[PATCH V4 05/13] perf pmu: Add support for PMU capabilities

[kan . liang]

From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

The PMU capabilities information, which is located at
/sys/bus/event_source/devices/<dev>/caps, is required by perf tool.
For example, the max LBR information is required to stitch LBR call
stack.

Add perf_pmu__caps_parse() to parse the PMU capabilities information.
The information is stored in a list.

Add perf_pmu__scan_caps() to scan the capabilities once by one.

The following patch will store the capabilities information in perf
header.

Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
---
 tools/perf/util/pmu.c | 87 +++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/pmu.h | 12 ++++++
 2 files changed, 99 insertions(+)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index db1e57113f4b..150f24bb7e1a 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -853,6 +853,7 @@ static struct perf_pmu *pmu_lookup(const char *name)
 
 	INIT_LIST_HEAD(&pmu->format);
 	INIT_LIST_HEAD(&pmu->aliases);
+	INIT_LIST_HEAD(&pmu->caps);
 	list_splice(&format, &pmu->format);
 	list_splice(&aliases, &pmu->aliases);
 	list_add_tail(&pmu->list, &pmus);
@@ -1567,3 +1568,89 @@ int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt,
 	va_end(args);
 	return ret;
 }
+
+static int perf_pmu__new_caps(struct list_head *list, char *name, char *value)
+{
+	struct perf_pmu_caps *caps;
+
+	caps = zalloc(sizeof(*caps));
+	if (!caps)
+		return -ENOMEM;
+
+	caps->name = strdup(name);
+	caps->value = strndup(value, strlen(value) - 1);
+	list_add_tail(&caps->list, list);
+	return 0;
+}
+
+/*
+ * Reading/parsing the given pmu capabilities, which should be located at:
+ * /sys/bus/event_source/devices/<dev>/caps as sysfs group attributes.
+ * Return the number of capabilities
+ */
+int perf_pmu__caps_parse(struct perf_pmu *pmu)
+{
+	struct stat st;
+	char caps_path[PATH_MAX];
+	const char *sysfs = sysfs__mountpoint();
+	DIR *caps_dir;
+	struct dirent *evt_ent;
+	int nr_caps = 0;
+
+	if (!sysfs)
+		return -1;
+
+	snprintf(caps_path, PATH_MAX,
+		 "%s" EVENT_SOURCE_DEVICE_PATH "%s/caps", sysfs, pmu->name);
+
+	if (stat(caps_path, &st) < 0)
+		return 0;	/* no error if caps does not exist */
+
+	caps_dir = opendir(caps_path);
+	if (!caps_dir)
+		return -EINVAL;
+
+	while ((evt_ent = readdir(caps_dir)) != NULL) {
+		char *name = evt_ent->d_name;
+		char path[PATH_MAX];
+		char value[128];
+		FILE *file;
+
+		if (!strcmp(name, ".") || !strcmp(name, ".."))
+			continue;
+
+		snprintf(path, PATH_MAX, "%s/%s", caps_path, name);
+
+		file = fopen(path, "r");
+		if (!file)
+			break;
+
+		if (!fgets(value, sizeof(value), file) ||
+		    (perf_pmu__new_caps(&pmu->caps, name, value) < 0)) {
+			fclose(file);
+			break;
+		}
+
+		nr_caps++;
+		fclose(file);
+	}
+
+	closedir(caps_dir);
+
+	return nr_caps;
+}
+
+struct perf_pmu_caps *perf_pmu__scan_caps(struct perf_pmu *pmu,
+					  struct perf_pmu_caps *caps)
+{
+	if (!pmu)
+		return NULL;
+
+	if (!caps)
+		caps = list_prepare_entry(caps, &pmu->caps, list);
+
+	list_for_each_entry_continue(caps, &pmu->caps, list)
+		return caps;
+
+	return NULL;
+}
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 3e8cd31a89cc..f7dc94c3ae8a 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -21,6 +21,12 @@ enum {
 
 struct perf_event_attr;
 
+struct perf_pmu_caps {
+	char *name;
+	char *value;
+	struct list_head list;
+};
+
 struct perf_pmu {
 	char *name;
 	__u32 type;
@@ -31,6 +37,7 @@ struct perf_pmu {
 	struct perf_cpu_map *cpus;
 	struct list_head format;  /* HEAD struct perf_pmu_format -> list */
 	struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
+	struct list_head caps;    /* HEAD struct perf_pmu_caps -> list */
 	struct list_head list;    /* ELEM */
 };
 
@@ -100,4 +107,9 @@ struct pmu_events_map *perf_pmu__find_map(struct perf_pmu *pmu);
 
 int perf_pmu__convert_scale(const char *scale, char **end, double *sval);
 
+int perf_pmu__caps_parse(struct perf_pmu *pmu);
+
+struct perf_pmu_caps *perf_pmu__scan_caps(struct perf_pmu *pmu,
+					  struct perf_pmu_caps *caps);
+
 #endif /* __PMU_H */
-- 
2.17.1