cas_tx_desc
struct cas_tx_desc *txds;
struct cas_tx_desc *txd = txds + entry;
struct cas_tx_desc *txd = cp->init_txds[ring] + entry;
struct cas_tx_desc *txd = cp->init_txds[ring];
struct cas_tx_desc txds[N_TX_RINGS][INIT_BLOCK_TX];
struct cas_tx_desc *init_txds[MAX_TX_RINGS];