disk: Support GUID Partition Tables (GPT)

Notes:

 * Currently limited to 32-bit sector addresses due to internal Rockbox
   APIs. So this means a practical limit of 2TiB per drive.
 * Only 'General Data' GPT partition type is recognised, as that's
   what SD cards seem to use for exFAT/FAT32.

Note that _booting_ off GPT-partitioned drive will require rebuilding
the various rockbox bootloaders, and even then there may be platform
limitations that preclude this.

Change-Id: Ibfaae1960adcb1e81976d4b60dd596c6d16318e4

1 files changed, 3 insertions, 0 deletions

diff --git a/firmware/export/disk.h b/firmware/export/disk.h
index c66028fe45..e465552fdc 100644
--- a/firmware/export/disk.h
+++ b/firmware/export/disk.h
@@ -35,6 +35,9 @@ struct partinfo
 #define PARTITION_TYPE_FAT32_LBA            0x0c
 #define PARTITION_TYPE_FAT16                0x06
 #define PARTITION_TYPE_OS2_HIDDEN_C_DRIVE   0x84
+#define PARTITION_TYPE_GPT_GUARD            0xee
+
+#define MAX_PARTITIONS_PER_DRIVE 4  /* Needs to be at least 4 */
 
 bool disk_init(IF_MD_NONVOID(int drive));
 bool disk_partinfo(int partition, struct partinfo *info);