没有这样的设备或地址 - Linux 设备驱动程序开发

Question

当我尝试 cat /dev/gpio-reflect 时，出现错误： No such device or address

cat proc/devices 使用正确的主编号列出我的驱动程序。

dmesg 打印初始化和退出函数的日志。

我也在/dev下创建了相应的文件（major是正确的）

cdev_add 和 alloc_chrdev_region 不 return 错误代码。

我不知道我做错了什么。请帮我。

static struct file_operations fops = {
.owner = THIS_MODULE,
.read = device_read,
.write = device_write,
.open = device_open,
.release = device_release
};


static int __init gpio_reflect_init(void)
{

int err,res=alloc_chrdev_region(&dev, 0, 1, dname);
classptr = class_create(THIS_MODULE, "socledclass");
device_create(classptr, NULL, MAJOR(dev), NULL, dname);
cdev_init(&c_dev, &fops);
c_dev.ops=&fops;
c_dev.owner=THIS_MODULE;
err=cdev_add(&c_dev, MAJOR(dev), 1);

if(err){
    printk(KERN_INFO "Could not add device");
}

if(res<0){
    printk(KERN_INFO "Could not alloc device");
    return res;
}else{
    printk(KERN_INFO "Major: %i",MAJOR(dev));
}
printk(KERN_INFO "Input Pin is: %i\n",in);
printk(KERN_INFO "Output Pin is: %i\n",out);


return 0;
}

static void __exit gpio_reflect_cleanup(void)
{
cdev_del(&c_dev);
unregister_chrdev_region(dev,1);
printk(KERN_INFO "%s unloaded\n",dname);

}

static int device_open(struct inode *inode, struct file *file)
{
printk(KERN_INFO "open\n");
if (Device_Open)
    return -EBUSY;

Device_Open++;
sprintf(msg, "Hello\n");
msg_Ptr = msg;
try_module_get(THIS_MODULE);

return SUCCESS;
}

static int device_release(struct inode *inode, struct file *file)
{
printk(KERN_INFO "release\n");
Device_Open--;

module_put(THIS_MODULE);

return SUCCESS;
}

 static ssize_t device_read(struct file *filp, char *buffer,size_t length,  loff_t * offset){
int bytes_read = 0;
printk(KERN_INFO "read\n");

if (*msg_Ptr == 0)
    return 0;
while (length && *msg_Ptr) {
    put_user(*(msg_Ptr++), buffer++);

    length--;
    bytes_read++;
}
return bytes_read;
}


static ssize_t
device_write(struct file *filp, const char *buff, size_t len, loff_t *       off)
{
printk(KERN_INFO "write\n");
printk(KERN_ALERT "Sorry, this operation isn't supported.\n");
return -EINVAL;
}

module_init(gpio_reflect_init);
module_exit(gpio_reflect_cleanup);

对于格式错误的代码深表歉意:)

Answer 1

如果您在 /dev/ 下的设备节点是 /dev/gpio-reflect 尝试 cat /dev/gpio-reflect

Answer 2

万一有人遇到同样的问题。这只是一个愚蠢的错误。

错误：cdev_add(&c_dev, MAJOR(dev), 1);

右：cdev_add(&c_dev, dev, 1);

没有这样的设备或地址 - Linux 设备驱动程序开发

No such device or address - Linux device driver development

linux-device-driver

kernel-module