From c2890547a035e019df646be5d56adc0ee1b0a327 Mon Sep 17 00:00:00 2001 From: Daniel Baluta Date: Fri, 5 Jun 2015 14:03:12 +0300 Subject: iio: magnetometer: mmc35240: Fix broken processed value 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 milli 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 Signed-off-by: Jonathan Cameron --- drivers/iio/magnetometer/mmc35240.c | 43 +++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 16 deletions(-) (limited to 'drivers/iio/magnetometer/mmc35240.c') diff --git a/drivers/iio/magnetometer/mmc35240.c b/drivers/iio/magnetometer/mmc35240.c index 78da0d15c8eb..146ae6613537 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 milli 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 milli 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); -- cgit v1.2.3