rx+1:
nic->rxs;rx->prev=(i==0)?
nic->rxs+count-1:
rx-1;if(e100_rx_alloc_skb(nic,rx)){/*分配缓存*/e100_rx_clean_list(nic);return-ENOMEM;}}nic->rx_to_use=nic->rx_to_clean=nic->rxs;nic->ru_running=RU_SUSPENDED;return0;}
#defineRFD_BUF_LEN(sizeof(structrfd)+VLAN_ETH_FRAME_LEN)
1.static
inline
inte100_rx_alloc_skb(structnic*nic,structrx*rx)
2.{
3./*skb缓存的分配,是通过调用系统函数dev_alloc_skb来完成的,它同内核栈中通常调用alloc_skb的区别在于,
4.它是原子的,所以,通常在中断上下文中使用*/
5.if(!
(rx->skb=dev_alloc_skb(RFD_BUF_LEN+NET_IP_ALIGN)))
6.return-ENOMEM;
7.
8./*初始化必要的成员*/
9.rx->skb->dev=nic->netdev;
10.skb_reserve(rx->skb,NET_IP_ALIGN);
11./*这里在数据区之前,留了一块sizeof(structrfd)这么大的空间,该结构的
12.一个重要作用,用来保存一些状态信息,比如,在接收数据之前,可以先通过
13.它,来判断是否真有数据到达等,诸如此类*/
14.memcpy(rx->skb->data,&nic->blank_rfd,sizeof(structrfd));
15./*这是最关键的一步,建立DMA映射,把每一个缓冲区rx->skb->data都映射给了设备,缓存区节点
16.rx利用dma_addr保存了每一次映射的地址,这个地址后面会被用到*/
17.rx->dma_addr=pci_map_single(nic->pdev,rx->skb->data,
18.RFD_BUF_LEN,PCI_DMA_BIDIRECTIONAL);
19.
20.if(pci_dma_mapping_error(rx->dma_addr)){
21.dev_kfree_skb_any(rx->skb);
22.rx->skb=0;
23.rx->dma_addr=0;
24.return-ENOMEM;
25.}
26.
27./*LinktheRFDtoendofRFAbylinkingpreviousRFDto
28.*thisone,andclearingELbitofprevious.*/
29.if(rx->prev->skb){
30.structrfd*prev_rfd=(structrfd*)rx->prev->skb->data;
31./*put_unaligned(val,ptr);用到把var放到ptr指针的地方,它能处理处理内存对齐的问题
32.prev_rfd是在缓冲区开始处保存的一点空间,它的link成员,也保存了映射后的地址*/
33.put_unaligned(cpu_to_le32(rx->dma_addr),
34.(u32*)&prev_rfd->link);
35.wmb();
36.prev_rfd->command&=~cpu_to_le16(cb_el);
37.pci_dma_sync_single_for_device(nic->pdev,rx->prev->dma_addr,
38.sizeof(structrfd),PCI_DMA_TODEVICE);
39.}
40.
41.return0;
42.}
#defineRFD_BUF_LEN(sizeof(structrfd)+VLAN_ETH_FRAME_LEN)staticinlineinte100_rx_alloc_skb(structnic*nic,structrx*rx){/*skb缓存的分配,是通过调用系统函数dev_alloc_skb来完成的,它同内核栈中通常调用alloc_skb的区别在于,它是原子的,所以,通常在中断上下文中使用*/if(!
(rx->skb=dev_alloc_skb(RFD_BUF_LEN+NET_IP_ALIGN)))return-ENOMEM;/*初始化必要的成员*/rx->skb->dev=nic->netdev;skb_reserve(rx->skb,NET_IP_ALIGN);/*这里在数据区之前,留了一块sizeof(structrfd)这么大的空间,该结构的一个重要作用,用来保存一些状态信息,比如,在接收数据之前,可以先通过它,来判断是否真有数据到达等,诸如此类*/memcpy(rx->skb->data,&nic->blank_rfd,sizeof(structrfd));/*这是最关键的一步,建立DMA映射,把每一个缓冲区rx->skb->data都映射给了设备,缓存区节点rx利用dma_addr保存了每一次映射的地址,这个地址后面会被用到*/rx->dma_addr=pci_map_single(nic->pdev,rx->skb->data,RFD_BUF_LEN,PCI_DMA_BIDIRECTIONAL);if(pci_dma_mapping_error(rx->dma_addr)){dev_kfree_skb_any(rx->skb);rx->skb=0;rx->dma_addr=0;return-ENOMEM;}/*LinktheRFDtoendofRFAbylinkingpreviousRFDto*thisone,andclearingELbitofprevious.*/if(rx->prev->skb){structrfd*prev_rfd=(structrfd*)rx->prev->skb->data;/*put_unaligned(val,ptr);用到把var放到ptr指针的地方,它能处理处理内存对齐的问题prev_rfd是在缓冲区开始处保存的一点空间,它的link成员,也保存了映射后的地址*/put_unaligned(cpu_to_le32(rx->dma_addr),(u32*)&prev_rfd->link);wmb();prev_rfd->command&=~cpu_to_le16(cb_el);pci_dma_sync_single_for_device(nic->pdev,rx->prev->dma_addr,sizeof(structrfd),PCI_DMA_TODEVICE);}return0;}
e100_rx_alloc_list函数在一个循环中,建立了环形缓冲区,并调用e100_rx_alloc_skb为每个缓冲区分配了空间,并做了
DMA映射。
这样,我们就可以来看接收数据的过程了。
前面我们讲过,中断函数中,调用netif_rx_schedule,表明使用轮询技术,系统会在未来某一时刻,调用设备的poll函数:
static
inte100_poll(structnet_device*netdev,int*budget)
1.{
2.structnic*nic=netdev_priv(netdev);
3.unsignedintwork_to_do=min(netdev->quota,*budget);
4.unsignedintwork_done=0;
5.inttx_cleaned;
6.
