linux-kernel - Re: [PATCH v11 11/15] iio: test: add basic tests for the iio-rescale driver

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Date:   Wed, 22 Dec 2021 14:38:13 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Liam Beguin <liambeguin@...il.com>
Cc:     Peter Rosin <peda@...ntia.se>, Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v11 11/15] iio: test: add basic tests for the iio-rescale driver

On Wed, Dec 22, 2021 at 5:47 AM Liam Beguin <liambeguin@...il.com> wrote:
>
> From: Liam Beguin <lvb@...hos.com>
>
> The iio-rescale driver supports various combinations of scale types and
> offsets. These can often result in large integer multiplications. Make
> sure these calculations are done right by adding a set of kunit test
> cases that build on top of iio-test-format.

...

> +       int fract_mult = 100000000LL;

Perhaps also change to use the prefix?

...

> +       *nano = (s64)tmp * 10 * fract_mult + tmp2;

I'm also puzzled what the meaning of the 10 is here?

...

> +       err = 1000000 * abs(exp - real);

Prefix?

...

> +       err = div64_u64(err, abs(exp));
> +       return (int)err;

return div64_u64();

-- 
With Best Regards,
Andy Shevchenko