linux-kernel - Re: [PATCH 2/2] iio: afe: rescale: Implement write

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Date:   Sat, 15 Feb 2020 18:32:49 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Peter Rosin <peda@...ntia.se>, od@...c.me,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: afe: rescale: Implement write_raw

On Mon, 10 Feb 2020 19:54:38 -0300
Paul Cercueil <paul@...pouillou.net> 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@...pouillou.net>
> ---
>  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?

> +	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,
>  };