perf pmu: Remove duplication around EVENT_SOURCE_DEVICE_PATH

The pattern for accessing EVENT_SOURCE_DEVICE_PATH is duplicated in a
few places, so add two utility functions to cover it. Also just use
perf_pmu__scan_file() instead of pmu_type() which already does the same
thing.

No functional changes.
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: James Clark <james.clark@arm.com>
Acked-by: Suzuki Poulouse <suzuki.poulose@arm.com>
Tested-by: Tanmay Jagdale <tanmay@marvell.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Bharat Bhushan <bbhushan2@marvell.com>
Cc: George Cherian <gcherian@marvell.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Linu Cherian <lcherian@marvell.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Cc: Will Deacon <will@kernel.org>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20230120143702.4035046-2-james.clark@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/arm/util/auxtrace.c

@@ -55,17 +55,16 @@ static struct perf_pmu **find_all_arm_spe_pmus(int *nr_spes, int *err)
 
 static struct perf_pmu **find_all_hisi_ptt_pmus(int *nr_ptts, int *err)
 {
-	const char *sysfs = sysfs__mountpoint();
 	struct perf_pmu **hisi_ptt_pmus = NULL;
 	struct dirent *dent;
 	char path[PATH_MAX];
 	DIR *dir = NULL;
 	int idx = 0;
 
-	snprintf(path, PATH_MAX, "%s" EVENT_SOURCE_DEVICE_PATH, sysfs);
+	perf_pmu__event_source_devices_scnprintf(path, sizeof(path));
 	dir = opendir(path);
 	if (!dir) {
-		pr_err("can't read directory '%s'\n", EVENT_SOURCE_DEVICE_PATH);
+		pr_err("can't read directory '%s'\n", path);
 		*err = -EINVAL;
 		return NULL;
 	}

tools/perf/arch/arm64/util/pmu.c

@@ -44,8 +44,8 @@ double perf_pmu__cpu_slots_per_cycle(void)
 	struct perf_pmu *pmu = pmu__find_core_pmu();
 
 	if (pmu) {
-		scnprintf(path, PATH_MAX,
-			EVENT_SOURCE_DEVICE_PATH "%s/caps/slots", pmu->name);
+		perf_pmu__pathname_scnprintf(path, sizeof(path),
+					     pmu->name, "caps/slots");
 		/*
 		 * The value of slots is not greater than 32 bits, but sysfs__read_int
 		 * can't read value with 0x prefix, so use sysfs__read_ull instead.

tools/perf/arch/x86/util/pmu.c

@@ -15,8 +15,6 @@
 #include "../../../util/pmu.h"
 #include "../../../util/fncache.h"
 
-#define TEMPLATE_ALIAS	"%s/bus/event_source/devices/%s/alias"
-
 struct pmu_alias {
 	char *name;
 	char *alias;
@@ -72,18 +70,14 @@ static int setup_pmu_alias_list(void)
 	char path[PATH_MAX];
 	DIR *dir;
 	struct dirent *dent;
-	const char *sysfs = sysfs__mountpoint();
 	struct pmu_alias *pmu_alias;
 	char buf[MAX_PMU_NAME_LEN];
 	FILE *file;
 	int ret = -ENOMEM;
 
-	if (!sysfs)
+	if (!perf_pmu__event_source_devices_scnprintf(path, sizeof(path)))
 		return -1;
 
-	snprintf(path, PATH_MAX,
-		 "%s" EVENT_SOURCE_DEVICE_PATH, sysfs);
-
 	dir = opendir(path);
 	if (!dir)
 		return -errno;
@@ -93,9 +87,7 @@ static int setup_pmu_alias_list(void)
 		    !strcmp(dent->d_name, ".."))
 			continue;
 
-		snprintf(path, PATH_MAX,
-			 TEMPLATE_ALIAS, sysfs, dent->d_name);
-
+		perf_pmu__pathname_scnprintf(path, sizeof(path), dent->d_name, "alias");
 		if (!file_available(path))
 			continue;
 

tools/perf/util/pmu.c

@@ -108,14 +108,10 @@ int perf_pmu__format_parse(char *dir, struct list_head *head)
 static int pmu_format(const char *name, struct list_head *format)
 {
 	char path[PATH_MAX];
-	const char *sysfs = sysfs__mountpoint();
 
