> From: Jonathan Cameron <jic23@xxxxxxxxxx>
> Sent: Saturday, May 1, 2021 7:25 PM
> To: linux-iio@xxxxxxxxxxxxxxx
> Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>; Sa, Nuno
> <Nuno.Sa@xxxxxxxxxx>
> Subject: [RFC PATCH 4/4] iio: imu: adis16400: Fix buffer alignment
> requirements.
>
>
> From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>
> iio_push_to_buffers_with_timestamp() requires that the buffer
> is 8 byte alignment to ensure an inserted timestamp is naturally
> aligned.
>
> This requirement was not met here when burst mode is in use beause
> of a leading u16. Use the new iio_push_to_buffers_with_ts_na()
> function
> that has more relaxed requirements.
>
> It is somewhat complex to access that actual data length, but a
> safe bound can be found by using scan_bytes - sizeof(timestamp) so
> that
> is used in this path.
>
> More efficient approaches exist, but this ensure correctness at the
> cost of using a bounce buffer.
>
> Fixes: 5075e0720d93 ("iio: imu: adis: generalize burst mode support")
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Cc: Nuno Sa <nuno.sa@xxxxxxxxxx>
> ---
> drivers/iio/imu/adis16400.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iio/imu/adis16400.c b/drivers/iio/imu/adis16400.c
> index 768aa493a1a6..c6d03a37373b 100644
> --- a/drivers/iio/imu/adis16400.c
> +++ b/drivers/iio/imu/adis16400.c
> @@ -663,13 +663,23 @@ static irqreturn_t
> adis16400_trigger_handler(int irq, void *p)
> spi_setup(st->adis.spi);
> }
>
> - if (st->variant->flags & ADIS16400_BURST_DIAG_STAT)
> + if (st->variant->flags & ADIS16400_BURST_DIAG_STAT) {
> buffer = adis->buffer + sizeof(u16);
> - else
> - buffer = adis->buffer;
> + /*
> + * The size here is always larger than, or equal to the
> true
> + * size of the channel data. This may result in a larger
> copy
> + * than necessary, but as the target buffer will be
> + * buffer->scan_bytes this will be safe.
> + */
> + iio_push_to_buffers_with_ts_na(indio_dev, buffer,
> + indio_dev->scan_bytes -
> sizeof(pf->timestamp),
> + pf->timestamp);
> + } else {
> + iio_push_to_buffers_with_timestamp(indio_dev,
> + adis->buffer,
> + pf->timestamp);
> + }
>
Hi Jonathan,
This looks good to me although I think there's some stuff to care in
' iio_push_to_buffers_with_ts_na()'. However, for this patch alone:
Reviewed-by: Nuno Sá <nuno.sa@xxxxxxxxxx>
I will also check if I find any HW to test this...
- Nuno Sá
