ixgbe 驱动 为xxx驱动做准备1

　　网卡都是pci设备，因此这里每个网卡驱动其实就是一个pci驱动。并且intel这里是把好几个万兆网卡(82599/82598/x540)的驱动做在一起的。V4L2 一样几个类型摄像头合并在一起

　　先说一下 驱动总线平台；实际上就是platform_device(设备)与platform_driver（驱动）在platform(虚拟总线)上的注册、匹配，相互绑定。 但是最核心的还是cdev file_opterations 等

• ：struct bus_type-->它包含的最关键的函数：match() (要注意的是，这块由内核完成，我们不参与)
• ：struct platform_device-->注册：platform_device_register(unregister)
• ：struct platform_driver-->注册：platform_driver_register(unregister)

设备(或驱动)注册的时候，都会引发总线调用自己的match函数来寻找目前platform总线是否挂载有与该设备(或驱动)名字匹配的驱动（或设备），如果存在则将双方绑定；

platform_device:提供设备的硬件资源 比如 中断号 寄存器地址  DMA

platform_driver ： 提供  match id 绑定驱动和device资源的回调probe

详细 就不说了 很简单。。。。 之前在csdn上写过。。后续慢慢找回吧！！！！！！

假设：device先注册， 后续注册driver时，根据platform_match 匹配到了设备；

那么就会调用probe 实现资源的绑定！！！  一般都是  创建设备  注册中断  初始化 file_opteriton 等回调函数

看下 ixgbe_probe 就知道：

static int ixgbe_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
{
    struct net_device *netdev;
    struct ixgbe_adapter *adapter = NULL;
    struct ixgbe_hw *hw;
    /*
static const struct ixgbe_info *ixgbe_info_tbl[] = {
    [board_82598]        = &ixgbe_82598_info,
    [board_82599]        = &ixgbe_82599_info,
    [board_X540]        = &ixgbe_X540_info,
    [board_X550]        = &ixgbe_X550_info,
    [board_X550EM_x]    = &ixgbe_X550EM_x_info,
    [board_x550em_a]    = &ixgbe_x550em_a_info,
};有很多网卡，根据mactch的记过选择对用的设备信息
    */
    const struct ixgbe_info *ii = ixgbe_info_tbl[ent->driver_data];

 根据硬件的参数来取得对应的devices info

通过对应的netdev的结构取得adapter，然后所有的核心操作都是保存在adapter中：

netdev = alloc_etherdev_mq(sizeof(struct ixgbe_adapter), indices);
// 分配net_device和ixgbe_adapter，发送队列数为MAX_TX_QUEUE
    if (!netdev) {
        err = -ENOMEM;
        goto err_alloc_etherdev;
    }

    SET_NETDEV_DEV(netdev, &pdev->dev);

    adapter = netdev_priv(netdev);// 得到ixgbe_adapter的指针

    adapter->netdev = netdev;
    adapter->pdev = pdev;
    hw = &adapter->hw;// 得到ixgbe_hw的指针
    hw->back = adapter;
    adapter->msg_enable = netif_msg_init(debug, DEFAULT_MSG_ENABLE);
 // 将BAR0中的总线地址映射成内存地址，赋给hw->hw_addr，允许网卡驱动通过hw->hw_addr访问网卡的BAR0对应的Memory空间
    hw->hw_addr = ioremap(pci_resource_start(pdev, 0),
                  pci_resource_len(pdev, 0));
    adapter->io_addr = hw->hw_addr;

netdev->netdev_ops = &ixgbe_netdev_ops;// 注册ixgbe_netdev_ops
    ixgbe_set_ethtool_ops(netdev);
    netdev->watchdog_timeo = 5 * HZ;
    strlcpy(netdev->name, pci_name(pdev), sizeof(netdev->name));

    /* Setup hw api */
    hw->mac.ops   = *ii->mac_ops;
    hw->mac.type  = ii->mac;
    hw->mvals     = ii->mvals;

    /* EEPROM */
    hw->eeprom.ops = *ii->eeprom_ops;
    eec = IXGBE_READ_REG(hw, IXGBE_EEC(hw));
    if (ixgbe_removed(hw->hw_addr)) {
        err = -EIO;
        goto err_ioremap;
    }
    /* If EEPROM is valid (bit 8 = 1), use default otherwise use bit bang */
    if (!(eec & BIT(8)))
        hw->eeprom.ops.read = &ixgbe_read_eeprom_bit_bang_generic;

