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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Alison Schofield <amsfield22@gmail.com>,
        Jonathan Cameron <jic23@kernel.org>,
        Sasha Levin <alexander.levin@verizon.com>
Subject: [PATCH 4.9 22/87] iio: pressure: ms5611: claim direct mode during oversampling changes
Date:   Mon, 13 Nov 2017 13:55:39 +0100
Message-Id: <20171113125617.423505106@linuxfoundation.org>
In-Reply-To: <20171113125615.304035578@linuxfoundation.org>
References: <20171113125615.304035578@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alison Schofield <amsfield22@gmail.com>


[ Upstream commit 3bc1abcddb24f55b9c251e03caa4f9bd22ff748b ]

Driver was checking for direct mode before changing oversampling
ratios, but was not locking it.  Use the claim/release helper
functions to guarantee the device stays in direct mode while the
oversampling ratios are being updated.  Continue to use the drivers
private state lock to protect against conflicting direct mode access
of the state data.

Signed-off-by: Alison Schofield <amsfield22@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/iio/pressure/ms5611_core.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/iio/pressure/ms5611_core.c
+++ b/drivers/iio/pressure/ms5611_core.c
@@ -308,6 +308,7 @@ static int ms5611_write_raw(struct iio_d
 {
 	struct ms5611_state *st = iio_priv(indio_dev);
 	const struct ms5611_osr *osr = NULL;
+	int ret;
 
 	if (mask != IIO_CHAN_INFO_OVERSAMPLING_RATIO)
 		return -EINVAL;
@@ -321,12 +322,11 @@ static int ms5611_write_raw(struct iio_d
 	if (!osr)
 		return -EINVAL;
 
-	mutex_lock(&st->lock);
+	ret = iio_device_claim_direct_mode(indio_dev);
+	if (ret)
+		return ret;
 
-	if (iio_buffer_enabled(indio_dev)) {
-		mutex_unlock(&st->lock);
-		return -EBUSY;
-	}
+	mutex_lock(&st->lock);
 
 	if (chan->type == IIO_TEMP)
 		st->temp_osr = osr;
@@ -334,6 +334,8 @@ static int ms5611_write_raw(struct iio_d
 		st->pressure_osr = osr;
 
 	mutex_unlock(&st->lock);
+	iio_device_release_direct_mode(indio_dev);
+
 	return 0;
 }
 

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