ahdi: first cut at Atari partition formats

diff --git a/Kernel/dev/ahdi.c b/Kernel/dev/ahdi.c
new file mode 100644 (file)
index 0000000..6568d7e
--- /dev/null
+++ b/Kernel/dev/ahdi.c
@@ -0,0 +1,153 @@
+/*
+ *     Atari hard disk boot sectors
+ *
+ *     This is an initial simple minded parser. The original format was extended
+ *     in two ways at least. ICD stuffed extra partition entries into the end of
+ *     the bootcode space, whilst the XGM format changes the partition table to
+ *     a linked list of entries where each entry is a partition definition and
+ *     pointer to a next block.
+ *
+ *     For more information see Atari AHDI 3.00 Release Notes
+ *
+ *     FIXME: currently only works on big endian
+ */
+
+#include <kernel.h>
+#include <kdata.h>
+#include <printf.h>
+#include <blkdev.h>
+#include "ahdi.h"
+
+/*
+ *     Check a partition table looks sane. That is the entries have
+ *     ASCII and valid sizes. If we find no entries then we don't
+ *     consider it valid, because it doesn't matter whether it is or not.
+ */
+static uint_fast8_t check_sane(struct atari_bootblock *br,
+                              struct atari_partition *ap, uint_fast8_t n)
+{
+       uint_fast8_t i;
+       uint_fast8_t found = 0;
+
+       for (i = 0; i < n; i++) {
+               if (ap->flags & 1) {
+                       found++;
+                       if (!ap->start || !ap->length)
+                               return 0;
+                       if (ap->start >= br->size
+                           || ap->start + ap->length >= br->size)
+                               return 0;
+                       if ((ap->id[0] | ap->id[1] | ap->id[2]) & 0x80)
+                               return 0;
+                       if (ap->id[0] < 32 || ap->id[1] < 32
+                           || ap->id[2] < 32)
+                               return 0;
+               }
+               ap++;
+       }
+       return found;
+}
+
+/*
+ *     AHDI 3.0 added extended partitions but as with all of this stuff
+ *     had to be different to the PC. GEM extended partitions form a chain.
+ *     We follow the chain each of which has a partition and then an XGM
+ *     entry pointing the next one
+ */
+static uint_fast8_t ahdi_extended_partition(struct atari_partition *bap,
+                                           uint_fast8_t next,
+                                           uint8_t letter)
+{
+       struct atari_bootblock *ext = (struct atari_bootblock *) tmpbuf();
+       struct atari_partition *ap;
+       uint_fast8_t i;
+
+       blk_op.addr = (uint8_t *) ext;
+       blk_op.lba = bap->start;
+
+       do {
+               if (!blk_op.blkdev->transfer())
+                       return next;
+
+               ap = ext->part;
+
+               for (i = 0; i < 3; i++) {
+                       if (ap->flags & 1)
+                               break;
+                       ap++;
+               }
+               if (i == 3)
+                       break;
+               /* Can't just be an XGM */
+               if (memcmp(ap->id, "XGM", 3) == 0)
+                       break;
+
+               /* Ok looks believable */
+               /* TODO : check we don't overrun table */
+               blk_op.blkdev->lba_first[next] = bap->start + ap->start;
+               blk_op.blkdev->lba_count[next] = ap->length;
+               next++;
+               kprintf("hd%c%d (%c%c%c) ",
+                       letter, next, ap->id[0], ap->id[1], ap->id[2]);
+               blk_op.lba = ap[1].start;
+       }
+       while((ap[1].flags & 1) && memcmp(ap[1].id, "XGM", 3) == 0);
+       tmpfree(ext);
+       return next;
+}
+
+static uint_fast8_t ahdi_install(struct atari_partition *ap,
+                                uint_fast8_t n, uint_fast8_t next,
+                                uint8_t letter)
+{
+       uint_fast8_t i;
+
+       for (i = 0; i < n; i++) {
+               if (ap->flags & 1) {
+                       /* TODO : check we don't overrun table */
+                       blk_op.blkdev->lba_first[next] = ap->start;
+                       blk_op.blkdev->lba_count[next] = ap->length;
+                       next++;
+                       kprintf("hd%c%d (%c%c%c) ",
+                               letter, next, ap->id[0], ap->id[1],
+                               ap->id[2]);
+                       /* AHDI 3 adds chains of partitions */
+                       if (memcmp(ap->id, "XGM", 3) == 0)
+                               next =
+                                   ahdi_extended_partition(ap, next,
+                                                           letter);
+               }
+               ap++;
+       }
+       return next;
+}
+
+void ahdi_parse(uint_fast8_t letter)
+{
+       struct atari_bootblock *br;
+       uint_fast8_t next = 0;
+
+       kprintf("hd%c:", letter);
+
+       br = (struct atari_bootblock *) tmpbuf();
+
+       blk_op.is_read = true;
+       blk_op.is_user = false;
+       blk_op.addr = (uint8_t *) br;
+       blk_op.lba = 0;
+
+       blk_op.nblock = 1;
+       if (!blk_op.blkdev->transfer())
+               goto none;
+
+       if (!check_sane(br, br->part, 8))
+               goto none;
+       /* Probably a valid partition table */
+       next = ahdi_install(br->part, 4, next, letter);
+       /* Look for an ICD partition table */
+       if (check_sane(br, br->icd, 8))
+               next = ahdi_install(br->icd, 8, next, letter);
+      none:
+       tmpfree(br);
+       kputchar('\n');
+}

diff --git a/Kernel/dev/ahdi.h b/Kernel/dev/ahdi.h
new file mode 100644 (file)
index 0000000..0b3e379
--- /dev/null
+++ b/Kernel/dev/ahdi.h
@@ -0,0 +1,42 @@
+/*
+ *     Atari partitions
+ *
+ *     BGM             : Big GEM
+ *     GEM             : GEM
+ *
+ *     XGM             : Extended GEM (extended partition table)
+ *
+ */
+
+struct atari_partition {
+    uint8_t flags;
+#define AP_ACTIVE      0x01
+#define AP_BOOTABLE    0x80
+    uint8_t id[3];
+    uint32_t start;
+    uint32_t length;
+} __attribute((packed));
+
+struct atari_bootblock {
+    uint8_t bootcode[0x156];
+    struct atari_partition icd[8];     /* ICD devices stick extra entries here */
+    /* These are only used on very old devices and in fact it's not clear to me
+       if any Atari STthing uses them! */
+    uint16_t cylinders;
+    uint8_t heads;
+    uint8_t scsiflag;                  /* FF for SCSI else SASI (but in fact
+                                           it's ACSI! */
+    uint16_t precomp;
+    uint16_t rwcurrent;
+    uint8_t park_offset;
+    uint8_t step;
+    uint8_t interleave;
+    uint8_t spt;
+    uint32_t size;                     /* In blocks */
+    struct atari_partition part[4];    /* Real partitions */
+
+    uint32_t badsect;          /* We will need to deal with bad sectors */
+    uint32_t badlen;           /* eventually... */
+    uint16_t checksum;         /* _only_ if bootable */
+} __attribute((packed));
+