Re: [PATCH v2 4/5] iio: buffer: iio: core: move to the cleanup.h magic

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 23 Feb 2024 13:43:47 +0100
Nuno Sa <nuno.sa@analog.com> wrote:

> Use the new cleanup magic for handling mutexes in IIO. This allows us to
> greatly simplify some code paths.
> 
> Signed-off-by: Nuno Sa <nuno.sa@analog.com>

I think we can do more in here as a result of early returns being available.

> ---
>  drivers/iio/industrialio-buffer.c | 105 ++++++++++++++------------------------
>  1 file changed, 38 insertions(+), 67 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index b581a7e80566..ec6bc881cf13 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -10,6 +10,7 @@
>   * - Alternative access techniques?
>   */
>  #include <linux/anon_inodes.h>
> +#include <linux/cleanup.h>
>  #include <linux/kernel.h>
>  #include <linux/export.h>
>  #include <linux/device.h>
> @@ -533,28 +534,25 @@ static ssize_t iio_scan_el_store(struct device *dev,
>  	ret = kstrtobool(buf, &state);
>  	if (ret < 0)
>  		return ret;
> -	mutex_lock(&iio_dev_opaque->mlock);
> -	if (iio_buffer_is_active(buffer)) {
> -		ret = -EBUSY;
> -		goto error_ret;
> -	}
> +
> +	guard(mutex)(&iio_dev_opaque->mlock);
> +	if (iio_buffer_is_active(buffer))
> +		return -EBUSY;
> +
>  	ret = iio_scan_mask_query(indio_dev, buffer, this_attr->address);
>  	if (ret < 0)
> -		goto error_ret;
> +		return ret;

We could short cut this I think and end up with a simpler flow.
The early returns allow something like

	if (state && ret)  /* Nothing to do */
		return len;

	if (state)
  		ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
	else
		ret = iio_scan_mask_clear(buffer, this_attr->address);
	if (ret)
		return ret;

	return len;

>  	if (!state && ret) {
>  		ret = iio_scan_mask_clear(buffer, this_attr->address);
>  		if (ret)
> -			goto error_ret;
> +			return ret;
>  	} else if (state && !ret) {
>  		ret = iio_scan_mask_set(indio_dev, buffer, this_attr->address);
>  		if (ret)
> -			goto error_ret;
> +			return ret;
>  	}
>  
> -error_ret:
> -	mutex_unlock(&iio_dev_opaque->mlock);
> -
> -	return ret < 0 ? ret : len;
> +	return len;
>  }
>  



...

>  
> @@ -1326,21 +1305,19 @@ static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
>  	if (ret < 0)
>  		return ret;
>  
> -	mutex_lock(&iio_dev_opaque->mlock);
> +	guard(mutex)(&iio_dev_opaque->mlock);
>  
>  	/* Find out if it is in the list */
>  	inlist = iio_buffer_is_active(buffer);
>  	/* Already in desired state */
>  	if (inlist == requested_state)
> -		goto done;
> +		return len;
>  
>  	if (requested_state)
>  		ret = __iio_update_buffers(indio_dev, buffer, NULL);
>  	else
>  		ret = __iio_update_buffers(indio_dev, NULL, buffer);
>  
> -done:
> -	mutex_unlock(&iio_dev_opaque->mlock);
>  	return (ret < 0) ? ret : len;
Maybe just switch this for

	if (ret < 0)
		return ret;

	return len;

So it looks more like the new return len above?

>  }

>