/*
 * 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.
 */

#include <linux/module.h>
#include <linux/stat.h>
#include <linux/ioctl.h>
#include <linux/capability.h>
#include <mtd/ubi-user.h>
#include <asm/uaccess.h>
#include <asm/div64.h>
#include "ubi.h"

/*
 * Maximum sequence numbers of UBI and volume character device IOCTLs (direct
 * logical eraseblock erase is a debug-only feature).
 */
#define UBI_CDEV_IOC_MAX_SEQ 2
#ifndef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
#define VOL_CDEV_IOC_MAX_SEQ 1
#else
#define VOL_CDEV_IOC_MAX_SEQ 2
#endif

/**
 * major_to_device - get UBI device object by character device major number.
 * @major: major number
 *
 * This function returns a pointer to the UBI device object.
 */
static struct ubi_device *major_to_device(int major)
{
        int i;

        for (i = 0; i < ubi_devices_cnt; i++)
                if (ubi_devices[i] && ubi_devices[i]->major == major)
                        return ubi_devices[i];
        BUG();
        return NULL;
}

/**
 * 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;
        const struct ubi_device *ubi = major_to_device(imajor(inode));
        int vol_id = iminor(inode) - 1;
        int mode;

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

        dbg_msg("open volume %d, mode %d", vol_id, mode);

        desc = ubi_open_volume(ubi->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_msg("release volume %d, mode %d", vol->vol_id, desc->mode);

        if (vol->updating) {
                ubi_warn("update of volume %d not finished, volume is damaged",
                         vol->vol_id);
                vol->updating = 0;
                vfree(vol->upd_buf);
        }

        ubi_close_volume(desc);
        return 0;
}

static loff_t vol_cdev_llseek(struct file *file, loff_t offset, int origin)
{
        struct ubi_volume_desc *desc = file->private_data;
        struct ubi_volume *vol = desc->vol;
        loff_t new_offset;

        if (vol->updating) {
                 /* Update is in progress, seeking is prohibited */
                dbg_err("updating");
                return -EBUSY;
        }

        switch (origin) {
        case 0: /* SEEK_SET */
                new_offset = offset;
                break;
        case 1: /* SEEK_CUR */
                new_offset = file->f_pos + offset;
                break;
        case 2: /* SEEK_END */
                new_offset = vol->used_bytes + offset;
                break;
        default:
                return -EINVAL;
        }

        if (new_offset < 0 || new_offset > vol->used_bytes) {
                dbg_err("bad seek %lld", new_offset);
                return -EINVAL;
        }

        dbg_msg("seek volume %d, offset %lld, origin %d, new offset %lld",
                vol->vol_id, offset, origin, new_offset);

        file->f_pos = new_offset;
        return new_offset;
}

static ssize_t vol_cdev_read(struct file *file, __user char *buf, size_t count,
                             loff_t *offp)
{
        struct ubi_volume_desc *desc = file->private_data;
        struct ubi_volume *vol = desc->vol;
        struct ubi_device *ubi = vol->ubi;
        int err, lnum, off, len,  vol_id = desc->vol->vol_id, tbuf_size;
        size_t count_save = count;
        void *tbuf;
        uint64_t tmp;

        dbg_msg("read %zd bytes from offset %lld of volume %d",
                count, *offp, vol_id);

        if (vol->updating) {
                dbg_err("updating");
                return -EBUSY;
        }
        if (vol->upd_marker) {
                dbg_err("damaged volume, update marker is set");
                return -EBADF;
        }
        if (*offp == vol->used_bytes || count == 0)
                return 0;

        if (vol->corrupted)
                dbg_msg("read from corrupted volume %d", vol_id);

        if (*offp + count > vol->used_bytes)
                count_save = count = vol->used_bytes - *offp;

        tbuf_size = vol->usable_leb_size;
        if (count < tbuf_size)
                tbuf_size = ALIGN(count, ubi->min_io_size);
        tbuf = vmalloc(tbuf_size);
        if (!tbuf)
                return -ENOMEM;

