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iio: introduce IIO_DECLARE_BUFFER_WITH_TS macros

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Add new macros 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.

To avoid double __align() attributes in cases where we also need DMA
alignment, add a 2nd variant IIO_DECLARE_DMA_BUFFER_WITH_TS().

Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250507-iio-introduce-iio_declare_buffer_with_ts-v6-2-4aee1b9f1b89@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
David Lechner
2025-05-07 15:42:41 -05:00
committed by Jonathan Cameron
parent fa19c30325
commit 63fc53526d
1 changed files with 32 additions and 0 deletions
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32
include/linux/iio/iio.h
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@@ -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>
@@ -784,6 +785,37 @@ static inline void *iio_device_get_drvdata(const struct iio_dev *indio_dev)
*/
#define IIO_DMA_MINALIGN MAX(ARCH_DMA_MINALIGN, sizeof(s64))
#define __IIO_DECLARE_BUFFER_WITH_TS(type, name, count) \
type name[ALIGN((count), sizeof(s64) / sizeof(type)) + sizeof(s64) / sizeof(type)]
/**
* 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) \
__IIO_DECLARE_BUFFER_WITH_TS(type, name, count) __aligned(sizeof(s64))
/**
* IIO_DECLARE_DMA_BUFFER_WITH_TS() - Declare a DMA-aligned buffer with timestamp
* @type: element type of the buffer
* @name: identifier name of the buffer
* @count: number of elements in the buffer
*
* Same as IIO_DECLARE_BUFFER_WITH_TS(), but is uses __aligned(IIO_DMA_MINALIGN)
* to ensure that the buffer doesn't share cachelines with anything that comes
* before it in a struct. This should not be used for stack-allocated buffers
* as stack memory cannot generally be used for DMA.
*/
#define IIO_DECLARE_DMA_BUFFER_WITH_TS(type, name, count) \
__IIO_DECLARE_BUFFER_WITH_TS(type, name, count) __aligned(IIO_DMA_MINALIGN)
struct iio_dev *iio_device_alloc(struct device *parent, int sizeof_priv);
/* The information at the returned address is guaranteed to be cacheline aligned */