[PATCH 1/2] iio: add IIO_DECLARE_REPEATED_ELEMENT() macro

[David Lechner]

Add a new IIO_DECLARE_REPEATED_ELEMENT() macro that is used to declare
the field in an IIO buffer struct that contains a repeated element.

There are only a few iio drivers that actually make use of the .repeat
feature of struct iio_scan_type. This has an implicit rule that the
element in the buffer must be aligned to the entire size of the repeated
element. This macro will make that requirement explicit.

Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
---
 include/linux/iio/iio.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 872ebdf0dd77..28b708166b9b 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -816,6 +816,19 @@ static inline void *iio_device_get_drvdata(const struct iio_dev *indio_dev)
 #define IIO_DECLARE_DMA_BUFFER_WITH_TS(type, name, count) \
 	__IIO_DECLARE_BUFFER_WITH_TS(type, name, count) __aligned(IIO_DMA_MINALIGN)
 
+/**
+ * IIO_DECLARE_REPEATED_ELEMENT() - Declare a repeated element
+ * @type: element type of the repeated element
+ * @name: identifier name of the repeated element
+ * @repeat: number of times the element is repeated
+ *
+ * For special cases with repeated elements, like IIO_MOT_QUATERNION, a multi-
+ * word element is treated as a single element of a larger size in the buffer.
+ * As such, it requires alignment to the size of the entire repeated element.
+ */
+#define IIO_DECLARE_REPEATED_ELEMENT(type, name, repeat) \
+	type name[repeat] __aligned(sizeof(type) * repeat)
+
 struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv);
 
 /* The information at the returned address is guaranteed to be cacheline aligned */

-- 
2.43.0