        len = count > tbuf_size ? tbuf_size : count;

        tmp = *offp;
        off = do_div(tmp, vol->usable_leb_size);
        lnum = tmp;

        do {
                cond_resched();

                if (off + len >= vol->usable_leb_size)
                        len = vol->usable_leb_size - off;

                err = ubi_eba_read_leb(ubi, vol_id, lnum, tbuf, off, len, 0);
                if (err)
                        break;

                off += len;
                if (off == vol->usable_leb_size) {
                        lnum += 1;
                        off -= vol->usable_leb_size;
                }

                count -= len;
                *offp += len;

                err = copy_to_user(buf, tbuf, len);
                if (err) {
                        err = -EFAULT;
                        break;
                }

                buf += len;
                len = count > tbuf_size ? tbuf_size : count;
        } while (count);

        vfree(tbuf);
        return err ? err : count_save - count;
}

#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO

/*
 * This function allows to directly write to dynamic UBI volumes, without
 * issuing the volume update operation. Available only as a debugging feature.
 * Very useful for testing UBI.
 */
static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
                                     size_t count, loff_t *offp)
{
        struct ubi_volume_desc *desc = file->private_data;
        struct ubi_volume *vol = desc->vol;
        struct ubi_device *ubi = vol->ubi;
        int lnum, off, len, tbuf_size, vol_id = vol->vol_id, err = 0;
        size_t count_save = count;
        char *tbuf;
        uint64_t tmp;

        dbg_msg("requested: write %zd bytes to offset %lld of volume %u",
                count, *offp, desc->vol->vol_id);

        if (vol->vol_type == UBI_STATIC_VOLUME)
                return -EROFS;

        tmp = *offp;
        off = do_div(tmp, vol->usable_leb_size);
        lnum = tmp;

        if (off % ubi->min_io_size) {
                dbg_err("unaligned position");
                return -EINVAL;
        }

        if (*offp + count > vol->used_bytes)
                count_save = count = vol->used_bytes - *offp;

        /* We can write only in fractions of the minimum I/O unit */
        if (count % ubi->min_io_size) {
                dbg_err("unaligned write length");
                return -EINVAL;
        }

        tbuf_size = vol->usable_leb_size;
        if (count < tbuf_size)
                tbuf_size = ALIGN(count, ubi->min_io_size);
        tbuf = vmalloc(tbuf_size);
        if (!tbuf)
                return -ENOMEM;

        len = count > tbuf_size ? tbuf_size : count;

        while (count) {
                cond_resched();

                if (off + len >= vol->usable_leb_size)
                        len = vol->usable_leb_size - off;

                err = copy_from_user(tbuf, buf, len);
                if (err) {
                        err = -EFAULT;
                        break;
                }

                err = ubi_eba_write_leb(ubi, vol_id, lnum, tbuf, off, len,
                                        UBI_UNKNOWN);
                if (err)
                        break;

                off += len;
                if (off == vol->usable_leb_size) {
                        lnum += 1;
                        off -= vol->usable_leb_size;
                }

                count -= len;
                *offp += len;
                buf += len;
                len = count > tbuf_size ? tbuf_size : count;
        }

        vfree(tbuf);
        return err ? err : count_save - count;
}

#else
#define vol_cdev_direct_write(file, buf, count, offp) -EPERM
#endif /* CONFIG_MTD_UBI_DEBUG_USERSPACE_IO */

static ssize_t vol_cdev_write(struct file *file, const char __user *buf,
                              size_t count, loff_t *offp)
{
        int err = 0;
        struct ubi_volume_desc *desc = file->private_data;
        struct ubi_volume *vol = desc->vol;
        struct ubi_device *ubi = vol->ubi;

        if (!vol->updating)
                return vol_cdev_direct_write(file, buf, count, offp);

        err = ubi_more_update_data(ubi, vol->vol_id, buf, count);
        if (err < 0) {
                ubi_err("cannot write %zd bytes of update data", count);
                return err;
        }

        if (err) {
                /*
                 * Update is finished, @err contains number of actually written
                 * bytes now.
                 */
                count = err;

                err = ubi_check_volume(ubi, vol->vol_id);
                if (err < 0)
                        return err;

                if (err) {
                        ubi_warn("volume %d on UBI device %d is corrupted",
                                 vol->vol_id, ubi->ubi_num);
                        vol->corrupted = 1;
                }
                vol->checked = 1;
                ubi_gluebi_updated(vol);
                revoke_exclusive(desc, UBI_READWRITE);
        }

