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@xxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxxxxx
> > Description:
> With those changes...
>
> Reviewed-by: David Lechner <dlechner@xxxxxxxxxxxx>
