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Subject[RFC][PATCH] filesystem: VMUFAT filesystem
From
Date
The SEGA Dreamcast visual memory unit implements a file allocation table
based filesystem which is somewhat similar to FAT16. This filesystem
code implements that filesystem and I have used it to successfully
manage Dreamcast VMUs and VMU images mounted via loop.

You can read more about the filesystem here:
http://mc.pp.se/dc/vms/flashmem.html

I intend to fully document the filesystem and write an appropriate user
tool to create a drive image, but in the meantime here is an early cut
of the filesystem itself for comment.

(A version of this for the 2.4 kernel existed in the Dreamcast CVS on
Sourceforge but wasn't truly hardware independent).

fs/Kconfig | 1 +
fs/Makefile | 1 +
fs/vmufat/Kconfig | 14 +
fs/vmufat/Makefile | 7 +
fs/vmufat/inode.c | 702 ++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/vmufat/super.c | 533 +++++++++++++++++++++++++++++++++++++++
fs/vmufat/vmufat.h | 58 +++++

Signed-off-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
---
diff --git a/fs/Kconfig b/fs/Kconfig
index 93945dd..6c108b1 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -222,6 +222,7 @@ source "fs/qnx4/Kconfig"
source "fs/romfs/Kconfig"
source "fs/sysv/Kconfig"
source "fs/ufs/Kconfig"
+source "fs/vmufat/Kconfig"

endif # MISC_FILESYSTEMS

diff --git a/fs/Makefile b/fs/Makefile
index 38bc735..196c9dc 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -122,3 +122,4 @@ obj-$(CONFIG_DEBUG_FS) += debugfs/
obj-$(CONFIG_OCFS2_FS) += ocfs2/
obj-$(CONFIG_BTRFS_FS) += btrfs/
obj-$(CONFIG_GFS2_FS) += gfs2/
+obj-$(CONFIG_VMUFAT_FS) += vmufat/
diff --git a/fs/vmufat/Kconfig b/fs/vmufat/Kconfig
new file mode 100644
index 0000000..bdad4c6
--- /dev/null
+++ b/fs/vmufat/Kconfig
@@ -0,0 +1,14 @@
+config VMUFAT_FS
+ tristate "Dreamcast VMU FAT filesystem"
+ depends on BLOCK
+ help
+ This implements the simple FAT type filesystem found on SEGA
+ Dreamcast visual memory units.
+
+ Dreamcast users who want to mount their VMUs to view the native
+ filesystem will say 'Y' here. The filesystem is hardware independent
+ but is not recommended for any serious use in other circumstances, so
+ just about everyone else should say 'N'.
+
+ To compile this as a module say 'M' here. The module will be called
+ vmufat
diff --git a/fs/vmufat/Makefile b/fs/vmufat/Makefile
new file mode 100644
index 0000000..e7f9bbf
--- /dev/null
+++ b/fs/vmufat/Makefile
@@ -0,0 +1,7 @@
+#
+# Makefile for VMUFAT filesystem
+#
+
+obj-$(CONFIG_VMUFAT_FS) += vmufat.o
+
+vmufat-objs := super.o inode.o
diff --git a/fs/vmufat/inode.c b/fs/vmufat/inode.c
new file mode 100644
index 0000000..3639351
--- /dev/null
+++ b/fs/vmufat/inode.c
@@ -0,0 +1,702 @@
+/*
+ * inode operations for the VMU file system
+ *
+ * Copyright (C) 2002 - 2009 Adrian McMenamin
+ * Copyright (C) 2002 Paul Mundt
+ *
+ * Released under the terms of the GNU GPL v2.0.
+ */
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+#include <linux/mtd/mtd.h>
+#include "vmufat.h"
+
+struct dentry *vmufat_inode_lookup(struct inode *in, struct dentry *dent,
+ struct nameidata *nd)
+{
+ struct super_block *sb;
+ struct memcard *vmudetails;
+ struct buffer_head *bh;
+ struct inode *ino;
+ char name[VMUFAT_NAMELEN];
+ long blck_read;
+ int error = 0, fno = 0, filenamelen;
+
+ if (dent->d_name.len > VMUFAT_NAMELEN) {
+ error = -ENAMETOOLONG;
+ goto out;
+ }
+
+ sb = in->i_sb;
+ vmudetails = (struct memcard *)sb->s_fs_info;
+ blck_read = vmudetails->dir_bnum;
+
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh) {
+ error = -EIO;
+ goto out;
+ }
+
+ do {
+ /* Have we got a file? */
+ if (((__u8 *)bh->b_data)[(fno % 0x10) * 0x20] == 0) {
+ error = -ENOENT;
+ goto release_bh;
+ }
+
+ /* get file name */
+ memcpy(name,
+ bh->b_data + 4 + (fno % 0x10) * 0x20, VMUFAT_NAMELEN);
+ /* do names match ?*/
+ filenamelen = strlen(dent->d_name.name);
+ if (memcmp(dent->d_name.name, name, filenamelen) == 0) {
+ /* read the inode number from the directory */
+ ino = vmufat_get_inode(sb,
+ le16_to_cpu(((__u16 *) bh->b_data)
+ [1 + (fno % 0x10) * 0x10]));
+ if (!ino || IS_ERR(ino)) {
+ error = -EACCES;
+ goto release_bh;
+ }
+ /* return the entry */
+ d_add(dent, ino);
+ goto release_bh;
+ }
+
+ /* did not match, so try the next file */
+ fno++;
