[PATCH] perf record: Allow to disable callchains by setting mode to "none"

[Milian Wolff <milian.wolff@kdab.com>]

This change is mostly useful for symmetry purposes. Before, we could:

    --event foo/call-graph=fp/
    --event bar/call-graph=dwarf/
    --event asdf/call-graph=lbr/

Now, we can also use

    --event xyz/call-graph=none/

The latter is equivalent to

    --event xyz

when the `perf record` invocation does not specify a global call-graph
option. If it does, then this patch also allows us to selectively
disable the call-graph for single events.

Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
---
 tools/perf/util/util.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 85c5680..a549fee 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -536,6 +536,14 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
 				pr_err("callchain: No more arguments "
 					"needed for --call-graph lbr\n");
 			break;
+		} else if (!strncmp(name, "none", sizeof("none"))) {
+			if (!strtok_r(NULL, ",", &saveptr)) {
+				param->record_mode = CALLCHAIN_NONE;
+				ret = 0;
+			} else
+				pr_err("callchain: No more arguments "
+					"needed for --call-graph none\n");
+			break;
 		} else {
 			pr_err("callchain: Unknown --call-graph option "
 			       "value: %s\n", arg);
-- 
2.9.3