linux-kernel - [PATCH v1 04/15] iio: adc: ad7768-1: Fix conversion result sign

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Message-ID: <e521bb5cb60d413edbcd1ea582fd81073218eaf5.1736201898.git.Jonathan.Santos@analog.com>
Date: Tue, 7 Jan 2025 12:25:07 -0300
From: Jonathan Santos <Jonathan.Santos@...log.com>
To: <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC: Sergiu Cuciurean <sergiu.cuciurean@...log.com>, <lars@...afoo.de>,
        <Michael.Hennerich@...log.com>, <jic23@...nel.org>, <robh@...nel.org>,
        <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
        <marcelo.schmitt1@...il.com>
Subject: [PATCH v1 04/15] iio: adc: ad7768-1: Fix conversion result sign

From: Sergiu Cuciurean <sergiu.cuciurean@...log.com>

The ad7768-1 is a fully differential ADC, meaning that the voltage
conversion result is a signed value. Since the value is a 24 bit one,
stored in a 32 bit variable, the sign should be extended in order to get
the correct representation.

Also the channel description has been updated to signed representation,
to match the ADC specifications.

Fixes: a5f8c7da3dbe ("iio: adc: Add AD7768-1 ADC basic support")
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
---
 drivers/iio/adc/ad7768-1.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 113703fb7245..c3cf04311c40 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -142,7 +142,7 @@ static const struct iio_chan_spec ad7768_channels[] = {
 		.channel = 0,
 		.scan_index = 0,
 		.scan_type = {
-			.sign = 'u',
+			.sign = 's',
 			.realbits = 24,
 			.storagebits = 32,
 			.shift = 8,
@@ -371,7 +371,7 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
 
 		ret = ad7768_scan_direct(indio_dev);
 		if (ret >= 0)
-			*val = ret;
+			*val = sign_extend32(ret, chan->scan_type.realbits - 1);
 
 		iio_device_release_direct_mode(indio_dev);
 		if (ret < 0)
-- 
2.34.1