L2_add_head
L2_add_head(&(cccp)->ccc_doneq, &(gcmdp)->cmd_q, (gcmdp)); \
void L2_add_head(L2el_t *headp, L2el_t *elementp, void *private);
L2_add_head(&GHBA_QHEAD(cccp), &gcmdp->cmd_q, gcmdp);
void L2_add_head(L2el_t *headp, L2el_t *elementp, void *priv);