[PATCH v3] iio: afe: rescale: expose offset if rescaler or source has one

[Andrea Amer via B4 Relay <devnull+and.amer.gmail.com@kernel.org>]

From: Andrea Amer <and.amer@gmail.com>

A rescale channel advertises IIO_CHAN_INFO_OFFSET only when its own
offset is non-zero. A child rescale therefore hides a source offset,
and consumers apply raw * scale and drop it, even though
rescale_read_raw() folds the source offset in.

Expose the attribute when either the rescaler or the source channel
provides an offset.

Fixes: a29c3283653b ("iio: afe: rescale: add offset support")
Signed-off-by: Andrea Amer <and.amer@gmail.com>
---
Changes in v3:
- Only expose offset if the rescaler or the source has one (Jonathan Cameron)
- Link to v2: https://lore.kernel.org/r/20261016-iio-rescale-offset-v2-1-02c825967139@gmail.com

Changes in v2:
- Keep the IIO_CHAN_INFO_SCALE line unchanged (Andy Shevchenko)
- Link to v1: https://lore.kernel.org/r/20261012-iio-rescale-offset-v1-1-14ed15979ff2@gmail.com
---
 drivers/iio/afe/iio-rescale.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/afe/iio-rescale.c b/drivers/iio/afe/iio-rescale.c
index 3a6a09ffa5267ddfd5131fbd04a5df928836589d..c01292a15a29d02afa8de80a778c2c2a2aeecd3f 100644
--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -303,7 +303,8 @@ static int rescale_configure_channel(struct device *dev,
 	chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
 		BIT(IIO_CHAN_INFO_SCALE);
 
-	if (rescale->offset)
+	if (rescale->offset ||
+	    iio_channel_has_info(schan, IIO_CHAN_INFO_OFFSET))
 		chan->info_mask_separate |= BIT(IIO_CHAN_INFO_OFFSET);
 
 	/*

---
base-commit: a3b3580713f3ac5a32dc2874ee546828977a1d68
change-id: 20261012-iio-rescale-offset-41254a33b6d6

Best regards,
-- 
Andrea Amer <and.amer@gmail.com>