linux-kernel - Re: [PATCH 3/4] docs: iio: new docs for ad4052 driver

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Message-ID: <20250310195629.47ca023f@jic23-huawei>
Date: Mon, 10 Mar 2025 19:56:29 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Jorge Marques <gastmaier@...il.com>, Jorge Marques
 <jorge.marques@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, Michael
 Hennerich <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Jonathan Corbet <corbet@....net>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 3/4] docs: iio: new docs for ad4052 driver

On Mon, 10 Mar 2025 09:31:45 -0500
David Lechner <dlechner@...libre.com> wrote:

> On 3/9/25 3:49 PM, Jorge Marques wrote:
> >>> +.. list-table:: Driver attributes
> >>> +   :header-rows: 1
> >>> +
> >>> +   * - Attribute
> >>> +     - Description
> >>> +   * - ``in_voltage0_raw``
> >>> +     - Raw ADC voltage value
> >>> +   * - ``in_voltage0_oversampling_ratio``
> >>> +     - Enable the device's burst averaging mode to over sample using
> >>> +       the internal sample rate.
> >>> +   * - ``in_voltage0_oversampling_ratio_available``
> >>> +     - List of available oversampling values. Value 0 disable the burst
> >>> +       averaging mode.
> >>> +   * - ``sample_rate``
> >>> +     - Device internal sample rate used in the burst averaging mode.
> >>> +   * - ``sample_rate_available``
> >>> +     - List of available sample rates.  
> >>
> >> Why not using the standard sampling_frequency[_available] attributes?  
> > Because sampling_frequency is the sampling frequency for the pwm trigger
> > during buffer readings.
> > sample_rate is the internal device clock used during monitor and burst
> > averaging modes.  
> 
> I haven't done a chips with a monitor mode yet where we aren't reading
> the samples, so hopefully Jonathan will chime in here on the usual way
> to handle that.
> 
> For the burst averaging mode, I understand the need for a separate attribute
> now. I would suggest to call this the conversion_frequency rather than
> sampling_rate since IIO already defines "sampling" to be the data read
> from the chip to Linux even if it is an averaged value, it still counts
> as one sample.

I should have read on.  I'd like this more closely associated with oversampling.
As per other reply we use sampling_frequency in the events directory for
the monitoring frequency case.  One of our very first drivers did this
(max1363) so it's been in the ABI a long time!

Jonathan