Patch "iio: afe: rescale: Accept only offset channels" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    iio: afe: rescale: Accept only offset channels

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     iio-afe-rescale-accept-only-offset-channels.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9017f1c97947dfb8054891f3acdda2dc84964813
Author: Linus Walleij <linus.walleij@xxxxxxxxxx>
Date:   Sat Sep 2 21:46:20 2023 +0200

    iio: afe: rescale: Accept only offset channels
    
    [ Upstream commit bee448390e5166d019e9e037194d487ee94399d9 ]
    
    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>
    Reviewed-by: Peter Rosin <peda@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230902-iio-rescale-only-offset-v2-1-988b807754c8@xxxxxxxxxx
    Cc: <Stable@xxxxxxxxxxxxxxx>
    Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 84f21dc94a2f7..ea0a39882eb25 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -152,8 +152,18 @@ 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;
@@ -218,8 +228,9 @@ 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;