Re: [PATCH v4 06/11] iio: adc: ad4170: Add support for buffered data capture

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

...
> > diff --git a/drivers/iio/adc/ad4170.c b/drivers/iio/adc/ad4170.c
> > index 3d83c3ace569..86ef70acbf21 100644
> > --- a/drivers/iio/adc/ad4170.c
> > +++ b/drivers/iio/adc/ad4170.c
> > @@ -13,7 +13,11 @@
> 
> > +static bool ad4170_validate_scan_mask(struct iio_dev *indio_dev,
> > +				      const unsigned long *scan_mask)
> > +{
> > +	unsigned int masklength = iio_get_masklength(indio_dev);
> 
> If this becomes a useability issue we could probably generative appropriate
> available_scan_masks entries and let the demuxer in the IIO core deal with
> dropping the unwanted first channel.  That might be preferable to just
> failing if the channel isn't enabled.

Yes, we can do that. I also think that would probably be the preferred way from
the user's perspective. Though, that tinkering may result in a few more tens of
lines of code, which I'm reluctant to add, given the size of this set.

> 
> As a general rule, I think we've always used validate_scan_mask
> to prevent too many channels being turned on, or incompatible sets of channels
> rather than to prevent too few being enabled.
> 
> Anyhow that would be a relaxation of constraints so can be done if it
> turns out to be needed later.
> 

Added to my list of patch ideas :)

> > +
> > +	/*
> > +	 * The channel sequencer cycles through the enabled channels in
> > +	 * sequential order, from channel 0 to channel 15, bypassing disabled
> > +	 * channels. When more than one channel is enabled, channel 0 must
> > +	 * always be enabled. See datasheet channel_en register description at
> > +	 * page 95.
> > +	 */
> > +	if (bitmap_weight(scan_mask, masklength) > 1)
> > +		return test_bit(0, scan_mask);
> > +
> > +	return bitmap_weight(scan_mask, masklength) == 1;
> > +}