写个PCiE的字符驱动

好的，下面是一个简单的PCIE字符驱动的例子：

1. 首先，我们需要包含一些必要的头文件：

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/uaccess.h>

2. 定义一些必要的宏和变量：

#define DEVICE_NAME "pcie_char_drv"
#define VENDOR_ID 0x1234
#define DEVICE_ID 0x5678

static dev_t dev_num;
static struct class *dev_class;
static struct device *dev;
static struct pci_device_id pci_id_tbl[] = {
    { PCI_DEVICE(VENDOR_ID, DEVICE_ID) },
    { 0 }
};
static struct pci_driver pci_drv = {
    .name = DEVICE_NAME,
    .id_table = pci_id_tbl,
    .probe = pcie_char_probe,
    .remove = pcie_char_remove
};
static struct cdev cdev;
static struct file_operations fops = {
    .owner = THIS_MODULE,
    .read = pcie_char_read,
    .write = pcie_char_write,
    .open = pcie_char_open,
    .release = pcie_char_release
};
static char *buffer;
static int buffer_size;

3. 实现驱动的初始化和卸载函数：

static int __init pcie_char_init(void)
{
    int ret;

    ret = pci_register_driver(&pci_drv);
    if (ret) {
        pr_err("Failed to register PCI driver: %d\n", ret);
        return ret;
    }

    ret = alloc_chrdev_region(&dev_num, 0, 1, DEVICE_NAME);
    if (ret) {
        pr_err("Failed to allocate device numbers: %d\n", ret);
        pci_unregister_driver(&pci_drv);
        return ret;
    }

    cdev_init(&cdev, &fops);
    ret = cdev_add(&cdev, dev_num, 1);
    if (ret) {
        pr_err("Failed to add char device: %d\n", ret);
        unregister_chrdev_region(dev_num, 1);
        pci_unregister_driver(&pci_drv);
        return ret;
    }

    dev_class = class_create(THIS_MODULE, DEVICE_NAME);
    if (IS_ERR(dev_class)) {
        pr_err("Failed to create class: %ld\n", PTR_ERR(dev_class));
        cdev_del(&cdev);
        unregister_chrdev_region(dev_num, 1);
        pci_unregister_driver(&pci_drv);
        return PTR_ERR(dev_class);
    }

    dev = device_create(dev_class, NULL, dev_num, NULL, DEVICE_NAME);
    if (IS_ERR(dev)) {
        pr_err("Failed to create device: %ld\n", PTR_ERR(dev));
        class_destroy(dev_class);
        cdev_del(&cdev);
        unregister_chrdev_region(dev_num, 1);
        pci_unregister_driver(&pci_drv);
        return PTR_ERR(dev);
    }

    return 0;
}

static void __exit pcie_char_exit(void)
{
    device_destroy(dev_class, dev_num);
    class_destroy(dev_class);
    cdev_del(&cdev);
    unregister_chrdev_region(dev_num, 1);
    pci_unregister_driver(&pci_drv);
}

4. 实现驱动的probe和remove函数：

static int pcie_char_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
    int ret;

    ret = pci_enable_device(pdev);
    if (ret) {
        pr_err("Failed to enable PCI device: %d\n", ret);
        return ret;
    }

    ret = pci_request_region(pdev, 0, DEVICE_NAME);
    if (ret) {
        pr_err("Failed to request PCI region: %d\n", ret);
        pci_disable_device(pdev);
        return ret;
    }

    buffer_size = pci_resource_len(pdev, 0);
    buffer = pci_ioremap_bar(pdev, 0, buffer_size, PCI_DMA_BIDIRECTIONAL);
    if (!buffer) {
        pr_err("Failed to remap PCI memory\n");
        pci_release_region(pdev, 0);
        pci_disable_device(pdev);
        return -EFAULT;
    }

    return 0;
}

static void pcie_char_remove(struct pci_dev *pdev)
{
    pci_iounmap(pdev, buffer);
    pci_release_region(pdev, 0);
    pci_disable_device(pdev);
}

5. 实现驱动的文件操作函数：

static int pcie_char_open(struct inode *inode, struct file *file)
{
    return 0;
}

static int pcie_char_release(struct inode *inode, struct file *file)
{
    return 0;
}

static ssize_t pcie_char_read(struct file *file, char __user *buf, size_t count, loff_t *offset)
{
    if (*offset + count > buffer_size)
        count = buffer_size - *offset;

    if (copy_to_user(buf, buffer + *offset, count))
        return -EFAULT;

    *offset += count;

    return count;
}

static ssize_t pcie_char_write(struct file *file, const char __user *buf, size_t count, loff_t *offset)
{
    if (*offset + count > buffer_size)
        count = buffer_size - *offset;

    if (copy_from_user(buffer + *offset, buf, count))
        return -EFAULT;

    *offset += count;

    return count;
}

6. 最后，在模块初始化函数中注册驱动：

static int __init pcie_char_init(void)
{
    ...

    return pci_register_driver(&pci_drv);
}

module_init(pcie_char_init);
module_exit(pcie_char_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("PCIe character driver");

这是一个简单的PCIE字符驱动的实现。注意，这只是一个例子，实际上，驱动的实现需要根据硬件设备的具体特征进行调整。