[PATCH 5.15 182/570] iio: dac: ds4424: reject -128 RAW value

Greg Kroah-Hartman
2026-04-13T16:25:56Z

From: Oleksij Rempel <o.rempel@pengutronix.de>

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>
---
drivers/iio/dac/ds4424.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iio/dac/ds4424.c
+++ b/drivers/iio/dac/ds4424.c
@@ -141,7 +141,7 @@ static int ds4424_write_raw(struct iio_d

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) {