驱动使用dma_alloc_coherent代码示例-DPDK中文网

dma_alloc_coherent 是 Linux 内核中用于分配 DMA 共享内存的一种方法，它通常在驱动程序中用于分配可以被设备访问的内存。以下是一个简单的代码示例，展示了如何在 Linux 驱动中使用 dma_alloc_coherent。

示例代码

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/dma-mapping.h>

struct my_device {
    struct device *dev;
    void *buffer;
    dma_addr_t dma_handle;
};

static int my_probe(struct platform_device *pdev)
{
    struct my_device *my_dev;
    
    // 分配设备结构体
    my_dev = devm_kzalloc(&pdev->dev, sizeof(*my_dev), GFP_KERNEL);
    if (!my_dev) {
        dev_err(&pdev->dev, "Failed to allocate memory for device\n");
        return -ENOMEM;
    }

    // 将设备指针保存在结构体中
    my_dev->dev = &pdev->dev;

    // 分配 DMA 一致性内存
    my_dev->buffer = dma_alloc_coherent(my_dev->dev, 1024, &my_dev->dma_handle, GFP_KERNEL);
    if (!my_dev->buffer) {
        dev_err(&pdev->dev, "Failed to allocate coherent DMA buffer\n");
        return -ENOMEM;
    }

    // 此处可以进行其他初始化操作

    return 0; // 成功
}

static int my_remove(struct platform_device *pdev)
{
    struct my_device *my_dev = platform_get_drvdata(pdev);

    // 释放DMA一致性内存
    if (my_dev && my_dev->buffer) {
        dma_free_coherent(my_dev->dev, 1024, my_dev->buffer, my_dev->dma_handle);
    }
    
    return 0; // 移除成功
}

// 驱动结构体和模块初始化代码
static const struct of_device_id my_of_match[] = {
   { .compatible = "my-device", },
   {},
};
MODULE_DEVICE_TABLE(of, my_of_match);

static struct platform_driver my_driver = {
   .probe      = my_probe,
   .remove     = my_remove,
   .driver     = {
       .name   = "my-driver",
       .of_match_table = of_match_ptr(my_of_match),
   },
};

module_platform_driver(my_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("A simple example of using dma_alloc_coherent");