    /* PHY  硬件资源的初始化。。。。。。。。*/
    hw->phy.ops = *ii->phy_ops;
    hw->phy.sfp_type = ixgbe_sfp_type_unknown;
    /* ixgbe_identify_phy_generic will set prtad and mmds properly */
    hw->phy.mdio.prtad = MDIO_PRTAD_NONE;
    hw->phy.mdio.mmds = 0;
    hw->phy.mdio.mode_support = MDIO_SUPPORTS_C45 | MDIO_EMULATE_C22;
    hw->phy.mdio.dev = netdev;
    hw->phy.mdio.mdio_read = ixgbe_mdio_read;
    hw->phy.mdio.mdio_write = ixgbe_mdio_write;

    ii->get_invariants(hw);

设置网卡属性 ethtool 可以查看

#define IXGBE_GSO_PARTIAL_FEATURES (NETIF_F_GSO_GRE | \
                    NETIF_F_GSO_GRE_CSUM | \
                    NETIF_F_GSO_IPXIP4 | \
                    NETIF_F_GSO_IPXIP6 | \
                    NETIF_F_GSO_UDP_TUNNEL | \
                    NETIF_F_GSO_UDP_TUNNEL_CSUM)

    netdev->gso_partial_features = IXGBE_GSO_PARTIAL_FEATURES;
    netdev->features |= NETIF_F_GSO_PARTIAL |
                IXGBE_GSO_PARTIAL_FEATURES;

    if (hw->mac.type >= ixgbe_mac_82599EB)
        netdev->features |= NETIF_F_SCTP_CRC;ixgbe_msix_clean_rings

    /* copy netdev features into list of user selectable features */
    netdev->hw_features |= netdev->features |
                   NETIF_F_HW_VLAN_CTAG_RX |
                   NETIF_F_HW_VLAN_CTAG_TX |
                   NETIF_F_RXALL |
                   NETIF_F_HW_L2FW_DOFFLOAD;

    if (hw->mac.type >= ixgbe_mac_82599EB)
        netdev->hw_features |= NETIF_F_NTUPLE |
                       NETIF_F_HW_TC;

    if (pci_using_dac)
        netdev->features |= NETIF_F_HIGHDMA;

    netdev->vlan_features |= netdev->features | NETIF_F_TSO_MANGLEID;
    netdev->hw_enc_features |= netdev->vlan_features;

还有注册中断

在enable 设备时 就会ixgbe_request_irq

        err = request_irq(entry->vector, &ixgbe_msix_clean_rings, 0,
                  q_vector->name, q_vector);

static irqreturn_t ixgbe_msix_clean_rings(int irq, void *data)
{
    struct ixgbe_q_vector *q_vector = data;

    /* EIAM disabled interrupts (on this vector) for us */

    if (q_vector->rx.ring || q_vector->tx.ring)
        napi_schedule_irqoff(&q_vector->napi);

    return IRQ_HANDLED;
}
也就是 注册了napi 回调函数。。。 最后执行其对应的poll

    /* initialize NAPI */
    netif_napi_add(adapter->netdev, &q_vector->napi,
               ixgbe_poll, 64);
void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
            int (*poll)(struct napi_struct *, int), int weight)
{
    INIT_LIST_HEAD(&napi->poll_list);
    hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
    napi->timer.function = napi_watchdog;
    napi->gro_count = 0;
    napi->gro_list = NULL;
    napi->skb = NULL;
    napi->poll = poll;
    if (weight > NAPI_POLL_WEIGHT)
        pr_err_once("netif_napi_add() called with weight %d on device %s\n",
                weight, dev->name);
    napi->weight = weight;
    list_add(&napi->dev_list, &dev->napi_list);
    napi->dev = dev;
#ifdef CONFIG_NETPOLL
    spin_lock_init(&napi->poll_lock);
    napi->poll_owner = -1;
#endif
    set_bit(NAPI_STATE_SCHED, &napi->state);
    napi_hash_add(napi);
}

注册网络设备dev

strcpy(netdev->name, "eth%d");
    err = register_netdev(netdev);----->if (dev->netdev_ops->ndo_init) {ret = dev->netdev_ops->ndo_init(dev)

netdev->netdev_ops = &ixgbe_netdev_ops;

poll：NAPI驱动最终是会调用网卡驱动挂载的poll回调，在ixgbe中，对应的回调就是ixgbe_poll

/**
 * ixgbe_poll - NAPI Rx polling callback
 * @napi: structure for representing this polling device
 * @budget: how many packets driver is allowed to clean
 *
 * This function is used for legacy and MSI, NAPI mode
 **/
int ixgbe_poll(struct napi_struct *napi, int budget)
{
    struct ixgbe_q_vector *q_vector =
                container_of(napi, struct ixgbe_q_vector, napi);
    struct ixgbe_adapter *adapter = q_vector->adapter;
    struct ixgbe_ring *ring;
    int per_ring_budget, work_done = 0;
    bool clean_complete = true;

