From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Matti Vaittinen <mazziesaccount@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
Subhajit Ghosh <subhajit.ghosh@tweaklogic.com>,
Lars-Peter Clausen <lars@metafoo.de>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Conor Dooley <conor+dt@kernel.org>,
Paul Gazzillo <paul@pgazz.com>, Matt Ranostay <matt@ranostay.sg>,
Stefan Windfeldt-Prytz <stefan.windfeldt-prytz@axis.com>,
linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] iio: light: Add support for APDS9306 Light Sensor
Date: Thu, 2 Nov 2023 14:50:00 +0200 [thread overview]
Message-ID: <ZUOa-Ml7YdWoAXBe@smile.fi.intel.com> (raw)
In-Reply-To: <6d553aaa-279f-48bf-96c9-30fdac1ae372@gmail.com>
On Wed, Nov 01, 2023 at 08:16:32AM +0200, Matti Vaittinen wrote:
> On 10/31/23 15:42, Andy Shevchenko wrote:
> > 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?
>
> Now that I know of this macro - Maybe. It's just always scary to touch
> things which seem like fundamental building blocks and which may be used by
> many. Odds are something breaks, so I tend to be very conservative when
> suggesting changes to widely used stuff. Especially when I have no idea when
> and why the API has been added - and if the thing I'm trying to "fix" has
> been a deliberate choice.
Welcome to the club of the div overflow in macros discussion:
https://lore.kernel.org/linux-clk/20231024161931.78567-1-sebastian.reichel@collabora.com/T/#t
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2023-11-02 12:50 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-27 7:45 [PATCH v2 0/2] Support for Avago APDS9306 Ambient Light Sensor Subhajit Ghosh
2023-10-27 7:45 ` [PATCH v2 1/2] dt-bindings: iio: light: Avago APDS9306 Subhajit Ghosh
2023-10-27 8:11 ` Krzysztof Kozlowski
2023-10-27 8:55 ` Subhajit Ghosh
2023-10-27 11:03 ` Krzysztof Kozlowski
2023-10-28 13:29 ` Jonathan Cameron
2023-10-27 7:45 ` [PATCH v2 2/2] iio: light: Add support for APDS9306 Light Sensor Subhajit Ghosh
2023-10-27 8:13 ` Krzysztof Kozlowski
2023-10-27 8:42 ` Subhajit Ghosh
2023-10-27 11:04 ` Krzysztof Kozlowski
2023-10-27 11:42 ` Subhajit Ghosh
2023-10-28 13:36 ` Jonathan Cameron
2023-10-27 11:07 ` Andy Shevchenko
2023-10-27 11:36 ` Subhajit Ghosh
2023-10-28 6:29 ` kernel test robot
2023-10-28 15:20 ` Jonathan Cameron
2023-10-29 15:51 ` Matti Vaittinen
2023-10-30 10:21 ` Matti Vaittinen
2023-10-31 7:11 ` Matti Vaittinen
2023-10-31 8:20 ` Subhajit Ghosh
2023-10-31 10:38 ` Andy Shevchenko
2023-10-31 11:39 ` Matti Vaittinen
2023-10-31 12:07 ` Matti Vaittinen
2023-10-31 13:42 ` Andy Shevchenko
2023-11-01 6:16 ` Matti Vaittinen
2023-11-02 12:50 ` Andy Shevchenko [this message]
2023-10-31 8:38 ` Subhajit Ghosh
2023-11-06 11:13 ` Jonathan Cameron
2023-11-06 12:04 ` Subhajit Ghosh
2023-11-06 12:10 ` Matti Vaittinen
2023-12-04 9:51 ` Jonathan Cameron
2023-11-05 14:22 ` kernel test robot
2023-11-06 10:07 ` Andy Shevchenko
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