Re: [PATCH v1 1/9] iio: inkern: always apply scale requested by consumer

Peter Rosin
2021-05-31T14:03:23Z

Hi!

On 2021-05-30 02:59, Liam Beguin wrote:
> From: Liam Beguin <lvb@xiphos.com>
>
> When a consumer calls iio_read_channel_processed() and no scaling is
> available on the channel, it's assumed that the scale is one and the raw
> value is returned as expected.
>
> On the other hand, if the consumer calls iio_convert_raw_to_processed()
> the scaling factor requested by the consumer is not applied.
> This for example causes the consumer to process mV when expecting uV.
>
> Make sure to always apply the scaling factor requested by the consumer.
>
> Signed-off-by: Liam Beguin <lvb@xiphos.com>
> ---
> drivers/iio/inkern.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index db77a2d4a56b..4b6a8e11116a 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -601,11 +601,7 @@ static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
> scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
> IIO_CHAN_INFO_SCALE);
> if (scale_type < 0) {
> - /*
> - * Just pass raw values as processed if no scaling is
> - * available.
> - */
> - *processed = raw;
> + *processed = raw * scale;

I would keep the comment. Sure, it's now completely confusing since it's from
before the function had a scale parameter. Perhaps reword it to talk about
"no channel scaling" instead of plain old "no scaling"?

Also, this looks like a bugfix, no more, no less, and should perhaps have a
fixes tag?

Cheers,
Peter

> return 0;
> }
>
>