xdma端口例子程序

以下是一个 XDMA 端口的例子程序，它使用了 Linux 内核的 DMA API。

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>

#define XDMA_DEVICE_NAME "xdma"
#define BUFFER_SIZE 1024

struct xdma_dev {
    struct dma_chan *chan;
    dma_addr_t dma_addr;
    void *buffer;
};

static struct xdma_dev xdma;

static int xdma_open(struct inode *inode, struct file *file)
{
    struct dma_async_tx_descriptor *desc;
    int rc;

    xdma.buffer = dma_alloc_coherent(NULL, BUFFER_SIZE, &xdma.dma_addr, GFP_KERNEL);
    if (!xdma.buffer) {
        dev_err(dev, "Failed to allocate buffer\n");
        rc = -ENOMEM;
        goto fail;
    }

    xdma.chan = dma_request_chan(&pdev->dev, "dma");
    if (IS_ERR(xdma.chan)) {
        dev_err(dev, "Failed to request DMA channel\n");
        rc = PTR_ERR(xdma.chan);
        goto fail_free_buffer;
    }

    desc = dmaengine_prep_dma_memcpy(xdma.chan, xdma.dma_addr, (dma_addr_t)xdma.buffer, BUFFER_SIZE, DMA_MEM_TO_DEV);
    if (!desc) {
        dev_err(dev, "Failed to prepare DMA descriptor\n");
        rc = -EINVAL;
        goto fail_release_chan;
    }

    dmaengine_submit(desc);
    dma_async_issue_pending(xdma.chan);

    return 0;

fail_release_chan:
    dma_release_channel(xdma.chan);

fail_free_buffer:
    dma_free_coherent(NULL, BUFFER_SIZE, xdma.buffer, xdma.dma_addr);

fail:
    return rc;
}

static int xdma_release(struct inode *inode, struct file *file)
{
    dmaengine_terminate_all(xdma.chan);
    dma_release_channel(xdma.chan);
    dma_free_coherent(NULL, BUFFER_SIZE, xdma.buffer, xdma.dma_addr);

    return 0;
}

static struct file_operations xdma_fops = {
    .owner = THIS_MODULE,
    .open = xdma_open,
    .release = xdma_release,
};

static int __init xdma_init(void)
{
    int rc;

    rc = register_chrdev(0, XDMA_DEVICE_NAME, &xdma_fops);
    if (rc < 0) {
        pr_err("Failed to register device\n");
        return rc;
    }

    return 0;
}

static void __exit xdma_exit(void)
{
    unregister_chrdev(0, XDMA_DEVICE_NAME);
}

module_init(xdma_init);
module_exit(xdma_exit);

MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("XDMA Example");
MODULE_LICENSE("GPL");

该程序在打开设备时，分配了一块 DMA 缓冲区，并使用 DMA 引擎将其复制到设备。在关闭设备时，它终止了正在进行的 DMA 传输，并释放了缓冲区和 DMA 通道。注意，该程序仅为示例，实际使用时需要根据具体的硬件平台和需求进行修改。