On Thu, 8 Dec 2022 15:19:08 +0800
carlos.song@xxxxxxx wrote:
> From: Carlos Song <carlos.song@xxxxxxx>
>
> ACCEL output data registers contain the X-axis, Y-axis, and Z-axis
> 14-bit left-justified sample data and MAGN output data registers
> contain the X-axis, Y-axis, and Z-axis 16-bit sample data. The ACCEL
> raw register output data should be divided by 4 before sent to
> userspace.
>
> Apply a 2 bits signed right shift to the raw data from ACCEL output
> data register but keep that from MAGN sensor as the origin.
>
> Fixes: 84e5ddd5c46e ("iio: imu: Add support for the FXOS8700 IMU")
> Signed-off-by: Carlos Song <carlos.song@xxxxxxx>
I made one tweak (see below).
Applied to the fixes-togreg branch of iio.git and marked for stable inclusion.
> ---
> Changes for V2:
> - Store the shift in the switch and apply a shift by 2 for ACCEL
> and shift by 0 for MAGN
> - Confirm the scaling is still correct for the acceleration channels
> given we are effectively dividing by 4 compared to the previous code
> - Rework the comment
>
> diff --git a/drivers/iio/imu/fxos8700_core.c b/drivers/iio/imu/fxos8700_core.c
> index b62bc92bbacc..d2e784628820 100644
> --- a/drivers/iio/imu/fxos8700_core.c
> +++ b/drivers/iio/imu/fxos8700_core.c
> @@ -394,6 +394,7 @@ static int fxos8700_get_data(struct fxos8700_data *data, int chan_type,
> int axis, int *val)
> {
> u8 base, reg;
> + s16 tmp;
> int ret;
>
> /*
> @@ -421,8 +422,33 @@ static int fxos8700_get_data(struct fxos8700_data *data, int chan_type,
> /* Convert axis to buffer index */
> reg = axis - IIO_MOD_X;
>
> + /*
> + * Convert to native endianness. The accel data and magn data
> + * are signed, so a forced type conversion is needed.
> + */
> + tmp = be16_to_cpu(data->buf[reg]);
> +
> + /*
> + * ACCEL output data registers contain the X-axis, Y-axis, and Z-axis
> + * 14-bit left-justified sample data and MAGN output data registers
> + * contain the X-axis, Y-axis, and Z-axis 16-bit sample data. Apply
> + * a signed 2 bits right shift to the readback raw data from ACCEL
> + * output data register and keep that from MAGN sensor as the origin.
> + * Value should be extended to 32 bit.
> + */
> + switch (chan_type) {
> + case IIO_ACCEL:
> + tmp = tmp >> 2;
> + break;
> + case IIO_MAGN:
> + tmp = tmp >> 0;
I replaced this no operation line with a comment
/* Nothing to do */
otherwise it's the sort of thing some static checker might moan about :)
Jonathan
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> /* Convert to native endianness */
> - *val = sign_extend32(be16_to_cpu(data->buf[reg]), 15);
> + *val = sign_extend32(tmp, 15);
>
> return 0;
> }
