Commit 63fc5352 authored by David Lechner's avatar David Lechner Committed by Jonathan Cameron
Browse files

iio: introduce IIO_DECLARE_BUFFER_WITH_TS macros 



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: default avatarNuno Sá <nuno.sa@analog.com>
Signed-off-by: default avatarDavid 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: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent fa19c303

include/linux/iio/iio.h

+32 −0
Original line number Diff line number Diff line
@@ -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 */