+ /* do we need to move to the next block in the directory? */
+ if ((fno / 0x10) > (vmudetails->dir_bnum - blck_read)) {
+ brelse(bh);
+ blck_read--;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh) {
+ error = -EIO;
+ goto out;
+ }
+ }
+ } while (1);
+
+release_bh:
+ brelse(bh);
+out:
+ return ERR_PTR(error);
+}
+
+static int vmufat_inode_unlink(struct inode *in, struct dentry *de)
+{
+ /* find the inode of the specified dentry
+ * and then call the superblock delete_inode */
+ struct super_block *sb = in->i_sb;
+ sb->s_op->delete_inode(de->d_inode);
+ return 0;
+}
+
+static int vmufat_inode_create(struct inode *dir, struct dentry *de,
+ int imode, struct nameidata *nd)
+{
+ /* Create an inode */
+ int y, z;
+ long nextblock, blck_read;
+ struct inode *inode;
+ struct super_block *sb;
+ struct memcard *vmudetails;
+ struct buffer_head *bh_fat, *bh;
+ unsigned long unix_date;
+ int year, day, nl_day, month; /*inspired by FAT driver */
+ __u16 fatdata;
+ __u8 century, u8year;
+
+
+ if (de->d_name.len > VMUFAT_NAMELEN)
+ return -ENAMETOOLONG;
+
+ sb = dir->i_sb;
+ vmudetails = (struct memcard *) sb->s_fs_info;
+
+ inode = new_inode(sb);
+ if (!inode)
+ return -ENOSPC;
+
+ /* Walk through blocks looking for place to write
+ * Is this an executible file? */
+ if (imode & 73) { /*Octal 111 */
+ inode->i_ino = VMUFAT_ZEROBLOCK;
+ /* But this already allocated? */
+ bh_fat =
+ vmufat_sb_bread(sb, vmudetails->fat_bnum);
+ if (!bh_fat)
+ return -EIO;
+
+ fatdata = ((__u16 *) bh_fat->b_data)[0];
+ if (fatdata != 0xfffc) {
+ printk(KERN_ERR
+ "vmufat: cannot write executible file to"
+ " filesystem - block 0 already allocated.\n");
+ brelse(bh_fat);
+ return -ENOSPC;
+ }
+
+ } else {
+ /*Look for a free block in the FAT */
+ nextblock = vmudetails->numblocks - 1;
+ bh_fat =
+ vmufat_sb_bread(sb, vmudetails->fat_bnum);
+ if (!bh_fat)
+ return -EIO;
+
+ do {
+ fatdata = ((__u16 *) bh_fat->b_data)[nextblock];
+ if (fatdata == 0xfffc)
+ break; /*empty block */
+ if (--nextblock < 0)
+ break;
+ } while (1);
+
+ if (nextblock < 0) {
+ iput(inode);
+ brelse(bh_fat);
+ return -ENOSPC;
+ }
+ inode->i_ino = nextblock;
+ }
+ brelse(bh_fat);
+
+ inode->i_uid = 0;
+ inode->i_gid = 0;
+ inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+ inode->i_mode = imode;
+ inode->i_blocks = 0;
+ inode->i_sb = sb;
+ insert_inode_hash(inode);
+ mark_inode_dirty(inode);
+ inode->i_op = &vmufat_inode_operations;
+ inode->i_fop = &vmufat_file_operations;
+
+ /* Write to the directory
+ * Now search for space for the directory entry */
+ blck_read = vmudetails->dir_bnum;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return -EIO;
+
+ for (y = 0; y < (vmudetails->dir_len * 0x10); y++) {
+ if ((y / 0x10) > (vmudetails->dir_bnum - blck_read)) {
+ brelse(bh);
+ blck_read--;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return -EIO;
+ }
+ if (((bh->b_data)[(y % 0x10) * 0x20]) == 0)
+ break;
+ }
+ /* Have the directory entry
+ * so now update it */
+ z = (y % 0x10) * 0x20;
+ if (inode->i_ino != VMUFAT_ZEROBLOCK)
+ bh->b_data[z] = 0x33; /* data file */
+ else
+ bh->b_data[z] = 0xcc;
+
+ if ((bh->b_data[z + 1] != (char) 0x00) &&
+ (bh->b_data[z + 1] != (char) 0xff))
+ bh->b_data[z + 1] = (char) 0x00;
+
+ if (inode->i_ino != VMUFAT_ZEROBLOCK) {
+ ((__u16 *) bh->b_data)[z / 2 + 1] =
+ cpu_to_le16(inode->i_ino);
+ ((__u16 *) bh->b_data)[z / 2 + 0x0D] = 0;
+ } else {
+ ((__u16 *) bh->b_data)[z / 2 + 1] = 0;
+ ((__u16 *) bh->b_data)[z / 2 + 0x0D] = 1;
+ }
+
+ /* Name */
+ memset((char *) (bh->b_data + z + 0x04), '\0', 0x0C);
+ memcpy((char *) (bh->b_data + z + 0x04), ((de->d_name).name),
+ de->d_name.len);
+
+ /* BCD timestamp it */
+ unix_date = CURRENT_TIME.tv_sec;
+ day = unix_date / 86400 - 3652;
+ year = day / 365;
+
+ if ((year + 3) / 4 + 365 * year > day)
+ year--;
+
+ day -= (year + 3) / 4 + 365 * year;
+ if (day == 59 && !(year & 3)) {
+ nl_day = day;
+ month = 2;
+ } else {
+ nl_day = (year & 3) || day <= 59 ? day : day - 1;
+ for (month = 0; month < 12; month++)
+ if (day_n[month] > nl_day)
+ break;
+ }
+
+ century = 19;
+ if (year > 19)
+ century = 20;
+
+ bh->b_data[z + 0x10] = bcd_from_u8(century);
+ u8year = year + 80;
+ if (u8year > 99)
+ u8year = u8year - 100;
+
+ bh->b_data[z + 0x11] = bcd_from_u8(u8year);
+ bh->b_data[z + 0x12] = bcd_from_u8((__u8) month);
+ bh->b_data[z + 0x13] =
+ bcd_from_u8((__u8) day - day_n[month - 1] + 1);