-	if (!sysfs)
+	if (!perf_pmu__pathname_scnprintf(path, sizeof(path), name, "format"))
 		return -1;
 
-	snprintf(path, PATH_MAX,
-		 "%s" EVENT_SOURCE_DEVICE_PATH "%s/format", sysfs, name);
-
 	if (!file_available(path))
 		return 0;
 
@@ -514,14 +510,10 @@ static int pmu_aliases_parse(char *dir, struct list_head *head)
 static int pmu_aliases(const char *name, struct list_head *head)
 {
 	char path[PATH_MAX];
-	const char *sysfs = sysfs__mountpoint();
 
-	if (!sysfs)
+	if (!perf_pmu__pathname_scnprintf(path, sizeof(path), name, "events"))
 		return -1;
 
-	snprintf(path, PATH_MAX,
-		 "%s/bus/event_source/devices/%s/events", sysfs, name);
-
 	if (!file_available(path))
 		return 0;
 
@@ -555,52 +547,16 @@ static int pmu_alias_terms(struct perf_pmu_alias *alias,
 	return 0;
 }
 
-/*
- * Reading/parsing the default pmu type value, which should be
- * located at:
- * /sys/bus/event_source/devices/<dev>/type as sysfs attribute.
- */
-static int pmu_type(const char *name, __u32 *type)
-{
-	char path[PATH_MAX];
-	FILE *file;
-	int ret = 0;
-	const char *sysfs = sysfs__mountpoint();
-
-	if (!sysfs)
-		return -1;
-
-	snprintf(path, PATH_MAX,
-		 "%s" EVENT_SOURCE_DEVICE_PATH "%s/type", sysfs, name);
-
-	if (access(path, R_OK) < 0)
-		return -1;
-
-	file = fopen(path, "r");
-	if (!file)
-		return -EINVAL;
-
-	if (1 != fscanf(file, "%u", type))
-		ret = -1;
-
-	fclose(file);
-	return ret;
-}
-
 /* Add all pmus in sysfs to pmu list: */
 static void pmu_read_sysfs(void)
 {
 	char path[PATH_MAX];
 	DIR *dir;
 	struct dirent *dent;
-	const char *sysfs = sysfs__mountpoint();
 
-	if (!sysfs)
+	if (!perf_pmu__event_source_devices_scnprintf(path, sizeof(path)))
 		return;
 
-	snprintf(path, PATH_MAX,
-		 "%s" EVENT_SOURCE_DEVICE_PATH, sysfs);
-
 	dir = opendir(path);
 	if (!dir)
 		return;
@@ -697,14 +653,9 @@ static char *pmu_id(const char *name)
 static int is_arm_pmu_core(const char *name)
 {
 	char path[PATH_MAX];
-	const char *sysfs = sysfs__mountpoint();
 
-	if (!sysfs)
+	if (!perf_pmu__pathname_scnprintf(path, sizeof(path), name, "cpus"))
 		return 0;
-
-	/* Look for cpu sysfs (specific to arm) */
-	scnprintf(path, PATH_MAX, "%s/bus/event_source/devices/%s/cpus",
-				sysfs, name);
 	return file_available(path);
 }
 
@@ -970,11 +921,8 @@ static struct perf_pmu *pmu_lookup(const char *lookup_name)
 		return NULL;
 
 	/*
-	 * Check the type first to avoid unnecessary work.
+	 * Check the aliases first to avoid unnecessary work.
 	 */
-	if (pmu_type(name, &type))
-		return NULL;
-
 	if (pmu_aliases(name, &aliases))
 		return NULL;
 
@@ -984,9 +932,14 @@ static struct perf_pmu *pmu_lookup(const char *lookup_name)
 
 	pmu->cpus = pmu_cpumask(name);
 	pmu->name = strdup(name);
+
 	if (!pmu->name)
 		goto err;
 
