int ustctl_get_mmap_read_offset(struct shm_handle *handle,
struct lib_ring_buffer *buf, unsigned long *off);
int ustctl_get_subbuf_size(struct shm_handle *handle,
int ustctl_get_mmap_read_offset(struct shm_handle *handle,
struct lib_ring_buffer *buf, unsigned long *off);
int ustctl_get_subbuf_size(struct shm_handle *handle,