From 91908c0a78baddc8572aa3ab69e62ee2eb496ba4 Mon Sep 17 00:00:00 2001 From: Cong Nguyen Date: Mon, 10 Aug 2026 23:44:46 +0700 Subject: [PATCH] iio: adc: max1363: sign-extend bipolar differential channel reads MAX1363 differential channels are bipolar, but max1363_read_single_chan() masks the raw value to the ADC resolution without sign-extending it. Negative differential readings are therefore reported to userspace as large positive values (e.g. -1 as 4095 on a 12-bit part). Sign-extend the masked value from the resolution bit for differential channels. Single-ended channels are unipolar and are left unchanged. Fixes: d1325cf45077 ("Staging: IIO: max1363 ADC driver") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4 Signed-off-by: Cong Nguyen Reviewed-by: Andy Shevchenko Signed-off-by: Jonathan Cameron --- drivers/iio/adc/max1363.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c index 65a2d92bb112..629c53af6472 100644 --- a/drivers/iio/adc/max1363.c +++ b/drivers/iio/adc/max1363.c @@ -404,6 +404,14 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev, data = rxbuf[0]; } + + /* + * Differential channels are bipolar and the device returns the sample + * in two's complement, so sign-extend it from the resolution bit. + */ + if (chan->differential) + data = sign_extend32(data, st->chip_info->bits - 1); + *val = data; return 0;