[PATCH v2 1/6] perf list: Add tracepoint encoding to detailed output

[Ian Rogers]

The tracepoint id holds the config value and is probed in determining
what an event is. Add reading of the id so that we can display the
event encoding as:

```
$ perf list --details
..
  alarmtimer:alarmtimer_cancel                       [Tracepoint event]
        tracepoint/config=0x18c/
..
```

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/print-events.c | 35 ++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c
index 7b54e9385442..e0d2b49bab66 100644
--- a/tools/perf/util/print-events.c
+++ b/tools/perf/util/print-events.c
@@ -9,6 +9,7 @@
 #include <unistd.h>
 
 #include <api/fs/tracing_path.h>
+#include <api/io.h>
 #include <linux/stddef.h>
 #include <linux/perf_event.h>
 #include <linux/zalloc.h>
@@ -92,34 +93,48 @@ void print_tracepoint_events(const struct print_callbacks *print_cb __maybe_unus
 
 		evt_items = scandirat(events_fd, sys_dirent->d_name, &evt_namelist, NULL, alphasort);
 		for (int j = 0; j < evt_items; j++) {
+			/*
+			 * Buffer sized at twice the max filename length + 1
+			 * separator + 1 \0 terminator.
+			 */
+			char buf[NAME_MAX * 2 + 2];
+			/* 16 possible hex digits and 22 other characters and \0. */
+			char encoding[16 + 22];
 			struct dirent *evt_dirent = evt_namelist[j];
-			char evt_path[MAXPATHLEN];
-			int evt_fd;
+			struct io id;
+			__u64 config;
 
 			if (evt_dirent->d_type != DT_DIR ||
 			    !strcmp(evt_dirent->d_name, ".") ||
 			    !strcmp(evt_dirent->d_name, ".."))
 				goto next_evt;
 
-			snprintf(evt_path, sizeof(evt_path), "%s/id", evt_dirent->d_name);
-			evt_fd = openat(dir_fd, evt_path, O_RDONLY);
-			if (evt_fd < 0)
+			snprintf(buf, sizeof(buf), "%s/id", evt_dirent->d_name);
+			io__init(&id, openat(dir_fd, buf, O_RDONLY), buf, sizeof(buf));
+
+			if (id.fd < 0)
+				goto next_evt;
+
+			if (io__get_dec(&id, &config) < 0) {
+				close(id.fd);
 				goto next_evt;
-			close(evt_fd);
+			}
+			close(id.fd);
 
-			snprintf(evt_path, MAXPATHLEN, "%s:%s",
+			snprintf(buf, sizeof(buf), "%s:%s",
 				 sys_dirent->d_name, evt_dirent->d_name);
+			snprintf(encoding, sizeof(encoding), "tracepoint/config=0x%llx/", config);
 			print_cb->print_event(print_state,
 					/*topic=*/NULL,
-					/*pmu_name=*/NULL,
-					evt_path,
+					/*pmu_name=*/NULL, /* really "tracepoint" */
+					/*event_name=*/buf,
 					/*event_alias=*/NULL,
 					/*scale_unit=*/NULL,
 					/*deprecated=*/false,
 					"Tracepoint event",
 					/*desc=*/NULL,
 					/*long_desc=*/NULL,
-					/*encoding_desc=*/NULL);
+					encoding);
 next_evt:
 			free(evt_namelist[j]);
 		}
-- 
2.44.0.278.ge034bb2e1d-goog