Re: can i see a driver's registered *minor* number(s)?

[Rene Herman <rene.herman@xxxxxxxxxxxx>]

On 11-04-08 13:34, Robert P. J. Day wrote:

> > Historically, no way. The driver just gets everything for its
> > registered major and has to switch on minor itself. That is, no such
> > thing as "allocated" minors as far as the system is concerned.
>
> just to be pedantic here, when you say there are no such things as
> "allocated" minors, i'm assuming that what you mean is that it's
> always up to a loaded module to choose what minors it wants to try to
> allocate and register, right?  or, put another way, there are no such
> things as *pre*-allocated minors.  am i parsing that the right way?

No, really no such thing as allocated minors. You don't register them with 
anything historically. I've attached a very minimal char driver using The 
Olden Ways and you see that it itself checks in its open method -- doesn't 
register a minor anyhere and gets called for every minor; only the major is 
significant to the system.

Rene.

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

#define FOO_MAJOR 240
#define FOO_MINOR 0

static const char * const foo_name = "foo";

static int foo_open(struct inode *inode, struct file *filp)
{
	if (iminor(inode) != FOO_MINOR)
		return -ENXIO;
	
	printk(KERN_INFO "%s: foo_open\n", foo_name);
	return 0;
}

static int foo_release(struct inode *inode, struct file *filp)
{
	printk(KERN_INFO "%s: foo_release\n", foo_name);
	return 0;
}

static struct file_operations foo_fops = {
	.open		= foo_open,
	.release	= foo_release,
	.owner		= THIS_MODULE
};

static int foo_init(void)
{
	return register_chrdev(FOO_MAJOR, foo_name, &foo_fops) < 0 ? -ENODEV : 0;
}

static void foo_exit(void)
{
	unregister_chrdev(FOO_MAJOR, foo_name);
}

module_init(foo_init);
module_exit(foo_exit);

MODULE_LICENSE("GPL");