Re: [PATCH 2/2] iio: afe: rescale: Implement write_raw

[Paul Cercueil]

Hi Jonathan,

Le sam. 15 févr. 2020 à 18:32, Jonathan Cameron <jic23@xxxxxxxxxx> a 
écrit :
> On Mon, 10 Feb 2020 19:54:38 -0300
> Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:
>
> >  Implement write_raw by converting the value if writing the scale, or
> >  just calling the managed channel driver's write_raw otherwise.
> >
> >  Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  ---
> >   drivers/iio/afe/iio-rescale.c | 22 ++++++++++++++++++++++
> >   1 file changed, 22 insertions(+)
> >
> >  diff --git a/drivers/iio/afe/iio-rescale.c 
> > b/drivers/iio/afe/iio-rescale.c
> >  index 95802d9ee25e..a48f6af9316d 100644
> >  --- a/drivers/iio/afe/iio-rescale.c
> >  +++ b/drivers/iio/afe/iio-rescale.c
> >  @@ -35,6 +35,27 @@ struct rescale {
> >   	int *scale_data;
> >   };
> >
> >  +static int rescale_write_raw(struct iio_dev *indio_dev,
> >  +			     struct iio_chan_spec const *chan,
> >  +			     int val, int val2, long mask)
> >  +{
> >  +	struct rescale *rescale = iio_priv(indio_dev);
> >  +	unsigned long long tmp;
> >  +
> >  +	switch (mask) {
> >  +	case IIO_CHAN_INFO_SCALE:
> >  +		tmp = val * 1000000000LL;
> >  +		do_div(tmp, rescale->numerator);
> >  +		tmp *= rescale->denominator;
> >  +		do_div(tmp, 1000000000LL);
> >  +		return iio_write_channel_attribute(rescale->source, tmp, 0,
> >  +						   IIO_CHAN_INFO_SCALE);
>
> Why is val2 always 0?  Won't that only work if the backend device
> has integer scales?

Sorry, somehow I didn't see your answer.

Indeed, this will only work if the backend device has integer scales, 
but what should I do? Just pass 'val2' instead of 0? Will the value be 
correct if I only apply the scale ratio to 'val'?

Cheers,
-Paul


> >  +	default:
> >  +		return iio_write_channel_attribute(rescale->source,
> >  +						   val, val2, mask);
> >  +	}
> >  +}
> >  +
> >   static int rescale_convert(struct rescale *rescale, int type,
> >   			   const int val, const int val2,
> >   			   int *val_out, int *val2_out)
> >  @@ -110,6 +131,7 @@ static int rescale_read_avail(struct iio_dev 
> > *indio_dev,
> >   }
> >
> >   static const struct iio_info rescale_info = {
> >  +	.write_raw = rescale_write_raw,
> >   	.read_raw = rescale_read_raw,
> >   	.read_avail = rescale_read_avail,
> >   };