[PATCH v4 2/7] iio: buffer: add back-ref from iio_buffer to iio_dev

[Alexandru Ardelean <alexandru.ardelean@analog.com>]

An IIO device will have multiple buffers, but it shouldn't be allowed that
an IIO buffer should belong to more than 1 IIO device.

Once things get moved more from IIO device to the IIO buffer, and an IIO
device will be able to have more than 1 buffer attached, there will be a
need for a back-ref to the IIO device [from the IIO buffer].

This change adds that.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/iio/industrialio-buffer.c | 2 ++
 include/linux/iio/buffer_impl.h   | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index f8706b065247..68c276edb071 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -1458,5 +1458,7 @@ void iio_device_attach_buffer(struct iio_dev *indio_dev,
 			      struct iio_buffer *buffer)
 {
 	indio_dev->buffer = iio_buffer_get(buffer);
+
+	indio_dev->buffer->indio_dev = indio_dev;
 }
 EXPORT_SYMBOL_GPL(iio_device_attach_buffer);
diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
index a63dc07b7350..67d73d465e02 100644
--- a/include/linux/iio/buffer_impl.h
+++ b/include/linux/iio/buffer_impl.h
@@ -69,6 +69,9 @@ struct iio_buffer_access_funcs {
  * those writing new buffer implementations.
  */
 struct iio_buffer {
+	/** @indio_dev: IIO device to which this buffer belongs to. */
+	struct iio_dev *indio_dev;
+
 	/** @length: Number of datums in buffer. */
 	unsigned int length;
 
-- 
2.17.1