Re: [PATCH v2 0/5] iio: buffer: fix timestamp alignment (in rare case)

[Nuno Sá]

On Sat, 2026-03-07 at 19:44 -0600, David Lechner wrote:
> In [1], it was pointed out that the iio_push_to_buffers_with_timestamp()
> function is not putting the timestamp at the correct offset in the scan
> buffer in rare cases where the largest scan element size is larger than
> sizeof(int64_t).
> 
> [1]: https://lore.kernel.org/linux-iio/20260215162351.79f40b32@jic23-huawei/
> 
> This only affected one driver, namely hid-sensor-rotation since it is
> the only driver that meets the condition. To fix things up, first we
> fix the hid-sensor-rotation driver in a way that preserves compatibility
> with the broken timestamp alignment. Then we are free to fix the core
> IIO code without affecting any users.
> 
> The first patch depends on [2] which is now in iio/fixes-togreg. It
> should be OK to apply the first patch there and let the rest of the
> patches go through iio/togreg (the later patches are just preventing
> future bugs).
> 
> [2]:
> https://lore.kernel.org/linux-iio/20260228-iio-fix-repeat-alignment-v2-0-d58bfaa2920d@xxxxxxxxxxxx/
> 
> Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
> ---

LGTM,

Reviewed-by: Nuno Sá <nuno.sa@xxxxxxxxxx>

> Changes in v2:
> - Don't say "HACK" in comments.
> - Cache timestamp offset instead of largest scan element size.
> - New patch to ensure size/alignment is always power of 2 bytes.
> - Link to v1:
> https://lore.kernel.org/r/20260301-iio-fix-timestamp-alignment-v1-0-1a54980bfb90@xxxxxxxxxxxx
> 
> ---
> David Lechner (5):
>       iio: orientation: hid-sensor-rotation: add timestamp hack to not break userspace
>       iio: buffer: check return value of iio_compute_scan_bytes()
>       iio: buffer: cache timestamp offset in scan buffer
>       iio: buffer: ensure repeat alignment is a power of two
>       iio: buffer: fix timestamp alignment when quaternion in scan
> 
>  drivers/iio/industrialio-buffer.c             | 46 ++++++++++++++++++++-------
>  drivers/iio/orientation/hid-sensor-rotation.c | 22 +++++++++++--
>  include/linux/iio/buffer.h                    | 12 +++++--
>  include/linux/iio/iio.h                       |  3 ++
>  4 files changed, 66 insertions(+), 17 deletions(-)
> ---
> base-commit: 6f25a6105c41a7d6b12986dbe80ded396a5667f8
> change-id: 20260228-iio-fix-timestamp-alignment-89ade1af458b
> prerequisite-message-id: <20260228-iio-fix-repeat-alignment-v2-0-d58bfaa2920d@xxxxxxxxxxxx>
> prerequisite-patch-id: e155a526d57c5759a2fcfbfca7f544cb419addfd
> prerequisite-patch-id: 6c69eaad0dd2ae69bd2745e7d387f739fc1a9ba0
> 
> Best regards,
> --  
> David Lechner <dlechner@xxxxxxxxxxxx>