1 files changed, 22 insertions, 0 deletions
diff --git a/block.c b/block.c
index 31ca4c5a43..4c65035313 100644
--- a/block.c
+++ b/block.c
@@ -665,6 +665,8 @@ void bdrv_close_all(void)
 
 void bdrv_delete(BlockDriverState *bs)
 {
+    assert(!bs->peer);
+
     /* remove from list, if necessary */
     if (bs->device_name[0] != '\0') {
         QTAILQ_REMOVE(&bdrv_states, bs, list);
@@ -678,6 +680,26 @@ void bdrv_delete(BlockDriverState *bs)
     qemu_free(bs);
 }
 
+int bdrv_attach(BlockDriverState *bs, DeviceState *qdev)
+{
+    if (bs->peer) {
+        return -EBUSY;
+    }
+    bs->peer = qdev;
+    return 0;
+}
+
+void bdrv_detach(BlockDriverState *bs, DeviceState *qdev)
+{
+    assert(bs->peer == qdev);
+    bs->peer = NULL;
+}
+
+DeviceState *bdrv_get_attached(BlockDriverState *bs)
+{
+    return bs->peer;
+}
+
 /*
  * Run consistency checks on an image
  *