> Allow to read the mount-matrix device tree property and provide the
> mount_matrix file for userspace to read.
> 
> Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
> ---
> 
> tested using the lsm9ds1 on the librem5-devkit (and userspace tools like
> iio-sensor-proxy) where this will be needed.
> 
> thanks,
> 
>                                martin
> 
> 
> 
>  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h      | 18 ++++++++++++++++++
>  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c |  4 ++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> index a763ff46f596..8483f770b233 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> @@ -76,6 +76,7 @@ enum st_lsm6dsx_hw_id {
>  		.endianness = IIO_LE,					\
>  	},								\
>  	.event_spec = &st_lsm6dsx_event,				\
> +	.ext_info = st_lsm6dsx_accel_ext_info,				\
>  	.num_event_specs = 1,						\
>  }
>  
> @@ -406,6 +407,8 @@ struct st_lsm6dsx_hw {
>  	struct iio_dev *iio_devs[ST_LSM6DSX_ID_MAX];
>  
>  	const struct st_lsm6dsx_settings *settings;
> +
> +	struct iio_mount_matrix orientation;

Could you please add doc for orientation struct as we did for all other member
of st_lsm6dsx_hw?

>  };
>  
>  static __maybe_unused const struct iio_event_spec st_lsm6dsx_event = {
> @@ -479,4 +482,19 @@ st_lsm6dsx_write_locked(struct st_lsm6dsx_hw *hw, unsigned int addr,
>  	return err;
>  }
>  
> +static const struct iio_mount_matrix *
> +st_lsm6dsx_get_mount_matrix(const struct iio_dev *iio_dev,
> +			    const struct iio_chan_spec *chan)

static const inline struct iio_mount_matrix *
st_lsm6dsx_get_mount_matrix(const struct iio_dev *iio_dev

> +{
> +	struct st_lsm6dsx_sensor *sensor = iio_priv(iio_dev);
> +	struct st_lsm6dsx_hw *hw = sensor->hw;
> +
> +	return &hw->orientation;
> +}
> +
> +static const struct iio_chan_spec_ext_info st_lsm6dsx_accel_ext_info[] = {
> +	IIO_MOUNT_MATRIX(IIO_SHARED_BY_ALL, st_lsm6dsx_get_mount_matrix),
> +	{ }
> +};
> +
>  #endif /* ST_LSM6DSX_H */
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> index 0c64e35c7599..587e02bb9be9 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> @@ -2325,6 +2325,10 @@ int st_lsm6dsx_probe(struct device *dev, int irq, int hw_id,
>  	    (pdata && pdata->wakeup_source))
>  		device_init_wakeup(dev, true);
>  
> +	err = iio_read_mount_matrix(hw->dev, "mount-matrix", &hw->orientation);
> +	if (err)
> +		return err;
> +
>  	return 0;

	return iio_read_mount_matrix(hw->dev, "mount-matrix",
				     &hw->orientation); 

>  }
>  EXPORT_SYMBOL(st_lsm6dsx_probe);
> -- 
> 2.20.1
>