Messages in this thread Patch in this message | | | Date | Thu, 19 Oct 2023 16:23:56 +0300 | From | Matti Vaittinen <> | Subject | [PATCH] iio: kx022a: Fix acceleration value scaling |
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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@gmail.com> Reported-by: Jagath Jog J <jagathjog1996@gmail.com> 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 =] [unhandled content-type:application/pgp-signature] | |