The enable_mask struct member keeps track of which sensors are enabled in
the IMU. When enabling and disabling the sensor fusion functionality, the
driver does not properly update this struct member. This prevents a correct
calculation of the number of samples that should be read from the hardware
FIFO; as a result, reads from the FIFO can be unnecessarily split into
multiple transactions, some of which can read past the FIFO length.

Fixes: cd4e1141bff8 ("iio: imu: st_lsm6dsx: Add support for rotation sensor")
Signed-off-by: Francesco Lavra <flavra@baylibre.com>
---
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
index 2e72c7ba94dd..5321033daebc 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
@@ -112,6 +112,11 @@ int st_lsm6dsx_fusion_set_enable(struct st_lsm6dsx_sensor *sensor, bool enable)
 		return err;
 	}
 
+	if (enable)
+		hw->enable_mask |= BIT(ST_LSM6DSX_ID_FUSION);
+	else
+		hw->enable_mask &= ~BIT(ST_LSM6DSX_ID_FUSION);
+
 	return st_lsm6dsx_fusion_page_disable(hw);
 }
 
-- 
2.39.5

> The enable_mask struct member keeps track of which sensors are enabled in
> the IMU. When enabling and disabling the sensor fusion functionality, the
> driver does not properly update this struct member. This prevents a correct
> calculation of the number of samples that should be read from the hardware
> FIFO; as a result, reads from the FIFO can be unnecessarily split into
> multiple transactions, some of which can read past the FIFO length.

Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>

> 
> Fixes: cd4e1141bff8 ("iio: imu: st_lsm6dsx: Add support for rotation sensor")
> Signed-off-by: Francesco Lavra <flavra@baylibre.com>
> ---
>  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
> index 2e72c7ba94dd..5321033daebc 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
> @@ -112,6 +112,11 @@ int st_lsm6dsx_fusion_set_enable(struct st_lsm6dsx_sensor *sensor, bool enable)
>  		return err;
>  	}
>  
> +	if (enable)
> +		hw->enable_mask |= BIT(ST_LSM6DSX_ID_FUSION);
> +	else
> +		hw->enable_mask &= ~BIT(ST_LSM6DSX_ID_FUSION);
> +
>  	return st_lsm6dsx_fusion_page_disable(hw);
>  }
>  
> -- 
> 2.39.5
> 

On Fri, 31 Jul 2026 22:44:44 +0200
Lorenzo Bianconi <lorenzo@kernel.org> wrote:

> > The enable_mask struct member keeps track of which sensors are enabled in
> > the IMU. When enabling and disabling the sensor fusion functionality, the
> > driver does not properly update this struct member. This prevents a correct
> > calculation of the number of samples that should be read from the hardware
> > FIFO; as a result, reads from the FIFO can be unnecessarily split into
> > multiple transactions, some of which can read past the FIFO length.  
> 
> Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
> 
> > 
Applied to the testing branch of iio.git and marked for stable.

Going the slow way because Linus has requested only breakage from current cycle
or critical fixes take the fast path. So this will take a few weeks to make
it into stable trees.

Thanks

Jonathan

> > Fixes: cd4e1141bff8 ("iio: imu: st_lsm6dsx: Add support for rotation sensor")
> > Signed-off-by: Francesco Lavra <flavra@baylibre.com>
> > ---
> >  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
> > index 2e72c7ba94dd..5321033daebc 100644
> > --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
> > +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_fusion.c
> > @@ -112,6 +112,11 @@ int st_lsm6dsx_fusion_set_enable(struct st_lsm6dsx_sensor *sensor, bool enable)
> >  		return err;
> >  	}
> >  
> > +	if (enable)
> > +		hw->enable_mask |= BIT(ST_LSM6DSX_ID_FUSION);
> > +	else
> > +		hw->enable_mask &= ~BIT(ST_LSM6DSX_ID_FUSION);
> > +
> >  	return st_lsm6dsx_fusion_page_disable(hw);
> >  }
> >  
> > -- 
> > 2.39.5
> >