+ bh->b_data[z + 0x14] =
+ bcd_from_u8((__u8) ((unix_date / 3600) % 24));
+ bh->b_data[z + 0x15] = bcd_from_u8((__u8) ((unix_date / 60) % 60));
+ bh->b_data[z + 0x16] = bcd_from_u8((__u8) (unix_date % 60));
+
+ ((__u16 *) bh->b_data)[z / 2 + 0x0C] =
+ cpu_to_le16(inode->i_blocks);
+
+ inode->i_mtime.tv_sec = unix_date;
+ mark_buffer_dirty(bh);
+ brelse(bh);
+
+ d_instantiate(de, inode);
+
+ return 0;
+}
+
+
+static int vmufat_inode_rename(struct inode *in_source,
+ struct dentry *de_source,
+ struct inode *in_target,
+ struct dentry *de_target)
+{
+ return -EPERM;
+}
+
+const struct inode_operations vmufat_inode_operations = {
+ .lookup = vmufat_inode_lookup,
+ .unlink = vmufat_inode_unlink,
+ .create = vmufat_inode_create,
+ .rename = vmufat_inode_rename,
+};
+
+
+static int vmufat_readdir(struct file *filp, void *dirent, filldir_t filldir)
+{
+ int filenamelen, i;
+ struct vmufat_file_info *saved_file = NULL;
+ struct dentry *dentry = filp->f_dentry;
+ struct inode *inode = dentry->d_inode;
+ struct super_block *sb = inode->i_sb;
+ struct memcard *vmudetails =
+ ((struct memcard *) sb->s_fs_info);
+ struct buffer_head *bh;
+
+ int blck_read = vmudetails->dir_bnum;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return -EIO;
+
+ i = filp->f_pos;
+
+ switch ((unsigned int) filp->f_pos) {
+ case 0:
+ if (filldir(dirent, ".", 1, i++, inode->i_ino, DT_DIR) < 0)
+ goto finish;
+
+ filp->f_pos++;
+ case 1:
+ if (filldir(dirent, "..", 2, i++,
+ dentry->d_parent->d_inode->i_ino, DT_DIR) < 0)
+ goto finish;
+
+ filp->f_pos++;
+ default:
+ break;
+ }
+
+ /* wander through the Directory and find files */
+ if ((i - 2) > (vmudetails->dir_len * 0x10)) {
+ brelse(bh);
+ return -1;
+ }
+
+ saved_file =
+ kmalloc(sizeof(struct vmufat_file_info), GFP_KERNEL);
+
+ do {
+ if ((i - 2) / 0x10 > (vmudetails->dir_bnum - blck_read)) {
+ /* move to next block in directory */
+ brelse(bh);
+ blck_read--;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh) {
+ kfree(saved_file);
+ return -EIO;
+ }
+ }
+
+ saved_file->ftype = bh->b_data[((i - 2) % 0x10) * 0x20];
+
+ if (saved_file->ftype == 0)
+ break;
+
+ saved_file->fblk =
+ le16_to_cpu(((__u16 *) bh->b_data)[1 +
+ ((i - 2) % 0x10) * 0x10]);
+ if (saved_file->fblk == 0)
+ saved_file->fblk = VMUFAT_ZEROBLOCK;
+
+ memcpy(saved_file->fname,
+ bh->b_data + 4 + ((i - 2) % 0x10) * 0x20, 12);
+ filenamelen = strlen(saved_file->fname);
+ if (filenamelen > VMUFAT_NAMELEN)
+ filenamelen = VMUFAT_NAMELEN;
+ if (filldir
+ (dirent, saved_file->fname, filenamelen, i++,
+ saved_file->fblk, DT_REG) < 0) {
+ goto finish;
+ }
+
+ filp->f_pos++;
+ } while (1);
+
+finish:
+
+ kfree(saved_file);
+ brelse(bh);
+
+ return 0;
+}
+
+const struct file_operations vmufat_file_dir_operations = {
+ .owner = THIS_MODULE,
+ .read = generic_read_dir,
+ .readdir = vmufat_readdir,
+ .fsync = file_fsync,
+};
+
+static int vmufat_game_write(struct file *file, const char *buf, char *writebuf,
+ size_t count, loff_t *ppos)
+{
+ __u16 fatdata;
+ struct buffer_head *bh_fat, *bh;
+ struct inode *in = (file->f_dentry)->d_inode;
+ struct super_block *sb = in->i_sb;
+ struct memcard *vmudetails =
+ ((struct memcard *) sb->s_fs_info);
+
+ unsigned long blkoffset = *ppos >> in->i_sb->s_blocksize_bits;
+ if (blkoffset < 1) {
+ /* Additional sanity check */
+ kfree(writebuf);
+ return -EIO;
+ }
+
+ /* Is the next block free in the VMU? */
+ bh_fat = vmufat_sb_bread(in->i_sb, vmudetails->fat_bnum);
+ if (!bh_fat) {
+ kfree(writebuf);
+ return -EIO;
+ }
+ fatdata = ((__u16 *) bh_fat->b_data)[(__u16) blkoffset];
+
+ if (fatdata != 0xfffc) {
+ printk(KERN_ERR
+ "vmufat: Cannot save game file - insufficient"
+ " linear space\n");
+ kfree(writebuf);
+ return -EFBIG;
+ }
+
+ /*Now we have the space - write the block out */
+ bh = vmufat_sb_bread(sb, blkoffset);
+ if (!bh) {
+ brelse(bh_fat);
+ kfree(writebuf);
+ return -EIO;
+ }
+ if (count < sb->s_blocksize)
+ memset((char *) (bh->b_data), '\0', sb->s_blocksize);
+ memcpy((char *) (bh->b_data), writebuf, count);
+ mark_buffer_dirty(bh);
+ brelse(bh);
+ in->i_size += count;
+ in->i_blocks++;
+
+ /*Now update the FAT */
+ ((__u16 *) (bh_fat->b_data))[(__u16) blkoffset] = 0xfffa;
+ ((__u16 *) (bh_fat->b_data))[((__u16) (blkoffset - 1))] =
+ cpu_to_le16(blkoffset);
+ mark_buffer_dirty(bh_fat);
+
+ brelse(bh_fat);
+
+ kfree(writebuf);
