stmmac_get_tx_desc
head_tx = stmmac_get_tx_desc(priv, tx_q, 0);
p = stmmac_get_tx_desc(priv, tx_q, i);
p = stmmac_get_tx_desc(priv, tx_q, i);
tx_desc = stmmac_get_tx_desc(priv, tx_q, entry);
p = stmmac_get_tx_desc(priv, tx_q, entry);
desc = stmmac_get_tx_desc(priv, tx_q, entry);
desc = stmmac_get_tx_desc(priv, tx_q, entry);
desc = stmmac_get_tx_desc(priv, tx_q, entry);
tx_desc = stmmac_get_tx_desc(priv, tx_q, entry);