【韦东山驱动代码移植高通平台之四】创建多个设备节点

创建多个设备节点

一次性创建多个设备，共用一个file_operations结构体里的函数

参考代码

#include <linux/init.h>
#include <linux/module.h>
#include <linux/major.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/fs.h>


#define TAG "hello"

static int hello_major;
static struct cdev hello_cdev;
static struct class *hello_class;

static ssize_t hello_read(struct file *file, char __user *buffer,
		size_t count, loff_t *ppos)
{
	printk(TAG" func:%s line:%d\n", __func__, __LINE__);

	return count;
}

ssize_t hello_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
	printk(TAG" func:%s line:%d\n", __func__, __LINE__);

	return count;
}

static int hello_open(struct inode *inode, struct file *file)
{
	printk(TAG" func:%s line:%d\n", __func__, __LINE__);

	return 0;
}

static int hello_release(struct inode *inode, struct file *file)
{

	printk(TAG" func:%s line:%d\n", __func__, __LINE__);

	return 0;
}

static const struct file_operations hello_ops = {
	.owner = THIS_MODULE,
	.read = hello_read,
	.write = hello_write,
	.open = hello_open,
	.release = hello_release,
};

static int hello_init(void)
{
	int retval;
	dev_t dev_id;
    int i;

	printk(TAG" func:%s line:%d\n", __func__, __LINE__);
	retval = alloc_chrdev_region(&dev_id, 0, 4, "hello"); //0,1
	hello_major = MAJOR(dev_id);
    printk(TAG"major is %d\n", hello_major);
	if (retval < 0) {
		printk(TAG"can't get major number\n");
		goto error;
	}

	cdev_init(&hello_cdev, &hello_ops);
	retval = cdev_add(&hello_cdev, dev_id, 4); //1
	if (retval < 0) {
		printk(TAG"cannot add cdev\n");
		goto cleanup_alloc_chrdev_region;
	}

	hello_class = class_create(THIS_MODULE, "hello");
	if (IS_ERR(hello_class)) {
		printk(TAG "Error creating hello class.\n");
		cdev_del(&hello_cdev);
		retval = PTR_ERR(hello_class);
		goto cleanup_alloc_chrdev_region;
	}

    for(i = 0; i < 4; i++) {
    	device_create(hello_class, NULL, MKDEV(hello_major, i), NULL, "hello%d", i);
    }
	return 0;

cleanup_alloc_chrdev_region:
	unregister_chrdev_region(dev_id, 4);
error:
	return retval;
}
static void hello_exit(void)
{
    int i;
	dev_t dev_id = MKDEV(hello_major, 0);

    class_destroy(hello_class);

    for(i = 0; i < 4; i++) {
    	device_destroy(hello_class, MKDEV(hello_major, i));
    }

	cdev_del(&hello_cdev);  
	unregister_chrdev_region(dev_id, 4);
	printk(TAG" func:%s line:%d\n", __func__, __LINE__);
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");

 

测试程序

int main(int argc, char **argv)
{
    int fd;
    char buf = '1';

    if(argc != 2) {
    	printf("Usage: %s [node]\n", argv[0]);
    	exit(1);
    }
    fd = open(argv[1], O_RDWR);
    if (fd < 0) {
    	printf("open %s failed\n", argv[1]);
    }

    write(fd, &buf, 1);
    read(fd, &buf, 1);

    close(fd);

    return 0;
}

编译好测试程序，假如编译好的程序名为testhello，push到机器里，运行

./testhello /dev/hello0

./testhello /dev/hello1

./testhello /dev/hello2

./testhello /dev/hello3

观察log，可以看出， /dev/hello0~3的节点都会调用到驱动file_operations结构体里对应的函数

 

问题

这些设备都是虚拟的设备，如何操作真实的设备？