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From: Peter Rosin <peda@axentia.se>
To: Liam Beguin <liambeguin@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>,
lars@metafoo.de, linux-kernel@vger.kernel.org,
linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
robh+dt@kernel.org
Subject: Re: [PATCH v8 09/14] iio: afe: rescale: fix accuracy for small fractional scales
Date: Thu, 2 Sep 2021 23:52:21 +0200 [thread overview]
Message-ID: <5a1e0243-263d-455a-83cd-c274d7d8befb@axentia.se> (raw)
In-Reply-To: <YTA2g2iHB3WtEMBp@shaak>
On 2021-09-02 04:27, Liam Beguin wrote:
> On Mon, Aug 30, 2021 at 04:30:54PM +0200, Peter Rosin wrote:
>>
>> Having said that, if 'scale' and 'offset' indeed are static, then the gcd
>> cost can be mitigated by caching the result. Exact rescaling is always
>> nice...
>>
>> If IIO_VAL_INT overflows while rescaling, we are SOL whichever way we turn,
>> so ignore doing anything about that.
>
> I was thinking of using check_mul_overflow() to do something about the
> overflow, but I'm happy to leave it out for now.
My mistake, you are right. A sufficiently large denominator can of course
be used to dodge overflow in the numerator by sacrificing some accuracy
even if our maximum scale is still limited to 32 bits.
I apparently didn't have my brains about when I wrote the above...
Cheers,
Peter
next prev parent reply other threads:[~2021-09-02 21:52 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-20 19:17 [PATCH v8 00/14] iio: afe: add temperature rescaling support Liam Beguin
2021-08-20 19:17 ` [PATCH v8 01/14] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2021-08-20 19:17 ` [PATCH v8 02/14] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2021-08-20 19:17 ` [PATCH v8 03/14] iio: inkern: make a best effort on offset calculation Liam Beguin
2021-08-20 19:17 ` [PATCH v8 04/14] iio: afe: rescale: expose scale processing function Liam Beguin
2021-08-20 19:17 ` [PATCH v8 05/14] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2021-08-26 8:11 ` Peter Rosin
2021-08-29 2:50 ` Liam Beguin
2021-08-20 19:17 ` [PATCH v8 06/14] iio: afe: rescale: add offset support Liam Beguin
2021-08-20 19:17 ` [PATCH v8 07/14] iio: afe: rescale: use s64 for temporary scale calculations Liam Beguin
2021-08-20 19:17 ` [PATCH v8 08/14] iio: afe: rescale: reduce risk of integer overflow Liam Beguin
2021-08-26 9:13 ` Peter Rosin
2021-08-29 4:01 ` Liam Beguin
2021-08-20 19:17 ` [PATCH v8 09/14] iio: afe: rescale: fix accuracy for small fractional scales Liam Beguin
2021-08-20 23:37 ` kernel test robot
2021-08-21 1:33 ` Liam Beguin
2021-08-23 6:53 ` Peter Rosin
2021-08-21 2:00 ` kernel test robot
2021-08-21 7:21 ` kernel test robot
2021-08-22 22:18 ` Peter Rosin
2021-08-24 20:28 ` [PATCH v8 09/14] iio: afe: rescale: fix accuracy for small Liam Beguin
2021-08-26 9:53 ` Peter Rosin
2021-08-29 4:41 ` Liam Beguin
2021-08-30 11:27 ` Jonathan Cameron
2021-09-11 23:31 ` Liam Beguin
2021-08-30 13:03 ` Peter Rosin
2021-09-11 23:20 ` Liam Beguin
2021-08-30 11:22 ` [PATCH v8 09/14] iio: afe: rescale: fix accuracy for small fractional scales Jonathan Cameron
2021-08-30 14:30 ` Peter Rosin
2021-08-30 17:03 ` Jonathan Cameron
2021-09-02 2:27 ` Liam Beguin
2021-09-02 21:52 ` Peter Rosin [this message]
2021-08-20 19:17 ` [PATCH v8 10/14] iio: test: add basic tests for the iio-rescale driver Liam Beguin
2021-08-20 19:17 ` [PATCH v8 11/14] iio: afe: rescale: add RTD temperature sensor support Liam Beguin
2021-08-20 19:17 ` [PATCH v8 12/14] iio: afe: rescale: add temperature transducers Liam Beguin
2021-08-26 8:56 ` Peter Rosin
2021-08-29 2:33 ` Liam Beguin
2021-08-20 19:17 ` [PATCH v8 13/14] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2021-08-20 19:17 ` [PATCH v8 14/14] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin
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