Re: [PATCH v3 5/5] iio: imu: inv_icm42600: use guard() to release mutexes

[Jonathan Cameron <jic23@kernel.org>]

> ...
> 
> > @@ -299,7 +298,7 @@ static int inv_icm42600_buffer_postenable(struct iio_dev *indio_dev)
> >  	struct inv_icm42600_state *st = iio_device_get_drvdata(indio_dev);
> >  	int ret;
> >  
> > -	mutex_lock(&st->lock);
> > +	guard(mutex)(&st->lock);
> >  
> >  	/* exit if FIFO is already on */
> >  	if (st->fifo.on) {
> > @@ -311,30 +310,29 @@ static int inv_icm42600_buffer_postenable(struct iio_dev *indio_dev)
> >  	ret = regmap_set_bits(st->map, INV_ICM42600_REG_INT_SOURCE0,
> >  			      INV_ICM42600_INT_SOURCE0_FIFO_THS_INT1_EN);
> >  	if (ret)
> > -		goto out_unlock;
> > +		return ret;
> >  
> >  	/* flush FIFO data */
> >  	ret = regmap_write(st->map, INV_ICM42600_REG_SIGNAL_PATH_RESET,
> >  			   INV_ICM42600_SIGNAL_PATH_RESET_FIFO_FLUSH);
> >  	if (ret)
> > -		goto out_unlock;
> > +		return ret;
> >  
> >  	/* set FIFO in streaming mode */
> >  	ret = regmap_write(st->map, INV_ICM42600_REG_FIFO_CONFIG,
> >  			   INV_ICM42600_FIFO_CONFIG_STREAM);
> >  	if (ret)
> > -		goto out_unlock;
> > +		return ret;
> >  
> >  	/* workaround: first read of FIFO count after reset is always 0 */
> >  	ret = regmap_bulk_read(st->map, INV_ICM42600_REG_FIFO_COUNT, st->buffer, 2);
> >  	if (ret)
> > -		goto out_unlock;
> > +		return ret;
> >  
> >  out_on:
> >  	/* increase FIFO on counter */
> >  	st->fifo.on++;  
> 
> I would be tempted to get rid of out_on as well even if we have to repeat
> `st->fifo.on++;` in two places.

There is strong guidance in cleanup.h on basically never mixing gotos
and cleanup (including guard).  It is probably fine here but some compilers
(gcc) are very bad at detecting uninitialized conditions that can happen with
gotos.  More generally Linus has expressed that if you need to mix the two
cleanup.h magic is not appropriate. Following David's suggestion the problem
is solved through duplication of that increment.

> 
> > -out_unlock:
> > -	mutex_unlock(&st->lock);
> > +
> >  	return ret;  
> 
> Can just return 0 here and simplify if (st->fifo.on).