linux-kernel - Re: [PATCH 2/4] iio: add processed write API

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Message-ID: <20250920125600.182971d9@jic23-huawei>
Date: Sat, 20 Sep 2025 12:56:00 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Romain Gantois <romain.gantois@...tlin.com>
Cc: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, David Lechner
 <dlechner@...libre.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-iio@...r.kernel.org
Subject: Re: [PATCH 2/4] iio: add processed write API

On Wed, 17 Sep 2025 17:46:00 +0200
Romain Gantois <romain.gantois@...tlin.com> wrote:

> Hello David,
> 
> On Tuesday, 16 September 2025 21:23:04 CEST David Lechner wrote:
> > On 9/16/25 5:24 AM, Romain Gantois wrote:  
> > > Add a function to allow IIO consumers to write a processed value to a  
> ...
> > > +		case IIO_VAL_FRACTIONAL:
> > > +			tmp_num = (s64)processed * (s64)scale_val2;
> > > +			tmp_den = scale_val;
> > > +			break;
> > > +		case IIO_VAL_FRACTIONAL_LOG2:
> > > +			tmp_num = (s64)processed << scale_val2;
> > > +			tmp_den = scale_val;
> > > +			break;
> > > +		default:
> > > +			return -EINVAL;
> > > +		}
> > > +
> > > +		tmp_den *= scale;
> > > +
> > > +		*raw = div64_s64(tmp_num, tmp_den);
> > > +	}  
> > 
> > It can be quite tricky to get all of these combinations right. I would
> > prefer if added some unit tests like we did in [1].
> > 
> > [1]:
> > https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=tes
> > ting&id=c732e60ee10ed0611a59513cbf9c8d35fbe7cf65  
> 
> Agreed, that would be nice, I'll look into it.
> 
> Thanks,
> 

Overall code looks fine to me but unit tests would indeed be great.
Thanks,

Jonathan