add_path
static DEVICE_ATTR_RW(add_path);
r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
int (*add_path)(struct path_selector *ps, struct dm_path *path,
.add_path = hst_add_path,
.add_path = ioa_add_path,
.add_path = ql_add_path,
.add_path = rr_add_path,
.add_path = st_add_path,
add_path(&new_path, tmp);
add_path(&new_path, argv0_path);