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static int rtl8139_rx(struct net_device *dev, struct rtl8139_private
*tp,
int budget)
{
void *ioaddr = tp->mmio_addr;
int received = 0;
unsigned char *rx_ring = tp->rx_ring;
// / 网卡不断的把数据放进环形接收缓冲区， CPU 读出来的时候，读到
哪里的顺序需要自己维护，
//tp−>c u r r x 记录上次读到哪里，这里将接着从上一次的地方拷贝。/
unsigned int cur_rx = tp->cur_rx;
DPRINTK ("%s: In rtl8139_rx(), current %4.4x BufAddr %4.4x,"
" free to %4.4x, Cmd %2.2x.\n", dev->name, cur_rx,
RTL_R16 (RxBufAddr),
RTL_R16 (RxBufPtr), RTL_R8 (ChipCmd));
//轮询寄存器，当ChipCmd RxBufEmpty 位没被网卡设置的时候，
//则说明环形缓冲区中有接收到的数据等待处理。
while (netif_running(dev) && received < budget
&& (RTL_R8 (ChipCmd) & RxBufEmpty) == 0) {
u32 ring_offset = cur_rx % RX_BUF_LEN;
u32 rx_status;
unsigned int rx_size;
unsigned int pkt_size;
struct sk_buff *skb;
u16 status;
rmb();
/* read size+status of next frame from DMA ring buffer */
rx_status = le32_to_cpu (*(u32 *) (rx_ring + ring_offset));
rx_size = rx_status >> 16;
pkt_size = rx_size - 4;
if (netif_msg_rx_status(tp))
printk(KERN_DEBUG "%s: rtl8139_rx() status %4.4x,
size %4.4x,"
" cur %4.4x.\n", dev->name, rx_status,
rx_size, cur_rx);
#if RTL8139_DEBUG > 2
{
int i;
DPRINTK ("%s: Frame contents ", dev->name);
for (i = 0; i < 70; i++)
printk (" %2.2x",
rx_ring[ring_offset + i]);
printk (".\n");
}
#endif
/* Packet copy from FIFO still in progress.
* Theoretically, this should never happen
* since EarlyRx is disabled.
*/
//当EarlyRX 允许的时候，可能会发生这种情况，一个完整的数据包
的一部分已经通过DMA
//传送到了内存中，而另外一部分还在网卡内部FIFO 中，网卡的DMA
操作还在进行中。
if (unlikely(rx_size == 0xfff0)) {
tp->xstats.early_rx++;
goto done;
}
/* If Rx err or invalid rx_size/rx_status received
* (which happens if we get lost in the ring),
* Rx process gets reset, so we abort any further
* Rx processing.
*/
if (unlikely((rx_size > (MAX_ETH_FRAME_SIZE+4)) ||
(rx_size < 8) ||
(!(rx_status & RxStatusOK)))) {
rtl8139_rx_err (rx_status, dev, tp, ioaddr);
return -1;
}
/* Malloc up new buffer, compatible with net-2e. */
/* Omit the four octet CRC from the length. */
// / 把数据拷贝到SKB 中来。/
skb = dev_alloc_skb (pkt_size + 2);
if (likely(skb)) {
skb->dev = dev;
skb_reserve (skb, 2); /* 16 byte align the IP fields. */
#if RX_BUF_IDX == 3
wrap_copy(skb, rx_ring, ring_offset+4, pkt_size);
#else
eth_copy_and_sum (skb, &rx_ring[ring_offset + 4], pkt_size,
0);
#endif
skb_put (skb, pkt_size);
// / 判断包的协议。/
skb->protocol = eth_type_trans (skb, dev);
dev->last_rx = jiffies;
// / 更新统计信息，这些信息就是我们用i f c o n f i g 命
令看到的。􀗛/
tp->stats.rx_bytes += pkt_size;
tp->stats.rx_packets++;
//调用系统函数通知上层协议驱动数据包的到来
netif_receive_skb (skb);
} else {
if (net_ratelimit())
printk (KERN_WARNING
"%s: Memory squeeze, dropping packet.\n",
dev->name);
tp->stats.rx_dropped++;
}
received++;
cur_rx = (cur_rx + rx_size + 4 + 3) & ~3;
RTL_W16 (RxBufPtr, (u16) (cur_rx - 16));
/* Clear out errors and receive interrupts */
status = RTL_R16 (IntrStatus) & RxAckBits;
if (likely(status != 0)) {
if (unlikely(status & (RxFIFOOver | RxOverflow))) {
tp->stats.rx_errors++;
if (status & RxFIFOOver)
tp->stats.rx_fifo_errors++;
}
RTL_W16_F (IntrStatus, RxAckBits);
}
}
done:
#if RTL8139_DEBUG > 1
DPRINTK ("%s: Done rtl8139_rx(), current %4.4x BufAddr %4.4x,"
" free to %4.4x, Cmd %2.2x.\n", dev->name, cur_rx,
RTL_R16 (RxBufAddr),
RTL_R16 (RxBufPtr), RTL_R8 (ChipCmd));
#endif
tp->cur_rx = cur_rx;
return received;
}
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