linux-kernel - Re: [PATCH v2 0/3] Re-add filter_type/filter

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Message-ID: <Z31n9C8FwgzV0hs0@debian-BULLSEYE-live-builder-AMD64>
Date: Tue, 7 Jan 2025 14:44:20 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: Marcelo Schmitt <marcelo.schmitt@...log.com>, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org, cosmin.tanislav@...log.com,
	jic23@...nel.org, lars@...afoo.de, granquet@...libre.com,
	u.kleine-koenig@...libre.com
Subject: Re: [PATCH v2 0/3] Re-add filter_type/filter_mode

On 01/07, David Lechner wrote:
> On 1/7/25 9:11 AM, Marcelo Schmitt wrote:
> > Better document sysfs ABI for ADC digital filter configuration.
> > 
> > Change log v1 -> v2
> > - Split into 3 patches.
> > - Re-added sysfs-bus-iio-adc-ad4130 to keep filter_mode separate from filter_type.
> 
> If ad7779 is the only driver with filter_type{,available} attributes while
> ad4130 and admv8818 both have filter_mode{,available} attributes, shouldn't we
> be deprecating filter_type and promoting filter_mode?

Oh, I had only grepped the adc dir and I didn't noticed admv8818 also had
filter_mode.
Hmm, don't know, though still biased towards filter_type.

- The admv8818 filter_mode_available ABI exports different values (auto,
  manual, bypass).
- AD7768-1, ADAQ7768-1, AD7768/AD7768-4, AD7124-4, and AD4170 datasheets
  refer to sinc filters as filter types (though not all of those designs are
  supported in IIO or have filter attributes).
- The AD4130 datasheets also refers to the digital filter as filter type in
  some occasions.

But some datasheets seem to use filter mode and filter type interchangeably
so I don't know. The admv8818 use case is valid and is both low and high-pass
filtering while the ADCs sinc digital filters act like low-pass filter.
Maybe even provide a different name for ADC digital filtering?
digital_filter_type (or digital_filter_mode)?.

Thanks for pointing that out.