On Wed, 30 Oct 2024 18:06:58 +0000 Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > On Wed, 30 Oct 2024 15:16:11 +0200 > Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote: > > > 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. > They shouldn't be doing that. Scaninfo is for buffered values only > This should indeed be signed. I added a note saying this isn't compliant with the ABI. Applied to the fixes-togreg branch fo iio.git and marked for stable. > > > > > 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. > > > > Reported-by: Kalle Niemi <kaleposti@xxxxxxxxx> > > Fixes: 7c1d1677b322 ("iio: accel: Support Kionix/ROHM KX022A accelerometer") > > Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx> > > Tested-by: Kalle Niemi <kaleposti@xxxxxxxxx> > > --- > > drivers/iio/accel/kionix-kx022a.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/iio/accel/kionix-kx022a.c b/drivers/iio/accel/kionix-kx022a.c > > index 53d59a04ae15..b6a828a6df93 100644 > > --- a/drivers/iio/accel/kionix-kx022a.c > > +++ b/drivers/iio/accel/kionix-kx022a.c > > @@ -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]); > LGTM. > > > > return IIO_VAL_INT; > > } > > > > base-commit: 81983758430957d9a5cb3333fe324fd70cf63e7e >