RE: [PATCH v6 3/4] iio: adc: ad4691: add triggered buffer support

[Sabau, Radu bogdan]

> -----Original Message-----
> From: David Lechner <dlechner@xxxxxxxxxxxx>
> Sent: Saturday, April 4, 2026 6:12 PM

...

> > +
> > +/*
> > + * Valid ACC_DEPTH values where the effective divisor equals the count.
> > + * From Table 13: ACC_DEPTH = 2^N yields right-shift = N, divisor = 2^N.
> > + */
> > +static const int ad4691_oversampling_ratios[] = { 1, 2, 4, 8, 16, 32 };
> 
> It would be nice to add oversampling in a separate commit as that is a
> separate feature.

Do you think this would be suitable after the offload commit?

> 
> Oversampling also affects sampling frequency. When there isn't oversampling,
> sample rate == conversion rate. However, with oversampling, sample rate ==
> conversion rate / oversampling ratio (because each sample involves #OSR
> conversions).
> 
> So more code will be required to make IIO_CHAN_INFO_SAMP_FREQ
> attributes
> (both read/write_raw and read_avail) adjust the values based on the current
> oversampling ratio.

I agree with this, the sampling frequency differs when oversampling is used.
Will add that in the next version.

> 
> > +	
> >  static const struct ad4691_chip_info ad4691_chip_info = {
> >  	.channels = ad4691_channels,

...

> > +
> > +	st->scan_msg.spi = spi;
> 
> This isn't how the SPI framework is intended to be used. We should
> have st->spi = spi in probe instead.

You are right. The spi pointer was removed from struct in earlier versions
since the message wasn't pre-prepared back then, though now it is needed.

> 
> > +
> > +	ret = spi_optimize_message(spi, &st->scan_msg);
> > +	if (ret) {

...

> > +};
> > +
> > +static irqreturn_t ad4691_irq(int irq, void *private)
> > +{
> > +	struct iio_dev *indio_dev = private;
> > +	struct ad4691_state *st = iio_priv(indio_dev);
> > +
> > +	/*
> > +	 * GPx has asserted: stop conversions before reading so the
> 
> Does this happen per-channel or only once per complete sequence?
> 

This one happens per complete sequence.