Re: [PATCH v3 3/3] Documentation: ABI: IIO: Re-add sysfs-bus-iio-adc-ad4130

[Marcelo Schmitt <marcelo.schmitt1@gmail.com>]

On 02/03, David Lechner wrote:
> On 2/3/25 1:11 PM, Marcelo Schmitt wrote:
> > The ad4130 driver exports in_voltageY-voltageZ_filter_mode and
> > in_voltage-voltage_filter_mode_available attributes to user space. A
> > previous patch merged the documentation for those attributes with the
> > documentation for filter_type/filter_type_available into sysfs-bus-iio.
> > Filter mode and filter type refer to the same feature which is the digital
> > filter applied over ADC samples. However, since datasheets use the term
> > `filter type` and ad4130 driver is the only one using filter_mode,
> > deprecate the filter_mode ABI in favor of filter_type and keep the docs
> > separate to avoid confusion and intricate attribute descriptions.
> > 
> 
> 
> > The digital filter helps shape the noise rejection bandwidth and is
> > supposed to be adjusted according to the signal of interest. Depending on
> > the particular ADC design, the digital filter configuration may have an
> > impact on the output data rate (ODR) (which is equivalent to the sampling
> > frequency for SAR ADCs - `sampling_frequency` ABI), 3dB cutoff frequency of
> > the filter (`_low_pass_3db_frequency` attributes), or settling time.
> > 
> > Digital filters are a common feature among sigma-delta ADCs and
> > IIO drivers set digital filters according to different attributes.
> > ad4130 and ad7779 filter options are supported through dedicated
> > filter_mode/filter_type attributes in sysfs.
> > ad7768-1 and ad7173 set the sinc filters according to the
> > sampling_frequency attribute. No filter_type attribute.
> > ad7124 sets the digital filter according to a filter_low_pass_3db_frequency
> > attribute so it doesn't export filter type attributes to user space.
> 
> These last two paragraphs seems a bit excessive and could be dropped.
> 
> > 
> > Fixes: 01bb12922b60 ("Documentation: ABI: added filter mode doc in sysfs-bus-iio")
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> > ---
> >  Documentation/ABI/testing/sysfs-bus-iio       |  1 -
> >  .../ABI/testing/sysfs-bus-iio-adc-ad4130      | 20 +++++++++++++++++++
> >  MAINTAINERS                                   |  1 +
> >  3 files changed, 21 insertions(+), 1 deletion(-)
> >  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> > index ff9cc09360dc..e4fd99c92d81 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-iio
> > +++ b/Documentation/ABI/testing/sysfs-bus-iio
> > @@ -2277,7 +2277,6 @@ Description:
> >  		representing the sensor unique ID number.
> >  
> >  What:		/sys/bus/iio/devices/iio:deviceX/filter_type_available
> > -What:		/sys/bus/iio/devices/iio:deviceX/in_voltage-voltage_filter_mode_available
> 
> Instead of removing the line, I think we need to replace it with:
> 
> /sys/bus/iio/devices/iio:deviceX/in_voltage-voltage_filter_type_available
> 
> (change mode to type)
> 
> This attribute is used in the previous patch.

Ah yes, good catch.
Will do. And will also reorder the patches so it gets documented before being used.

Thanks,
Marcelo

> 
> 
> >  KernelVersion:	6.1
> >  Contact:	linux-iio@vger.kernel.org
> >  Description:
> With those changes...
> 
> Reviewed-by: David Lechner <dlechner@baylibre.com>