linux-kernel - Re: [PATCH 1/2] iio: adc: ad4695: add offload-based oversampling support

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Message-ID: <ec8bf32b-2414-4538-9fe4-2b32d890bc66@baylibre.com>
Date: Wed, 8 Jan 2025 14:39:30 -0600
From: David Lechner <dlechner@...libre.com>
To: Trevor Gamblin <tgamblin@...libre.com>,
 Jonathan Cameron <jic23@...nel.org>
Cc: Michael Hennerich <michael.hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Lars-Peter Clausen <lars@...afoo.de>, Jonathan Corbet <corbet@....net>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/2] iio: adc: ad4695: add offload-based oversampling
 support

On 1/8/25 1:54 PM, Trevor Gamblin wrote:
> 
> On 2025-01-07 16:02, David Lechner wrote:
>> On 1/7/25 2:21 PM, Trevor Gamblin wrote:
>>> On 2025-01-04 07:30, Jonathan Cameron wrote:
>>>> On Thu, 2 Jan 2025 13:19:19 -0500
>>>> Trevor Gamblin <tgamblin@...libre.com> wrote:
>>>>
>>>>> On 2024-12-19 11:13, Jonathan Cameron wrote:
>>>>>> On Tue, 17 Dec 2024 16:47:28 -0500
>>>>>> Trevor Gamblin <tgamblin@...libre.com> wrote:
>>>>>>  
...

>>>          else
>>>                  val_calc = val * scale + val2 * scale / MICRO;
>>>
>>>          val_calc /= 2;
>>>
>>>          return clamp_t(int, val_calc, S16_MIN, S16_MAX);
>>> }
>>>
>>> This seems to match all of the expected outputs for the pre-simplification version in this patch series when I test it. If there are no issues with it, I'll send a v2.
>> Probably not a big deal, but there is unhanded overflow when val is near S32_MAX
>> or S32_MIN.
> Should I handle that with an extra call to clamp_t()?

It wouldn't hurt. val = clamp_t(int, val, S32_MIN / 8, S32_MAX / 8); before
the rest of the math should do the trick since the max scale is 8.