linux-kernel - Re: [PATCH v2 2/2] iio: light: Add support for APDS9306 Light Sensor

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Message-ID: <ZUEET34K7AOkFf4A@smile.fi.intel.com>
Date:   Tue, 31 Oct 2023 15:42:39 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Subhajit Ghosh <subhajit.ghosh@...aklogic.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Paul Gazzillo <paul@...zz.com>,
        Matt Ranostay <matt@...ostay.sg>,
        Stefan Windfeldt-Prytz <stefan.windfeldt-prytz@...s.com>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: light: Add support for APDS9306 Light Sensor

On Tue, Oct 31, 2023 at 02:07:46PM +0200, Matti Vaittinen wrote:
> On 10/31/23 12:38, Andy Shevchenko wrote:
> > On Tue, Oct 31, 2023 at 09:11:37AM +0200, Matti Vaittinen wrote:
> > > On 10/30/23 12:21, Matti Vaittinen wrote:
> > > > On 10/29/23 17:51, Matti Vaittinen wrote:
> > > > > On 10/28/23 18:20, Jonathan Cameron wrote:

...

> > > 	tmp = gts->max_scale;
> > > 
> > > 	rem = do_div(tmp, total_gain);
> > > 	if (total_gain > 1 && rem >= total_gain / 2)
> > > 		tmp += 1ULL;
> > 
> > ...which is NIH DIV_ROUND_CLOSEST_ULL()
> 
> There is a difference though. The DIV_ROUND_CLOSEST_ULL() does
> 
> tmp + total_gain / 2;
> 
> before division - which in theory may overflow.

Then you can fix it there for everybody, no?

-- 
With Best Regards,
Andy Shevchenko