From d05e3c1460e47aa61e58cc6947cf7c9fc1371d7e Mon Sep 17 00:00:00 2001 From: David Lechner Date: Sat, 7 Mar 2026 19:44:13 -0600 Subject: [PATCH] iio: buffer: fix timestamp alignment when quaternion in scan MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Nuno Sá Signed-off-by: Jonathan Cameron --- include/linux/iio/buffer.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h index d37f82678f71..8fd0d57d238f 100644 --- a/include/linux/iio/buffer.h +++ b/include/linux/iio/buffer.h @@ -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);