path: root/drivers/mtd/ubi/cdev.c

/*
 * Copyright (c) International Business Machines Corp., 2006
 *
 * 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
 *
 * Author: Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * This file includes implementation of UBI character device operations.
 *
 * There are two kinds of character devices in UBI: UBI character devices and
 * UBI volume character devices. UBI character devices allow users to
 * manipulate whole volumes: create, remove, and re-size them. Volume character
 * devices provide volume I/O capabilities.
 *
 * Major and minor numbers are assigned dynamically to both UBI and volume
 * character devices.
 *
 * Well, there is the third kind of character devices - the UBI control
 * character device, which allows to manipulate by UBI devices - create and
 * delete them. In other words, it is used for attaching and detaching MTD
 * devices.
 */

#include <linux/module.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/ioctl.h>
#include <linux/capability.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
#include <linux/math64.h>
#include <mtd/ubi-user.h>
#include "ubi.h"

/**
 * get_exclusive - get exclusive access to an UBI volume.
 * @desc: volume descriptor
 *
 * This function changes UBI volume open mode to "exclusive". Returns previous
 * mode value (positive integer) in case of success and a negative error code
 * in case of failure.
 */
static int get_exclusive(struct ubi_volume_desc *desc)
{
	int users, err;
	struct ubi_volume *vol = desc->vol;

	spin_lock(&vol->ubi->volumes_lock);
	users = vol->readers + vol->writers + vol->exclusive;
	ubi_assert(users > 0);
	if (users > 1) {
		dbg_err("%d users for volume %d", users, vol->vol_id);
		err = -EBUSY;
	} else {
		vol->readers = vol->writers = 0;
		vol->exclusive = 1;
		err = desc->mode;
		desc->mode = UBI_EXCLUSIVE;
	}
	spin_unlock(&vol->ubi->volumes_lock);

	return err;
}

/**
 * revoke_exclusive - revoke exclusive mode.
 * @desc: volume descriptor
 * @mode: new mode to switch to
 */
static void revoke_exclusive(struct ubi_volume_desc *desc, int mode)
{
	struct ubi_volume *vol = desc->vol;

	spin_lock(&vol->ubi->volumes_lock);
	ubi_assert(vol->readers == 0 && vol->writers == 0);
	ubi_assert(vol->exclusive == 1 && desc->mode == UBI_EXCLUSIVE);
	vol->exclusive = 0;
	if (mode == UBI_READONLY)
		vol->readers = 1;
	else if (mode == UBI_READWRITE)
		vol->writers = 1;
	else
		vol->exclusive = 1;
	spin_unlock(&vol->ubi->volumes_lock);

	desc->mode = mode;
}

static int vol_cdev_open(struct inode *inode, struct file *file)
{
	struct ubi_volume_desc *desc;
	int vol_id = iminor(inode) - 1, mode, ubi_num;

	ubi_num = ubi_major2num(imajor(inode));
	if (ubi_num < 0)
		return ubi_num;

	if (file->f_mode & FMODE_WRITE)
		mode = UBI_READWRITE;
	else
		mode = UBI_READONLY;

	dbg_gen("open device %d, volume %d, mode %d",
	        ubi_num, vol_id, mode);

	desc = ubi_open_volume(ubi_num, vol_id, mode);
	if (IS_ERR(desc))
		return PTR_ERR(desc);

	file->private_data = desc;
	return 0;
}

static int vol_cdev_release(struct inode *inode, struct file *file)
{
	struct ubi_volume_desc *desc = file->private_data;
	struct ubi_volume *vol = desc->vol;

	dbg_gen("release device %d, volume %d, mode %d",
		vol->ubi->ubi_num, vol->vol_id, desc