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Subject[PATCH v2] iio: adc: fsl-imx25-gcq: Replace indio_dev->mlock with own device lock
Date
From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock, to protect against any other accesses during the
reading of sample. Reading a sample requires multiple consecutive regmap
operations and a completion callback, so this requires that no other
read occurs until it completes.

This is part of a bigger cleanup.
Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/

Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
drivers/iio/adc/fsl-imx25-gcq.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/fsl-imx25-gcq.c b/drivers/iio/adc/fsl-imx25-gcq.c
index 8cb51cf7a816..ab5139e911c3 100644
--- a/drivers/iio/adc/fsl-imx25-gcq.c
+++ b/drivers/iio/adc/fsl-imx25-gcq.c
@@ -40,6 +40,15 @@ struct mx25_gcq_priv {
int irq;
struct regulator *vref[4];
u32 channel_vref_mv[MX25_NUM_CFGS];
+ /*
+ * Lock to protect the device state during a potential concurrent
+ * read access from userspace. Reading a raw value requires a sequence
+ * of register writes, then a wait for a completion callback,
+ * and finally a register read, during which userspace could issue
+ * another read request. This lock protects a read access from
+ * ocurring before another one has finished.
+ */
+ struct mutex lock;
};

#define MX25_CQG_CHAN(chan, id) {\
@@ -137,9 +146,9 @@ static int mx25_gcq_read_raw(struct iio_dev *indio_dev,

switch (mask) {
case IIO_CHAN_INFO_RAW:
- mutex_lock(&indio_dev->mlock);
+ mutex_lock(&priv->lock);
ret = mx25_gcq_get_raw_value(&indio_dev->dev, chan, priv, val);
- mutex_unlock(&indio_dev->mlock);
+ mutex_unlock(&priv->lock);
return ret;

case IIO_CHAN_INFO_SCALE:
@@ -314,6 +323,8 @@ static int mx25_gcq_probe(struct platform_device *pdev)
return PTR_ERR(priv->regs);
}

+ mutex_init(&priv->lock);
+
init_completion(&priv->completed);

ret = mx25_gcq_setup_cfgs(pdev, priv);
--
2.17.1
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