Re: [Outreachy kernel] [PATCH v6] staging: Use buf_lock instead of mlock and Refactor code

[Alison Schofield]

On Mon, Mar 20, 2017 at 01:36:21AM +0530, simran singhal wrote:

Hi Simran,  

I going to ask for a v7 without looking at the code ;)
Subject line needs subsystem and driver.
Subject and log message can be improved.

> 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 buf_lock in the devices global data.
           ^^^^^^^^^^^ this was not done
> 
> As buf_lock protects both the adis16060_spi_write() and
> adis16060_spi_read() functions and both are always called in
> pair. First write, then read. Thus, refactor the code to have
> one single function adis16060_spi_write_than_read() which is
> protected by the existing buf_lock.
This was done.  So, you were able to obsolete the need for mlock
by creating the paired function.

> 
> Removed nested locks as the function adis16060_read_raw call
> a lock on &st->buf_lock and then calls the function
> adis16060_spi_write which again tries to get hold
> of the same lock.
^^^^ this was not done.  Yes, you avoided nested locks through
proper coding, but we don't want to give the impression in the
log message that there was a pre-existing nested lock issue.

I did checkpatch & compile it...but looked no further yet.

alisons
> 
> Signed-off-by: simran singhal <singhalsimran0@xxxxxxxxx>
> ---
> 
>  v6:
>    -Change commit message
>    -Remove nested lock
> 
>  drivers/staging/iio/gyro/adis16060_core.c | 40 ++++++++++---------------------
>  1 file changed, 13 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/staging/iio/gyro/adis16060_core.c b/drivers/staging/iio/gyro/adis16060_core.c
> index c9d46e7..1c6de46 100644
> --- a/drivers/staging/iio/gyro/adis16060_core.c
> +++ b/drivers/staging/iio/gyro/adis16060_core.c
> @@ -40,25 +40,17 @@ struct adis16060_state {
>  
>  static struct iio_dev *adis16060_iio_dev;
>  
> -static int adis16060_spi_write(struct iio_dev *indio_dev, u8 val)
> +static int adis16060_spi_write_than_read(struct iio_dev *indio_dev,
> +					 u8 conf, u16 *val)
>  {
>  	int ret;
>  	struct adis16060_state *st = iio_priv(indio_dev);
>  
> -	mutex_lock(&st->buf_lock);
> -	st->buf[2] = val; /* The last 8 bits clocked in are latched */
> +	st->buf[2] = conf; /* The last 8 bits clocked in are latched */
>  	ret = spi_write(st->us_w, st->buf, 3);
> -	mutex_unlock(&st->buf_lock);
> -
> -	return ret;
> -}
> -
> -static int adis16060_spi_read(struct iio_dev *indio_dev, u16 *val)
> -{
> -	int ret;
> -	struct adis16060_state *st = iio_priv(indio_dev);
>  
> -	mutex_lock(&st->buf_lock);
> +	if (ret < 0)
> +		return ret;
>  
>  	ret = spi_read(st->us_r, st->buf, 3);
>  
> @@ -69,8 +61,8 @@ static int adis16060_spi_read(struct iio_dev *indio_dev, u16 *val)
>  	 */
>  	if (!ret)
>  		*val = ((st->buf[0] & 0x3) << 12) |
> -			(st->buf[1] << 4) |
> -			((st->buf[2] >> 4) & 0xF);
> +			 (st->buf[1] << 4) |
> +			 ((st->buf[2] >> 4) & 0xF);
>  	mutex_unlock(&st->buf_lock);
>  
>  	return ret;
> @@ -83,20 +75,18 @@ static int adis16060_read_raw(struct iio_dev *indio_dev,
>  {
>  	u16 tval = 0;
>  	int ret;
> +	struct adis16060_state *st = iio_priv(indio_dev);
>  
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
>  		/* Take the iio_dev status lock */
> -		mutex_lock(&indio_dev->mlock);
> -		ret = adis16060_spi_write(indio_dev, chan->address);
> +		mutex_lock(&st->buf_lock);
> +		ret = adis16060_spi_write_than_read(indio_dev,
> +						    chan->address, &tval);
> +		mutex_unlock(&st->buf_lock);
>  		if (ret < 0)
> -			goto out_unlock;
> +			return ret;
>  
> -		ret = adis16060_spi_read(indio_dev, &tval);
> -		if (ret < 0)
> -			goto out_unlock;
> -
> -		mutex_unlock(&indio_dev->mlock);
>  		*val = tval;
>  		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_OFFSET:
> @@ -110,10 +100,6 @@ static int adis16060_read_raw(struct iio_dev *indio_dev,
>  	}
>  
>  	return -EINVAL;
> -
> -out_unlock:
> -	mutex_unlock(&indio_dev->mlock);
> -	return ret;
>  }
>  
>  static const struct iio_info adis16060_info = {
> -- 
> 2.7.4
> 
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