tx_chan_num
for (i = tx_chan_num(0); i < tx_chan_num(CPDMA_MAX_CHANNELS); i++) {
min = tx_chan_num(0);
max = tx_chan_num(CPDMA_MAX_CHANNELS);
chan_num = rx_type ? rx_chan_num(chan_num) : tx_chan_num(chan_num);