The current computation for fractional part of the magnetic
field is broken. This patch fixes it by taking a different
approach. We expose the raw reading in mili Gauss (to avoid
rounding errors) with a scale of 0.001.
Thus the final computation is done in userspace where floating
point operation are more relaxed.
Fixes: abeb6b1e7b ("iio: magnetometer: Add support for MEMSIC MMC35240")
Signed-off-by: Daniel Baluta <daniel.baluta@xxxxxxxxx>
---
drivers/iio/magnetometer/mmc35240.c | 43 +++++++++++++++++++++++--------------
1 file changed, 27 insertions(+), 16 deletions(-)
diff --git a/drivers/iio/magnetometer/mmc35240.c b/drivers/iio/magnetometer/mmc35240.c
index 9d62c53..c520117 100644
--- a/drivers/iio/magnetometer/mmc35240.c
+++ b/drivers/iio/magnetometer/mmc35240.c
@@ -113,8 +113,9 @@ static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("100 200 333 666");
.modified = 1, \
.channel2 = IIO_MOD_ ## _axis, \
.address = AXIS_ ## _axis, \
- .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
- .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) |\
+ BIT(IIO_CHAN_INFO_SCALE), \
}
static const struct iio_chan_spec mmc35240_channels[] = {
@@ -241,9 +242,19 @@ static int mmc35240_read_measurement(struct mmc35240_data *data, __le16 buf[3])
3 * sizeof(__le16));
}
-static int mmc35240_raw_to_gauss(struct mmc35240_data *data, int index,
- __le16 buf[],
- int *val, int *val2)
+/**
+ * mmc35240_raw_to_mgauss - convert raw readings to mili gauss. Also apply
+ compensation for output value.
+ *
+ * @data: device private data
+ * @index: axis index for which we want the conversion
+ * @buf: raw data to be converted, 2 bytes in little endian format
+ * @val: compensated output reading (unit is mili gauss)
+ *
+ * Returns: 0 in case of success, -EINVAL when @index is not valid
+ */
+static int mmc35240_raw_to_mgauss(struct mmc35240_data *data, int index,
+ __le16 buf[], int *val)
{
int raw_x, raw_y, raw_z;
int sens_x, sens_y, sens_z;
@@ -261,18 +272,15 @@ static int mmc35240_raw_to_gauss(struct mmc35240_data *data, int index,
switch (index) {
case AXIS_X:
- *val = (raw_x - nfo) / sens_x;
- *val2 = ((raw_x - nfo) % sens_x) * 1000000;
+ *val = (raw_x - nfo) * 1000 / sens_x;
break;
case AXIS_Y:
- *val = (raw_y - nfo) / sens_y - (raw_z - nfo) / sens_z;
- *val2 = (((raw_y - nfo) % sens_y - (raw_z - nfo) % sens_z))
- * 1000000;
+ *val = (raw_y - nfo) * 1000 / sens_y -
+ (raw_z - nfo) * 1000 / sens_z;
break;
case AXIS_Z:
- *val = (raw_y - nfo) / sens_y + (raw_z - nfo) / sens_z;
- *val2 = (((raw_y - nfo) % sens_y + (raw_z - nfo) % sens_z))
- * 1000000;
+ *val = (raw_y - nfo) * 1000 / sens_y +
+ (raw_z - nfo) * 1000 / sens_z;
break;
default:
return -EINVAL;
@@ -290,16 +298,19 @@ static int mmc35240_read_raw(struct iio_dev *indio_dev,
__le16 buf[3];
switch (mask) {
- case IIO_CHAN_INFO_PROCESSED:
+ case IIO_CHAN_INFO_RAW:
mutex_lock(&data->mutex);
ret = mmc35240_read_measurement(data, buf);
mutex_unlock(&data->mutex);
if (ret < 0)
return ret;
- ret = mmc35240_raw_to_gauss(data, chan->address,
- buf, val, val2);
+ ret = mmc35240_raw_to_mgauss(data, chan->address, buf, val);
if (ret < 0)
return ret;
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = 0;
+ *val2 = 1000;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CHAN_INFO_SAMP_FREQ:
mutex_lock(&data->mutex);
--
1.9.1
--
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