root/fs/hfsplus/part_tbl.c

DEFINITIONS

1. hfs_part_find

/*
 * linux/fs/hfsplus/part_tbl.c
 *
 * Copyright (C) 1996-1997  Paul H. Hargrove
 * This file may be distributed under the terms of the GNU General Public License.
 *
 * Original code to handle the new style Mac partition table based on
 * a patch contributed by Holger Schemel (aeglos@valinor.owl.de).
 *
 * In function preconditions the term "valid" applied to a pointer to
 * a structure means that the pointer is non-NULL and the structure it
 * points to has all fields initialized to consistent values.
 *
 */

#include "hfsplus_fs.h"

/* offsets to various blocks */
#define HFS_DD_BLK              0 /* Driver Descriptor block */
#define HFS_PMAP_BLK            1 /* First block of partition map */
#define HFS_MDB_BLK             2 /* Block (w/i partition) of MDB */

/* magic numbers for various disk blocks */
#define HFS_DRVR_DESC_MAGIC     0x4552 /* "ER": driver descriptor map */
#define HFS_OLD_PMAP_MAGIC      0x5453 /* "TS": old-type partition map */
#define HFS_NEW_PMAP_MAGIC      0x504D /* "PM": new-type partition map */
#define HFS_SUPER_MAGIC         0x4244 /* "BD": HFS MDB (super block) */
#define HFS_MFS_SUPER_MAGIC     0xD2D7 /* MFS MDB (super block) */

/*
 * The new style Mac partition map
 *
 * For each partition on the media there is a physical block (512-byte
 * block) containing one of these structures.  These blocks are
 * contiguous starting at block 1.
 */
struct new_pmap {
        __be16  pmSig;          /* signature */
        __be16  reSigPad;       /* padding */
        __be32  pmMapBlkCnt;    /* partition blocks count */
        __be32  pmPyPartStart;  /* physical block start of partition */
        __be32  pmPartBlkCnt;   /* physical block count of partition */
        u8      pmPartName[32]; /* (null terminated?) string
                                   giving the name of this
                                   partition */
        u8      pmPartType[32]; /* (null terminated?) string
                                   giving the type of this
                                   partition */
        /* a bunch more stuff we don't need */
} __packed;

/*
 * The old style Mac partition map
 *
 * The partition map consists for a 2-byte signature followed by an
 * array of these structures.  The map is terminated with an all-zero
 * one of these.
 */
struct old_pmap {
        __be16          pdSig;  /* Signature bytes */
        struct  old_pmap_entry {
                __be32  pdStart;
                __be32  pdSize;
                __be32  pdFSID;
        }       pdEntry[42];
} __packed;

/*
 * hfs_part_find()
 *
 * Parse the partition map looking for the
 * start and length of the 'part'th HFS partition.
 */
int hfs_part_find(struct super_block *sb,
                  sector_t *part_start, sector_t *part_size)
{
        struct buffer_head *bh;
        __be16 *data;
        int i, size, res;

        res = -ENOENT;
        bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK, data);
        if (!bh)
                return -EIO;

        switch (be16_to_cpu(*data)) {
        case HFS_OLD_PMAP_MAGIC:
          {
                struct old_pmap *pm;
                struct old_pmap_entry *p;

                pm = (struct old_pmap *)bh->b_data;
                p = pm->pdEntry;
                size = 42;
                for (i = 0; i < size; p++, i++) {
                        if (p->pdStart && p->pdSize &&
                            p->pdFSID == cpu_to_be32(0x54465331)/*"TFS1"*/ &&
                            (HFSPLUS_SB(sb).part < 0 || HFSPLUS_SB(sb).part == i)) {
                                *part_start += be32_to_cpu(p->pdStart);
                                *part_size = be32_to_cpu(p->pdSize);
                                res = 0;
                        }
                }
                break;
          }
        case HFS_NEW_PMAP_MAGIC:
          {
                struct new_pmap *pm;

                pm = (struct new_pmap *)bh->b_data;
                size = be32_to_cpu(pm->pmMapBlkCnt);
                for (i = 0; i < size;) {
                        if (!memcmp(pm->pmPartType,"Apple_HFS", 9) &&
                            (HFSPLUS_SB(sb).part < 0 || HFSPLUS_SB(sb).part == i)) {
                                *part_start += be32_to_cpu(pm->pmPyPartStart);
                                *part_size = be32_to_cpu(pm->pmPartBlkCnt);
                                res = 0;
                                break;
                        }
                        brelse(bh);
                        bh = sb_bread512(sb, *part_start + HFS_PMAP_BLK + ++i, pm);
                        if (!bh)
                                return -EIO;
                        if (pm->pmSig != cpu_to_be16(HFS_NEW_PMAP_MAGIC))
                                break;
                }
                break;
          }
        }
        brelse(bh);

        return res;
}