[PATCH v5 02/15] iio: adc: ad4134: Sign extend sample data

[Marcelo Schmitt <marcelo.schmitt@analog.com>]

Sign extend ADC sample data for correct delivery of negative ADC input
difference.

Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>
Fixes: e0bc6d7e2584 ("iio: adc: Initial support for AD4134")
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v5
- Initialized local variable with 0 to avoid build warns.

 drivers/iio/adc/ad4134.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad4134.c b/drivers/iio/adc/ad4134.c
index 8400c3934925..40b27b01f126 100644
--- a/drivers/iio/adc/ad4134.c
+++ b/drivers/iio/adc/ad4134.c
@@ -172,6 +172,7 @@ static int ad4134_data_read(struct ad4134_state *st, unsigned int reg,
 			    unsigned int *val)
 {
 	unsigned int i;
+	u32 sample = 0;
 	int ret;
 
 	/*
@@ -196,8 +197,9 @@ static int ad4134_data_read(struct ad4134_state *st, unsigned int reg,
 		 * Clock out data from all channels to avoid that.
 		 */
 		if (i == AD4134_VREG_CH(reg))
-			*val = get_unaligned_be24(st->rx_buf);
+			sample = get_unaligned_be24(st->rx_buf);
 	}
+	*val = sign_extend32(sample, AD4134_CHAN_PRECISION_BITS - 1);
 
 	return 0;
 }
-- 
2.53.0