Hi!
2022-07-21 at 21:15, Paul Cercueil 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 5c9970b93384..0edb62ee4508 100644
> --- a/drivers/iio/afe/iio-rescale.c
> +++ b/drivers/iio/afe/iio-rescale.c
> @@ -141,6 +141,27 @@ int rescale_process_offset(struct rescale *rescale, int scale_type,
> }
> }
>
> +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);
do_div is for unsigned operands. Can val never ever be negative?
What about the numerator and denominator, can those be negative? I
think this code should live in a new rescale_process_inverse_scale
function, or something like that (and a few tests could be added to
drivers/iio/test/iio-test-rescale.c)
> + return iio_write_channel_attribute(rescale->source, tmp, 0,
> + IIO_CHAN_INFO_SCALE);
> + default:
What if the source driver has a .write_raw_get_fmt callback? That bit
of info is silently dropped (with no comment that a shortcut has been
taken). How does inverse rescaling mix with a .write_raw_get_fmt that
returns e.g. IIO_VAL_INT_PLUS_MICRO_DB anyway? I think all cases might
get a bit hairy to support, so I think you need to do some filtering
and somehow fail the .write_raw call if the .write_raw_get_fmt of the
source returns something that gets too difficult to support.
Cheers,
Peter
> + return iio_write_channel_attribute(rescale->source,
> + val, val2, mask);
> + }
> +}
> +
> static int rescale_read_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan,
> int *val, int *val2, long mask)
> @@ -250,6 +271,7 @@ 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,
> };
