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

Jorge Marques
2025-03-14T17:34:51Z

On Mon, Mar 10, 2025 at 07:56:29PM +0000, Jonathan Cameron wrote:
> On Mon, 10 Mar 2025 09:31:45 -0500
> David Lechner <dlechner@baylibre.com> wrote:
>
> > On 3/9/25 3:49 PM, Jorge Marques wrote:
> > >>> + * - ``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!
>

I get the idea but maybe the datasheet sample rate as conversion_frequency
and stored as a channel attribute (iio_chan_spec.ext_info) is clear enough.

The datasheet sample rate affects both the burst averaging mode (oversampling) and
monitor mode (threshold events).

The max1363 stores as an event attribute (iio_info.event_attr) and requires iio/sysfs.h include.
A last option is to store as a general purpose device attribute (iio_info.attrs).
As a channel attribute, the driver logic is slightly simpler by using the macros.

Jorge