Re: [PATCH v6 2/4] tools/perf: extend format_alias() to include event parameters

From: Cody P Schafer <redacted>

This causes `perf list pmu` to show parameters for parameterized events
like:

  pmu/event_name,param1=?,param2=?/ [Kernel PMU event]

An example:

  hv_24x7/HPM_TLBIE__PHYS_CORE,core=?/ [Kernel PMU event]

Changelog[v6]
	[Jir Olsa, Sukadev Bhattiprolu] Drop the '$' sign and go back to
	just printing whatevever sysfs provides (which is '=?') to identify
	required parameters. sysfs also now uses parameters like 'core'
	and 'vcpu' rather than 'starting_index'.

Changelog[v5]
	[Jiri Olsa, Peter Zijlstra] Use '$' to prefix parameterized events.

Changelog[v4]
	[Jiri Olsa] If the parameter for an event in sysfs is 'param=val',
	have perf-list show the event as 'param=?' rather than 'val=?'.

CC: Haren Myneni <redacted>
CC: Cody P Schafer <redacted>
Signed-off-by: Cody P Schafer <redacted>
Signed-off-by: Sukadev Bhattiprolu <redacted>
---
 tools/perf/util/pmu.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index cb516dd..d208fef 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c

@@ -810,10 +810,35 @@ void perf_pmu__set_format(unsigned long *bits, long from, long to)
 		set_bit(b, bits);
 }
 
+static int sub_non_neg(int a, int b)
+{
+	if (b > a)
+		return 0;
+	return a - b;
+}
+
 static char *format_alias(char *buf, int len, struct perf_pmu *pmu,
 			  struct perf_pmu_alias *alias)
 {
-	snprintf(buf, len, "%s/%s/", pmu->name, alias->name);
+	struct parse_events_term *term;
+	int used = snprintf(buf, len, "%s/%s", pmu->name, alias->name);
+
+	list_for_each_entry(term, &alias->terms, list)
+		if (term->type_val == PARSE_EVENTS__TERM_TYPE_STR)
+			used += snprintf(buf + used, sub_non_neg(len, used),
+					",%s=%s", term->config,
+					term->val.str);