[PATCH 11/15] iio: common: scmi_iio: do not use internal iio_dev lock

[Jonathan Cameron]

On Tue, 20 Sep 2022 13:28:17 +0200
Nuno Sá <nuno.sa at analog.com> wrote:

> The iio_device lock is only meant for internal use. Hence define a
> device local lock to protect against concurrent accesses.
> 
> Signed-off-by: Nuno Sá <nuno.sa at analog.com>
Ouch - this driver is fairly new and I missed that it was using mlock.
I guess this is a good example of why we need to finishing hiding it away!

Patch looks fine to me - I'll pick up in v2.

Jonathan

> ---
>  drivers/iio/common/scmi_sensors/scmi_iio.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/common/scmi_sensors/scmi_iio.c b/drivers/iio/common/scmi_sensors/scmi_iio.c
> index 54ccf19ab2bb..d92f7f651f7b 100644
> --- a/drivers/iio/common/scmi_sensors/scmi_iio.c
> +++ b/drivers/iio/common/scmi_sensors/scmi_iio.c
> @@ -15,6 +15,7 @@
>  #include <linux/kernel.h>
>  #include <linux/kthread.h>
>  #include <linux/module.h>
> +#include <linux/mutex.h>
>  #include <linux/scmi_protocol.h>
>  #include <linux/time.h>
>  #include <linux/types.h>
> @@ -27,6 +28,8 @@ struct scmi_iio_priv {
>  	struct scmi_protocol_handle *ph;
>  	const struct scmi_sensor_info *sensor_info;
>  	struct iio_dev *indio_dev;
> +	/* lock to protect against multiple access to the device */
> +	struct mutex lock;
>  	/* adding one additional channel for timestamp */
>  	s64 iio_buf[SCMI_IIO_NUM_OF_AXIS + 1];
>  	struct notifier_block sensor_update_nb;
> @@ -198,13 +201,14 @@ static int scmi_iio_write_raw(struct iio_dev *iio_dev,
>  			      struct iio_chan_spec const *chan, int val,
>  			      int val2, long mask)
>  {
> +	struct scmi_iio_priv *sensor = iio_priv(iio_dev);
>  	int err;
>  
>  	switch (mask) {
>  	case IIO_CHAN_INFO_SAMP_FREQ:
> -		mutex_lock(&iio_dev->mlock);
> +		mutex_lock(&sensor->lock);
>  		err = scmi_iio_set_odr_val(iio_dev, val, val2);
> -		mutex_unlock(&iio_dev->mlock);
> +		mutex_unlock(&sensor->lock);
>  		return err;
>  	default:
>  		return -EINVAL;
> @@ -586,6 +590,7 @@ scmi_alloc_iiodev(struct scmi_device *sdev,
>  	sensor->sensor_info = sensor_info;
>  	sensor->sensor_update_nb.notifier_call = scmi_iio_sensor_update_cb;
>  	sensor->indio_dev = iiodev;
> +	mutex_init(&sensor->lock);
>  
>  	/* adding one additional channel for timestamp */
>  	iiodev->num_channels = sensor_info->num_axis + 1;