DATA_BUF_XFERS
#define DATA_BUF_SZ (DATA_BUF_XFERS * DATA_XFER_SZ)
#define MAX_NUM_XFERS (MAX_DATA_BUFS * DATA_BUF_XFERS)
DIV_ROUND_UP(adap->num_bufs * DATA_BUF_XFERS, DESCS_IN_PAGE);