read_stage1_cb
pl->pl_cb.read = read_stage1_cb;
pl->pl_cb.read = read_stage1_cb;
if (!read_stage1_cb(pl))
pl->pl_cb.read = read_stage1_cb;
if (!read_stage1_cb(pl))
pl->pl_cb.read = read_stage1_cb;
pl->pl_cb.read = read_stage1_cb;