7.e100_rx_clean(nic,&work_done,work_to_do);
8.tx_cleaned=e100_tx_clean(nic);
9.
10./*IfnoRxandTxcleanupworkwasdone,exitpollingmode.*/
11.if((!
tx_cleaned&&(work_done==0))||!
netif_running(netdev)){
12.netif_rx_complete(netdev);
13.e100_enable_irq(nic);
14.return0;
15.}
16.
17.*budget-=work_done;
18.netdev->quota-=work_done;
19.
20.return1;
21.}
staticinte100_poll(structnet_device*netdev,int*budget){structnic*nic=netdev_priv(netdev);unsignedintwork_to_do=min(netdev->quota,*budget);unsignedintwork_done=0;inttx_cleaned;e100_rx_clean(nic,&work_done,work_to_do);tx_cleaned=e100_tx_clean(nic);/*IfnoRxandTxcleanupworkwasdone,exitpollingmode.*/if((!
tx_cleaned&&(work_done==0))||!
netif_running(netdev)){netif_rx_complete(netdev);e100_enable_irq(nic);return0;}*budget-=work_done;netdev->quota-=work_done;return1;}
目前,我们只关心rx,所以,e100_rx_clean函数就成了我们关注的对像,它用来从缓冲队列中接收全部数据(这或许是取名为clean的原因吧!
):
static
inline
voide100_rx_clean(structnic*nic,unsignedint*work_done,
1.unsignedintwork_to_do)
2.{
3.structrx*rx;
4.intrestart_required=0;
5.structrx*rx_to_start=NULL;
6.
7./*arewealreadyrnr?
thenpayattention!
!
!
thisensuresthat
8.*thestatemachineprogressionneverallowsastartwitha
9.*partiallycleanedlist,avoidingaracebetweenhardware
10.*andrx_to_cleanwheninNAPImode*/
11.if(RU_SUSPENDED==nic->ru_running)
12.restart_required=1;
13.
14./*函数最重要的工作,就是遍历环形缓冲区,接收数据*/
15.for(rx=nic->rx_to_clean;rx->skb;rx=nic->rx_to_clean=rx->next){
16.interr=e100_rx_indicate(nic,rx,work_done,work_to_do);
17.if(-EAGAIN==err){
18./*hitquotasohavemoreworktodo,restartonce
19.*cleanupiscomplete*/
20.restart_required=0;
21.break;
22.}else
if(-ENODATA==err)
23.break;/*Nomoretoclean*/
24.}
25.
26./*saveourstartingpointastheplacewe'llrestartthereceiver*/
27.if(restart_required)
28.rx_to_start=nic->rx_to_clean;
29.
30./*Allocnewskbstorefilllist*/
31.for(rx=nic->rx_to_use;!
rx->skb;rx=nic->rx_to_use=rx->next){
32.if(unlikely(e100_rx_alloc_skb(nic,rx)))
33.break;/*Betterlucknexttime(seewatchdog)*/
34.}
35.
36.if(restart_required){
37.//ackthernr?
38.writeb(stat_ack_rnr,&nic->csr->scb.stat_ack);
39.e100_start_receiver(nic,rx_to_start);
40.if(work_done)
41.(*work_done)++;
42.}
43.}
staticinlinevoide100_rx_clean(structnic*nic,unsignedint*work_done,unsignedintwork_to_do)
{
structrx*rx;
intrestart_required=0;
structrx*rx_to_start=NULL;/*arewealreadyrnr?
thenpayattention!
!
!
thisensuresthat*thestatemachineprogressionneverallowsastartwitha*partiallycleanedlist,avoidingaracebetweenhardware*andrx_to_cleanwheninNAPImode*/if(RU_SUSPENDED==nic->ru_running)
restart_required=1;
/*函数最重要的工作,就是遍历环形缓冲区,接收数据*/
for(rx=nic->rx_to_clean;rx->skb;rx=nic->rx_to_clean=rx->next)