MAX_CMDBUF_SZ
MAX_CMDBUF_SZ + XMITBUF_ALIGN_SZ,
pxmitbuf->pend = pxmitbuf->pbuf + MAX_CMDBUF_SZ;
pxmitbuf->alloc_sz = MAX_CMDBUF_SZ + XMITBUF_ALIGN_SZ;