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    Subject[PATCH 5.0 091/122] staging: iio: adt7316: fix the dac write calculation
    Date
    From: Jeremy Fertic <jeremyfertic@gmail.com>

    commit 78accaea117c1ae878774974fab91ac4a0b0e2b0 upstream.

    The lsb calculation is not masking the correct bits from the user input.
    Subtract 1 from (1 << offset) to correctly set up the mask to be applied
    to user input.

    The lsb register stores its value starting at the bit 7 position.
    adt7316_store_DAC() currently assumes the value is at the other end of the
    register. Shift the lsb value before storing it in a new variable lsb_reg,
    and write this variable to the lsb register.

    Fixes: 35f6b6b86ede ("staging: iio: new ADT7316/7/8 and ADT7516/7/9 driver")
    Signed-off-by: Jeremy Fertic <jeremyfertic@gmail.com>
    Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/staging/iio/addac/adt7316.c | 10 +++++++---
    1 file changed, 7 insertions(+), 3 deletions(-)

    --- a/drivers/staging/iio/addac/adt7316.c
    +++ b/drivers/staging/iio/addac/adt7316.c
    @@ -1442,7 +1442,7 @@ static ssize_t adt7316_show_DAC(struct a
    static ssize_t adt7316_store_DAC(struct adt7316_chip_info *chip,
    int channel, const char *buf, size_t len)
    {
    - u8 msb, lsb, offset;
    + u8 msb, lsb, lsb_reg, offset;
    u16 data;
    int ret;

    @@ -1460,9 +1460,13 @@ static ssize_t adt7316_store_DAC(struct
    return -EINVAL;

    if (chip->dac_bits > 8) {
    - lsb = data & (1 << offset);
    + lsb = data & ((1 << offset) - 1);
    + if (chip->dac_bits == 12)
    + lsb_reg = lsb << ADT7316_DA_12_BIT_LSB_SHIFT;
    + else
    + lsb_reg = lsb << ADT7316_DA_10_BIT_LSB_SHIFT;
    ret = chip->bus.write(chip->bus.client,
    - ADT7316_DA_DATA_BASE + channel * 2, lsb);
    + ADT7316_DA_DATA_BASE + channel * 2, lsb_reg);
    if (ret)
    return -EIO;
    }

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