linux-kernel - [PATCH 2/6] iio: adc: ti-adc128s052: Fix ADC value on BE systems

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Message-ID: <babe1eac3de30aa22e09266de1f5521fa9e0decd.1742474322.git.mazziesaccount@gmail.com>
Date: Mon, 31 Mar 2025 11:02:55 +0300
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>,
	Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc: Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matti Vaittinen <mazziesaccount@...il.com>,
	Nuno Sa <nuno.sa@...log.com>, David Lechner <dlechner@...libre.com>,
	Javier Carrasco <javier.carrasco.cruz@...il.com>,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/6] iio: adc: ti-adc128s052: Fix ADC value on BE systems

ADCs supported by the ti-adc128s052 driver do return the ADC data in 16
bits using big-endian format. The driver does unconditionally swap the
bytes. This leads to wrong values being reported to users on big endian
systems.

Fix this by using the be16_to_cpu() instead of doing unconditional byte
swapping.

Fixes: 913b86468674 ("iio: adc: Add TI ADC128S052")
Cc: stable@...r.kernel.org
Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
---
I have no big endian machines on my hands to test this. Problem was
spotted by reading the code, which leaves some room for errors.
Careful reviewing is appreciated!
---
 drivers/iio/adc/ti-adc128s052.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/adc/ti-adc128s052.c b/drivers/iio/adc/ti-adc128s052.c
index a456ea78462f..d1e31122ea0d 100644
--- a/drivers/iio/adc/ti-adc128s052.c
+++ b/drivers/iio/adc/ti-adc128s052.c
@@ -28,19 +28,20 @@ struct adc128 {
 	struct regulator *reg;
 	struct mutex lock;
 
-	u8 buffer[2] __aligned(IIO_DMA_MINALIGN);
+	__be16 buffer __aligned(IIO_DMA_MINALIGN);
 };
 
 static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
 {
 	int ret;
+	char *msg = (char *)&adc->buffer;
 
-	mutex_lock(&adc->lock);
+	msg[0] = channel << 3;
+	msg[1] = 0;
 
-	adc->buffer[0] = channel << 3;
-	adc->buffer[1] = 0;
+	mutex_lock(&adc->lock);
 
-	ret = spi_write(adc->spi, &adc->buffer, 2);
+	ret = spi_write(adc->spi, msg, 2);
 	if (ret < 0) {
 		mutex_unlock(&adc->lock);
 		return ret;
@@ -53,7 +54,7 @@ static int adc128_adc_conversion(struct adc128 *adc, u8 channel)
 	if (ret < 0)
 		return ret;
 
-	return ((adc->buffer[0] << 8 | adc->buffer[1]) & 0xFFF);
+	return be16_to_cpu(adc->buffer) & 0xFFF;
 }
 
 static int adc128_read_raw(struct iio_dev *indio_dev,
-- 
2.48.1


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