VB2_BUF_STATE_PREPARING
vb->state = VB2_BUF_STATE_PREPARING;
case VB2_BUF_STATE_PREPARING:
[VB2_BUF_STATE_PREPARING] = "preparing",
case VB2_BUF_STATE_PREPARING:
[VB2_BUF_STATE_PREPARING] = "preparing",
case VB2_BUF_STATE_PREPARING: