linux-kernel - [PATCH v3 03/10] iio: inkern: make a best effort on offset calculation

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Date:   Wed, 30 Jun 2021 21:00:27 -0400
From:   Liam Beguin <liambeguin@...il.com>
To:     liambeguin@...il.com, peda@...ntia.se, jic23@...nel.org,
        lars@...afoo.de, pmeerw@...erw.net
Cc:     linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, robh+dt@...nel.org
Subject: [PATCH v3 03/10] iio: inkern: make a best effort on offset calculation

From: Liam Beguin <lvb@...hos.com>

iio_convert_raw_to_processed_unlocked() assumes the offset is an
integer. Make a best effort to get a valid offset value for fractional
cases without breaking implicit truncations.

Fixes: 48e44ce0f881 ("iio:inkern: Add function to read the processed value")
Signed-off-by: Liam Beguin <lvb@...hos.com>
---
 drivers/iio/inkern.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index b69027690ed5..e1712c1099c5 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -578,13 +578,39 @@ EXPORT_SYMBOL_GPL(iio_read_channel_average_raw);
 static int iio_convert_raw_to_processed_unlocked(struct iio_channel *chan,
 	int raw, int *processed, unsigned int scale)
 {
-	int scale_type, scale_val, scale_val2, offset;
+	int scale_type, scale_val, scale_val2;
+	int offset_type, offset_val, offset_val2;
 	s64 raw64 = raw;
-	int ret;
+	int tmp;
 
-	ret = iio_channel_read(chan, &offset, NULL, IIO_CHAN_INFO_OFFSET);
-	if (ret >= 0)
-		raw64 += offset;
+	offset_type = iio_channel_read(chan, &offset_val, &offset_val2,
+				       IIO_CHAN_INFO_OFFSET);
+	if (offset_type >= 0) {
+		switch (offset_type) {
+		case IIO_VAL_INT:
+			break;
+		case IIO_VAL_INT_PLUS_MICRO:
+			fallthrough;
+		case IIO_VAL_INT_PLUS_NANO:
+			/*
+			 * Both IIO_VAL_INT_PLUS_MICRO and IIO_VAL_INT_PLUS_NANO
+			 * implicitely truncate the offset to it's integer form.
+			 */
+			break;
+		case IIO_VAL_FRACTIONAL:
+			tmp = offset_val / offset_val2;
+			offset_val = tmp;
+			break;
+		case IIO_VAL_FRACTIONAL_LOG2:
+			tmp = offset_val / (1 << offset_val2);
+			offset_val = tmp;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		raw64 += offset_val;
+	}
 
 	scale_type = iio_channel_read(chan, &scale_val, &scale_val2,
 					IIO_CHAN_INFO_SCALE);
-- 
2.30.1.489.g328c10930387