Man pages matching name hwloc_obj_attr_u in section 3:

hwloc_obj_attr_u.3.en	debian 10 / libhwloc-doc
hwloc_obj_attr_u.3.en	debian 11 / libhwloc-doc
hwloc_obj_attr_u.3.en	debian 12 / libhwloc-doc