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

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 25 Mar 2026 16:21:04 -0300
Matheus Giarola <matheustpgiarola@gmail.com> wrote:

> On Sat, Mar 21, 2026 at 12:55 PM Jonathan Cameron <jic23@kernel.org> wrote:
> >
> > On Thu, 19 Mar 2026 15:46:15 -0300
> > Matheus Giarola <matheustpgiarola@gmail.com> 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.
> > >
> > > Signed-off-by: Matheus Giarola <matheusgiarola@usp.br>  
> > Hi Matheus.
> >
> >  
> > > @@ -885,13 +875,12 @@ static int ad7280_read_raw(struct iio_dev *indio_dev,
> > >
> > >       switch (m) {
> > >       case IIO_CHAN_INFO_RAW:
> > > -             mutex_lock(&st->lock);
> > > +             guard(mutex)(&st->lock);  
> >
> > Scope missing...
> >
> > Thanks,
> >
> > Jonathan  
> 
> Hi Jonathan,
> 
> Thank you for the review and pointing out the missing scope, I'll fix
> it by using
> scoped_guard() to ensure the lock is released at the right time.
nope.  Whilst that would be correct it's not the nicest solution.
Instead do what you'd do if there was a variable declared in a case
block..
	case IIO_CHAN_INFO_RAW: {
		guard(...)(..);
...



	}

Under the hood guard is declaring a local variable.

> 
> I'm a bit busy with university work this week, so at most by next week I'll send
> a v2 of this patch.
> 
> Best regards,
> 
> Matheus
> >  
> > >               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;  
> >