The IIO ABI mandates acceleration values from accelerometer to be
emitted in m/s^2. The KX022A was emitting values in micro m/s^2.
Fix driver to report the correct scale values.
Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
Reported-by: Jagath Jog J <jagathjog1996@xxxxxxxxx>
Fixes: 7c1d1677b322 ("iio: accel: Support Kionix/ROHM KX022A accelerometer")
---
The fix is somewhat crude and just crops the last 3 digits (rounds) of the
scale while using IIO_VAL_INT_PLUS_NANO. I played with a thought of using
IIO_VAL_FRACTIONAL, which could have modelled the computation
G_range * g * scaling / (2^16 * scaling) - where scaling 10000 would
have allowed using g value 980665.
This would have worked fine for reporting scale and available scales -
but would be somewhat tricky when converting the user-supplied scale to
register values in write_raw().
Well, the g varies from 9.832 (poles) to 9.780 (equator) according to
some website - no proper source check done but this sounds about right -
so maybe the loss of accuracy is acceptable.
I did only very quick testing on KX022A and iio_generic_buffer. After
the patch the values seemed to be correct order of magnitude. Further
testing is appreciated :)
---
drivers/iio/accel/kionix-kx022a.c | 37 ++++++++++++++++++++++---------
1 file changed, 26 insertions(+), 11 deletions(-)
diff --git a/drivers/iio/accel/kionix-kx022a.c b/drivers/iio/accel/kionix-kx022a.c
index 4ea3c6718ed4..971fc60efef0 100644
--- a/drivers/iio/accel/kionix-kx022a.c
+++ b/drivers/iio/accel/kionix-kx022a.c
@@ -273,17 +273,17 @@ static const unsigned int kx022a_odrs[] = {
* (range / 2^bits) * g = (range / 2^bits) * 9.80665 m/s^2
* => KX022A uses 16 bit (HiRes mode - assume the low 8 bits are zeroed
* in low-power mode(?) )
- * => +/-2G => 4 / 2^16 * 9,80665 * 10^6 (to scale to micro)
- * => +/-2G - 598.550415
- * +/-4G - 1197.10083
- * +/-8G - 2394.20166
- * +/-16G - 4788.40332
+ * => +/-2G => 4 / 2^16 * 9,80665
+ * => +/-2G - 0.000598550415
+ * +/-4G - 0.00119710083
+ * +/-8G - 0.00239420166
+ * +/-16G - 0.00478840332
*/
static const int kx022a_scale_table[][2] = {
- { 598, 550415 },
- { 1197, 100830 },
- { 2394, 201660 },
- { 4788, 403320 },
+ { 0, 598550 },
+ { 0, 1197101 },
+ { 0, 2394202 },
+ { 0, 4788403 },
};
static int kx022a_read_avail(struct iio_dev *indio_dev,
@@ -302,7 +302,7 @@ static int kx022a_read_avail(struct iio_dev *indio_dev,
*vals = (const int *)kx022a_scale_table;
*length = ARRAY_SIZE(kx022a_scale_table) *
ARRAY_SIZE(kx022a_scale_table[0]);
- *type = IIO_VAL_INT_PLUS_MICRO;
+ *type = IIO_VAL_INT_PLUS_NANO;
return IIO_AVAIL_LIST;
default:
return -EINVAL;
@@ -366,6 +366,20 @@ static int kx022a_turn_on_unlock(struct kx022a_data *data)
return ret;
}
+static int kx022a_write_raw_get_fmt(struct iio_dev *idev,
+ struct iio_chan_spec const *chan,
+ long mask)
+{
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ return IIO_VAL_INT_PLUS_NANO;
+ case IIO_CHAN_INFO_SAMP_FREQ:
+ return IIO_VAL_INT_PLUS_MICRO;
+ default:
+ return -EINVAL;
+ }
+}
+
static int kx022a_write_raw(struct iio_dev *idev,
struct iio_chan_spec const *chan,
int val, int val2, long mask)
@@ -510,7 +524,7 @@ static int kx022a_read_raw(struct iio_dev *idev,
kx022a_reg2scale(regval, val, val2);
- return IIO_VAL_INT_PLUS_MICRO;
+ return IIO_VAL_INT_PLUS_NANO;
}
return -EINVAL;
@@ -712,6 +726,7 @@ static int kx022a_fifo_flush(struct iio_dev *idev, unsigned int samples)
static const struct iio_info kx022a_info = {
.read_raw = &kx022a_read_raw,
.write_raw = &kx022a_write_raw,
+ .write_raw_get_fmt = &kx022a_write_raw_get_fmt,
.read_avail = &kx022a_read_avail,
.validate_trigger = iio_validate_own_trigger,
--
2.41.0
--
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND
~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =]
Attachment:
signature.asc
Description: PGP signature
