Re: [PATCH v2 1/5] gpio: sysfs: use cleanup guards for gpiod_data::mutex

[Kent Gibson <warthog618@xxxxxxxxx>]

On Fri, Oct 25, 2024 at 02:18:51PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
>
> Shrink the code and drop some goto labels by using lock guards around
> gpiod_data::mutex.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> ---
>  drivers/gpio/gpiolib-sysfs.c | 81 ++++++++++++++++----------------------------
>  1 file changed, 29 insertions(+), 52 deletions(-)
>
> @@ -139,19 +132,17 @@ static ssize_t value_store(struct device *dev,
>  	long value;
>
>  	status = kstrtol(buf, 0, &value);
> +	if (status)
> +		return status;
>
> -	mutex_lock(&data->mutex);
> +	guard(mutex)(&data->mutex);
>
> -	if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
> -		status = -EPERM;
> -	} else if (status == 0) {
> -		gpiod_set_value_cansleep(desc, value);
> -		status = size;
> -	}
> +	if (!test_bit(FLAG_IS_OUT, &desc->flags))
> +		return -EPERM;
>
> -	mutex_unlock(&data->mutex);
> +	gpiod_set_value_cansleep(desc, value);
>
> -	return status;
> +	return size;
>  }

This is a behavioural change as you've moved the decode check before the
permission check.  Not sure if that is significant or not, so in my
suggestion I retained the old order.

Cheers,
Kent.