Code view 3 – the IXGB network driver's interrupt handler

Let's take a look at another example. Here, we're looking at the hardware interrupt handler of the Intel IXGB ethernet adapter's device driver, which we mentioned earlier:

// drivers/net/ethernet/intel/ixgb/ixgb_main.c
static irqreturn_t
ixgb_intr(int irq, void *data)
{
    struct net_device *netdev = data;
    struct ixgb_adapter *adapter = netdev_priv(netdev);
    struct ixgb_hw *hw = &adapter-hw;
    u32 icr = IXGB_READ_REG(hw, ICR);

    if (unlikely(!icr))
        return IRQ_NONE; /* Not our interrupt */
    [...]
    if (napi_schedule_prep(&adapter-napi)) {
        [...]
        IXGB_WRITE_REG(&adapter-hw, IMC, ~0);
        __napi_schedule(&adapter-napi);
    }
    return IRQ_HANDLED;
}

In the preceding code snippet, notice how the driver gains access to its private (or context) metadata structure (struct ixgb_adapter) from the net_device structure (the specialized structure for...