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. When a user asks for IIO_CHAN_INFO_OFFSET in rescale_read_raw() we now have to deal with the fact that OFFSET could be present but SCALE missing. Add code to simply scale 1:1 in this case. Link: https://lore.kernel.org/linux-iio/CACRpkdZXBjHU4t-GVOCFxRO-AHGxKnxMeHD2s4Y4PuC29gBq6g@xxxxxxxxxxxxxx/ Fixes: 53ebee949980 ("iio: afe: iio-rescale: Support processed channels") Fixes: 9decacd8b3a4 ("iio: afe: rescale: Fix boolean logic bug") Reported-by: Jonathan Cameron <jic23@xxxxxxxxxx> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> --- Changes in v2: - Fix rescale_read_raw() handle channels with offset but no scale. - Link to v1: https://lore.kernel.org/r/20230830-iio-rescale-only-offset-v1-1-40ab9f4436c7@xxxxxxxxxx --- drivers/iio/afe/iio-rescale.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c index 1f280c360701..56e5913ab82d 100644 --- a/drivers/iio/afe/iio-rescale.c +++ b/drivers/iio/afe/iio-rescale.c @@ -214,8 +214,18 @@ static int rescale_read_raw(struct iio_dev *indio_dev, return ret < 0 ? ret : -EOPNOTSUPP; } - ret = iio_read_channel_scale(rescale->source, &scale, &scale2); - return rescale_process_offset(rescale, ret, scale, scale2, + if (iio_channel_has_info(rescale->source->channel, + IIO_CHAN_INFO_SCALE)) { + ret = iio_read_channel_scale(rescale->source, &scale, &scale2); + return rescale_process_offset(rescale, ret, scale, scale2, + schan_off, val, val2); + } + + /* + * If we get here we have no scale so scale 1:1 but apply + * rescaler and offset, if any. + */ + return rescale_process_offset(rescale, IIO_VAL_FRACTIONAL, 1, 1, schan_off, val, val2); default: return -EINVAL; @@ -280,8 +290,9 @@ 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"); } 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, -- Linus Walleij <linus.walleij@xxxxxxxxxx>