The sysfs iio ABI states that a unit of radians per second is
expected, but the 12-bit angular velocity register has rps as its unit.
So a fractional scaling factor of approximately 2 * Pi is added to the
angular velocity channel.
Signed-off-by: David Veenstra <davidjulianveenstra@xxxxxxxxx>
---
drivers/staging/iio/resolver/ad2s1200.c | 82 ++++++++++++++++++++++-----------
1 file changed, 56 insertions(+), 26 deletions(-)
diff --git a/drivers/staging/iio/resolver/ad2s1200.c b/drivers/staging/iio/resolver/ad2s1200.c
index 7ee1d9f76dfb..4b97a106012c 100644
--- a/drivers/staging/iio/resolver/ad2s1200.c
+++ b/drivers/staging/iio/resolver/ad2s1200.c
@@ -61,40 +61,69 @@ static int ad2s1200_read_raw(struct iio_dev *indio_dev,
int ret = 0;
u16 vel;
- mutex_lock(&st->lock);
- gpiod_set_value(st->sample, 0);
+ switch (m) {
+ case IIO_CHAN_INFO_SCALE:
+ switch (chan->type) {
+ case IIO_ANGL_VEL:
+ /*
+ * 2 * Pi is almost equal to
+ * 2 * 103993 / 33102 = 103993 / (33102 / 2)
+ * This fraction is based on OEIS series of
+ * of nominator/denominator of convergents to Pi
+ * (A002485 and A002486).
+ *
+ * iio_convert_raw_to_processed_unlocked uses integer
+ * division. This will cause at most 5% error
+ * (for very small values). But for 99.5% of the values
+ * it will cause less that 1% error.
+ */
+ *val = 103993;
+ *val2 = 33102 / 2;
+ return IIO_VAL_FRACTIONAL;
+ default:
+ return -EINVAL;
+ }
+ break;
+ case IIO_CHAN_INFO_RAW:
+ mutex_lock(&st->lock);
+ gpiod_set_value(st->sample, 0);
+
+ /* delay (6 * AD2S1200_TSCLK + 20) nano seconds */
+ udelay(1);
+ gpiod_set_value(st->sample, 1);
+ gpiod_set_value(st->rdvel, !!(chan->type == IIO_ANGL));
+
+ ret = spi_read(st->sdev, st->rx, 2);
+ if (ret < 0) {
+ mutex_unlock(&st->lock);
+ return ret;
+ }
- /* delay (6 * AD2S1200_TSCLK + 20) nano seconds */
- udelay(1);
- gpiod_set_value(st->sample, 1);
- gpiod_set_value(st->rdvel, !!(chan->type == IIO_ANGL));
+ vel = be16_to_cpup((__be16 *)st->rx);
+ switch (chan->type) {
+ case IIO_ANGL:
+ *val = vel >> 4;
+ ret = IIO_VAL_INT;
+ break;
+ case IIO_ANGL_VEL:
+ *val = sign_extend32((s16)vel >> 4, 11);
+ ret = IIO_VAL_INT;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
- ret = spi_read(st->sdev, st->rx, 2);
- if (ret < 0) {
+ /* delay (2 * AD2S1200_TSCLK + 20) ns for sample pulse */
+ udelay(1);
mutex_unlock(&st->lock);
- return ret;
- }
- vel = be16_to_cpup((__be16 *)st->rx);
- switch (chan->type) {
- case IIO_ANGL:
- *val = vel >> 4;
- ret = IIO_VAL_INT;
- break;
- case IIO_ANGL_VEL:
- *val = sign_extend32((s16)vel >> 4, 11);
- ret = IIO_VAL_INT;
- break;
+ return ret;
default:
- ret = -EINVAL;
break;
}
- /* delay (2 * AD2S1200_TSCLK + 20) ns for sample pulse */
- udelay(1);
- mutex_unlock(&st->lock);
-
- return ret;
+ return -EINVAL;
}
static const struct iio_chan_spec ad2s1200_channels[] = {
@@ -108,6 +137,7 @@ static const struct iio_chan_spec ad2s1200_channels[] = {
.indexed = 1,
.channel = 0,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
}
};
--
2.16.2
_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
