Re: [PATCH v6 7/7] iio: imu: st_lsm6dsx: Add support for rotation sensor

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Wed, Feb 25, 2026 at 11:18:13AM +0100, Francesco Lavra wrote:
> Some IMU chips in the LSM6DSX family have sensor fusion features that
> combine data from the accelerometer and gyroscope. One of these features
> generates rotation vector data and makes it available in the hardware
> FIFO as a quaternion (more specifically, the X, Y and Z components of the
> quaternion vector, expressed as 16-bit half-precision floating-point
> numbers).
> 
> Add support for a new sensor instance that allows receiving sensor fusion
> data, by defining a new struct st_lsm6dsx_sf_settings (which contains
> chip-specific details for the sensor fusion functionality), and adding this
> struct as a new field in struct st_lsm6dsx_settings. In st_lsm6dsx_core.c,
> populate this new struct for the LSM6DSV and LSM6DSV16X chips, and add the
> logic to initialize an additional IIO device if this struct is populated
> for the hardware type being probed.
> Note: a new IIO device is being defined (as opposed to adding channels to
> an existing device) because the rate at which sensor fusion data is
> generated may not match the data rate from any of the existing devices.
> 
> Tested on LSMDSV16X.

...

> +int st_lsm6dsx_sf_probe(struct st_lsm6dsx_hw *hw, const char *name)
> +{
> +	const struct st_lsm6dsx_sf_settings *settings;
> +	struct st_lsm6dsx_sensor *sensor;
> +	struct iio_dev *iio_dev;

Maybe

	int ret; // choose better name if any

> +	iio_dev = devm_iio_device_alloc(hw->dev, sizeof(*sensor));
> +	if (!iio_dev)
> +		return -ENOMEM;
> +
> +	settings = &hw->settings->sf_settings;
> +	sensor = iio_priv(iio_dev);
> +	sensor->id = ST_LSM6DSX_ID_SF;
> +	sensor->hw = hw;
> +	sensor->hwfifo_odr_mHz = settings->odr_table.odr_avl[0].milli_hz;
> +	sensor->watermark = 1;
> +	iio_dev->modes = INDIO_DIRECT_MODE;
> +	iio_dev->info = &st_lsm6dsx_sf_info;
> +	iio_dev->channels = settings->chan;
> +	iio_dev->num_channels = settings->chan_len;

> +	if (snprintf(sensor->name, sizeof(sensor->name), "%s_sf", name) >=
> +	    sizeof(sensor->name))
> +		return -E2BIG;

	ret = snprintf(sensor->name, sizeof(sensor->name), "%s_sf", name);
	if (ret >= sizeof(sensor->name))
		return -E2BIG;

I find this easier to read and follow.

> +	iio_dev->name = sensor->name;
> +
> +	/*
> +	 *  Put the IIO device pointer in the iio_devs array so that the caller
> +	 *  can set up a buffer and register this IIO device.
> +	 */
> +	hw->iio_devs[ST_LSM6DSX_ID_SF] = iio_dev;
> +
> +	return 0;
> +}

-- 
With Best Regards,
Andy Shevchenko