patch "iio: accel: kx022a: Fix raw read format" added to char-misc-testing

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

iio: accel: kx022a: Fix raw read format

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From b7d2bc99b3bdc03fff9b416dd830632346d83530 Mon Sep 17 00:00:00 2001
From: Matti Vaittinen <[email protected]>
Date: Wed, 30 Oct 2024 15:16:11 +0200
Subject: iio: accel: kx022a: Fix raw read format

The KX022A provides the accelerometer data in two subsequent registers. The registers are laid out so that the value obtained via bulk-read of these registers can be interpreted as signed 16-bit little endian value. The read value is converted to cpu_endianes and stored into 32bit integer. The le16_to_cpu() casts value to unsigned 16-bit value, and when this is assigned to 32-bit integer the resulting value will always be positive.

This has not been a problem to users (at least not all users) of the sysfs interface, who know the data format based on the scan info and who have converted the read value back to 16-bit signed value. This isn't compliant with the ABI however.

This, however, will be a problem for those who use the in-kernel interfaces, especially the iio_read_channel_processed_scale().

The iio_read_channel_processed_scale() performs multiplications to the returned (always positive) raw value, which will cause strange results when the data from the sensor has been negative.

Fix the read_raw format by casting the result of the le_to_cpu() to signed 16-bit value before assigning it to the integer. This will make the negative readings to be correctly reported as negative.

This fix will be visible to users by changing values returned via sysfs to appear in correct (negative) format.

---
 drivers/iio/accel/kionix-kx022a.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 53d59a04ae15..b6a828a6df93 100644
@@ -594,7 +594,7 @@ static int kx022a_get_axis(struct kx022a_data *data,
 	if (ret)
 		return ret;
 
-	*val = le16_to_cpu(data->buffer[0]);
+	*val = (s16)le16_to_cpu(data->buffer[0]);
 
 	return IIO_VAL_INT;
 }

2.47.0