实现dma-buf读取网卡数据的例程

以下是一个简单的实现dma-buf读取网卡数据的例程，仅供参考：

#include <linux/dma-buf.h>
#include <linux/netdevice.h>

static struct dma_buf *dma_buf;
static struct scatterlist sg;
static struct sk_buff *skb;

int init_dma_buf(void)
{
    // 创建dma-buf对象
    dma_buf = dma_buf_alloc(size, GFP_KERNEL);
    if (!dma_buf) {
        printk(KERN_ERR "Failed to allocate dma-buf\n");
        return -ENOMEM;
    }

    // 分配内存
    struct sg_table *sgt = dma_buf_map_attachment(dma_buf, DMA_BIDIRECTIONAL);
    if (IS_ERR(sgt)) {
        printk(KERN_ERR "Failed to map dma-buf\n");
        dma_buf_put(dma_buf);
        return PTR_ERR(sgt);
    }

    // 分配网卡缓冲区
    skb = netdev_alloc_frag(size);
    if (!skb) {
        printk(KERN_ERR "Failed to allocate skb\n");
        dma_buf_unmap_attachment(dma_buf, sgt, DMA_BIDIRECTIONAL);
        dma_buf_put(dma_buf);
        return -ENOMEM;
    }

    // 将dma-buf对象映射到网卡缓冲区
    sg_init_one(&sg, dma_buf_vaddr(dma_buf), size);
    int nsegs = dma_map_sg(&dev->dev, &sg, 1, DMA_FROM_DEVICE);
    if (nsegs != 1) {
        printk(KERN_ERR "Failed to map sg\n");
        netdev_free_frag(skb);
        dma_buf_unmap_attachment(dma_buf, sgt, DMA_BIDIRECTIONAL);
        dma_buf_put(dma_buf);
        return -ENOMEM;
    }

    // 读取网络数据
    netif_receive_skb(skb);

    // 取消映射
    dma_unmap_sg(&dev->dev, &sg, 1, DMA_FROM_DEVICE);

    // 释放内存
    netdev_free_frag(skb);
    dma_buf_unmap_attachment(dma_buf, sgt, DMA_BIDIRECTIONAL);
    dma_buf_put(dma_buf);

    return 0;
}

需要注意的是，实际应用中，需要根据具体需求进行调整和完善，例如传入的参数、返回值等。