linux-kernel - Re: [PATCH v10 03/14] iio: inkern: make a best effort on offset calculation

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Message-ID: <YcIT3BSIKJKVWAgN@shaak>
Date:   Tue, 21 Dec 2021 12:50:20 -0500
From:   Liam Beguin <liambeguin@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...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 v10 03/14] iio: inkern: make a best effort on offset
 calculation

Hi Andy,

On Tue, Dec 21, 2021 at 07:42:31AM +0200, Andy Shevchenko wrote:
> On Mon, Dec 20, 2021 at 11:17 AM Liam Beguin <liambeguin@...il.com> wrote:
> >
> > From: Liam Beguin <lvb@...hos.com>
> >
> > iio_convert_raw_to_processed_unlocked() assumes the offset is an
> > integer. Make a best effort to get a valid offset value for fractional
> > cases without breaking implicit truncations.
> 
> ...
> 
> > +                       offset_val /= (1 << offset_val2);
> 
> Besides potentially being problematic (if arg is 31 for the left
> shift) why not simply
> 
> _val >>= _val2;

That is safer, and more elegant! I'll update.

Thanks,
Liam

> --
> With Best Regards,
> Andy Shevchenko