/* amiga.c - Read amiga partition tables (RDB).  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2002,2004,2005,2006,2007  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>

GRUB_MOD_LICENSE("GPLv3+");

#define AMIGA_CHECKSUM_WORDS 128

GRUB_PACKED_START
struct grub_amiga_rdsk
{
	/* "RDSK".  */
	grub_uint8_t magic[4];
#define GRUB_AMIGA_RDSK_MAGIC "RDSK"
	grub_uint32_t size;
	grub_int32_t checksum;
	grub_uint32_t scsihost;
	grub_uint32_t blksz;
	grub_uint32_t flags;
	grub_uint32_t badblcklst;
	grub_uint32_t partitionlst;
	grub_uint32_t fslst;

	grub_uint32_t unused[AMIGA_CHECKSUM_WORDS - 9];
};
GRUB_PACKED_END

GRUB_PACKED_START
struct grub_amiga_partition
{
	/* "PART".  */
	grub_uint8_t magic[4];
#define GRUB_AMIGA_PART_MAGIC "PART"
	grub_uint32_t size;
	grub_int32_t checksum;
	grub_uint32_t scsihost;
	grub_uint32_t next;
	grub_uint32_t flags;
	grub_uint32_t unused1[2];
	grub_uint32_t devflags;
	grub_uint8_t namelen;
	grub_uint8_t name[31];
	grub_uint32_t unused2[15];

	grub_uint32_t unused3[3];
	grub_uint32_t heads;
	grub_uint32_t unused4;
	grub_uint32_t block_per_track;
	grub_uint32_t unused5[3];
	grub_uint32_t lowcyl;
	grub_uint32_t highcyl;

	grub_uint32_t firstcyl;
	grub_uint32_t unused[AMIGA_CHECKSUM_WORDS - 44];
};
GRUB_PACKED_END

static struct grub_partition_map grub_amiga_partition_map;

static grub_uint32_t
amiga_partition_map_checksum(void* buf)
{
	grub_uint32_t* ptr = buf;
	grub_uint32_t r = 0;
	grub_size_t sz;
	/* Fancy and quick way of checking sz >= 512 / 4 = 128.  */
	if (ptr[1] & ~grub_cpu_to_be32_compile_time(AMIGA_CHECKSUM_WORDS - 1))
		sz = AMIGA_CHECKSUM_WORDS;
	else
		sz = grub_be_to_cpu32(ptr[1]);

	for (; sz; sz--, ptr++)
		r += grub_be_to_cpu32(*ptr);

	return r;
}

static grub_err_t
amiga_partition_map_iterate(grub_disk_t disk,
	grub_partition_iterate_hook_t hook,
	void* hook_data)
{
	struct grub_partition part;
	struct grub_amiga_rdsk rdsk;
	int partno = 0;
	int next = -1;
	unsigned pos;

	/* The RDSK block is one of the first 15 blocks.  */
	for (pos = 0; pos < 15; pos++)
	{
		/* Read the RDSK block which is a descriptor for the entire disk.  */
		if (grub_disk_read(disk, pos, 0, sizeof(rdsk), &rdsk))
			return grub_errno;

		if (grub_memcmp(rdsk.magic, GRUB_AMIGA_RDSK_MAGIC,
			sizeof(rdsk.magic)) == 0
			&& amiga_partition_map_checksum(&rdsk) == 0)
		{
			/* Found the first PART block.  */
			next = grub_be_to_cpu32(rdsk.partitionlst);
			break;
		}
	}

	if (next == -1)
		return grub_error(GRUB_ERR_BAD_PART_TABLE,
			"Amiga partition map not found");

	/* The end of the partition list is marked using "-1".  */
	while (next != -1)
	{
		struct grub_amiga_partition apart;

		/* Read the RDSK block which is a descriptor for the entire disk.  */
		if (grub_disk_read(disk, next, 0, sizeof(apart), &apart))
			return grub_errno;

		if (grub_memcmp(apart.magic, GRUB_AMIGA_PART_MAGIC,
			sizeof(apart.magic)) != 0
			|| amiga_partition_map_checksum(&apart) != 0)
			return grub_error(GRUB_ERR_BAD_PART_TABLE,
				"invalid Amiga partition map");
		/* Calculate the first block and the size of the partition.  */
		part.start = (grub_be_to_cpu32(apart.lowcyl)
			* grub_be_to_cpu32(apart.heads)
			* grub_be_to_cpu32(apart.block_per_track));
		part.len = ((grub_be_to_cpu32(apart.highcyl)
			- grub_be_to_cpu32(apart.lowcyl) + 1)
			* grub_be_to_cpu32(apart.heads)
			* grub_be_to_cpu32(apart.block_per_track));

		part.offset = next;
		part.number = partno;
		part.index = 0;
		part.partmap = &grub_amiga_partition_map;

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

		next = grub_be_to_cpu32(apart.next);
		partno++;
	}

	return 0;
}

/* Partition map type.  */
static struct grub_partition_map grub_amiga_partition_map =
{
	.name = "amiga",
	.iterate = amiga_partition_map_iterate,
};

GRUB_MOD_INIT(part_amiga)
{
	grub_partition_map_register(&grub_amiga_partition_map);
}

GRUB_MOD_FINI(part_amiga)
{
	grub_partition_map_unregister(&grub_amiga_partition_map);
}
