Mark Lord [mailto:mlord@xxxxxxxxx] > Sent: Friday, November 18, 2016 8:03 PM [..] > How does the RTL8152 know that the limit is 16KB, > rather than some other number? Is this a hardwired number > in the hardware, or is it a parameter that the software > sends to the chip during initialization? It is the limitation of the hardware. > I have a USB analyzer, but it is difficult to figure out how > to program an appropriate trigger point for the capture, > since the problem (with 16KB URBs) takes minutes to hours > or even days to trigger. It is good. Our hw engineers real want it. Maybe you could send a specific packet, and trigger it. You could allocate a skb and fill the data which you prefer, and call skb_queue_tail(&tp->tx_queue, skb); [...] > The first issue is that a packet sometimes begins in one URB, > and completes in the next URB, without an rx_desc at the start > of the second URB. This I have already reported earlier. However, our hw engineer says it wouldn't happen. Our hw always sends rx_desc + packet + padding. The hw wouldn't split it to two or more transmission. That is why I wonder who does it. > But the driver, as written, sometimes accesses bytes outside > of the 16KB URB buffer, because it trusts the non-existent > rx_desc in these cases, and also because it accesses bytes > from the rx_desc without first checking whether there is > sufficient remaining space in the URB to hold an rx_desc. I think I check them. According to the followning code, list_for_each_safe(cursor, next, &rx_queue) { struct rx_desc *rx_desc; struct rx_agg *agg; int len_used = 0; struct urb *urb; u8 *rx_data; ... rx_desc = agg->head; rx_data = agg->head; len_used += sizeof(struct rx_desc); //<-- add the size of next rx_desc while (urb->actual_length > len_used) { struct net_device *netdev = tp->netdev; struct net_device_stats *stats = &netdev->stats; unsigned int pkt_len; struct sk_buff *skb; pkt_len = le32_to_cpu(rx_desc->opts1) & RX_LEN_MASK; if (pkt_len < ETH_ZLEN) break; len_used += pkt_len; if (urb->actual_length < len_used) break; pkt_len -= CRC_SIZE; rx_data += sizeof(struct rx_desc); ... find_next_rx: rx_data = rx_agg_align(rx_data + pkt_len + CRC_SIZE); rx_desc = (struct rx_desc *)rx_data; len_used = (int)(rx_data - (u8 *)agg->head); len_used += sizeof(struct rx_desc); //<-- add the size of next rx_desc } submit: ... } The while loop would check if the next rx_desc is inside the urb buffer, because the len_used includes the size of the next rx_desc. Then, in the while loop, the len_used adds the packet size and check with urb->actual_length again. These make sure the rx_desc and the packet are inside the urb buffer. Except the urb->actual_length is more than agg_buf_sz. However, I don't think it would happen. Best Regards, Hayes ��.n��������+%������w��{.n�����{���)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
