[PATCH bpf-next v2] libbpf: Expose libbpf ringbufer epoll_fd

[Brendan Jackman <jackmanb@google.com>]

This provides a convenient perf ringbuf -> libbpf ringbuf migration
path for users of external polling systems. It is analogous to
perf_buffer__epoll_fd.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
Difference from v1: Added entry to libbpf.map.

 tools/lib/bpf/libbpf.h   | 1 +
 tools/lib/bpf/libbpf.map | 1 +
 tools/lib/bpf/ringbuf.c  | 6 ++++++
 3 files changed, 8 insertions(+)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 6909ee81113a..cde07f64771e 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -536,6 +536,7 @@ LIBBPF_API int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 				ring_buffer_sample_fn sample_cb, void *ctx);
 LIBBPF_API int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms);
 LIBBPF_API int ring_buffer__consume(struct ring_buffer *rb);
+LIBBPF_API int ring_buffer__epoll_fd(struct ring_buffer *rb);

 /* Perf buffer APIs */
 struct perf_buffer;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 7c4126542e2b..7be850271be6 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -348,4 +348,5 @@ LIBBPF_0.3.0 {
 		btf__new_split;
 		xsk_setup_xdp_prog;
 		xsk_socket__update_xskmap;
+                ring_buffer__epoll_fd;
 } LIBBPF_0.2.0;
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 5c6522c89af1..45a36648b403 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -282,3 +282,9 @@ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
 	}
 	return cnt < 0 ? -errno : res;
 }
+
+/* Get an fd that can be used to sleep until data is available in the ring(s) */
+int ring_buffer__epoll_fd(struct ring_buffer *rb)
+{
+	return rb->epoll_fd;
+}

base-commit: b4fe9fec51ef48011f11c2da4099f0b530449c92
--
2.29.2.576.ga3fc446d84-goog