+	/* Read type, and ensure that type value is successfully assigned (return 1) */
+	if (perf_pmu__scan_file(pmu, "type", "%u", &type) != 1)
+		goto err;
+
 	alias_name = pmu_find_alias_name(name);
 	if (alias_name) {
 		pmu->alias_name = strdup(alias_name);
@@ -1787,16 +1740,11 @@ bool pmu_have_event(const char *pname, const char *name)
 static FILE *perf_pmu__open_file(struct perf_pmu *pmu, const char *name)
 {
 	char path[PATH_MAX];
-	const char *sysfs;
 
-	sysfs = sysfs__mountpoint();
-	if (!sysfs)
+	if (!perf_pmu__pathname_scnprintf(path, sizeof(path), pmu->name, name) ||
+	    !file_available(path))
 		return NULL;
 
-	snprintf(path, PATH_MAX,
-		 "%s" EVENT_SOURCE_DEVICE_PATH "%s/%s", sysfs, pmu->name, name);
-	if (!file_available(path))
-		return NULL;
 	return fopen(path, "r");
 }
 
@@ -1850,7 +1798,6 @@ 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;
 
@@ -1859,12 +1806,9 @@ int perf_pmu__caps_parse(struct perf_pmu *pmu)
 
 	pmu->nr_caps = 0;
 
-	if (!sysfs)
+	if (!perf_pmu__pathname_scnprintf(caps_path, sizeof(caps_path), pmu->name, "caps"))
 		return -1;
 
-	snprintf(caps_path, PATH_MAX,
-		 "%s" EVENT_SOURCE_DEVICE_PATH "%s/caps", sysfs, pmu->name);
-
 	if (stat(caps_path, &st) < 0) {
 		pmu->caps_initialized = true;
 		return 0;	/* no error if caps does not exist */
@@ -1999,3 +1943,31 @@ double __weak perf_pmu__cpu_slots_per_cycle(void)
 {
 	return NAN;
 }
+
+int perf_pmu__event_source_devices_scnprintf(char *pathname, size_t size)
+{
+	const char *sysfs = sysfs__mountpoint();
+
+	if (!sysfs)
+		return 0;
+	return scnprintf(pathname, size, "%s/bus/event_source/devices/", sysfs);
+}
+
+/*
+ * Fill 'buf' with the path to a file or folder in 'pmu_name' in
+ * sysfs. For example if pmu_name = "cs_etm" and 'filename' = "format"
+ * then pathname will be filled with
+ * "/sys/bus/event_source/devices/cs_etm/format"
+ *
+ * Return 0 if the sysfs mountpoint couldn't be found or if no
+ * characters were written.
+ */
+int perf_pmu__pathname_scnprintf(char *buf, size_t size,
+				 const char *pmu_name, const char *filename)
+{
+	char base_path[PATH_MAX];
+
+	if (!perf_pmu__event_source_devices_scnprintf(base_path, sizeof(base_path)))
+		return 0;
+	return scnprintf(buf, size, "%s%s/%s", base_path, pmu_name, filename);
+}

tools/perf/util/pmu.h

@@ -22,7 +22,6 @@ enum {
 };
 
 #define PERF_PMU_FORMAT_BITS 64
-#define EVENT_SOURCE_DEVICE_PATH "/bus/event_source/devices/"
 #define CPUS_TEMPLATE_CPU	"%s/bus/event_source/devices/%s/cpus"
 #define MAX_PMU_NAME_LEN 128
 
@@ -260,4 +259,8 @@ int perf_pmu__cpus_match(struct perf_pmu *pmu, struct perf_cpu_map *cpus,
 char *pmu_find_real_name(const char *name);
 char *pmu_find_alias_name(const char *name);
 double perf_pmu__cpu_slots_per_cycle(void);
+int perf_pmu__event_source_devices_scnprintf(char *pathname, size_t size);
+int perf_pmu__pathname_scnprintf(char *buf, size_t size,
+				 const char *pmu_name, const char *filename);
+
 #endif /* __PMU_H */