linux-kernel - [PATCH 1/4] iio: introduce IIO_DECLARE_BUFFER_WITH

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Message-Id: <20250418-iio-introduce-iio_declare_buffer_with_ts-v1-1-ee0c62a33a0f@baylibre.com>
Date: Fri, 18 Apr 2025 17:58:32 -0500
From: David Lechner <dlechner@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>, 
 David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] iio: introduce IIO_DECLARE_BUFFER_WITH_TS

Add a new macro to help with the common case of declaring a buffer that
is safe to use with iio_push_to_buffers_with_ts(). This is not trivial
to do correctly because of the alignment requirements of the timestamp.
This will make it easier for both authors and reviewers.

Signed-off-by: David Lechner <dlechner@...libre.com>
---
 include/linux/iio/iio.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 638cf2420fbd85cf2924d09d061df601d1d4bb2a..f523b046c627037c449170b7490ce2a351c6b9c0 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -7,6 +7,7 @@
 #ifndef _INDUSTRIAL_IO_H_
 #define _INDUSTRIAL_IO_H_
 
+#include <linux/align.h>
 #include <linux/device.h>
 #include <linux/cdev.h>
 #include <linux/compiler_types.h>
@@ -770,6 +771,21 @@ static inline void *iio_device_get_drvdata(const struct iio_dev *indio_dev)
 	return dev_get_drvdata(&indio_dev->dev);
 }
 
+/**
+ * IIO_DECLARE_BUFFER_WITH_TS() - Declare a buffer with timestamp
+ * @type: element type of the buffer
+ * @name: identifier name of the buffer
+ * @count: number of elements in the buffer
+ *
+ * Declares a buffer that is safe to use with iio_push_to_buffer_with_ts(). In
+ * addition to allocating enough space for @count elements of @type, it also
+ * allocates space for a s64 timestamp at the end of the buffer and ensures
+ * proper alignment of the timestamp.
+ */
+#define IIO_DECLARE_BUFFER_WITH_TS(type, name, count) \
+	type name[ALIGN((count), sizeof(s64) / sizeof(type)) \
+		  + sizeof(s64)/ sizeof(type)] __aligned(sizeof(s64))
+
 /*
  * Used to ensure the iio_priv() structure is aligned to allow that structure
  * to in turn include IIO_DMA_MINALIGN'd elements such as buffers which

-- 
2.43.0