fdc: add disk field

Currently, 'drive' is used both to represent the current diskette
type as well as the current drive type.

This patch adds a 'disk' field that is updated explicitly to match
the type of the disk.

As of this patch, disk and drive are always the same, but forthcoming
patches to change the behavior of pick_geometry will invalidate this
assumption.

disk does not need to be migrated because it is not user-visible state
nor is it currently used for any calculations. It is purely informative,
and will be rebuilt automatically via fd_revalidate on the new host.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 1453495865-9649-5-git-send-email-jsnow@redhat.com

hw/block/fdc.c

@@ -141,6 +141,7 @@ typedef struct FDrive {
     uint8_t track;
     uint8_t sect;
     /* Media */
+    FloppyDriveType disk;     /* Current disk type      */
     FDiskFlags flags;
     uint8_t last_sect;        /* Nb sector per track    */
     uint8_t max_track;        /* Nb of tracks           */
@@ -158,6 +159,7 @@ static void fd_init(FDrive *drv)
     drv->drive = FLOPPY_DRIVE_TYPE_NONE;
     drv->perpendicular = 0;
     /* Disk */
+    drv->disk = FLOPPY_DRIVE_TYPE_NONE;
     drv->last_sect = 0;
     drv->max_track = 0;
 }
@@ -287,6 +289,7 @@ static void pick_geometry(FDrive *drv)
     drv->max_track = parse->max_track;
     drv->last_sect = parse->last_sect;
     drv->drive = parse->drive;
+    drv->disk = drv->media_inserted ? parse->drive : FLOPPY_DRIVE_TYPE_NONE;
     drv->media_rate = parse->rate;
 }