cuse_copy_in
int cuse_copy_in(const void *user_src, void *dst, int len);
error = cuse_copy_in(peer_data, &data, len);
error = cuse_copy_in(data.fir_filter.filter_data,
error = cuse_copy_in(data.fir_filter.filter_data,
error = cuse_copy_in(peer_ptr, buf_ptr, buf_len);
error = cuse_copy_in(peer_data, &data, len);
error = cuse_copy_in(peer_data, &data, len);