+ *ppos += count;
+ return count;
+}
+
+static ssize_t vmufat_file_write(struct file *file, const char *buf, size_t count,
+ loff_t *ppos)
+{
+ struct buffer_head *bh, *bh_fat;
+ unsigned long inode_num, currentblock, nextblock;
+ char *writebuf;
+ int previousblock;
+ __u16 fatdata;
+ struct inode *in = (file->f_dentry)->d_inode;
+ struct super_block *sb = in->i_sb;
+ struct memcard *vmudetails =
+ ((struct memcard *) sb->s_fs_info);
+ unsigned long blkoffset = *ppos >> in->i_sb->s_blocksize_bits;
+
+ if ((ssize_t) count < 0)
+ return -ENOENT;
+
+ /* We will assume that all files -
+ * unless having inode value of 0
+ * are data files
+ */
+
+ /* copy buffer */
+ if (count > sb->s_blocksize)
+ count = sb->s_blocksize;
+ writebuf = kzalloc(count, GFP_KERNEL);
+ copy_from_user(writebuf, buf, count);
+
+ /* Handle game files */
+ inode_num = in->i_ino;
+ if (inode_num == VMUFAT_ZEROBLOCK)
+ inode_num = 0;
+
+ /*Start by writing out to first block */
+ if (blkoffset == 0) {
+ currentblock = inode_num;
+ bh = vmufat_sb_bread(sb, inode_num);
+ if (!bh) {
+ kfree(writebuf);
+ return -EIO;
+ }
+ if (count < sb->s_blocksize)
+ memset((char *) (bh->b_data), '\0', sb->s_blocksize);
+ memcpy((char *) (bh->b_data), writebuf, count);
+ mark_buffer_dirty(bh);
+ brelse(bh);
+ in->i_size = sb->s_blocksize; /* will increment as we grow */
+ in->i_blocks = 1;
+
+ /* Update FAT */
+ bh_fat =
+ vmufat_sb_bread(in->i_sb, vmudetails->fat_bnum);
+ if (!bh_fat) {
+ kfree(writebuf);
+ return -EIO;
+ }
+
+ /*Wipe out any old FAT records for this inode */
+ do {
+ fatdata =
+ ((__u16 *) bh_fat->
+ b_data)[(__u16) currentblock];
+ if (fatdata == 0xfffc)
+ break; /* already empty */
+ ((__u16 *) (bh_fat->b_data))[(__u16) currentblock]
+ = 0xfffc;
+ mark_buffer_dirty(bh_fat);
+ if (fatdata == 0xfffa)
+ break; /* end of file */
+ } while (1);
+
+ /* Avoid writes to mtd if possible
+ * so check if a write is really
+ * required here */
+ fatdata = ((__u16 *) bh_fat->b_data)[(__u16) (inode_num)];
+ if (fatdata != 0xfffa) {
+ ((__u16 *) (bh_fat->b_data))[(__u16) (inode_num)]
+ = 0xfffa;
+ mark_buffer_dirty(bh_fat);
+ }
+ brelse(bh_fat);
+
+ }
+ /* Now every other block */
+ else {
+ if (inode_num == 0)
+ return vmufat_game_write(file, buf, writebuf,
+ count, ppos);
+ else {
+
+ /*Look for a free block in the FAT */
+ __u16 fatdata;
+ nextblock = inode_num - 1;
+ bh_fat =
+ vmufat_sb_bread(in->i_sb, vmudetails->fat_bnum);
+ if (!bh_fat) {
+ kfree(writebuf);
+ return -EIO;
+ }
+ do {
+ fatdata =
+ ((__u16 *) bh_fat->b_data)[nextblock];
+ if (fatdata == 0xfffc)
+ break; /*empty block */
+ if (--nextblock < 0)
+ break;
+ } while (1);
+ if ((long) nextblock < 0) {
+ brelse(bh_fat);
+ kfree(writebuf);
+ printk(KERN_ERR
+ "vmufs: Out of space on vmu device\n");
+ return -EFBIG;
+ }
+ /*Now we have the space - write the block out */
+ bh = vmufat_sb_bread(sb, nextblock);
+ if (!bh) {
+ brelse(bh_fat);
+ kfree(writebuf);
+ return -EIO;
+ }
+
+ if (count < sb->s_blocksize)
+ memset((char *) (bh->b_data), '\0',
+ sb->s_blocksize);
+ memcpy((char *) (bh->b_data), writebuf, count);
+ mark_buffer_dirty(bh);
+ brelse(bh);
+ in->i_size += sb->s_blocksize;
+ in->i_blocks++;
+ /*Now update the FAT if required */
+ fatdata =
+ ((__u16 *) bh_fat->b_data)[(__u16) nextblock];
+ if (fatdata != 0xfffa) {
+ ((__u16 *) (bh_fat->
+ b_data))[(__u16) nextblock] =
+ 0xfffa;
+ mark_buffer_dirty(bh_fat);
+ }
+ previousblock = inode_num;
+ do {
+ fatdata =
+ ((__u16 *) bh_fat->
+ b_data)[previousblock];
+ if (fatdata == 0xfffc
+ || fatdata == 0xfffa) {
+ ((__u16 *) bh_fat->
+ b_data)[previousblock] =
+ cpu_to_le16(nextblock);
+ mark_buffer_dirty(bh_fat);
+ break;
+ }
+ previousblock = fatdata;
+ blkoffset--;
+ } while (blkoffset > 0);
+
+ brelse(bh_fat);
+
+ if (blkoffset < 1) {
+ /* Additional sanity check */
+ kfree(writebuf);
+ return -EIO;
+ }
+
+ }
+
+
+ }
+
+
+ kfree(writebuf);
+ *ppos += count;
+ return count;
+}
+
+ssize_t vmufat_file_read(struct file *file, char *buf, size_t count,
+ loff_t *ppos)
+{
+ struct inode *in = file->f_dentry->d_inode;
+ unsigned long inode_num = in->i_ino;
+ unsigned long blkoffset = *ppos >> in->i_sb->s_blocksize_bits;
+ unsigned long blcks_to_read, x;
+ __u16 fatblk, next_block;
+ struct buffer_head *bh_file;
+ struct buffer_head *bh_fat;
+ long file_len = in->i_size;
+ char *readbuf;
+ struct super_block *sb = in->i_sb;
