[PATCH v2] libperf: Add perf_evsel__id() function

[Charlie Jenkins <charlie@rivosinc.com>]

Introduce perf_evsel__id() to collect the id of an evsel. This allows
applications to determine the allocated id of an evsel for each fd. The
"ids" argument is expected to be an array the size of the number of open
fd's for the evsel.  This will allow applications to link the id
returned by PERF_SAMPLE_ID to the event being sampled.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
Changes in v2:
- Replaced id argument with array of ids for perf_evsel__id() to support
  the id for each fd.
- Link to v1: https://lore.kernel.org/r/20240823-perf_evsel_get_id-v1-1-0ffa204c4164@rivosinc.com
---
 tools/lib/perf/Documentation/libperf.txt |  2 ++
 tools/lib/perf/evsel.c                   | 10 ++++++++++
 tools/lib/perf/include/perf/evsel.h      |  1 +
 3 files changed, 13 insertions(+)

diff --git a/tools/lib/perf/Documentation/libperf.txt b/tools/lib/perf/Documentation/libperf.txt
index fcfb9499ef9c..754c103f7b13 100644
--- a/tools/lib/perf/Documentation/libperf.txt
+++ b/tools/lib/perf/Documentation/libperf.txt
@@ -94,6 +94,8 @@ SYNOPSIS
   void perf_evlist__enable(struct perf_evlist *evlist);
   void perf_evlist__disable(struct perf_evlist *evlist);
 
+  void perf_evsel__id(struct perf_evsel *evsel, __u64 ids[]);
+
   #define perf_evlist__for_each_evsel(evlist, pos)
 
   void perf_evlist__set_maps(struct perf_evlist *evlist,
diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index c07160953224..d10dfcb605ba 100644
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -484,6 +484,16 @@ int perf_evsel__disable(struct perf_evsel *evsel)
 	return err;
 }
 
+int perf_evsel__id(struct perf_evsel *evsel, __u64 ids[])
+{
+	int i;
+	int err = 0;
+
+	for (i = 0; i < xyarray__max_x(evsel->fd) && !err; i++)
+		err = perf_evsel__run_ioctl(evsel, PERF_EVENT_IOC_ID, (unsigned long)&ids[i], i);
+	return err;
+}
+
 int perf_evsel__apply_filter(struct perf_evsel *evsel, const char *filter)
 {
 	int err = 0, i;
diff --git a/tools/lib/perf/include/perf/evsel.h b/tools/lib/perf/include/perf/evsel.h
index 6f92204075c2..13f19189839a 100644
--- a/tools/lib/perf/include/perf/evsel.h
+++ b/tools/lib/perf/include/perf/evsel.h
@@ -41,6 +41,7 @@ LIBPERF_API int perf_evsel__enable_cpu(struct perf_evsel *evsel, int cpu_map_idx
 LIBPERF_API int perf_evsel__enable_thread(struct perf_evsel *evsel, int thread);
 LIBPERF_API int perf_evsel__disable(struct perf_evsel *evsel);
 LIBPERF_API int perf_evsel__disable_cpu(struct perf_evsel *evsel, int cpu_map_idx);
+LIBPERF_API int perf_evsel__id(struct perf_evsel *evsel, __u64 ids[]);
 LIBPERF_API struct perf_cpu_map *perf_evsel__cpus(struct perf_evsel *evsel);
 LIBPERF_API struct perf_thread_map *perf_evsel__threads(struct perf_evsel *evsel);
 LIBPERF_API struct perf_event_attr *perf_evsel__attr(struct perf_evsel *evsel);

---
base-commit: 47ac09b91befbb6a235ab620c32af719f8208399
change-id: 20240822-perf_evsel_get_id-f7e11f15504b
-- 
- Charlie