linux-kernel - Re: [PATCH v2 2/5] iio: add processed write API

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Message-ID: <20250928100757.0fa73692@jic23-huawei>
Date: Sun, 28 Sep 2025 10:07:57 +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>, David Lechner <dlechner@...libre.com>,
 Nuno Sá <nuno.sa@...log.com>, Andy Shevchenko
 <andy@...nel.org>, Hans de Goede <hansg@...nel.org>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH v2 2/5] iio: add processed write API

On Thu, 25 Sep 2025 14:37:34 +0200
Romain Gantois <romain.gantois@...tlin.com> wrote:

> Add a function to allow IIO consumers to write a processed value to a
> channel.
> 
> Signed-off-by: Romain Gantois <romain.gantois@...tlin.com>
Just one trivial thing I noticed.
Thanks for adding the unit tests btw.  Makes me much more confident we don't have
the corner case sign errors that plagued the similar functions before unit tests and fixes
were applied.

J
> ---
>  drivers/iio/inkern.c         | 120 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/iio/consumer.h |  36 +++++++++++++
>  2 files changed, 156 insertions(+)
> 
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 2a1ecef2b82007f5ee8e8d0f8b35846bc4d2f94a..a6ec724b7c1fb197e6261c1162f8315deda20fd7 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -631,6 +631,57 @@ int iio_multiply_value(int *result, s64 multiplier,
>  }
>  EXPORT_SYMBOL_GPL(iio_multiply_value);
>  
> +int iio_divide_by_value(int *result, s64 numerator,
> +			unsigned int type, int val, int val2)
> +{
> +	s64 tmp_num, tmp_den;
> +
> +	switch (type) {
> +	case IIO_VAL_INT:
> +		tmp_num = numerator;
> +		tmp_den = val;
> +		break;
> +	case IIO_VAL_INT_PLUS_MICRO:
> +	case IIO_VAL_INT_PLUS_NANO:
> +		switch (type) {
> +		case IIO_VAL_INT_PLUS_MICRO:
> +			tmp_num = MICRO;
> +			tmp_den = MICRO;
> +			break;
> +
> +		case IIO_VAL_INT_PLUS_NANO:
> +			tmp_num = NANO;
> +			tmp_den = NANO;
> +			break;
> +		}
> +
> +		tmp_num *= (s64)numerator;

Seems to be casting an s64 to an s64.

> +		tmp_den = (s64)abs(val) * tmp_den + (s64)abs(val2);
> +
> +		if (val < 0 || val2 < 0)
> +			tmp_num *= -1;
> +
> +		break;
> +	case IIO_VAL_FRACTIONAL:
> +		tmp_num = (s64)numerator * (s64)val2;
> +		tmp_den = val;
> +		break;
> +	case IIO_VAL_FRACTIONAL_LOG2:
> +		tmp_num = (s64)numerator << val2;
> +		tmp_den = val;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	if (!tmp_den)
> +		return -ERANGE;
> +
> +	*result = div64_s64(tmp_num, tmp_den);
> +
> +	return IIO_VAL_INT;
> +}