Hi!
2023-08-30 at 10:52, Linus Walleij wrote:
> As noted by Jonathan Cameron: it is perfectly legal for a channel
> to have an offset but no scale in addition to the raw interface.
> The conversion will imply that scale is 1:1.
>
> Make rescale_configure_channel() accept just scale, or just offset
> to process a channel.
>
> The code to handle channels with just offset is already there.
>
> Link: https://lore.kernel.org/linux-iio/CACRpkdZXBjHU4t-GVOCFxRO-AHGxKnxMeHD2s4Y4PuC29gBq6g@mail.gmail.com/
> Fixes: 53ebee949980 ("iio: afe: iio-rescale: Support processed channels")
> Fixes: 9decacd8b3a4 ("iio: afe: rescale: Fix boolean logic bug")
> Reported-by: Jonathan Cameron <[email protected]>
> Signed-off-by: Linus Walleij <[email protected]>
> ---
> drivers/iio/afe/iio-rescale.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
> index 1f280c360701..18aafb4bdda0 100644
> --- a/drivers/iio/afe/iio-rescale.c
> +++ b/drivers/iio/afe/iio-rescale.c
> @@ -280,8 +280,9 @@ static int rescale_configure_channel(struct device *dev,
> chan->type = rescale->cfg->type;
>
> if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) &&
> - iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE)) {
> - dev_info(dev, "using raw+scale source channel\n");
> + (iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE) ||
> + iio_channel_has_info(schan, IIO_CHAN_INFO_OFFSET))) {
> + dev_info(dev, "using raw+scale/offset source channel\n");
I do not think it's that simple. The rescale_read_raw function, when asked
for IIO_CHAN_INFO_OFFSET, must know the scale of the source channel in
order to rescale the offset. After this patch, trying to get the rescaled
scale/offset when the source channel has an offset but lacks a scale will
simply return -EOPNOTSUPP.
Which is not what you intended, I think?
Cheers,
Peter
> } else if (iio_channel_has_info(schan, IIO_CHAN_INFO_PROCESSED)) {
> dev_info(dev, "using processed channel\n");
> rescale->chan_processed = true;
>
> ---
> base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
> change-id: 20230830-iio-rescale-only-offset-f28e05bd2deb
>
> Best regards,