int vmbus_uio_get_subchan(struct vmbus_channel *primary,
struct vmbus_channel **subchan);
int vmbus_uio_map_rings(struct vmbus_channel *chan);
int vmbus_uio_get_subchan(struct vmbus_channel *primary,
struct vmbus_channel **subchan);
int vmbus_uio_map_rings(struct vmbus_channel *chan);