Re: [PATCH 1/2] iio: afe: rescale: Add support for converting scale avail table

[Peter Rosin <peda@axentia.se>]

Hi!

On 2020-02-10 23:54, Paul Cercueil wrote:
> When the IIO channel has a scale_available attribute, we want the values
> contained to be properly converted the same way the scale value is.
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
>  drivers/iio/afe/iio-rescale.c | 125 ++++++++++++++++++++++++++++------
>  1 file changed, 103 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
> index e9ceee66d1e7..95802d9ee25e 100644
> --- a/drivers/iio/afe/iio-rescale.c
> +++ b/drivers/iio/afe/iio-rescale.c
> @@ -31,14 +31,45 @@ struct rescale {
>  	struct iio_chan_spec_ext_info *ext_info;
>  	s32 numerator;
>  	s32 denominator;
> +	int scale_type, scale_len;
> +	int *scale_data;
>  };
>  
> +static int rescale_convert(struct rescale *rescale, int type,
> +			   const int val, const int val2,
> +			   int *val_out, int *val2_out)
> +{
> +	unsigned long long tmp;
> +
> +	switch (type) {
> +	case IIO_VAL_FRACTIONAL:
> +		*val_out = val * rescale->numerator;
> +		*val2_out = val2 * rescale->denominator;
> +		return type;
> +	case IIO_VAL_INT:
> +		*val_out = val * rescale->numerator;
> +		if (rescale->denominator == 1)
> +			return type;
> +		*val2_out = rescale->denominator;
> +		return IIO_VAL_FRACTIONAL;
> +	case IIO_VAL_FRACTIONAL_LOG2:
> +		tmp = val * 1000000000LL;
> +		do_div(tmp, rescale->denominator);
> +		tmp *= rescale->numerator;
> +		do_div(tmp, 1000000000LL);
> +		*val_out = tmp;
> +		*val2_out = val2;
> +		return type;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
>  static int rescale_read_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;
>  	int ret;
>  
>  	switch (mask) {
> @@ -47,27 +78,7 @@ static int rescale_read_raw(struct iio_dev *indio_dev,
>  
>  	case IIO_CHAN_INFO_SCALE:
>  		ret = iio_read_channel_scale(rescale->source, val, val2);
> -		switch (ret) {
> -		case IIO_VAL_FRACTIONAL:
> -			*val *= rescale->numerator;
> -			*val2 *= rescale->denominator;
> -			return ret;
> -		case IIO_VAL_INT:
> -			*val *= rescale->numerator;
> -			if (rescale->denominator == 1)
> -				return ret;
> -			*val2 = rescale->denominator;
> -			return IIO_VAL_FRACTIONAL;
> -		case IIO_VAL_FRACTIONAL_LOG2:
> -			tmp = *val * 1000000000LL;
> -			do_div(tmp, rescale->denominator);
> -			tmp *= rescale->numerator;
> -			do_div(tmp, 1000000000LL);
> -			*val = tmp;
> -			return ret;
> -		default:
> -			return -EOPNOTSUPP;
> -		}
> +		return rescale_convert(rescale, ret, *val, *val2, val, val2);
>  	default:
>  		return -EINVAL;
>  	}
> @@ -85,6 +96,14 @@ static int rescale_read_avail(struct iio_dev *indio_dev,
>  		*type = IIO_VAL_INT;
>  		return iio_read_avail_channel_raw(rescale->source,
>  						  vals, length);
> +	case IIO_CHAN_INFO_SCALE:
> +		if (rescale->scale_len) {
> +			*type = rescale->scale_type;
> +			*length = rescale->scale_len;
> +			*vals = rescale->scale_data;
> +			return IIO_AVAIL_LIST;
> +		}
> +		/* fall-through */
>  	default:
>  		return -EINVAL;
>  	}
> @@ -119,11 +138,65 @@ static ssize_t rescale_write_ext_info(struct iio_dev *indio_dev,
>  					  buf, len);
>  }
>  
> +static int rescale_init_scale_avail(struct device *dev, struct rescale *rescale)
> +{
> +	const int *scale_raw;
> +	unsigned int i;
> +	int ret;
> +
> +	ret = iio_read_avail_channel_attribute(rescale->source, &scale_raw,
> +					       &rescale->scale_type,
> +					       &rescale->scale_len,
> +					       IIO_CHAN_INFO_SCALE);
> +	if (ret)
> +		return ret;
> +
> +	if (rescale->scale_type == IIO_VAL_INT && rescale->denominator > 1)
> +		rescale->scale_len *= 2;
> +
> +	rescale->scale_data = devm_kzalloc(dev,
> +					   sizeof(int) * rescale->scale_len,
> +					   GFP_KERNEL);
> +	if (!rescale->scale_len)
> +		return -ENOMEM;
> +
> +	if (rescale->scale_type != IIO_VAL_INT) {
> +		for (i = 0; i < rescale->scale_len; i += 2) {
> +			ret = rescale_convert(rescale, rescale->scale_type,
> +					      scale_raw[i], scale_raw[i + 1],
> +					      &rescale->scale_data[i],
> +					      &rescale->scale_data[i + 1]);
> +			if (ret < 0)
> +				return ret;
> +		}
> +	} else if (rescale->denominator == 1) {
> +		for (i = 0; i < rescale->scale_len; i++) {
> +			ret = rescale_convert(rescale, IIO_VAL_INT,
> +					      scale_raw[i], 0,
> +					      &rescale->scale_data[i], NULL);
> +			if (ret < 0)
> +				return ret;
> +		}
> +	} else {
> +		for (i = 0; i < rescale->scale_len / 2; i++) {
> +			ret = rescale_convert(rescale, IIO_VAL_INT,
> +					      scale_raw[i], 0,
> +					      &rescale->scale_data[i * 2],
> +					      &rescale->scale_data[i * 2 + 1]);
> +			if (ret < 0)
> +				return ret;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int rescale_configure_channel(struct device *dev,
>  				     struct rescale *rescale)
>  {
>  	struct iio_chan_spec *chan = &rescale->chan;
>  	struct iio_chan_spec const *schan = rescale->source->channel;
> +	int ret;
>  
>  	chan->indexed = 1;
>  	chan->output = schan->output;
> @@ -142,6 +215,14 @@ static int rescale_configure_channel(struct device *dev,
>  	if (iio_channel_has_available(schan, IIO_CHAN_INFO_RAW))
>  		chan->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW);
>  
> +	if (iio_channel_has_available(schan, IIO_CHAN_INFO_SCALE)) {
> +		chan->info_mask_separate_available |= BIT(IIO_CHAN_INFO_SCALE);
> +
> +		ret = rescale_init_scale_avail(dev, rescale);
> +		if (ret)
> +			return ret;
> +	}
> +

You unconditionally add a channel that in some cases then always return
"not supported" if you try to use it. Is that "safe" or can it cause
trouble for some unsuspecting application?

Cheers,
Peter