linux-kernel - Re: [PATCH v1 1/1] iio: adc: ad7192: Refactor filter config

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Message-ID: <df11dff4-7641-46f8-a604-8727918629c3@baylibre.com>
Date: Thu, 1 May 2025 09:49:20 -0500
From: David Lechner <dlechner@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Alisa-Dariana Roman <alisadariana@...il.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Alisa-Dariana Roman <alisa.roman@...log.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH v1 1/1] iio: adc: ad7192: Refactor filter config

On 4/26/25 7:32 AM, Jonathan Cameron wrote:
> On Fri, 25 Apr 2025 10:43:29 -0500
> David Lechner <dlechner@...libre.com> wrote:
> 
>> On 4/25/25 8:20 AM, Alisa-Dariana Roman wrote:

...

>>> +static const char *const ad7192_filter_modes_str[] = {
>>> +	[AD7192_FILTER_SINC4] =			"sinc4",
>>> +	[AD7192_FILTER_SINC3] =			"sinc3",
>>> +	[AD7192_FILTER_SINC4_CHOP] =		"sinc4+chop",
> 
> Is chop really a filter? I had to look it up and to me at least it
> seems like it isn't even though one thing it does is remove
> some types of noise.  It also removes linear offsets (some types
> of filter kind of do that, but the affect of chop smells more like
> a calibration tweak than a filter)  
> 
> Maybe we need a separate control for chop, rather than trying to
> force it through our already complex filter type attributes?
> 


I was looking at the datasheet for another ADC that popped up on the mailing
list today. https://www.ti.com/lit/ds/symlink/ads1262.pdf

It also has a chop mode and filters very similar to this one. So perhaps another
reason to make chop a separate bool attribute that could considered a "standard"
attribute.