Re: [PATCH v5 6/9] iio: adc: ad7606: rework available attributes for SW channels

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 7 Sep 2024 21:10:10 +0300
Alexandru Ardelean <aardelean@baylibre.com> wrote:

> On Sat, Sep 7, 2024 at 6:04 PM Jonathan Cameron <jic23@kernel.org> wrote:
> >
> > On Sat,  7 Sep 2024 09:50:39 +0300
> > Alexandru Ardelean <aardelean@baylibre.com> wrote:
> >  
> > > For SW mode, the oversampling and scales attributes are always present.
> > > So, they can be implemented via a 'read_avail' hook in iio_info.
> > >
> > > For HW mode, it's a bit tricky, as these attributes get assigned based on
> > > GPIO definitions.
> > >
> > > So, for SW mode, we define a separate AD7606_SW_CHANNEL() macro, and use
> > > that for the SW channels.
> > > And 'ad7606_info_os_range_and_debug' can be renamed to
> > > 'ad7606_info_sw_mode' as it is only used for SW mode.
> > >
> > > For the 'read_avail' hook, we'll need to allocate the SW scales, so that
> > > they are just returned userspace without any extra processing.
> > > The allocation will happen when then ad7606_state struct is allocated.
> > > The oversampling available parameters don't need any extra processing; they
> > > can just be passed back to userspace (as they are).
> > >
> > > Signed-off-by: Alexandru Ardelean <aardelean@baylibre.com>  
> >
> > One question inline.
> >  
> > >
> > >  int ad7606_probe(struct device *dev, int irq, void __iomem *base_address,
> > > diff --git a/drivers/iio/adc/ad7606.h b/drivers/iio/adc/ad7606.h
> > > index 635407c2acc0..fa175cff256c 100644
> > > --- a/drivers/iio/adc/ad7606.h
> > > +++ b/drivers/iio/adc/ad7606.h  
> >  
> > >  #define AD7616_CHANNEL(num)  AD7606_SW_CHANNEL(num, 16)
> > >
> > >  /**
> > > @@ -65,11 +84,15 @@ struct ad7606_chip_info {
> > >  /**
> > >   * struct ad7606_chan_scale - channel scale configuration
> > >   * @scale_avail              pointer to the array which stores the available scales
> > > + * @scale_avail_show a duplicate of 'scale_avail' which is readily formatted
> > > + *                   such that it can be read via the 'read_avail' hook
> > >   * @num_scales               number of elements stored in the scale_avail array
> > >   * @range            voltage range selection, selects which scale to apply
> > >   */
> > >  struct ad7606_chan_scale {
> > > +#define AD760X_MAX_SCALE_SHOW                (AD760X_MAX_CHANNELS * 2)  
> >
> > Why is the number of scales dependent on the number of channels?  
> 
> Well, that was just a lazy implementation.
> I doubt there would be 16 scales (channel range values) for any newer part.
> A value for a channel-range is 4-bits (for 0 to 15).
> 
> In IIO the current highest scale-count is 5; I guess I can update this
> to a macro, and use that.
Indeed defining this as 16 would make more sense than basing it on random
unconnected thing!

Jonathan

> 
> 
> >  
> > >       const unsigned int              *scale_avail;
> > > +     int                             scale_avail_show[AD760X_MAX_SCALE_SHOW];
> > >       unsigned int                    num_scales;
> > >       unsigned int                    range;
> > >  };  
> >