#ifdef CONFIG_IXGBE_DCA
    if (adapter->flags & IXGBE_FLAG_DCA_ENABLED)
        ixgbe_update_dca(q_vector);
#endif

    ixgbe_for_each_ring(ring, q_vector->tx) {  TX
        if (!ixgbe_clean_tx_irq(q_vector, ring, budget))
            clean_complete = false;
    }

    /* Exit if we are called by netpoll or busy polling is active */
    if ((budget <= 0) || !ixgbe_qv_lock_napi(q_vector))
        return budget;

    /* attempt to distribute budget to each queue fairly, but don't allow
     * the budget to go below 1 because we'll exit polling */
    if (q_vector->rx.count > 1)
        per_ring_budget = max(budget/q_vector->rx.count, 1);
    else
        per_ring_budget = budget;

    ixgbe_for_each_ring(ring, q_vector->rx) {RX
        int cleaned = ixgbe_clean_rx_irq(q_vector, ring,
                         per_ring_budget);

        work_done += cleaned;
        if (cleaned >= per_ring_budget)
            clean_complete = false;
    }

    ixgbe_qv_unlock_napi(q_vector);
    /* If all work not completed, return budget and keep polling */
    if (!clean_complete)
        return budget;

    /* all work done, exit the polling mode */
    napi_complete_done(napi, work_done);
    if (adapter->rx_itr_setting & 1)
        ixgbe_set_itr(q_vector);
    if (!test_bit(__IXGBE_DOWN, &adapter->state))
        ixgbe_irq_enable_queues(adapter, BIT_ULL(q_vector->v_idx));

    return min(work_done, budget - 1);
}

ndo_start_xmit---->ixgbe_xmit_frame，这个回调就是驱动提供给协议栈的发送回调接口。我们来看这个函数.

它的实现很简单，就是选取对应的队列，然后调用ixgbe_xmit_frame_ring来发送数据。

static netdev_tx_t __ixgbe_xmit_frame(struct sk_buff *skb,
                      struct net_device *netdev,
                      struct ixgbe_ring *ring)
{
    struct ixgbe_adapter *adapter = netdev_priv(netdev);
    struct ixgbe_ring *tx_ring;

    /*
     * The minimum packet size for olinfo paylen is 17 so pad the skb
     * in order to meet this minimum size requirement.
     */
    if (skb_put_padto(skb, 17))
        return NETDEV_TX_OK;

    tx_ring = ring ? ring : adapter->tx_ring[skb->queue_mapping];

    return ixgbe_xmit_frame_ring(skb, adapter, tx_ring);
}

用ixgbe_tx_map来发送数据。而ixgbe_tx_map所做的最主要是两步，第一步请求DMA，第二步写寄存器，通知网卡发送数据.

netdev_tx_t ixgbe_xmit_frame_ring(struct sk_buff *skb,
              struct ixgbe_adapter *adapter,
              struct ixgbe_ring *tx_ring)
{
    struct ixgbe_tx_buffer *first;
    int tso;
    u32 tx_flags = 0;
    unsigned short f;
    u16 count = TXD_USE_COUNT(skb_headlen(skb));
    __be16 protocol = skb->protocol;
    u8 hdr_len = 0;

    /*
     * need: 1 descriptor per page * PAGE_SIZE/IXGBE_MAX_DATA_PER_TXD,
     *       + 1 desc for skb_headlen/IXGBE_MAX_DATA_PER_TXD,
     *       + 2 desc gap to keep tail from touching head,
     *       + 1 desc for context descriptor,
     * otherwise try next time
     */
    for (f = 0; f < skb_shinfo(skb)->nr_frags; f++)
        count += TXD_USE_COUNT(skb_shinfo(skb)->frags[f].size);

    if (ixgbe_maybe_stop_tx(tx_ring, count + 3)) {
        tx_ring->tx_stats.tx_busy++;
        return NETDEV_TX_BUSY;
    }

    /* record the location of the first descriptor for this packet */
    first = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
    first->skb = skb;
    first->bytecount = skb->len;
    first->gso_segs = 1;

-------------------------------------
    ixgbe_tx_map(tx_ring, first, hdr_len);

    return NETDEV_TX_OK;

out_drop:
    dev_kfree_skb_any(first->skb);
    first->skb = NULL;

    return NETDEV_TX_OK;
}

上面的操作是异步的，此时内核还不能释放SKB，而是网卡硬件发送完数据之后，会再次产生中断通知内核，然后内核才能释放内存 ; 此时可以看到 napi的poll 回调函数  会清除tx 队列