MAX_DESC_BUF_SZ
if (buf_sz > MAX_DESC_BUF_SZ)
p->buf_size = cpu_to_le32(MAX_DESC_BUF_SZ |
(buf_sz - MAX_DESC_BUF_SZ) << DESC_BUFFER2_SZ_OFFSET);
if (len > MAX_DESC_BUF_SZ)
p->buf2_addr = cpu_to_le32(paddr + MAX_DESC_BUF_SZ);