Commit 05f958d0 authored by Hans de Goede's avatar Hans de Goede Committed by Jonathan Cameron
Browse files

iio: Improve iio_read_channel_processed_scale() precision 



Before this change iio_read_channel_processed_scale() always assumes that
channels which advertise IIO_CHAN_INFO_PROCESSED capability return
IIO_VAL_INT on success.

Ignoring any fractional values from drivers which return
IIO_VAL_INT_PLUS_MICRO / IIO_VAL_INT_PLUS_NANO. These fractional values
might become non fractional after scaling so these should be taken into
account for better precision.

Use the new iio_multiply_value() helper to do proper scaling taking
the fractionional values into account.

Reviewed-by: default avatarAndy Shevchenko <andy@kernel.org>
Signed-off-by: default avatarHans de Goede <hansg@kernel.org>
Link: https://patch.msgid.link/20250831104825.15097-5-hansg@kernel.org


Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent cec1aec9

drivers/iio/inkern.c

+3 −4
Original line number Diff line number Diff line
@@ -726,20 +726,19 @@ int iio_read_channel_processed_scale(struct iio_channel *chan, int *val, 
				     unsigned int scale)

{

	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(chan->indio_dev);

	int ret;

	int ret, pval, pval2;



	guard(mutex)(&iio_dev_opaque->info_exist_lock);

	if (!chan->indio_dev->info)

		return -ENODEV;



	if (iio_channel_has_info(chan->channel, IIO_CHAN_INFO_PROCESSED)) {

		ret = iio_channel_read(chan, val, NULL,

		ret = iio_channel_read(chan, &pval, &pval2,

				       IIO_CHAN_INFO_PROCESSED);

		if (ret < 0)

			return ret;

		*val *= scale;



		return ret;

		return iio_multiply_value(val, scale, ret, pval, pval2);

	} else {

		ret = iio_channel_read(chan, val, NULL, IIO_CHAN_INFO_RAW);

		if (ret < 0)