write_channel_raw);

include/linux/iio/consumer.h

@@ -150,6 +150,16 @@ int iio_read_channel_average_raw(struct iio_channel *chan, int *val);
  */
 int iio_read_channel_processed(struct iio_channel *chan, int *val);
 
+/**
+ * iio_write_channel_raw() - write to a given channel
+ * @chan:		The channel being queried.
+ * @val:		Value being written.
+ *
+ * Note raw writes to iio channels are in dac counts and hence
+ * scale will need to be applied if standard units required.
+ */
+int iio_write_channel_raw(struct iio_channel *chan, int val);
+
 /**
  * iio_get_channel_type() - get the type of a channel
  * @channel:		The channel being queried.