        *offp += count;
        return count;
}

static int vol_cdev_ioctl(struct inode *inode, struct file *file,
                          unsigned int cmd, unsigned long arg)
{
        int err = 0;
        struct ubi_volume_desc *desc = file->private_data;
        struct ubi_volume *vol = desc->vol;
        struct ubi_device *ubi = vol->ubi;
        void __user *argp = (void __user *)arg;

        switch (cmd) {
        /* Volume update command */
        case UBI_IOCVOLUP:
        {
                int64_t bytes, rsvd_bytes;

                if (!capable(CAP_SYS_RESOURCE)) {
                        err = -EPERM;
                        break;
                }

                err = copy_from_user(&bytes, argp, sizeof(int64_t));
                if (err) {
                        err = -EFAULT;
                        break;
                }

                if (desc->mode == UBI_READONLY) {
                        err = -EROFS;
                        break;
                }

                rsvd_bytes = vol->reserved_pebs * (ubi->leb_size-vol->data_pad);
                if (bytes < 0 || bytes > rsvd_bytes) {
                        err = -EINVAL;
                        break;
                }

                err = get_exclusive(desc);
                if (err < 0)
                        break;

                err = ubi_start_update(ubi, vol->vol_id, bytes);
                if (bytes == 0)
                        revoke_exclusive(desc, UBI_READWRITE);

                file->f_pos = 0;
                break;
        }

#ifdef CONFIG_MTD_UBI_DEBUG_USERSPACE_IO
        /* Logical eraseblock erasure command */
        case UBI_IOCEBER:
        {
                int32_t lnum;

                err = get_user(lnum, (__user int32_t *)argp);
                if (err) {
                        err = -EFAULT;
                        break;
                }

                if (desc->mode == UBI_READONLY) {
                        err = -EROFS;
                        break;
                }

                if (lnum < 0 || lnum >= vol->reserved_pebs) {
                        err = -EINVAL;
                        break;
                }

                if (vol->vol_type != UBI_DYNAMIC_VOLUME) {
                        err = -EROFS;
                        break;
                }

                dbg_msg("erase LEB %d:%d", vol->vol_id, lnum);
                err = ubi_eba_unmap_leb(ubi, vol->vol_id, lnum);
                if (err)
                        break;

                err = ubi_wl_flush(ubi);
                break;
        }
#endif

        default:
                err = -ENOTTY;
                break;
        }

        return err;
}

/**
 * verify_mkvol_req - verify volume creation request.
 * @ubi: UBI device description object
 * @req: the request to check
 *
 * This function zero if the request is correct, and %-EINVAL if not.
 */
static int verify_mkvol_req(const struct ubi_device *ubi,
                            const struct ubi_mkvol_req *req)
{
        int n, err = -EINVAL;

        if (req->bytes < 0 || req->alignment < 0 || req->vol_type < 0 ||
            req->name_len < 0)
                goto bad;

        if ((req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots) &&
            req->vol_id != UBI_VOL_NUM_AUTO)
                goto bad;

        if (req->alignment == 0)
                goto bad;

        if (req->bytes == 0)
                goto bad;

        if (req->vol_type != UBI_DYNAMIC_VOLUME &&
            req->vol_type != UBI_STATIC_VOLUME)
                goto bad;

        if (req->alignment > ubi->leb_size)
                goto bad;

        n = req->alignment % ubi->min_io_size;
        if (req->alignment != 1 && n)
                goto bad;

        if (req->name_len > UBI_VOL_NAME_MAX) {
                err = -ENAMETOOLONG;
                goto bad;
        }

        return 0;

bad:
        dbg_err("bad volume creation request");
        ubi_dbg_dump_mkvol_req(req);
        return err;
}

