iio_get_channel_ext_info_count
sizeof_ext_info = iio_get_channel_ext_info_count(source);
EXPORT_SYMBOL_GPL(iio_get_channel_ext_info_count);
num_ext_info = iio_get_channel_ext_info_count(mux->parent);
sizeof_ext_info = iio_get_channel_ext_info_count(parent);
unsigned int iio_get_channel_ext_info_count(struct iio_channel *chan);