On 01/07, David Lechner wrote: > On 1/7/25 9:24 AM, Jonathan Santos wrote: > > Add ABI documentation specific to the ad7768-1 device, detailing > > the decimation_rate attribute for better clarity and usability. > > > > Signed-off-by: Jonathan Santos <Jonathan.Santos@xxxxxxxxxx> > > --- > > .../ABI/testing/sysfs-bus-iio-adc-ad7768-1 | 13 +++++++++++++ > > 1 file changed, 13 insertions(+) > > create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-adc-ad7768-1 > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-adc-ad7768-1 b/Documentation/ABI/testing/sysfs-bus-iio-adc-ad7768-1 > > new file mode 100644 > > index 000000000000..065247f07cfb > > --- /dev/null > > +++ b/Documentation/ABI/testing/sysfs-bus-iio-adc-ad7768-1 > > @@ -0,0 +1,13 @@ > > +What: /sys/bus/iio/devices/iio:deviceX/decimation_rate_available > > +KernelVersion: > > +Contact: linux-iio@xxxxxxxxxxxxxxx > > +Description: > > + Reading returns a range of possible decimation rate values. > > + > > +What: /sys/bus/iio/devices/iio:deviceX/decimation_rate > > +KernelVersion: > > +Contact: linux-iio@xxxxxxxxxxxxxxx > > +Description: > > + Sets up the decimation rate for the digital filter. This can > > + directly impact in the final sampling frequency. Reading returns > > + the decimation rate. Writing sets the decimation rate. > > If this only affects the filter, I would suggest to add `filter_` to the > beginning of the attribute names. > > Also, an explanation of how to interpret the numbers would be helpful. It looks > like a unitless number that acts a sort of a multiplier or divider, but that > part isn't so clear to me. > > Or... > > Since the decimation rate affects the -3dB point of the filters we could use > the standard IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY instead of introducing > a new attribute. Well, here the -3dB cutoff depends on the ODR, which is determined by both the MCLK divider and decimation rate. Wideband: -3dB at 0.433 × ODR Sinc5: -3dB at 0.204 × ODR Sinc3: -3dB at 0.2617 × ODR If we use _filter_low_pass_3db_frequency to control the decimation and _sampling_frequency to control the MCLK divider, wouldn’t it be confusing for one to always affect the other? A different ODR would result in a different cutoff, and vice versa. Would something like <type>[_name]_oversampling_ratio make more sense? Let me know what you think
