iio: dac: ds4424: reject -128 RAW value

commit 5187e03b817c26c1c3bcb2645a612ea935c4be89 upstream.

The DS442x DAC uses sign-magnitude encoding, so -128 cannot be represented
in hardware (7-bit magnitude).

Previously, passing -128 resulted in a truncated value that programmed
0mA (magnitude 0) instead of the expected maximum negative current,
effectively failing silently.

Reject -128 to avoid producing the wrong current.

Fixes: d632a2bd8ffc ("iio: dac: ds4422/ds4424 dac driver")
Cc: stable@vger.kernel.org
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/dac/ds4424.c b/drivers/iio/dac/ds4424.c
index a8198ba4f98a625b93803b3c30605485a1e98866..059acca45f64fa187726f31dcd077b8cffe674f2 100644 (file)
--- a/drivers/iio/dac/ds4424.c
+++ b/drivers/iio/dac/ds4424.c
@@ -141,7 +141,7 @@ static int ds4424_write_raw(struct iio_dev *indio_dev,
 
        switch (mask) {
        case IIO_CHAN_INFO_RAW:
-               if (val < S8_MIN || val > S8_MAX)
+               if (val <= S8_MIN || val > S8_MAX)
                        return -EINVAL;
 
                if (val > 0) {