diskgeom: disk geometry and mini partitions for small boxen

diff --git a/Kernel/include/diskgeom.h b/Kernel/include/diskgeom.h
new file mode 100644 (file)
index 0000000..f285778
--- /dev/null
+++ b/Kernel/include/diskgeom.h
@@ -0,0 +1,45 @@
+#ifndef _DISKGEOM_H
+#define _DISKGEOM_H
+
+/*
+ *     The mini partition system used for legacy CHS environments or
+ *     very small boxes.
+ *
+ *     The partitions are laid out in strict cylinder order. Each one ends
+ *     at the start of the next with any spaces being a partition of type 0
+ *     with start/end. The final partition and any beyond have mp_pcyl[n]
+ *     set to mp_cyl.
+ *
+ *     mp_cyl is after the array so that it is always true that pcyl[n+1] is
+ *     the first cylinder after partition n
+ */
+struct diskgeom {
+  uint32_t magic;      /* Magic number */
+#define MP_SIG_0       0x01CAD15CUL
+  uint16_t cyl;                /* Cylinders on the drive. Must directly follow pcyl */
+  uint8_t head;                /* Heads on the drive */
+  uint8_t sec;         /* Sectors per track */
+  uint16_t precomp;    /* Precompensation cylinder start (inclusive) */
+#define PRECOMP_NONE   0xFFFF
+  uint16_t land;       /* Usually cyl + 1 */
+  uint8_t seek;                /* Seek step rate in ms */
+  uint8_t secsize;     /* Sector size as power of 2 */
+  uint8_t pad[2];      /* Takes us to 16 bytes */
+};
+
+/* Labelling bits needed for a CHS drive */
+struct minipart {
+  struct diskgeom g;
+  uint16_t cyl[15];
+  uint8_t type[15];
+};
+
+/* The full entry, including the LBA offsets added by the labeller
+   for use if in LBA mode. The LBAs must match the cyl pointers */
+struct minipart_lba {
+  struct diskgeom g;
+  uint16_t cyl[15];
+  uint32_t lba[15];
+};
+
+#endif