EIOCBQUEUED aio驱动应用代码编写示例-DPDK中文网

在 Linux 中，EIOCBQUEUED 是指示 I/O 控制块（IOCB）已成功排队的状态码。通常情况下，这种状态在内核 AIO 的上下文中使用。然而，在编写驱动程序时，直接使用 EIOCBQUEUED 通常不是用户空间代码会遇到的事情。

下面是一个简单的例子，演示了如何创建一个简单的字符设备驱动，并在驱动中使用异步 I/O 的概念。这个例子不直接涉及 EIOCBQUEUED 的状态，而是为您提供一个大致框架，以便理解如何处理异步操作。

示例：简单字符设备驱动

1. 驱动代码

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/aio.h>

#define DEVICE_NAME "async_char_device"
#define BUFFER_SIZE 1024

static int majorNumber;
static char message[BUFFER_SIZE] = {0};
static struct class* deviceClass = NULL;
static struct device* deviceDevice = NULL;

ssize_t async_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t *pos) {
    if (count > BUFFER_SIZE)
        count = BUFFER_SIZE;

    if (copy_from_user(message, buf, count))
        return -EFAULT;

    printk(KERN_INFO "Async write: %s\n", message);
    
    // Simulate that the IO operation is queued
    iocb->ki_complete(iocb, count); // Call completion callback
    
    return count;
}

static int dev_open(struct inode *inodep, struct file *filep) {
    printk(KERN_INFO "Device opened\n");
    return 0;
}

static ssize_t dev_read(struct file *filep, char *buffer, size_t len, loff_t *offset) {
    ssize_t bytes_read = strlen(message);

    if (bytes_read == 0)
        return 0; // End of file

    if (copy_to_user(buffer, message, bytes_read)) {
        return -EFAULT;
    }
    
    printk(KERN_INFO "Read from device: %s\n", message);
    
    return bytes_read; 
}

static long dev_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) {
   // 可以添加更多的 IOCTL 操作以支持异步特性
   return 0;
}

struct file_operations fops = {
   .open = dev_open,
   .read = dev_read,
   .aio_write = async_write,
};

static int __init async_device_init(void) {
    majorNumber = register_chrdev(0, DEVICE_NAME, &fops);
    
    if (majorNumber<0){
      printk(KERN_ALERT "Failed to register a major number\n");
      return majorNumber;
    }
    
    deviceClass = class_create(THIS_MODULE,"chardrv");
    
    if (IS_ERR(deviceClass)){                
      unregister_chrdev(majorNumber, DEVICE_NAME);
      printk(KERN_ALERT "Failed to register device class\n");
      return PTR_ERR(deviceClass);
    }

     deviceDevice = device_create(deviceClass, NULL, MKDEV(majorNumber, 0), NULL, DEVICE_NAME); 
    
     if (IS_ERR(deviceDevice)){
      class_destroy(deviceClass);
      unregister_chrdev(majorNumber);
      printk(KERN_ALERT "Failed to create the device\n");
      return PTR_ERR(deviceDevice);
     }

     printk(KERN_INFO "Async Char Device initialized with major number %d\n", majorNumber);

     return 0;
}

static void __exit async_device_exit(void) {
   device_destroy(deviceClass, MKDEV(majorNumber, 0));
   class_unregister(deviceClass);
   class_destroy(deviceClass);
   unregister_chrdev(majorNumber);
   
   printk(KERN_INFO "Async Char Device unregistered successfully\n");
}

module_init(async_device_init);
module_exit(async_device_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("A simple Async Character Device Driver Example");

2. 编译和加载模块

要编译此代码并将其加载到内核，请按照以下步骤进行操作：

创建一个名为 Makefile 的文件，并输入以下内容：

obj-m += async_char_device.o

all:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean