linux-kernel - Re: [PATCH v3 2/2] staging: iio: ade7753: Replace mlock with driver private lock

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Date:   Wed, 22 Mar 2017 20:25:40 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     simran singhal <singhalsimran0@...il.com>, lars@...afoo.de
Cc:     Michael.Hennerich@...log.com, knaack.h@....de, pmeerw@...erw.net,
        gregkh@...uxfoundation.org, linux-iio@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        outreachy-kernel@...glegroups.com
Subject: Re: [PATCH v3 2/2] staging: iio: ade7753: Replace mlock with driver
 private lock

On 21/03/17 18:03, simran singhal wrote:
> The IIO subsystem is redefining iio_dev->mlock to be used by
> the IIO core only for protecting device operating mode changes.
> ie. Changes between INDIO_DIRECT_MODE, INDIO_BUFFER_* modes.
> 
> In this driver, mlock was being used to protect hardware state
> changes.  Replace it with a lock in the devices global data.
> 
> Signed-off-by: simran singhal <singhalsimran0@...il.com>
Mutex is not initialized...
> ---
>  drivers/staging/iio/meter/ade7753.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/iio/meter/ade7753.c b/drivers/staging/iio/meter/ade7753.c
> index b71fbd3..9674e05 100644
> --- a/drivers/staging/iio/meter/ade7753.c
> +++ b/drivers/staging/iio/meter/ade7753.c
> @@ -80,11 +80,13 @@
>   * @us:         actual spi_device
>   * @tx:         transmit buffer
>   * @rx:         receive buffer
> + * @lock:       protect sensor state
>   * @buf_lock:       mutex to protect tx and rx
>   **/
>  struct ade7753_state {
>  	struct spi_device   *us;
>  	struct mutex        buf_lock;
> +	struct mutex	    lock;  /* protect sensor state */
>  	u8          tx[ADE7753_MAX_TX] ____cacheline_aligned;
>  	u8          rx[ADE7753_MAX_RX];
>  };
> @@ -484,7 +486,7 @@ static ssize_t ade7753_write_frequency(struct device *dev,
>  	if (!val)
>  		return -EINVAL;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&st->lock);
>  
>  	t = 27900 / val;
>  	if (t > 0)
> @@ -505,7 +507,7 @@ static ssize_t ade7753_write_frequency(struct device *dev,
>  	ret = ade7753_spi_write_reg_16(dev, ADE7753_MODE, reg);
>  
>  out:
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&st->lock);
>  
>  	return ret ? ret : len;
>  }
>