From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: Vidhu Sarwal <vidhu.linux@gmail.com>
Cc: "Andy Shevchenko" <andy.shevchenko@gmail.com>,
"Jonathan Cameron" <jic23@kernel.org>,
"David Lechner" <dlechner@baylibre.com>,
"Nuno Sá" <nuno.sa@analog.com>,
"Andy Shevchenko" <andy@kernel.org>,
"Matti Vaittinen" <mazziesaccount@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@baylibre.com>,
"Siratul Islam" <email@sirat.me>,
"Tiberiu Breana" <tiberiu.a.breana@intel.com>,
linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
skhan@linuxfoundation.org
Subject: Re: [PATCH] iio: humidity: am2315: fix negative temperature decoding
Date: Tue, 29 Sep 2026 00:45:52 +0300 [thread overview]
Message-ID: <arrgEPs779q9ck8q@ashevche-desk.local> (raw)
In-Reply-To: <CAFqz8LL0bgOu3TKfxz0Ri=qw09wVHC68CbVS2yZZjv7oKTGwVw@mail.gmail.com>
On Tue, Sep 29, 2026 at 02:37:41AM +0530, Vidhu Sarwal wrote:
> On Mon, Sep 28, 2026 at 9:01 PM Andy Shevchenko
> <andy.shevchenko@gmail.com> wrote:
...
> > Can you use sign_extend32()?
> I checked whether sign_extend32() can be used here, but I don't
> think itcan be applied since as per datasheet [1], The temperature value
> is sign-magnitude such that bit 15 is the sign and bits 14 to 0
> contain the magnitude. For eg., 0x8065 represents -101.
> sign_extend32(temp_raw, 15) would instead interpret 0x8065 as a
> two's-complement value, giving us -32667.
>
> So I think the sign bit needs to be decoded explicitly by masking
> bit 15 and negating the magnitude when set.
Oh, okay, we (IIO community) already discussed the possibility to have a helper
like sign_extend32() for this type of cases, but it appears not so worth it,
IIRC.
> [1] https://cdn-shop.adafruit.com/datasheets/AM2315.pdf
--
With Best Regards,
Andy Shevchenko
prev parent reply other threads:[~2026-09-28 21:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-28 14:24 [PATCH] iio: humidity: am2315: fix negative temperature decoding Vidhu Sarwal
2026-09-28 15:30 ` Andy Shevchenko
2026-09-28 21:07 ` Vidhu Sarwal
2026-09-28 21:45 ` Andy Shevchenko [this message]
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