From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: Victor Chernyakin <chernyakin.victor.j@outlook.com>
Cc: "Jonathan Cameron" <jic23@kernel.org>,
"David Lechner" <dlechner@baylibre.com>,
"Nuno Sá" <nuno.sa@analog.com>,
"Andy Shevchenko" <andy@kernel.org>,
linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/3] iio: add IIO_VAL_DECIMAL64_{ATTO,ZEPTO,YOCTO} formats
Date: Sun, 25 Oct 2026 21:41:23 +0200 [thread overview]
Message-ID: <at5bYwbaQhFoO0Ac@ashevche-desk.local> (raw)
In-Reply-To: <SN1PR12MB2528A44C0997DAEB1C632F0BA5622@SN1PR12MB2528.namprd12.prod.outlook.com>
On Sun, Oct 25, 2026 at 12:48:04AM -0500, Victor Chernyakin wrote:
> The highest-precision format IIO has right now is IIO_VAL_DECIMAL64_FEMTO,
> which gives 15 decimal digits of precision after the decimal point. This
> is not enough for the upcoming TI FDC1004 driver, which needs 22 digits
> of precision to exactly express its scale value. This patch adds higher-
> precision formats, up to IIO_VAL_DECIMAL64_YOCTO (24 digits of precision).
...
> +/* An abs() function that doesn't have undefined behavior for LLONG_MIN. */
Can you elaborate how so?
> +static inline u64 abs_s64_no_overflow(s64 x)
> +{
> + return x < 0 ? -(u64)x : (u64)x;
> +}
So, the trick you use is to update the type from signed to unsigned.
'-' operator is always defined on unsigned types and produces modulo
results in case the representation requires more bits than type has.
FWIW, it's not MISRA-compliant :-)
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2026-10-25 19:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-25 5:48 [PATCH v2 0/3] iio: cdc: add Texas Instruments FDC1004 driver Victor Chernyakin
2026-10-25 5:48 ` [PATCH v2 1/3] iio: add IIO_VAL_DECIMAL64_{ATTO,ZEPTO,YOCTO} formats Victor Chernyakin
2026-10-25 19:41 ` Andy Shevchenko [this message]
2026-10-25 5:48 ` [PATCH v2 2/3] dt-bindings: iio: cdc: add Texas Instruments FDC1004 Victor Chernyakin
2026-10-25 5:48 ` [PATCH v2 3/3] iio: cdc: add Texas Instruments FDC1004 driver Victor Chernyakin
2026-10-25 21:24 ` Andy Shevchenko
2026-10-25 20:47 ` [PATCH v2 0/3] " Andy Shevchenko
2026-10-25 21:35 ` Victor Chernyakin
2026-10-25 22:26 ` [PATCH v2 3/3] " Victor Chernyakin
2026-10-25 22:39 ` [PATCH v2 0/3] " Jonathan Cameron
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