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Date: Mon, 29 Apr 2024 20:44:09 +0100
From: Jonathan Cameron <jic23@kernel.org>
To: Andrew Hepp <andrew.hepp@ahepp.dev>
Cc: Dimitri Fedrau <dima.fedrau@gmail.com>, Marcelo Schmitt
 <marcelo.schmitt1@gmail.com>, Lars-Peter Clausen <lars@metafoo.de>,
 linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iio: temperature: mcp9600: Fix temperature reading for
 negative values
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On Sun, 28 Apr 2024 14:46:39 -0400
Andrew Hepp <andrew.hepp@ahepp.dev> wrote:

> Hi all,
>=20
> On Apr 28, 2024, at 9:46=E2=80=AFAM, Jonathan Cameron <jic23@kernel.org> =
wrote:
>=20
> > Agreed - by my reading the original patch is correct. Maybe it would act
> > as cleaner 'documentation' to have the sign_extend32() for the cold jun=
ction be
> > from bit 12 rather than 15, but I'm not sure it's worth the effort.
> >=20
> > Andrew, would be great if you can review this fix in case we are all mi=
ssing
> > something! =20
>=20
> I also agree that Dimitri=E2=80=99s original patch appears correct per th=
e data sheet.
>=20
> I think of the cold junction register as a 16 bit 2s complement signed in=
teger,=20
> despite the limited range. I like sign extending it from bit 15 rather th=
an from 12.
>=20
> I applied Dimitri=E2=80=99s patch and stuck a dev board in my icebox.
>=20
> Before patch:
>     # cat /sys/bus/iio/devices/iio:device0/in_temp_raw=20
>     65222
>     # cat /sys/bus/iio/devices/iio:device0/in_temp_ambient_raw
>     65256
>=20
> After patch:
>     # cat /sys/bus/iio/devices/iio:device0/in_temp_raw
>     -260
>     # cat /sys/bus/iio/devices/iio:device0/in_temp_ambient_raw
>     -212
>=20
> Looks good to me! Thanks for the patch Dimitri, and thanks to all for the=
 review!
>=20
> Andrew
That definitely deserves a Tested-by tag so I added one. Hope you don't min=
d!

Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan