MBOX_CMD_NAK
case MBOX_CMD_NAK:
if (!(msg->cmd == MBOX_CMD_ACK || msg->cmd == MBOX_CMD_NAK)) {
rsp.cmd = MBOX_CMD_NAK;
rsp.cmd = MBOX_CMD_NAK;
rsp.cmd = MBOX_CMD_NAK;
rsp.cmd = MBOX_CMD_NAK;
rsp.cmd = MBOX_CMD_NAK;