From a58460b5c780fd651e25e6e22eef5cda7f1ee1f4 Mon Sep 17 00:00:00 2001
From: Thomas Richter <tmricht@linux.ibm.com>
Date: Thu, 28 Apr 2022 15:53:15 +0200
Subject: [PATCH] libcpumf: Function to return PMU name
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Return the PMU name as found in the sysfs tree given a PMU type number.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
---
 include/lib/libcpumf.h      | 14 +++++++++++++
 libcpumf/Makefile           |  2 +-
 libcpumf/libcpumf_example.c |  9 +++++++++
 libcpumf/libcpumf_pmutype.c | 39 +++++++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/include/lib/libcpumf.h b/include/lib/libcpumf.h
index 299291f6..1f7468e2 100644
--- a/include/lib/libcpumf.h
+++ b/include/lib/libcpumf.h
@@ -30,6 +30,20 @@
  */
 int libcpumf_pmutype(const char *dirname);
 
+/**
+ * Read out the PMU name from a given type.
+ *
+ * Return the PMU name this PMU was registered in kernel. If the PMU was
+ * registered without a name, it is not listed in the directory.
+ * The caller must free the memory returned by name.
+ *
+ * @param[in]    wanted_type Type number of the PMU
+ * @param[out]   name        Name of the PMU (when retval is 0)
+ * @retval       0           PMU wanted_type detected and PMU name valid
+ * @retval       -1          No PMU with wanted_type
+ */
+int libcpumf_pmuname(unsigned int wanted_type, char **name);
+
 /**
  * Read out the CPU list from a given file name, for example from files
  * /sys/devices/system/cpu/online or /sys/devices/system/cpu/possible.
diff --git a/libcpumf/Makefile b/libcpumf/Makefile
index b7f27f48..929c3296 100644
--- a/libcpumf/Makefile
+++ b/libcpumf/Makefile
@@ -13,7 +13,7 @@ $(lib): $(objects)
 
 install: all
 
-libcpumf_example: libcpumf_example.o $(lib)
+libcpumf_example: libcpumf_example.o $(lib) $(rootdir)/libutil/libutil.a
 
 clean:
 	rm -f *.o $(lib) $(examples)
diff --git a/libcpumf/libcpumf_example.c b/libcpumf/libcpumf_example.c
index dde13cad..57e17603 100644
--- a/libcpumf/libcpumf_example.c
+++ b/libcpumf/libcpumf_example.c
@@ -14,6 +14,7 @@ int main(void)
 {
 	unsigned long min, max, speed, sfb_min, sfb_max;
 	int rc, pmu, cfvn, csvn, auth;
+	char *pmuname;
 	cpu_set_t set;
 
 	pmu = libcpumf_pmutype(S390_CPUMF_CF);
@@ -74,5 +75,13 @@ int main(void)
 	putchar('\n');
 
 	printf("PAI crypto support %d\n", libcpumf_have_pai_crypto());
+
+	rc = libcpumf_pmuname(10, &pmuname);
+	if (rc) {
+		printf("PMU type 10 PMU name lookup error %d\n", rc);
+	} else {
+		printf("PMU type 10 PMU name %s\n", pmuname);
+		free(pmuname);
+	}
 	return EXIT_SUCCESS;
 }
diff --git a/libcpumf/libcpumf_pmutype.c b/libcpumf/libcpumf_pmutype.c
index e89e3ebd..f301e74d 100644
--- a/libcpumf/libcpumf_pmutype.c
+++ b/libcpumf/libcpumf_pmutype.c
@@ -4,10 +4,16 @@
  * it under the terms of the MIT license. See LICENSE for details.
  */
 
+#include <err.h>
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
+#include "lib/util_file.h"
+#include "lib/util_libc.h"
+#include "lib/util_path.h"
+#include "lib/util_scandir.h"
 #include "lib/libcpumf.h"
 
 int libcpumf_pmutype(const char *dirname)
@@ -31,3 +37,36 @@ int libcpumf_pmutype(const char *dirname)
 	}
 	return ret;
 }
+
+int libcpumf_pmuname(unsigned int wanted_type, char **name)
+{
+	struct dirent **de_vec;
+	unsigned int type;
+	char *dirname;
+	char *path;
+	int count;
+	int rc;
+
+	path = util_path_sysfs("devices");
+	count = util_scandir(&de_vec, alphasort, path, "(pai|cpum_).*");
+	free(path);
+
+	*name = NULL;
+	for (int i = 0; i < count; i++) {
+		if (de_vec[i]->d_type == DT_DIR) {
+			dirname = de_vec[i]->d_name;
+			path = util_path_sysfs("devices/%s/type", dirname);
+			rc = util_file_read_ui(&type, 10, path);
+			if (rc)
+				warn("Failed to open %s", path);
+			free(path);
+			if (!rc && type == wanted_type) {
+				*name = util_strdup(dirname);
+				goto out;
+			}
+		}
+	}
+out:
+	util_scandir_free(de_vec, count);
+	return *name ? 0 : -1;
+}