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    Subject[PATCH 4.0 034/105] iio: adis16400: Fix burst mode
    Date
    4.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Paul Cercueil <paul.cercueil@analog.com>

    commit 9df560350c90f3d3909fe653399b3584c9a17b61 upstream.

    There are a few issues with the burst mode support. For one we don't setup
    the rx buffer, so the buffer will never be filled and all samples will read
    as the zero. Furthermore the tx buffer has the wrong type, which means the
    driver sends the wrong command and not the right data is returned.

    The final issue is that in burst mode all channels are transferred. Hence
    the length of the transfer length should be the number of hardware
    channels * 2 bytes. Currently the driver uses indio_dev->scan_bytes for
    this. But if the timestamp channel is enabled the scan_bytes will be larger
    than the burst length. Fix this by just calculating the burst length based
    on the number of hardware channels.

    Signed-off-by: Paul Cercueil <paul.cercueil@analog.com>
    Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
    Fixes: 5eda3550a3cc ("staging:iio:adis16400: Preallocate transfer message")
    Signed-off-by: Jonathan Cameron <jic23@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/iio/imu/adis16400_buffer.c | 16 +++++++++-------
    1 file changed, 9 insertions(+), 7 deletions(-)

    --- a/drivers/iio/imu/adis16400_buffer.c
    +++ b/drivers/iio/imu/adis16400_buffer.c
    @@ -18,7 +18,8 @@ int adis16400_update_scan_mode(struct ii
    {
    struct adis16400_state *st = iio_priv(indio_dev);
    struct adis *adis = &st->adis;
    - uint16_t *tx;
    + unsigned int burst_length;
    + u8 *tx;

    if (st->variant->flags & ADIS16400_NO_BURST)
    return adis_update_scan_mode(indio_dev, scan_mask);
    @@ -26,26 +27,27 @@ int adis16400_update_scan_mode(struct ii
    kfree(adis->xfer);
    kfree(adis->buffer);

    + /* All but the timestamp channel */
    + burst_length = (indio_dev->num_channels - 1) * sizeof(u16);
    +
    adis->xfer = kcalloc(2, sizeof(*adis->xfer), GFP_KERNEL);
    if (!adis->xfer)
    return -ENOMEM;

    - adis->buffer = kzalloc(indio_dev->scan_bytes + sizeof(u16),
    - GFP_KERNEL);
    + adis->buffer = kzalloc(burst_length + sizeof(u16), GFP_KERNEL);
    if (!adis->buffer)
    return -ENOMEM;

    - tx = adis->buffer + indio_dev->scan_bytes;
    -
    + tx = adis->buffer + burst_length;
    tx[0] = ADIS_READ_REG(ADIS16400_GLOB_CMD);
    tx[1] = 0;

    adis->xfer[0].tx_buf = tx;
    adis->xfer[0].bits_per_word = 8;
    adis->xfer[0].len = 2;
    - adis->xfer[1].tx_buf = tx;
    + adis->xfer[1].rx_buf = adis->buffer;
    adis->xfer[1].bits_per_word = 8;
    - adis->xfer[1].len = indio_dev->scan_bytes;
    + adis->xfer[1].len = burst_length;

    spi_message_init(&adis->msg);
    spi_message_add_tail(&adis->xfer[0], &adis->msg);

    --
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