linux-kernel - [PATCH v2 11/16] iio: adc: max1027: Prevent single channel accesses during buffer reads

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Message-Id: <20210902211437.503623-12-miquel.raynal@bootlin.com>
Date:   Thu,  2 Sep 2021 23:14:32 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Nuno Sa <Nuno.Sa@...log.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: [PATCH v2 11/16] iio: adc: max1027: Prevent single channel accesses during buffer reads

When hardware buffers are enabled (the cnvst pin being the trigger), one
should not mess with the device state by requesting a single channel
read.

There is already a iio_buffer_enabled() check in *_read_single_value()
to merely prevent this situation but the check is inconsistent since
buffers can be enabled after the if clause anyway. Instead, use the core
mutex by calling iio_device_claim/release_direct_mode().

Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 drivers/iio/adc/max1027.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
index f4cb5c75604b..57f62ea2d7aa 100644
--- a/drivers/iio/adc/max1027.c
+++ b/drivers/iio/adc/max1027.c
@@ -296,10 +296,9 @@ static int max1027_read_single_value(struct iio_dev *indio_dev,
 	int ret;
 	struct max1027_state *st = iio_priv(indio_dev);
 
-	if (iio_buffer_enabled(indio_dev)) {
-		dev_warn(&indio_dev->dev, "trigger mode already enabled");
-		return -EBUSY;
-	}
+	ret = iio_device_claim_direct_mode(indio_dev);
+	if (ret)
+		return ret;
 
 	/* Configure conversion register with the requested chan */
 	st->reg = MAX1027_CONV_REG | MAX1027_CHAN(chan->channel) |
@@ -325,6 +324,8 @@ static int max1027_read_single_value(struct iio_dev *indio_dev,
 	if (ret < 0)
 		return ret;
 
+	iio_device_release_direct_mode(indio_dev);
+
 	*val = be16_to_cpu(st->buffer[0]);
 
 	return IIO_VAL_INT;
-- 
2.27.0