Re: [PATCH v3] iio: adc: ad7280a: replace mutex_lock() with guard(mutex)

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Thu, Apr 02, 2026 at 12:15:06AM -0300, Matheus Giarola wrote:
> Use guard(mutex) instead of mutex_lock()/mutex_unlock(),
> ensuring the mutex is released automatically when leaving
> the function scope. The change improves error handling and
> avoids issues such as missing unlocks. It also simplifies the
> code by removing 'err_unlock' label and several mutex_unlock()
> calls.
> 
> As suggested, in ad7280_read_raw(), wrap the IIO_CHAN_INFO_RAW
> case in braces, providing a scope for the implicit variable
> declared by guard(mutex).

...

> static ssize_t ad7280_show_balance_timer(struct iio_dev *indio_dev,

>  	unsigned int msecs;
>  	int ret;
>  
> -	mutex_lock(&st->lock);
> +	guard(mutex)(&st->lock);
>  	ret = ad7280_read_reg(st, chan->address >> 8,
>  			      (chan->address & 0xFF) + AD7280A_CB1_TIMER_REG);
> -	mutex_unlock(&st->lock);
>  
>  	if (ret < 0)
>  		return ret;

This will include the sysfs_emit() and other things in the critical section. Why?

...

> static int ad7280_read_raw(struct iio_dev *indio_dev,

>  	switch (m) {
> -	case IIO_CHAN_INFO_RAW:
> -		mutex_lock(&st->lock);
> +	case IIO_CHAN_INFO_RAW: {
> +		guard(mutex)(&st->lock);
>  		if (chan->address == AD7280A_ALL_CELLS)
>  			ret = ad7280_read_all_channels(st, st->scan_cnt, NULL);
>  		else
>  			ret = ad7280_read_channel(st, chan->address >> 8,
>  						  chan->address & 0xFF);
> -		mutex_unlock(&st->lock);
>  
>  		if (ret < 0)
>  			return ret;

>  		*val = ret;

This also will be under the lock, but it's fine.

>  		return IIO_VAL_INT;
> +	}

-- 
With Best Regards,
Andy Shevchenko