transfer_msg_items

Hello, Why was a sender's send item (e.g. mr[0] and mr[1] ) merged and stored into the receiver's mr[0]? Basically I have trouble understanding the following code. *rcv_words=(item->b.raw() & ~0x0ff7) | (sfp.raw())&0x0ff0); rcv_word +=2 ; Why didn't we use receiver's mr[1] as well? In the case of page fault handling IPC, the pf address stored in sender's mr[1] is not used ? Thanks. Chen