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iio: buffer: fix timestamp alignment when quaternion in scan

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Fix timestamp alignment when a scan buffer contains an element larger
than sizeof(int64_t). Currently s32 quaternions are the only such
element, and the one driver that has this (hid-sensor-rotation) has a
workaround in place already so this change does not affect it.

Previously, we assumed that the timestamp would always be 8-byte aligned
relative to the end of the scan buffer, but in the case of a scan buffer
a 16-byte quaternion vector, scan_bytes == 32, but the timestamp needs
to be placed at offset 16, not 24.

ts_offset is now a value in bytes so we have to change how the array
access is done.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
David Lechner 2026-03-07 19:44:13 -06:00 committed by Jonathan Cameron
parent 9957725014
commit d05e3c1460
1 changed files with 10 additions and 2 deletions
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12
include/linux/iio/buffer.h
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@ -34,8 +34,16 @@ static inline int iio_push_to_buffers_with_timestamp(struct iio_dev *indio_dev,
void *data, int64_t timestamp)
{
if (ACCESS_PRIVATE(indio_dev, scan_timestamp)) {
size_t ts_offset = indio_dev->scan_bytes / sizeof(int64_t) - 1;
((int64_t *)data)[ts_offset] = timestamp;
size_t ts_offset = ACCESS_PRIVATE(indio_dev, scan_timestamp_offset);
/*
* The size of indio_dev->scan_bytes is always aligned to the
* largest scan element's alignment (see iio_compute_scan_bytes()).
* So there may be padding after the timestamp. ts_offset contains
* the offset in bytes that was already computed for correctly
* aligning the timestamp.
*/
*(int64_t *)(data + ts_offset) = timestamp;
}
return iio_push_to_buffers(indio_dev, data);