/**
 * verify_rsvol_req - verify volume re-size request.
 * @ubi: UBI device description object
 * @req: the request to check
 *
 * This function returns zero if the request is correct, and %-EINVAL if not.
 */
static int verify_rsvol_req(const struct ubi_device *ubi,
                            const struct ubi_rsvol_req *req)
{
        if (req->bytes <= 0)
                return -EINVAL;

        if (req->vol_id < 0 || req->vol_id >= ubi->vtbl_slots)
                return -EINVAL;

        return 0;
}

static int ubi_cdev_ioctl(struct inode *inode, struct file *file,
                          unsigned int cmd, unsigned long arg)
{
        int err = 0;
        struct ubi_device *ubi;
        struct ubi_volume_desc *desc;
        void __user *argp = (void __user *)arg;

        if (!capable(CAP_SYS_RESOURCE))
                return -EPERM;

        ubi = major_to_device(imajor(inode));
        if (IS_ERR(ubi))
                return PTR_ERR(ubi);

        switch (cmd) {
        /* Create volume command */
        case UBI_IOCMKVOL:
        {
                struct ubi_mkvol_req req;

                dbg_msg("create volume");
                err = copy_from_user(&req, argp,
                                       sizeof(struct ubi_mkvol_req));
                if (err) {
                        err = -EFAULT;
                        break;
                }

                err = verify_mkvol_req(ubi, &req);
                if (err)
                        break;

                req.name[req.name_len] = '\0';

                err = ubi_create_volume(ubi, &req);
                if (err)
                        break;

                err = put_user(req.vol_id, (__user int32_t *)argp);
                if (err)
                        err = -EFAULT;

                break;
        }

        /* Remove volume command */
        case UBI_IOCRMVOL:
        {
                int vol_id;

                dbg_msg("remove volume");
                err = get_user(vol_id, (__user int32_t *)argp);
                if (err) {
                        err = -EFAULT;
                        break;
                }

                desc = ubi_open_volume(ubi->ubi_num, vol_id, UBI_EXCLUSIVE);
                if (IS_ERR(desc)) {
                        err = PTR_ERR(desc);
                        break;
                }

                err = ubi_remove_volume(desc);
                if (err)
                        ubi_close_volume(desc);

                break;
        }

        /* Re-size volume command */
        case UBI_IOCRSVOL:
        {
                int pebs;
                uint64_t tmp;
                struct ubi_rsvol_req req;

                dbg_msg("re-size volume");
                err = copy_from_user(&req, argp,
                                       sizeof(struct ubi_rsvol_req));
                if (err) {
                        err = -EFAULT;
                        break;
                }

                err = verify_rsvol_req(ubi, &req);
                if (err)
                        break;

                desc = ubi_open_volume(ubi->ubi_num, req.vol_id, UBI_EXCLUSIVE);
                if (IS_ERR(desc)) {
                        err = PTR_ERR(desc);
                        break;
                }

                tmp = req.bytes;
                pebs = !!do_div(tmp, desc->vol->usable_leb_size);
                pebs += tmp;

                err = ubi_resize_volume(desc, pebs);
                ubi_close_volume(desc);
                break;
        }

        default:
                err = -ENOTTY;
                break;
        }

        return err;
}

/* UBI character device operations */
struct file_operations ubi_cdev_operations = {
        .owner = THIS_MODULE,
        .ioctl = ubi_cdev_ioctl,
        .llseek = no_llseek,
};

/* UBI volume character device operations */
struct file_operations ubi_vol_cdev_operations = {
        .owner   = THIS_MODULE,
        .open    = vol_cdev_open,
        .release = vol_cdev_release,
        .llseek  = vol_cdev_llseek,
        .read    = vol_cdev_read,
        .write   = vol_cdev_write,
        .ioctl   = vol_cdev_ioctl,
};