/*
 * 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 <linux/slab.h>
#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;

static int hfs_parse_old_pmap(struct super_block *sb, struct old_pmap *pm,
                sector_t *part_start, sector_t *part_size)
{
        struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
        int i;

        for (i = 0; i < 42; i++) {
                struct old_pmap_entry *p = &pm->pdEntry[i];

                if (p->pdStart && p->pdSize &&
                    p->pdFSID == cpu_to_be32(0x54465331)/*"TFS1"*/ &&
                    (sbi->part < 0 || sbi->part == i)) {
                        *part_start += be32_to_cpu(p->pdStart);
                        *part_size = be32_to_cpu(p->pdSize);
                        return 0;
                }
        }

        return -ENOENT;
}

static int hfs_parse_new_pmap(struct super_block *sb, void *buf,
                struct new_pmap *pm, sector_t *part_start, sector_t *part_size)
{
        struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
        int size = be32_to_cpu(pm->pmMapBlkCnt);
        int buf_size = hfsplus_min_io_size(sb);
        int res;
        int i = 0;

        do {
                if (!memcmp(pm->pmPartType, "Apple_HFS", 9) &&
                    (sbi->part < 0 || sbi->part == i)) {
                        *part_start += be32_to_cpu(pm->pmPyPartStart);
                        *part_size = be32_to_cpu(pm->pmPartBlkCnt);
                        return 0;
                }

                if (++i >= size)
                        return -ENOENT;

                pm = (struct new_pmap *)((u8 *)pm + HFSPLUS_SECTOR_SIZE);
                if ((u8 *)pm - (u8 *)buf >= buf_size) {
                        res = hfsplus_submit_bio(sb,
                                                 *part_start + HFS_PMAP_BLK + i,
                                                 buf, (void **)&pm, REQ_OP_READ);
                        if (res)
                                return res;
                }
        } while (pm->pmSig == cpu_to_be16(HFS_NEW_PMAP_MAGIC));

        return -ENOENT;
}

/*
 * Parse the partition map looking for the start and length of a
 * HFS/HFS+ partition.
 */
int hfs_part_find(struct super_block *sb,
                sector_t *part_start, sector_t *part_size)
{
        void *buf, *data;
        int res;

        buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        res = hfsplus_submit_bio(sb, *part_start + HFS_PMAP_BLK,
                                 buf, &data, REQ_OP_READ);
        if (res)
                goto out;

        switch (be16_to_cpu(*((__be16 *)data))) {
        case HFS_OLD_PMAP_MAGIC:
                res = hfs_parse_old_pmap(sb, data, part_start, part_size);
                break;
        case HFS_NEW_PMAP_MAGIC:
                res = hfs_parse_new_pmap(sb, buf, data, part_start, part_size);
                break;
        default:
                res = -ENOENT;
                break;
        }
out:
        kfree(buf);
        return res;
}