/* acorn.c - Read Linux/ADFS partition tables.  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2005  Free Software Foundation, Inc.
 *
 *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <grub/disk.h>
#include <grub/misc.h>
#include <grub/mm.h>
#include <grub/partition.h>
#include <grub/acorn_filecore.h>

#define LINUX_NATIVE_MAGIC grub_cpu_to_le32 (0xdeafa1de)
#define LINUX_SWAP_MAGIC   grub_cpu_to_le32 (0xdeafab1e)
#define LINUX_MAP_ENTRIES  (512 / 12)

#define NONADFS_PARTITON_TYPE_LINUX 9
#define NONADFS_PARTITON_TYPE_MASK 15

struct grub_acorn_boot_block
{
  grub_uint8_t misc[0x1C0];
  struct grub_filecore_disc_record disc_record;
  grub_uint8_t flags;
  grub_uint16_t start_cylinder;
  grub_uint8_t checksum;
} __attribute__ ((packed, aligned));

struct linux_part
{
  grub_uint32_t magic;
  grub_uint32_t start;
  grub_uint32_t size;
};

static struct grub_partition_map grub_acorn_partition_map;

static grub_err_t
find (grub_disk_t disk, struct linux_part *m, unsigned *sector)
{
  int i;
  struct grub_acorn_boot_block boot;
  grub_err_t err = grub_disk_read (disk, 0xC00 / GRUB_DISK_SECTOR_SIZE, 0,
				   sizeof (struct grub_acorn_boot_block),
				   &boot);
  if (err)
    return err;

  if ((boot.flags & NONADFS_PARTITON_TYPE_MASK) != NONADFS_PARTITON_TYPE_LINUX)
    goto fail;

  unsigned checksum = 0;
  for (i = 0; i != 0x1ff; ++i)
    checksum = (checksum & 0xff) + (checksum >> 8) + boot.misc[i];

  if ((grub_uint8_t) checksum != boot.checksum)
    goto fail;

  unsigned heads = (boot.disc_record.heads
		    + ((boot.disc_record.lowsector >> 6) & 1));
  unsigned sectors_per_cylinder = boot.disc_record.secspertrack * heads;
  *sector = grub_le_to_cpu16 (boot.start_cylinder) * sectors_per_cylinder;

  return grub_disk_read (disk, *sector, 0,
			 sizeof (struct linux_part) * LINUX_MAP_ENTRIES, m);

fail:
  return grub_error (GRUB_ERR_BAD_PART_TABLE,
		     "Linux/ADFS partition map not found.");

}


static grub_err_t
acorn_partition_map_iterate (grub_disk_t disk,
			     int (*hook) (grub_disk_t disk,
					  const grub_partition_t partition))
{
  int i;
  unsigned sector;
  struct grub_partition part;
  struct grub_disk raw;
  struct linux_part map[LINUX_MAP_ENTRIES];

  /* Enforce raw disk access.  */
  raw = *disk;
  raw.partition = 0;

  grub_err_t err = find (&raw, map, &sector);
  if (err)
    return err;

  part.partmap = &grub_acorn_partition_map;

  for (i = 0; i != LINUX_MAP_ENTRIES; ++i)
    {
      if (map[i].magic != LINUX_NATIVE_MAGIC
	  && map[i].magic != LINUX_SWAP_MAGIC)
	return GRUB_ERR_NONE;

      part.start = (grub_disk_addr_t)sector + map[i].start;
      part.len = map[i].size;
      part.offset = 6;
      part.index = i;

      if (hook (disk, &part))
	return grub_errno;
    }

  return GRUB_ERR_NONE;
}


static grub_partition_t
acorn_partition_map_probe (grub_disk_t disk, const char *str)
{
  unsigned sector;
  struct linux_part map[LINUX_MAP_ENTRIES];

  /* Enforce raw disk access.  */
  struct grub_disk raw = *disk;
  raw.partition = 0;

  /* Get the partition number.  */
  unsigned long partnum = grub_strtoul (str, 0, 10);
  if (partnum > LINUX_MAP_ENTRIES)
    goto fail;

  grub_err_t err = find (&raw, map, &sector);
  if (err)
    return 0;

  if (map[partnum].magic != LINUX_NATIVE_MAGIC
      && map[partnum].magic != LINUX_SWAP_MAGIC)
    goto fail;

  grub_partition_t p = grub_malloc (sizeof (struct grub_partition));
  if (!p)
    return 0;

  p->start = (grub_disk_addr_t)sector + map[partnum].start;
  p->len = map[partnum].size;
  p->offset = 6;
  p->index = partnum;
  return p;

fail:
  grub_error (GRUB_ERR_BAD_FILENAME, "invalid partition");
  return 0;
}


static char *
acorn_partition_map_get_name (const grub_partition_t p)
{
  char *name;

  name = grub_malloc (13);
  if (!name)
    return 0;

  grub_sprintf (name, "%d", p->index);
  return name;
}


/* Partition map type.  */
static struct grub_partition_map grub_acorn_partition_map =
{
  .name = "Linux/ADFS partition map",
  .iterate = acorn_partition_map_iterate,
  .probe = acorn_partition_map_probe,
  .get_name = acorn_partition_map_get_name
};

GRUB_MOD_INIT(acorn_partition_map)
{
  grub_partition_map_register (&grub_acorn_partition_map);
}

GRUB_MOD_FINI(acorn_partition_map)
{
  grub_partition_map_unregister (&grub_acorn_partition_map);
}