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SubjectRe: [PATCH v2] iio: adc: fsl-imx25-gcq: Replace indio_dev->mlock with own device lock
On Wed, 16 Sep 2020 12:29:28 +0300
Alexandru Ardelean <alexandru.ardelean@analog.com> wrote:

> 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>
This seems simple enough so I've applied it to the togreg branch of iio.git

Thanks,

Jonathan

> ---
> 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);

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