+ struct memcard *vmudetails =
+ ((struct memcard *) sb->s_fs_info);
+
+ if (inode_num == VMUFAT_ZEROBLOCK)
+ inode_num = 0;
+
+ if (*ppos > file_len)
+ return -EINVAL;
+ if (*ppos + count > file_len)
+ count = file_len - *ppos;
+
+ blcks_to_read = count >> in->i_sb->s_blocksize_bits;
+ if (blcks_to_read == 0)
+ return 0;
+ readbuf = kzalloc(count, GFP_KERNEL);
+ /* Traverse through FAT to read the blocks in */
+ x = 0;
+ next_block = inode_num;
+ bh_fat = vmufat_sb_bread(in->i_sb, vmudetails->fat_bnum);
+ if (!bh_fat) {
+ kfree(readbuf);
+ return -EIO;
+ }
+ /*Walk through to where we are */
+ if (blkoffset > 0) {
+ do {
+ next_block =
+ ((__u16 *) bh_fat->b_data)[next_block];
+ blkoffset--;
+ } while (blkoffset > 0);
+ }
+ do {
+ bh_file = vmufat_sb_bread(in->i_sb, next_block);
+ if (!bh_file)
+ goto out;
+
+ memcpy(readbuf + x * sb->s_blocksize, bh_file->b_data,
+ sb->s_blocksize);
+ x++;
+ fatblk = ((__u16 *) bh_fat->b_data)[next_block];
+ brelse(bh_file);
+ if (fatblk == 0xfffa)
+ break;
+ next_block = fatblk;
+ } while (x < blcks_to_read);
+
+
+ /* Copy to user space */
+ copy_to_user(buf, readbuf, count);
+ *ppos += count;
+out:
+ kfree(readbuf);
+ brelse(bh_fat);
+ return count;
+}
+
+static int vmufat_file_open(struct inode *in, struct file *f)
+{
+ return 0;
+}
+
+const struct file_operations vmufat_file_operations = {
+ .read = vmufat_file_read,
+ .write = vmufat_file_write,
+ .open = vmufat_file_open,
+};
+
+const struct inode_operations vmufat_file_inode_operations = {
+};
diff --git a/fs/vmufat/super.c b/fs/vmufat/super.c
new file mode 100644
index 0000000..7697757
--- /dev/null
+++ b/fs/vmufat/super.c
@@ -0,0 +1,533 @@
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/statfs.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/mtd/mtd.h>
+#include <linux/maple.h>
+#include <linux/time.h>
+#include <linux/buffer_head.h>
+#include "vmufat.h"
+
+/*
+ * VMUFAT - file system support
+ * for Sega Dreamcast visual
+ * memory unit flash memory
+ *
+ * This software is copyright (c) 2002 - 2009
+ * Adrian McMenamin <adrian@mcmen.demon.co.uk>
+ *
+ * This software is licensed under the
+ * terms of the GNU General Public
+ * Licence version 2.
+ * http://www.fsf.org
+ */
+
+__u8 bcd_from_u8(__u8 num)
+{
+ __u8 topnib = num / 10;
+ __u8 botnib = num % 10;
+ return topnib << 4 | botnib;
+}
+
+inline int int_from_bcd(__u8 bcd)
+{
+ int topnib = (bcd >> 4) & 0x000f;
+ int botnib = bcd & 0x000f;
+
+ return (topnib * 10) + botnib;
+}
+
+struct inode *vmufat_get_inode(struct super_block *sb, int ino)
+{
+ int y, blck_read;
+ struct inode *in;
+ struct buffer_head *bh;
+ struct memcard *vmudetails =
+ ((struct memcard *) sb->s_fs_info);
+ long superblock_bno = vmudetails->sb_bnum;
+ int century, year, month, day, hour, minute, second;
+
+ in = iget_locked(sb, ino);
+ if (!in)
+ return ERR_PTR(-ENOMEM);
+
+ if (ino == superblock_bno) {
+ bh = vmufat_sb_bread(sb, ino);
+ if (!bh)
+ goto failed;
+
+ century = int_from_bcd((bh->b_data)[0x30]);
+ year = int_from_bcd((bh->b_data)[0x31]);
+ month = int_from_bcd((bh->b_data)[0x32]);
+ day = int_from_bcd((bh->b_data)[0x33]);
+ hour = int_from_bcd((bh->b_data)[0x34]);
+ minute = int_from_bcd((bh->b_data)[0x35]);
+ second = int_from_bcd((bh->b_data)[0x36]);
+
+ /*
+ * As a temporary workaround, clear out any
+ * existing type mask and force it as a
+ * directory type.
+ */
+ in->i_ino = ino;
+ in->i_mode &= ~S_IFMT;
+ in->i_mode |= S_IFDIR | S_IRUGO | S_IXUGO;
+ in->i_atime = CURRENT_TIME;
+
+ in->i_ctime.tv_sec = in->i_mtime.tv_sec =
+ mktime(century * 100 + year, month, day, hour, minute,
+ second);
+ in->i_uid = in->i_gid = 0;
+
+ in->i_op = &vmufat_inode_operations;
+ in->i_fop = &vmufat_file_dir_operations;
+
+ /*Not in FAT table */
+ in->i_size = sb->s_blocksize;
+ in->i_blocks = 1;
+ brelse(bh);
+ } else {
+ if (in->i_ino > vmudetails->numblocks) {
+ /* Not here */
+ printk(KERN_INFO
+ "vmufat: Attempt to access file which cannot"
+ " exist on this size of VMU\n");
+ iget_failed(in);
+ return ERR_PTR(-ESPIPE);
+ }
+
+ blck_read = vmudetails->dir_bnum;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ goto failed;
+
+ /*
+ * Do the same here.. clear out the old mask, and force
+ * the inode as a regular file.. Workaround for spontaneous
+ * referencing of symlinks and other garbage -- do a proper
+ * fix later.
