Re: [PATCH v4 1/9] iio: imu: st_lsm6dsx: fix iio_chan_spec for sensors without event detection

[Jonathan Cameron <jic23@kernel.org>]

On Mon,  1 Dec 2025 11:00:10 +0100
Francesco Lavra <flavra@baylibre.com> wrote:

> The st_lsm6dsx_acc_channels array of struct iio_chan_spec has a non-NULL
> event_spec field, indicating support for IIO events. However, event
> detection is not supported for all sensors, and if userspace tries to
> configure accelerometer wakeup events on a sensor device that does not
> support them (e.g. LSM6DS0), st_lsm6dsx_write_event() dereferences a NULL
> pointer when trying to write to the wakeup register.
> Define an additional struct iio_chan_spec array whose members have a NULL
> event_spec field, and use this array instead of st_lsm6dsx_acc_channels for
> sensors without event detection capability.
> 
> Fixes: b5969abfa8b8 ("iio: imu: st_lsm6dsx: add motion events")
> Signed-off-by: Francesco Lavra <flavra@baylibre.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Applied to the fixes-togreg branch of iio.git (which I might not push out
until I can rebase on rc1) and marked for stable.

If this causes conflicts with the rest of the series that will have to wait
until this is in upstream and can merge that into the main iio tree.

This feels to urgent to sit on for a whole extra cycle.

Thanks,

Jonathan

> ---
>  drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> index 216160549b5a..a09df9d772dd 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
> @@ -103,6 +103,13 @@ static const struct iio_chan_spec st_lsm6dsx_acc_channels[] = {
>  	IIO_CHAN_SOFT_TIMESTAMP(3),
>  };
>  
> +static const struct iio_chan_spec st_lsm6ds0_acc_channels[] = {
> +	ST_LSM6DSX_CHANNEL(IIO_ACCEL, 0x28, IIO_MOD_X, 0),
> +	ST_LSM6DSX_CHANNEL(IIO_ACCEL, 0x2a, IIO_MOD_Y, 1),
> +	ST_LSM6DSX_CHANNEL(IIO_ACCEL, 0x2c, IIO_MOD_Z, 2),
> +	IIO_CHAN_SOFT_TIMESTAMP(3),
> +};
> +
>  static const struct iio_chan_spec st_lsm6dsx_gyro_channels[] = {
>  	ST_LSM6DSX_CHANNEL(IIO_ANGL_VEL, 0x22, IIO_MOD_X, 0),
>  	ST_LSM6DSX_CHANNEL(IIO_ANGL_VEL, 0x24, IIO_MOD_Y, 1),
> @@ -144,8 +151,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
>  		},
>  		.channels = {
>  			[ST_LSM6DSX_ID_ACC] = {
> -				.chan = st_lsm6dsx_acc_channels,
> -				.len = ARRAY_SIZE(st_lsm6dsx_acc_channels),
> +				.chan = st_lsm6ds0_acc_channels,
> +				.len = ARRAY_SIZE(st_lsm6ds0_acc_channels),
>  			},
>  			[ST_LSM6DSX_ID_GYRO] = {
>  				.chan = st_lsm6ds0_gyro_channels,
> @@ -1445,8 +1452,8 @@ static const struct st_lsm6dsx_settings st_lsm6dsx_sensor_settings[] = {
>  		},
>  		.channels = {
>  			[ST_LSM6DSX_ID_ACC] = {
> -				.chan = st_lsm6dsx_acc_channels,
> -				.len = ARRAY_SIZE(st_lsm6dsx_acc_channels),
> +				.chan = st_lsm6ds0_acc_channels,
> +				.len = ARRAY_SIZE(st_lsm6ds0_acc_channels),
>  			},
>  			[ST_LSM6DSX_ID_GYRO] = {
>  				.chan = st_lsm6dsx_gyro_channels,