Re: [PATCH] iio: adc: mcp320x: Use guard(mutex) for lock handling

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 22 Apr 2026 18:11:05 -0300
Eduardo Augusto <eduardoaugustoabc@ime.usp.br> wrote:

> Replace the explicit mutex_lock() and mutex_unlock() calls in
> mcp320x_read_raw() with guard(mutex)().
> 
> This simplifies the error handling paths by removing the need for
> the explicit unlock label while keeping the locking semantics
> unchanged.
> 
> Signed-off-by: Eduardo Augusto <eduardoaugustoabc@ime.usp.br>
> Co-developed-by: Gustavo Pagnotta Faria <gustavo.pagnotta@ime.usp.br>
> Signed-off-by: Gustavo Pagnotta Faria <gustavo.pagnotta@ime.usp.br>
> Co-developed-by: Christian Barry <christian.barry@ime.usp.br>
> Signed-off-by: Christian Barry <christian.barry@ime.usp.br>
> ---
>  drivers/iio/adc/mcp320x.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
> index 57cff3772..799756f4c 100644
> --- a/drivers/iio/adc/mcp320x.c
> +++ b/drivers/iio/adc/mcp320x.c
> @@ -44,6 +44,7 @@
>  #include <linux/mod_devicetable.h>
>  #include <linux/iio/iio.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/cleanup.h>
>  
>  enum {
>  	mcp3001,
> @@ -198,8 +199,7 @@ static int mcp320x_read_raw(struct iio_dev *indio_dev,
>  	struct mcp320x *adc = iio_priv(indio_dev);
>  	int ret = -EINVAL;
>  	int device_index = 0;
> -
> -	mutex_lock(&adc->lock);
> +	guard(mutex)(&adc->lock);
>  
>  	device_index = spi_get_device_id(adc->spi)->driver_data;
>  
> @@ -208,7 +208,7 @@ static int mcp320x_read_raw(struct iio_dev *indio_dev,
>  		ret = mcp320x_adc_conversion(adc, channel->address,
>  			channel->differential, device_index, val);
>  		if (ret < 0)
> -			goto out;
> +			return ret;
>  
>  		ret = IIO_VAL_INT;
>  		break;
> @@ -216,7 +216,7 @@ static int mcp320x_read_raw(struct iio_dev *indio_dev,
>  	case IIO_CHAN_INFO_SCALE:
>  		ret = regulator_get_voltage(adc->reg);
>  		if (ret < 0)
> -			goto out;
> +			return ret;
>  
>  		/* convert regulator output voltage to mV */
>  		*val = ret / 1000;
> @@ -225,9 +225,6 @@ static int mcp320x_read_raw(struct iio_dev *indio_dev,
>  		break;
>  	}
>  
> -out:
> -	mutex_unlock(&adc->lock);
> -
>  	return ret;
Can do early returns now in all branches.  As Andy said, check for
reviews of similar code that has been posted recently.

If anyone who is doing this sort of work feels like taking the
combined feedback from those reviewing and writing a doc with examples
etc that would be great.  Maybe a blog or similar or we could see
if we could find a home for it in tree.

Too many patches to review for Andy or I to have the time, though
maybe when things calm down a bit...

Jonathan

>  }
>