prop_get
if ((pv = prop_get(node, pgname, pname, args, err)) == NULL) {
if ((pv = prop_get(node, pgname, pname, NULL, err))
const struct propval *prop_get(struct propctx *ctx);
const struct propval *(*prop_get)(struct propctx *ctx);
utils->prop_get=&prop_get;
int (*prop_get)(pcie_hp_slot_t *, const char **);
ret = prop->prop_get(slot_p, &value);