/*
 * pubsys - exploting driverfs for fun and profit
 *
 * Copyright (c) 2002 Patrick Mochel
 *                    Open Source Development Lab
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * This is a sample subsystem to illustrate how easy it is to latch on to
 * driverfs and exploit it. It is the 'pub' subsystem. Objects of type 'beer' 
 * can be registered and unregistered with the pub via beer_register and 
 * beer_unregister.
 * 
 * Every time a beer is registered with the pub subsystem, a directory is
 * created for it. The pub subsystem could then create files on behalf of
 * the beer, in the beer's directory. Once the beer has registered, it
 * can create files for itself in its directory. A second, more robust
 * example will surely follow. 
 *
 * Compiled with

CFLAGS = -Wall -O2 -fomit-frame-pointer -DMODULE -D__KERNEL__
IDIR = /home/mochel/src/kernel/devel/linux-2.5/include

pubsys.o:: pubsys.c
        $(CC) $(CFLAGS) -I$(IDIR) -c -o $@ $<
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/stat.h>
#include <linux/err.h>
#include <linux/driverfs_fs.h>

static LIST_HEAD(beer_list);
static struct driver_dir_entry * pub_dir;

struct beer {
	char			* name;
	struct list_head	node;
	struct module		* owner;
	struct driver_dir_entry * dir;
};

int beer_create_file(struct beer * beer, struct driver_file_entry * entry)
{
	int error = -EINVAL;
	if (beer)
		error = driverfs_create_file(entry,beer->dir);
	return error;
}

void beer_remove_file(struct beer * beer, struct driver_file_entry * entry)
{
	if (beer)
		driverfs_remove_file(beer->dir,entry);
}

static int make_one_dir(char * name, 
			struct driver_dir_entry ** dir, 
			struct driver_dir_entry * parent,
			void * object)
{
	struct driver_dir_entry * d;
	int error;

	d = kmalloc(sizeof(struct driver_dir_entry),GFP_KERNEL);
	if (!d)
		return -ENOMEM;
	memset(d,0,sizeof(struct driver_dir_entry));
	d->name = name;
	d->mode = (S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO);
	INIT_LIST_HEAD(&d->files);
	d->object = object;

	if (!(error = driverfs_create_dir(d,parent)))
		*dir = d;
	else
		kfree(d);
	return error;
}

static int beer_make_dir(struct beer * beer)
{
	return make_one_dir(beer->name,&beer->dir,pub_dir,beer);
}

static void beer_remove_dir(struct beer * beer)
{
	struct driver_dir_entry * dir = beer->dir;
	beer->dir = NULL;
	driverfs_remove_dir(dir);
}

int beer_register(struct beer * beer)
{
	int error;
	MOD_INC_USE_COUNT;
	error = beer_make_dir(beer);
	if (!error)
		list_add_tail(&beer->node,&beer_list);
	else
		MOD_DEC_USE_COUNT;
	return error;
}

void beer_unregister(struct beer * beer)
{
	beer_remove_dir(beer);
	list_del(&beer->node);
	MOD_DEC_USE_COUNT;
}

static int __init pub_init(void)
{
	return make_one_dir("pub",&pub_dir,NULL,NULL);
}

static void __exit pub_exit(void)
{
	driverfs_remove_dir(pub_dir);
}

module_init(pub_init);
module_exit(pub_exit);