Re: [PATCH] iio: chemical: sps30: Replace manual locking with RAII locking

[David Lechner <dlechner@baylibre.com>]

On 5/9/26 7:52 AM, Maxwell Doose wrote:
> Replace manual mutex_lock() and mutex_unlock() calls with the much newer
> guard(mutex)() and scoped_guard() macros to enable RAII patterns,
> modernize the driver, and to increase readability.
> 
> Signed-off-by: Maxwell Doose <m32285159@gmail.com>
> ---
>  drivers/iio/chemical/sps30.c | 60 +++++++++++++++++-------------------
>  1 file changed, 29 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/iio/chemical/sps30.c b/drivers/iio/chemical/sps30.c
> index a934bf0298dd..186dec4cfd78 100644
> --- a/drivers/iio/chemical/sps30.c
> +++ b/drivers/iio/chemical/sps30.c
> @@ -5,6 +5,7 @@
>   * Copyright (c) Tomasz Duszynski <tduszyns@gmail.com>
>   */
>  
> +#include <linux/cleanup.h>
>  #include <linux/crc8.h>
>  #include <linux/delay.h>
>  #include <linux/i2c.h>
> @@ -111,9 +112,9 @@ static irqreturn_t sps30_trigger_handler(int irq, void *p)
>  		aligned_s64 ts;
>  	} scan;
>  
> -	mutex_lock(&state->lock);
> -	ret = sps30_do_meas(state, scan.data, ARRAY_SIZE(scan.data));
> -	mutex_unlock(&state->lock);
> +	scoped_guard(mutex, &state->lock)
> +		ret = sps30_do_meas(state, scan.data, ARRAY_SIZE(scan.data));
> +
>  	if (ret)
>  		goto err;
>  
> @@ -136,23 +137,23 @@ static int sps30_read_raw(struct iio_dev *indio_dev,
>  	case IIO_CHAN_INFO_PROCESSED:
>  		switch (chan->type) {
>  		case IIO_MASSCONCENTRATION:
> -			mutex_lock(&state->lock);
> -			/* read up to the number of bytes actually needed */
> -			switch (chan->channel2) {
> -			case IIO_MOD_PM1:
> -				ret = sps30_do_meas(state, data, 1);
> -				break;
> -			case IIO_MOD_PM2P5:
> -				ret = sps30_do_meas(state, data, 2);
> -				break;
> -			case IIO_MOD_PM4:
> -				ret = sps30_do_meas(state, data, 3);
> -				break;
> -			case IIO_MOD_PM10:
> -				ret = sps30_do_meas(state, data, 4);
> -				break;

We can do it like this:

  		case IIO_MASSCONCENTRATION: {
			guard(mutex)(&state->lock);

			/* read up to the number of bytes actually needed */
			switch (chan->channel2) {
			case IIO_MOD_PM1:
				ret = sps30_do_meas(state, data, 1);
				break;
			case IIO_MOD_PM2P5:
				ret = sps30_do_meas(state, data, 2);
				break;
			case IIO_MOD_PM4:
				ret = sps30_do_meas(state, data, 3);
				break;
			case IIO_MOD_PM10:
				ret = sps30_do_meas(state, data, 4);
				break;
			default:
				return -EINVAL;
			}
			if (ret)
				return ret;

		
			*val = data[chan->address] / 100;
			*val2 = (data[chan->address] % 100) * 10000;

			return IIO_VAL_INT_PLUS_MICRO;
		}
		default:
			return -EINVAL;

Make less indent and we don't have to initialize ret at the start of
the function anymore.

> +			scoped_guard(mutex, &state->lock) {
> +				/* read up to the number of bytes actually needed */
> +				switch (chan->channel2) {
> +				case IIO_MOD_PM1:
> +					ret = sps30_do_meas(state, data, 1);
> +					break;
> +				case IIO_MOD_PM2P5:
> +					ret = sps30_do_meas(state, data, 2);
> +					break;
> +				case IIO_MOD_PM4:
> +					ret = sps30_do_meas(state, data, 3);
> +					break;
> +				case IIO_MOD_PM10:
> +					ret = sps30_do_meas(state, data, 4);
> +					break;
> +				}
>  			}
> -			mutex_unlock(&state->lock);
>  			if (ret)
>  				return ret;
>  
> @@ -197,9 +198,9 @@ static ssize_t start_cleaning_store(struct device *dev,
>  	if (kstrtoint(buf, 0, &val) || val != 1)
>  		return -EINVAL;
>  
> -	mutex_lock(&state->lock);
> -	ret = state->ops->clean_fan(state);
> -	mutex_unlock(&state->lock);
> +	scoped_guard(mutex, &state->lock)

Doesn't need to be scoped. there is just return after this.

> +		ret = state->ops->clean_fan(state);
> +
>  	if (ret)
>  		return ret;
>  
> @@ -215,9 +216,9 @@ static ssize_t cleaning_period_show(struct device *dev,
>  	__be32 val;
>  	int ret;
>  
> -	mutex_lock(&state->lock);
> -	ret = state->ops->read_cleaning_period(state, &val);
> -	mutex_unlock(&state->lock);
> +	scoped_guard(mutex, &state->lock)
> +		ret = state->ops->read_cleaning_period(state, &val);
> +

IMHO, this one just make the code uglier, not really an improvement.

>  	if (ret)
>  		return ret;
>