/* $NetBSD: dkwedge_tos.c,v 1.2 2024/04/06 09:51:34 hannken Exp $ */

/*
 * Copyright (c) 2024 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Charlotte Koch.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * dk(4) support for Atari "TOS" partition schemes.
 *
 * Technical details taken from:
 *
 * - "Atari Hard Disk File Systems Reference Guide" v1.2b by Jean
 * Louis-Guerin (DrCoolZic) (September 2014)
 *
 * https://info-coach.fr/atari/documents/_mydoc/Atari_HD_File_Sytem_Reference_Guide.pdf
 */

#include <sys/buf.h>
#include <sys/disk.h>
#include <sys/endian.h>
#include <sys/vnode.h>

#define TOS_PART_TYPE_LEN       3
#define TOS_GEM_PARTITION       "GEM"
#define TOS_BGM_PARTITION       "BGM"
#define TOS_XGM_PARTITION       "XGM"

#define TOS_CXNMETHOD_SASI      0x00
#define TOS_CXNMETHOD_SCSI      0xFF

#define TOS_MAX_PART_COUNT      4
#define TOS_SECTOR_SIZE         512

struct tos_partition {
        uint8_t status;
        char type[TOS_PART_TYPE_LEN];
        uint32_t offset;
        uint32_t size;
} __packed;
__CTASSERT(sizeof(struct tos_partition) == 12);

struct tos_root_sector {
        uint8_t unused1[441];
        uint8_t connection_method;
        uint8_t unused2[8];
        uint32_t size;
        struct tos_partition parts[TOS_MAX_PART_COUNT];
        uint8_t unused3[10];
} __packed;
__CTASSERT(sizeof(struct tos_root_sector) == TOS_SECTOR_SIZE);

static int dkwedge_discover_tos(struct disk *pdk, struct vnode *vp);

static int
dkwedge_discover_tos(struct disk *pdk, struct vnode *vp)
{
        struct dkwedge_info dkw;
        int error = 0;
        size_t i;
        char safe_type[4];

        /* Get ourselves a fistful of memory. */
        buf_t *bp = geteblk(TOS_SECTOR_SIZE);

        error = dkwedge_read(pdk, vp, 0L, bp->b_data, TOS_SECTOR_SIZE);
        if (error) {
                aprint_error("unable to read TOS Root Sector: error = %d",
                    error);
                goto out;
        }

        struct tos_root_sector *trs = bp->b_data;

        /*
         * If the "connection method" isn't recognized, then this is
         * probably NOT an Atari-style partition, so get outta here. Note
         * that there really isn't a magic number we can rely on; this check
         * is somewhat made up. But at least it's better than nothing.
         */
        switch (trs->connection_method) {
        case TOS_CXNMETHOD_SASI: /* FALLTHROUGH */
        case TOS_CXNMETHOD_SCSI:
                ; /* OK */
                break;
        default:
                error = ESRCH;
                goto out;
        }

        /*
         * Make a wedge for each partition that exists (i.e., has the "exist"
         * bit set).
         */
        for (i = 0; i < TOS_MAX_PART_COUNT; i++) {
                struct tos_partition part = trs->parts[i];

                if (!(part.status & 0x01))
                        continue;

                /* Ignore if we see it's an extended "XGM" partition. */
                if (!strncmp(part.type, TOS_XGM_PARTITION, TOS_PART_TYPE_LEN)) {
                        aprint_normal(
                            "WARNING: XGM partitions are not yet supported\n");
                        continue;
                }

                /*
                 * Otherwise, get outta here if it's not the partition-types
                 * we *do* support.
                 */
                if (strncmp(part.type, TOS_GEM_PARTITION, TOS_PART_TYPE_LEN) &&
                    strncmp(part.type, TOS_BGM_PARTITION, TOS_PART_TYPE_LEN)) {
                        error = ESRCH;
                        goto out;
                }

                memset(&dkw, 0, sizeof(dkw));
                memset(safe_type, 0, sizeof(safe_type));

                /*
                 * The partition type string is NOT NUL-terminated, so let's
                 * play it safe.
                 */
                memcpy(safe_type, part.type, TOS_PART_TYPE_LEN);
                safe_type[TOS_PART_TYPE_LEN] = '\0';

                /* Finally, make the wedge. */
                snprintf(dkw.dkw_wname, sizeof(dkw.dkw_wname), "ATARI_%s_%02zu",
                    safe_type, i);
                dkw.dkw_offset = be32toh(trs->parts[i].offset);
                dkw.dkw_size = be32toh(trs->parts[i].size);
                strlcpy(dkw.dkw_ptype, DKW_PTYPE_FAT, sizeof(dkw.dkw_ptype));
                strlcpy(dkw.dkw_parent, pdk->dk_name, sizeof(dkw.dkw_parent));
                error = dkwedge_add(&dkw);

                if (error == EEXIST) {
                        aprint_error("partition named \"%s\" already exists",
                            dkw.dkw_wname);
                        goto out;
                }
        }

        error = 0;

out:
        brelse(bp, 0);
        return error;
}

DKWEDGE_DISCOVERY_METHOD_DECL(TOS, 10, dkwedge_discover_tos);