/* acorn.c - Read Linux/ADFS partition tables.  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2005,2007  Free Software Foundation, Inc.
 *
 *  GRUB 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 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

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

GRUB_MOD_LICENSE("GPLv3+");

#define LINUX_NATIVE_MAGIC grub_cpu_to_le32_compile_time (0xdeafa1de)
#define LINUX_SWAP_MAGIC   grub_cpu_to_le32_compile_time (0xdeafab1e)
#define LINUX_MAP_ENTRIES  (512 / 12)

#define NONADFS_PARTITION_TYPE_LINUX 9
#define NONADFS_PARTITION_TYPE_MASK 15

GRUB_PACKED_START
struct grub_acorn_boot_block
{
	union
	{
		GRUB_PACKED_START
		struct
		{
			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;
		};
		GRUB_PACKED_END
		grub_uint8_t bin[0x200];
	};
};
GRUB_PACKED_END

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
acorn_partition_map_find(grub_disk_t disk, struct linux_part* m,
	grub_disk_addr_t* sector)
{
	struct grub_acorn_boot_block boot;
	grub_err_t err;
	unsigned int checksum = 0;
	unsigned int heads;
	unsigned int sectors_per_cylinder;
	int i;

	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_PARTITION_TYPE_MASK) != NONADFS_PARTITION_TYPE_LINUX)
		goto fail;

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

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

	heads = (boot.disc_record.heads
		+ ((boot.disc_record.lowsector >> 6) & 1));
	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,
	grub_partition_iterate_hook_t hook,
	void* hook_data)
{
	struct grub_partition part;
	struct linux_part map[LINUX_MAP_ENTRIES];
	int i;
	grub_disk_addr_t sector = 0;
	grub_err_t err;

	err = acorn_partition_map_find(disk, 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 = sector + map[i].start;
		part.len = map[i].size;
		part.offset = 6;
		part.number = part.index = i;

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

	return GRUB_ERR_NONE;
}

/* Partition map type.  */
static struct grub_partition_map grub_acorn_partition_map =
{
	.name = "acorn",
	.iterate = acorn_partition_map_iterate,
};

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

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