+struct stream_subbuffer {
+ union {
+ /*
+ * CONSUMER_CHANNEL_SPLICE
+ * No ownership assumed.
+ */
+ int fd;
+ /* CONSUMER_CHANNEL_MMAP */
+ struct lttng_buffer_view buffer;
+ } buffer;
+ union {
+ /*
+ * Common members are fine to access through either
+ * union entries (as per C11, Common Initial Sequence).
+ */
+ struct {
+ unsigned long subbuf_size;
+ unsigned long padded_subbuf_size;
+ uint64_t version;
+ /*
+ * Left unset when unsupported.
+ *
+ * Indicates that this is the last sub-buffer of
+ * a series of sub-buffer that makes-up a coherent
+ * (parseable) unit of metadata.
+ */
+ LTTNG_OPTIONAL(bool) coherent;
+ } metadata;
+ struct {
+ unsigned long subbuf_size;
+ unsigned long padded_subbuf_size;
+ uint64_t packet_size;
+ uint64_t content_size;
+ uint64_t timestamp_begin;
+ uint64_t timestamp_end;
+ uint64_t events_discarded;
+ /* Left unset when unsupported. */
+ LTTNG_OPTIONAL(uint64_t) sequence_number;
+ uint64_t stream_id;
+ /* Left unset when unsupported. */
+ LTTNG_OPTIONAL(uint64_t) stream_instance_id;
+ } data;
+ } info;
+};
+
+/*
+ * Perform any operation required to acknowledge
+ * the wake-up of a consumer stream (e.g. consume a byte on a wake-up pipe).
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*on_wake_up_cb)(struct lttng_consumer_stream *);
+
+/*
+ * Perform any operation required before a consumer stream is put
+ * to sleep before awaiting a data availability notification.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*on_sleep_cb)(struct lttng_consumer_stream *,
+ struct lttng_consumer_local_data *);
+
+/*
+ * Acquire the subbuffer at the current 'consumed' position.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*get_next_subbuffer_cb)(struct lttng_consumer_stream *,
+ struct stream_subbuffer *);
+
+/*
+ * Populate the stream_subbuffer's info member. The info to populate
+ * depends on the type (metadata/data) of the stream.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*extract_subbuffer_info_cb)(
+ struct lttng_consumer_stream *, struct stream_subbuffer *);
+
+/*
+ * Invoked after a subbuffer's info has been filled.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*pre_consume_subbuffer_cb)(struct lttng_consumer_stream *,
+ const struct stream_subbuffer *);
+
+/*
+ * Consume subbuffer contents.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef ssize_t (*consume_subbuffer_cb)(struct lttng_consumer_local_data *,
+ struct lttng_consumer_stream *,
+ const struct stream_subbuffer *);
+
+/*
+ * Release the current subbuffer and advance the 'consumed' position by
+ * one subbuffer.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*put_next_subbuffer_cb)(struct lttng_consumer_stream *,
+ struct stream_subbuffer *);
+
+/*
+ * Invoked after consuming a subbuffer.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*post_consume_cb)(struct lttng_consumer_stream *,
+ const struct stream_subbuffer *,
+ struct lttng_consumer_local_data *);
+
+/*
+ * Send a live beacon if no data is available.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef int (*send_live_beacon_cb)(struct lttng_consumer_stream *);
+
+/*
+ * Lock the stream and channel locks and any other stream-type specific
+ * lock that need to be acquired during the processing of an
+ * availability notification.
+ */
+typedef void (*lock_cb)(struct lttng_consumer_stream *);
+
+/*
+ * Unlock the stream and channel locks and any other stream-type specific
+ * lock before sleeping until the next availability notification.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef void (*unlock_cb)(struct lttng_consumer_stream *);
+
+/*
+ * Assert that the stream and channel lock and any other stream type specific
+ * lock that need to be acquired during the processing of a read_subbuffer
+ * operation is acquired.
+ */
+typedef void (*assert_locked_cb)(struct lttng_consumer_stream *);
+
+/*
+ * Invoked when a subbuffer's metadata version does not match the last
+ * known metadata version.
+ *
+ * Stream and channel locks are acquired during this call.
+ */
+typedef void (*reset_metadata_cb)(struct lttng_consumer_stream *);
+