[PATCH v5 5/8] rtla: make struct trace_events double linked

[Valentin Schneider <vschneid@redhat.com>]

The events list is currently a single linked list. New events are prepended
to the list, making them the new head.

This makes it easy to fetch the last-defined event when handling trigger
and filter options on the cmdline, as they apply to the last-defined event,
but means the events are then processed in LIFO order with regards to the
command line order.

To prepare for processing the events in the user-defined order, make the
events list double linked.

Signed-off-by: Valentin Schneider <vschneid@redhat.com>
---
 tools/tracing/rtla/src/cli_p.h | 4 +++-
 tools/tracing/rtla/src/trace.h | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/tracing/rtla/src/cli_p.h b/tools/tracing/rtla/src/cli_p.h
index f2dd7c610093d..7e3a713f97c62 100644
--- a/tools/tracing/rtla/src/cli_p.h
+++ b/tools/tracing/rtla/src/cli_p.h
@@ -394,8 +394,10 @@ static int opt_event_cb(const struct option *opt, const char *arg, int unset)
 	if (!tevent)
 		fatal("Error alloc trace event");
 
-	if (*events)
+	if (*events) {
 		tevent->next = *events;
+		(*events)->prev = tevent;
+	}
 	*events = tevent;
 
 	return 0;
diff --git a/tools/tracing/rtla/src/trace.h b/tools/tracing/rtla/src/trace.h
index 95b911a2228b2..eacafc0c96b31 100644
--- a/tools/tracing/rtla/src/trace.h
+++ b/tools/tracing/rtla/src/trace.h
@@ -4,6 +4,7 @@
 
 struct trace_events {
 	struct trace_events *next;
+	struct trace_events *prev;
 	char *system;
 	char *event;
 	char *filter;
-- 
2.55.0