+ */
+ in->i_mode &= ~S_IFMT;
+ in->i_mode |= S_IFREG;
+
+ /* Scan through the directory to find the matching file */
+ for (y = 0; y < vmudetails->numblocks; y++) {
+ if ((y / 0x10) >
+ (vmudetails->dir_bnum - blck_read)) {
+ brelse(bh);
+ blck_read--;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ goto failed;
+ }
+ if (le16_to_cpu
+ (((__u16 *) bh->b_data)[(y % 0x10) * 0x10 +
+ 0x01]) == in->i_ino)
+ break;
+ }
+
+ if (y >= vmudetails->numblocks) {
+ brelse(bh);
+ printk(KERN_INFO
+ "vmufat: could not find this file on "
+ " filesystem\n");
+ iget_failed(in);
+ return ERR_PTR(-ENOENT);
+ }
+
+ /* identified the correct directory entry */
+ century =
+ int_from_bcd((bh->b_data)[0x10 + (y % 0x10) * 0x20]);
+ year =
+ int_from_bcd((bh->b_data)[0x11 + (y % 0x10) * 0x20]);
+ month =
+ int_from_bcd((bh->b_data)[0x12 + (y % 0x10) * 0x20]);
+ day = int_from_bcd((bh->b_data)[0x13 + (y % 0x10) * 0x20]);
+ hour =
+ int_from_bcd((bh->b_data)[0x14 + (y % 0x10) * 0x20]);
+ minute =
+ int_from_bcd((bh->b_data)[0x15 + (y % 0x10) * 0x20]);
+ second =
+ int_from_bcd((bh->b_data)[0x16 + (y % 0x10) * 0x20]);
+
+ in->i_ctime.tv_sec = in->i_mtime.tv_sec =
+ mktime(century * 100 + year, month, day, hour, minute,
+ second);
+
+ /* Execute if a game, write if not copy protected */
+ in->i_mode &= ~(S_IWUGO | S_IXUGO);
+ in->i_mode |= S_IRUGO;
+
+
+ /* Mode - is the file copiable? */
+ if ((((__u8 *) bh->b_data)[0x01 + (y % 0x10) * 0x20] ==
+ 0x00) & ~(sb->s_flags & MS_RDONLY))
+ in->i_mode |= S_IWUGO;
+ /* Is file executible - ie a game */
+ if ((((__u8 *) bh->b_data)[(y % 0x10) * 0x20] ==
+ 0xcc) & ~(sb->s_flags & MS_NOEXEC))
+ in->i_mode |= S_IXUGO;
+
+
+ in->i_uid = in->i_gid = 0;
+
+ in->i_op = &vmufat_file_inode_operations;
+ in->i_fop = &vmufat_file_operations;
+
+ in->i_blocks =
+ le16_to_cpu(((__u16 *) bh->b_data)[(y % 0x10) * 0x10 +
+ 0x0C]);
+ in->i_size = in->i_blocks * VMU_BLK_SZ;
+ brelse(bh);
+ }
+
+ unlock_new_inode(in);
+ return in;
+
+failed:
+ iget_failed(in);
+ return ERR_PTR(-EIO);
+}
+
+static void vmufat_put_super(struct super_block *sb)
+{
+ struct memcard *vmudetails;
+ sb->s_dev = 0;
+ vmudetails = (struct memcard *) (sb->s_fs_info);
+ kfree(vmudetails);
+}
+
+static int vmufat_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+ buf->f_type = 0x55555555;
+ buf->f_bsize = VMU_BLK_SZ;
+ buf->f_bfree = 256; /* TO DO: Fix */
+ buf->f_bavail = 0;
+ buf->f_ffree = 0;
+ buf->f_namelen = 12;
+
+ return 0;
+}
+
+static void vmufat_delete_inode(struct inode *in)
+{
+ /* Delete inode by marking space as free in FAT
+ * no need to waste time and effort by actually
+ * wiping underlying data on media */
+ struct buffer_head *bh, *bh_old;
+ struct super_block *sb;
+ struct memcard *vmudetails;
+ int z, y, x, blck_read;
+ __u16 nextblock, fatdata;
+
+ if (in->i_ino == VMUFAT_ZEROBLOCK)
+ in->i_ino = 0;
+ sb = in->i_sb;
+ vmudetails = (struct memcard *) sb->s_fs_info;
+ bh = vmufat_sb_bread(sb, vmudetails->fat_bnum);
+ if (!bh)
+ return;
+
+ /* FAT now read in - seek start of file and wonder through FAT */
+ nextblock = in->i_ino;
+ do {
+ fatdata = ((__u16 *) bh->b_data)[nextblock];
+ ((__u16 *) bh->b_data)[nextblock] = 0xfffc;
+ if (fatdata == 0xfffa)
+ break; /*end of file */
+ nextblock = fatdata;
+ } while (1);
+ mark_buffer_dirty(bh);
+ brelse(bh);
+
+ /* Now clean the directory entry
+ * Have to wander through this
+ * to find the appropriate entry */
+ blck_read = vmudetails->dir_bnum;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return;
+
+ for (y = 0; y < (vmudetails->dir_len * 0x10); y++) {
+ if ((y / 0x10) > (vmudetails->dir_bnum - blck_read)) {
+ brelse(bh);
+ blck_read--;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return;
+ }
+ if (le16_to_cpu
+ (((__u16 *) bh->b_data)[(y % 0x10) * 0x10 +
+ 0x01]) == in->i_ino)
+ break;
+ }
+
+ /* Found directory entry - so NULL it now */
+ for (z = 0; z < 0x10; z++)
+ ((__u16 *) bh->b_data)[(y % 0x10) * 0x10 + z] = 0;
+ /* Replace it with another entry - if one exists */
+ mark_buffer_dirty(bh);
+ x = y; /* save for later use */
