Re: [PATCH v2 02/27] iio: chemical: scd30: Use guard(mutex) to allow early returns

["Nuno Sá" <noname.nuno@gmail.com>]

On Sun, 2025-02-09 at 18:05 +0000, Jonathan Cameron wrote:
> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> Auto cleanup based release of the lock allows for simpler code flow in a
> few functions with large multiplexing style switch statements and no
> common operations following the switch.
> 
> Suggested-by: David Lechner <dlechner@baylibre.com>
> Cc: Tomasz Duszynski <tomasz.duszynski@octakon.com>
> Reviewed-by: David Lechner <dlechner@baylibre.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> ---
> v2: Fix include ordering (David)
> ---
>  drivers/iio/chemical/scd30_core.c | 63 ++++++++++++++-----------------
>  include/linux/iio/iio.h           |  1 +
>  2 files changed, 29 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/iio/chemical/scd30_core.c
> b/drivers/iio/chemical/scd30_core.c
> index d613c54cb28d..23ba46f7ca32 100644
> --- a/drivers/iio/chemical/scd30_core.c
> +++ b/drivers/iio/chemical/scd30_core.c
> @@ -5,6 +5,7 @@
>   * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
>   */
>  #include <linux/bits.h>
> +#include <linux/cleanup.h>
>  #include <linux/completion.h>
>  #include <linux/delay.h>
>  #include <linux/device.h>
> @@ -198,112 +199,104 @@ static int scd30_read_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const
>  			  int *val, int *val2, long mask)
>  {
>  	struct scd30_state *state = iio_priv(indio_dev);
> -	int ret = -EINVAL;
> +	int ret;
>  	u16 tmp;
>  
> -	mutex_lock(&state->lock);
> +	guard(mutex)(&state->lock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_RAW:
>  	case IIO_CHAN_INFO_PROCESSED:
>  		if (chan->output) {
>  			*val = state->pressure_comp;
> -			ret = IIO_VAL_INT;
> -			break;
> +			return IIO_VAL_INT;
>  		}
>  
>  		ret = iio_device_claim_direct_mode(indio_dev);
>  		if (ret)
> -			break;
> +			return ret;
>  
>  		ret = scd30_read(state);
>  		if (ret) {
>  			iio_device_release_direct_mode(indio_dev);
> -			break;
> +			return ret;
>  		}
>  
>  		*val = state->meas[chan->address];
>  		iio_device_release_direct_mode(indio_dev);
> -		ret = IIO_VAL_INT;
> -		break;
> +		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_SCALE:
>  		*val = 0;
>  		*val2 = 1;
> -		ret = IIO_VAL_INT_PLUS_MICRO;
> -		break;
> +		return IIO_VAL_INT_PLUS_MICRO;
>  	case IIO_CHAN_INFO_SAMP_FREQ:
>  		ret = scd30_command_read(state, CMD_MEAS_INTERVAL, &tmp);
>  		if (ret)
> -			break;
> +			return ret;
>  
>  		*val = 0;
>  		*val2 = 1000000000 / tmp;
> -		ret = IIO_VAL_INT_PLUS_NANO;
> -		break;
> +		return IIO_VAL_INT_PLUS_NANO;
>  	case IIO_CHAN_INFO_CALIBBIAS:
>  		ret = scd30_command_read(state, CMD_TEMP_OFFSET, &tmp);
>  		if (ret)
> -			break;
> +			return ret;
>  
>  		*val = tmp;
> -		ret = IIO_VAL_INT;
> -		break;
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
>  	}
> -	mutex_unlock(&state->lock);
> -
> -	return ret;
>  }
>  
>  static int scd30_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec
> const *chan,
>  			   int val, int val2, long mask)
>  {
>  	struct scd30_state *state = iio_priv(indio_dev);
> -	int ret = -EINVAL;
> +	int ret;
>  
> -	mutex_lock(&state->lock);
> +	guard(mutex)(&state->lock);
>  	switch (mask) {
>  	case IIO_CHAN_INFO_SAMP_FREQ:
>  		if (val)
> -			break;
> +			return -EINVAL;
>  
>  		val = 1000000000 / val2;
>  		if (val < SCD30_MEAS_INTERVAL_MIN_S || val >
> SCD30_MEAS_INTERVAL_MAX_S)
> -			break;
> +			return -EINVAL;
>  
>  		ret = scd30_command_write(state, CMD_MEAS_INTERVAL, val);
>  		if (ret)
> -			break;
> +			return ret;
>  
>  		state->meas_interval = val;
> -		break;
> +		return 0;
>  	case IIO_CHAN_INFO_RAW:
>  		switch (chan->type) {
>  		case IIO_PRESSURE:
>  			if (val < SCD30_PRESSURE_COMP_MIN_MBAR ||
>  			    val > SCD30_PRESSURE_COMP_MAX_MBAR)
> -				break;
> +				return -EINVAL;
>  
>  			ret = scd30_command_write(state, CMD_START_MEAS,
> val);
>  			if (ret)
> -				break;
> +				return ret;
>  
>  			state->pressure_comp = val;
> -			break;
> +			return 0;
>  		default:
> -			break;
> +			return -EINVAL;
>  		}
> -		break;
>  	case IIO_CHAN_INFO_CALIBBIAS:
>  		if (val < 0 || val > SCD30_TEMP_OFFSET_MAX)
> -			break;
> +			return -EINVAL;
>  		/*
>  		 * Manufacturer does not explicitly specify min/max sensible
>  		 * values hence check is omitted for simplicity.
>  		 */
> -		ret = scd30_command_write(state, CMD_TEMP_OFFSET / 10, val);
> +		return scd30_command_write(state, CMD_TEMP_OFFSET / 10, val);
> +	default:
> +		return -EINVAL;
>  	}
> -	mutex_unlock(&state->lock);
> -
> -	return ret;
>  }
>  
>  static int scd30_write_raw_get_fmt(struct iio_dev *indio_dev, struct
> iio_chan_spec const *chan,
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index fe33835b19cf..5ed03e36178f 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -10,6 +10,7 @@
>  #include <linux/device.h>
>  #include <linux/cdev.h>
>  #include <linux/cleanup.h>
> +#include <linux/compiler_types.h>

Hmm, here it is... I guess some messed rebase and squash :)

- Nuno Sá