Hello,
Following is a simple kernel module of 40 lines which only registers a
misc device. I insmod the module and it is ok; the return value of
misc_register() is 0.
ls -al /dev/mymodule
gives:
crw-rw---- 1 root root 10, 300 22-02-09 20:58 /dev/mymodule
which is ok.
However, when I try, from a user space program, to open the device,
by calling open("/dev/mymodule", O_RDONLY) , I get an error.
The error I get when running the user space program is:
open: No such device or address
I would appreciate if anyone has an idea why is it so. The kernel
module and the user space
program are below.
kernel module:
#define MY_MINOR 300
static long my_ioctl(struct file *filp, unsigned int cmd, unsigned long data)
{
return 0;
}
struct file_operations mymodule_fops =
{
.owner = THIS_MODULE,
.unlocked_ioctl = my_ioctl,
.compat_ioctl = my_ioctl,
};
static struct miscdevice my_dev = {
MY_MINOR,
"mymodule",
&mymodule_fops,
};
static int __init mymodule_init(void)
{
int ret;
mymodule_fops.owner = THIS_MODULE;
ret = misc_register(&my_dev);
printk("ret = %d\n",ret);
if (ret)
return -1;
return 0;
}
static void __exit mymodule_exit(void)
{
misc_deregister(&my_dev);
}
module_init(mymodule_init)
module_exit(mymodule_exit)
-----------------
The user space program:
int main()
{
int fd;
fd = open("/dev/mymodule", O_RDONLY);
if (fd == -1) {
perror("open");
exit(1);
}
printf("open succeeded\n");
}
Regards,
Kevin
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