+ for (y = x + 1; y < (vmudetails->dir_len * 0x10); y++) {
+ if ((y / 0x10) > (vmudetails->dir_bnum - blck_read)) {
+ brelse(bh);
+ blck_read--;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return;
+ }
+ if (bh->b_data[(y % 0x10) * 0x20] == 0x00) { /* Not a file */
+ y--;
+ if (y == x)
+ break; /* At the end in any case */
+ brelse(bh);
+
+ /* force read of correct block */
+ bh = vmufat_sb_bread(sb, vmudetails->dir_bnum -
+ y / 0x10);
+ if (!bh)
+ return;
+ bh_old =
+ vmufat_sb_bread(sb, vmudetails->dir_bnum -
+ x / 0x10);
+ if (!bh_old) {
+ brelse(bh);
+ return;
+ }
+
+ /* Copy this directory entry over */
+ for (z = 0; z < 0x10; z++) {
+ ((__u16 *) bh_old->b_data)[(x % 0x10) *
+ 0x10 + z] =
+ ((__u16 *) bh->b_data)[(y % 0x10) *
+ 0x10 + z];
+ ((__u16 *) bh->b_data)[(y % 0x10) * 0x10 +
+ z] = 0x00;
+ }
+ mark_buffer_dirty(bh);
+ /* In case written back already */
+ mark_buffer_dirty(bh_old);
+ brelse(bh_old);
+ break;
+ }
+ }
+
+ brelse(bh);
+}
+
+static int vmufat_write_inode(struct inode *in, int wait)
+{
+ struct buffer_head *bh;
+ __u8 century, u8year;
+ unsigned long inode_num;
+ int y, blck_read, z;
+ unsigned long unix_date;
+ int year, day, nl_day, month;
+ struct super_block *sb = in->i_sb;
+ struct memcard *vmudetails =
+ ((struct memcard *) sb->s_fs_info);
+
+ if (in->i_ino == VMUFAT_ZEROBLOCK)
+ inode_num = 0;
+ else
+ inode_num = in->i_ino;
+
+ /* update the directory and inode details */
+ /* Now search for the directory entry */
+ blck_read = vmudetails->dir_bnum;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return -EIO;
+
+ for (y = 0; y < vmudetails->numblocks; y++) {
+ if ((y / 0x10) > (vmudetails->dir_bnum - blck_read)) {
+ brelse(bh);
+ blck_read--;
+ bh = vmufat_sb_bread(sb, blck_read);
+ if (!bh)
+ return -EIO;
+ }
+ if (le16_to_cpu
+ (((__u16 *) bh->b_data)[(y % 0x10) * 0x10 +
+ 0x01]) == inode_num)
+ break;
+ }
+ /* Have the directory entry
+ * so now update it */
+ z = (y % 0x10) * 0x20;
+ if (inode_num != 0)
+ bh->b_data[z] = 0x33; /* data file */
+ else
+ bh->b_data[z] = 0xcc;
+ if ((bh->b_data[z + 1] != (char) 0x00)
+ && (bh->b_data[z + 1] != (char) 0xff))
+ bh->b_data[z + 1] = (char) 0x00;
+ ((__u16 *) bh->b_data)[z / 2 + 1] = cpu_to_le16(inode_num);
+
+ /* BCD timestamp it */
+ unix_date = CURRENT_TIME.tv_sec;
+ day = unix_date / 86400 - 3652;
+ year = day / 365;
+ if ((year + 3) / 4 + 365 * year > day)
+ year--;
+ day -= (year + 3) / 4 + 365 * year;
+ if (day == 59 && !(year & 3)) {
+ nl_day = day;
+ month = 2;
+ } else {
+ nl_day = (year & 3) || day <= 59 ? day : day - 1;
+ for (month = 0; month < 12; month++)
+ if (day_n[month] > nl_day)
+ break;
+ }
+
+ century = 19;
+ if (year > 19)
+ century = 20;
+ bh->b_data[z + 0x10] = bcd_from_u8(century);
+ u8year = year + 80;
+ if (u8year > 99)
+ u8year = u8year - 100;
+ bh->b_data[z + 0x11] = bcd_from_u8(u8year);
+ bh->b_data[z + 0x12] = bcd_from_u8((__u8) month);
+ bh->b_data[z + 0x13] =
+ bcd_from_u8((__u8) day - day_n[month - 1] + 1);
+ bh->b_data[z + 0x14] =
+ bcd_from_u8((__u8) ((unix_date / 3600) % 24));
+ bh->b_data[z + 0x15] = bcd_from_u8((__u8) ((unix_date / 60) % 60));
+ bh->b_data[z + 0x16] = bcd_from_u8((__u8) (unix_date % 60));
+
+ ((__u16 *) bh->b_data)[z / 2 + 0x0C] = cpu_to_le16(in->i_blocks);
+ if (inode_num != 0)
+ ((__u16 *) bh->b_data)[z / 2 + 0x0D] = 0;
+ else /* game */
+ ((__u16 *) bh->b_data)[z / 2 + 0x0D] = cpu_to_le16(1);
+ in->i_mtime.tv_sec = unix_date;
+ mark_buffer_dirty(bh);
+ brelse(bh);
+
+ return 0;
+}
+
+static const struct super_operations vmufat_super_operations = {
+ .write_inode = vmufat_write_inode,
+ .delete_inode = vmufat_delete_inode,
+ .put_super = vmufat_put_super,
+ .statfs = vmufat_statfs,
+};
+
+static int check_sb_format(struct buffer_head *bh)
+{
+ __u32 s_magic = 0x55555555;
+
+ if (!((((__u32 *) bh->b_data)[0] == s_magic)
+ && (((__u32 *) bh->b_data)[1] == s_magic)
+ && (((__u32 *) bh->b_data)[2] == s_magic)
+ && (s_magic == ((__u32 *) bh->b_data)[3])))
+ return 0;
+ else
+ return 1;
+}
+
+static int vmufat_fill_super(struct super_block *sb,
+ void *data, int silent)
+{
