linux-kernel - Re: [PATCH v5 3/3] drivers: iio: adc: add support for ad777x family

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Message-ID: <20240914174653.1c8788de@jic23-huawei>
Date: Sat, 14 Sep 2024 17:46:53 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Ramona Alexandra Nechita <ramona.nechita@...log.com>, Lars-Peter Clausen
 <lars@...afoo.de>, Cosmin Tanislav <cosmin.tanislav@...log.com>, Michael
 Hennerich <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Nuno Sa <nuno.sa@...log.com>, Andy Shevchenko
 <andy@...nel.org>, David Lechner <dlechner@...libre.com>, Marcelo Schmitt
 <marcelo.schmitt@...log.com>, Olivier Moysan <olivier.moysan@...s.st.com>,
 Dumitru Ceclan <mitrutzceclan@...il.com>, Matteo Martelli
 <matteomartelli3@...il.com>, AngeloGioacchino Del Regno
 <angelogioacchino.delregno@...labora.com>, Alisa-Dariana Roman
 <alisadariana@...il.com>, Ivan Mikhaylov <fr0st61te@...il.com>, Mike
 Looijmans <mike.looijmans@...ic.nl>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v5 3/3] drivers: iio: adc: add support for ad777x family


> ...
> 
> > +       iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
> > +               switch (mask) {
> > +               case IIO_CHAN_INFO_CALIBSCALE:
> > +                       *val = ad7779_get_calibscale(st, chan->channel);
> > +                       if (*val < 0)
> > +                               return -EINVAL;
> > +                       *val2 = GAIN_REL;
> > +                       return IIO_VAL_FRACTIONAL;
> > +               case IIO_CHAN_INFO_CALIBBIAS:
> > +                       *val = ad7779_get_calibbias(st, chan->channel);
> > +                       if (*val < 0)
> > +                               return -EINVAL;
> > +                       return IIO_VAL_INT;
> > +               case IIO_CHAN_INFO_SAMP_FREQ:
> > +                       *val = st->sampling_freq;
> > +                       if (*val < 0)
> > +                               return -EINVAL;
> > +                       return IIO_VAL_INT;
> > +               }
> > +               return -EINVAL;
> > +       }  
> 
> > +       unreachable();  
> 
> Hmm... Is it necessary? Same Q for other similar cases. I.o.w. what
> will be if we don't add this line?

The compiler can't tell that the contents of iio_device_claim_direct_scoped()
always runs.  Hence normal result is it complains that nothing was returned.

Why the compiler can't figure out?  Who knows... 

Jonathan