sg_chain_ptr
req->src = sg_chain_ptr(req->src);
req->src = sg_chain_ptr(req->src);
sg = sg_chain_ptr(sg);
sg = sg_is_last(sg) ? NULL : sg_chain_ptr(sg);
sg = sg_chain_ptr(sg);
iter = sg_chain_ptr(iter);
sg = sg_chain_ptr(sg);
next = sg_chain_ptr(&sgl[curr_max_ents - 1]);
sgp = sg_chain_ptr(&sg);
sg = sg_chain_ptr(sg);