+ /*Search for the superblock - assuming likely sizes are
+ * 128, 256, 512 and 1024 blocks */
+
+ struct buffer_head *bh;
+ struct memcard *vmudata;
+ int z;
+ struct inode *root_i;
+ int erasesize, log_2 = 0, ret = -EINVAL;
+
+ sb_set_blocksize(sb, VMU_BLK_SZ);
+
+ /* Have to try lowest number first to avoid oops */
+ for (z = 128; z < 1024; z = z * 2) {
+ bh = vmufat_sb_bread(sb, z - 1);
+ if (!bh)
+ return -EIO;
+ if (check_sb_format(bh))
+ break;
+ brelse(bh);
+ if (z == 1024) { /* failed */
+ printk(KERN_ERR
+ "vmufat: attempted to mount non vmufat medium"
+ " as vmufat\n");
+ return ret;
+ }
+ }
+ /* Store this data in the super block */
+
+ vmudata = kmalloc(sizeof(struct memcard), GFP_KERNEL);
+
+ /* user blocks */
+ vmudata->numblocks = le16_to_cpu(((__u16 *) bh->b_data)[0x50 / 2]);
+ vmudata->sb_bnum = z - 1;
+ vmudata->fat_bnum = le16_to_cpu(((__u16 *) bh->b_data)[0x46 / 2]);
+ vmudata->fat_len = le16_to_cpu(((__u16 *) bh->b_data)[0x48 / 2]);
+ vmudata->dir_bnum = le16_to_cpu(((__u16 *) bh->b_data)[0x4a / 2]);
+ vmudata->dir_len = le16_to_cpu(((__u16 *) bh->b_data)[0x4c / 2]);
+ sb->s_fs_info = vmudata;
+
+ erasesize = VMU_BLK_SZ;
+
+ while ((erasesize /= 2) != 0)
+ log_2++; /* thanks to MR Brown */
+
+ sb->s_blocksize_bits = log_2;
+ sb->s_magic = 0x55555555;
+ sb->s_op = &vmufat_super_operations;
+ brelse(bh);
+
+ root_i = vmufat_get_inode(sb, vmudata->sb_bnum);
+ if (!root_i || IS_ERR(root_i)) {
+ printk(KERN_ERR "vmufs: get root inode failed\n");
+ return ret;
+ }
+
+ sb->s_root = d_alloc_root(root_i);
+
+ if (!sb->s_root) {
+ iput(root_i);
+ return ret;
+ }
+
+ return 0;
+
+}
+
+static int vmufat_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data, struct vfsmount *mnt)
+{
+ return get_sb_bdev(fs_type, flags, dev_name, data, vmufat_fill_super,
+ mnt);
+}
+
+static struct file_system_type vmufat_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "vmufat",
+ .get_sb = vmufat_get_sb,
+ .kill_sb = kill_block_super,
+ .fs_flags = FS_REQUIRES_DEV,
+};
+
+static int __init init_vmufat_fs(void)
+{
+ return register_filesystem(&vmufat_fs_type);
+}
+
+static void __exit exit_vmufat_fs(void)
+{
+ unregister_filesystem(&vmufat_fs_type);
+}
+
+module_init(init_vmufat_fs);
+module_exit(exit_vmufat_fs);
+
+MODULE_DESCRIPTION("Filesystem for Sega Dreamcast VMU");
+MODULE_AUTHOR("Adrian McMenamin <adrian@mcmen.demon.co.uk>");
+MODULE_LICENSE("GPL v2");
diff --git a/fs/vmufat/vmufat.h b/fs/vmufat/vmufat.h
new file mode 100644
index 0000000..32ae5e9
--- /dev/null
+++ b/fs/vmufat/vmufat.h
@@ -0,0 +1,58 @@
+/* Licenced under the GPL v2
+ * Copyright Adrian McMenamin, 2002 - 2009
+ * adrian@mcmen.demon.co.uk */
+
+#define VMUFAT_NAMELEN 12
+
+/* GNU utils won't list files with inode num 0 */
+#define VMUFAT_ZEROBLOCK 32768
+#define VMU_BLK_SZ 512
+
+extern const struct inode_operations vmufat_inode_operations;
+extern const struct inode_operations vmufat_file_inode_operations;
+extern const struct file_operations vmufat_file_dir_operations;
+extern const struct file_operations vmufat_file_operations;
+
+/* Memory card details */
+struct memcard {
+ long sb_bnum;
+ long fat_bnum;
+ long fat_len;
+ long dir_bnum;
+ long dir_len;
+ long numblocks;
+};
+
+struct vmufat_file_info {
+ struct vmufat_file_info *prev;
+ struct vmufat_file_info *next;
+ __u8 ftype;
+ __u8 copy_pro;
+ __u16 fblk;
+ char fname[12];
+ int date[8];
+
+ __u16 blk_cnt;
+ __u16 hd_off;
+};
+
+extern __u8 bcd_from_u8(__u8 num);
+extern struct inode *vmufat_get_inode(struct super_block *sb, int ino);
+
+/* VMU hardware is flaky, so let's compensate for that
+ * without losing hardare independence -
+ * as it is likely to be where this filesystem is used
+ */
+static inline struct buffer_head *vmufat_sb_bread(struct super_block *sb,
+ sector_t block)
+{
+ struct buffer_head *bh;
+ bh = sb_bread(sb, block);
+ if (bh)
+ return bh;
+ return sb_bread(sb, block);
+}
+
+/* Linear day numbers of the respective 1sts in non-leap years. */
+static int day_n[] =
+ {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};



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