字符设备异步通知

driver:
[cpp]
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/syscalls.h>

#include <linux/uaccess.h>
#include <linux/string.h>

struct fpga_key_dev
{
    struct cdev cdev;
    dev_t devno;
    char test[20];
    struct class *fpga_key_class;
    struct fasync_struct *async_queue;

    int message_cdev_open;
};

static int fpga_key_open(struct inode *node, struct file *fd)
{
    struct fpga_key_dev *dev;

    printk("fpga_key_open()++\n");

    printk("node->i_cdev = %x\n", (unsigned int)node->i_cdev);
    dev = container_of(node->i_cdev, struct fpga_key_dev, cdev);
    printk("dev->cdev = %x\n", (unsigned int)&dev->cdev);
    printk("dev = %x\n", (unsigned int)dev);

    if (!dev->message_cdev_open) {
        dev->message_cdev_open = 1;
        fd->private_data = dev;
    }
    else{
        return -EFAULT;
    }

    printk("test[20] = %s\n",dev->test);

    printk("fpga_key_open()--\n");

    return 0;
}

static ssize_t fpga_key_write(struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
{
    char temp_buffer [20];
    int print_size = 0;
    struct fpga_key_dev *dev = fd->private_data;

    printk("fpga_key_wirte()++\n");
    if(len > 20)
        print_size = 20;
    else
        print_size = len;
    printk("print_size = %d; len = %d\n", print_size, len);
    if(copy_from_user(temp_buffer, buf, print_size))
        return -EFAULT;

    if (dev->async_queue)
        kill_fasync(&dev->async_queue, SIGIO, POLL_IN);

    printk("writing data:%s", temp_buffer);

    printk("fpga_key_wirte()--\n");

    return print_size;
}
static ssize_t fpga_key_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
{
      char *temp_buffer = "Hello fpga_key_read !\n";
      int print_size = 0;

    printk("fpga_key_read()++\n");

    if(len > strnlen(temp_buffer,20))
        print_size = strnlen(temp_buffer,20);
    else
        print_size = len;
    printk("print_size = %d; len = %d\n", print_size, len);
    if(copy_to_user(buf, temp_buffer, print_size))
        return -EFAULT;
    printk("%s", temp_buffer);
    printk("fpga_key_read()--\n");

    return print_size;
}

static int fpga_key_fasync(int fd, struct file *filp, int mode)
{
    struct fpga_key_dev     *dev = filp->private_data;

    printk("fpga_key_fasync()++\n");

    fasync_helper(fd, filp, mode, &dev->async_queue);

    printk("fpga_key_fasync()--\n");

    return 0;
}

static int fpga_key_release(struct inode *node, struct file *fd)
{
    struct fpga_key_dev *dev = fd->private_data;

    printk("fpga_key_release()++\n");

    dev->message_cdev_open = 0;
    fpga_key_fasync(-1, fd, 0);

    printk("fpga_key_release()--\n");
    return 0;
}

struct file_operations meassage_operatons =
{
    .owner = THIS_MODULE,
    .open = fpga_key_open,
    .write = fpga_key_write,
    .read = fpga_key_read,
    .fasync = fpga_key_fasync,
    .release = fpga_key_release,
};

struct fpga_key_dev fpga_key_dev;
static int __init fpga_key_init(void)
{
    struct fpga_key_dev * dev;
    char * temp_char = "hello world\n";

    printk("fpga_key_to_app_init(void)++\n");

    dev = &fpga_key_dev;
    strcpy(dev->test, temp_char);
    printk("%s",dev->test);

补充：软件开发 , C++ ,