On 01/09/16 10:44, Linus Walleij wrote:
> This fixes several errors in the offset and scaling of the raw
> values from the KXSD9 sensor:
>
> - The code did not convert the big endian value from the sensor
> into the endianness of the host CPU. Fix this with
> be16_to_cpu() on the raw obtained value.
>
> - The code did not regard the fact that only the upper 12 bits of
> the accelerometer values are valid. Shift these
> down four bits to yield the real raw value.
>
> - Further the sensor provides 2048 at zero g. This means that an
> offset of 2048 must be subtracted from the raw value before
> scaling. This was not taken into account by the driver,
> yielding a weird value. Fix this by providing this offset in
> sysfs.
>
> To house the scaling code better, the value reading code was
> factored into the raw reading function.
>
> This proper scaling and offseting is necessary to get proper
> values out of triggered buffer by offsetting, shifting and scaling
> them.
>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Perhaps this should have gone in as a fix, but never mind.
Applied to the togreg branch of iio.git.
Jonathan
> ---
> ChangeLog v1->v2:
> - Rebase on the rest of the series.
> ---
> drivers/iio/accel/kxsd9.c | 35 ++++++++++++++++++-----------------
> 1 file changed, 18 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/iio/accel/kxsd9.c b/drivers/iio/accel/kxsd9.c
> index dc0bea7cbf4f..6a1e67723d0c 100644
> --- a/drivers/iio/accel/kxsd9.c
> +++ b/drivers/iio/accel/kxsd9.c
> @@ -55,6 +55,8 @@ struct kxsd9_state {
> /* reverse order */
> static const int kxsd9_micro_scales[4] = { 47853, 35934, 23927, 11978 };
>
> +#define KXSD9_ZERO_G_OFFSET -2048
> +
> static int kxsd9_write_scale(struct iio_dev *indio_dev, int micro)
> {
> int ret, i;
> @@ -82,19 +84,6 @@ error_ret:
> return ret;
> }
>
> -static int kxsd9_read(struct iio_dev *indio_dev, u8 address)
> -{
> - int ret;
> - struct kxsd9_state *st = iio_priv(indio_dev);
> - __be16 raw_val;
> -
> - ret = regmap_bulk_read(st->map, address, &raw_val, sizeof(raw_val));
> - if (ret)
> - return ret;
> - /* Only 12 bits are valid */
> - return be16_to_cpu(raw_val) & 0xfff0;
> -}
> -
> static IIO_CONST_ATTR(accel_scale_available,
> KXSD9_SCALE_2G " "
> KXSD9_SCALE_4G " "
> @@ -131,13 +120,24 @@ static int kxsd9_read_raw(struct iio_dev *indio_dev,
> int ret = -EINVAL;
> struct kxsd9_state *st = iio_priv(indio_dev);
> unsigned int regval;
> + __be16 raw_val;
> + u16 nval;
>
> switch (mask) {
> case IIO_CHAN_INFO_RAW:
> - ret = kxsd9_read(indio_dev, chan->address);
> - if (ret < 0)
> + ret = regmap_bulk_read(st->map, chan->address, &raw_val,
> + sizeof(raw_val));
> + if (ret)
> goto error_ret;
> - *val = ret;
> + nval = be16_to_cpu(raw_val);
> + /* Only 12 bits are valid */
> + nval >>= 4;
> + *val = nval;
> + ret = IIO_VAL_INT;
> + break;
> + case IIO_CHAN_INFO_OFFSET:
> + /* This has a bias of -2048 */
> + *val = KXSD9_ZERO_G_OFFSET;
> ret = IIO_VAL_INT;
> break;
> case IIO_CHAN_INFO_SCALE:
> @@ -161,7 +161,8 @@ error_ret:
> .modified = 1, \
> .channel2 = IIO_MOD_##axis, \
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> - .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \
> + BIT(IIO_CHAN_INFO_OFFSET), \
> .address = KXSD9_REG_##axis, \
> }
>
>
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