[PATCH v2 04/26] selftests/resctrl: Refactor get_cbm_mask() and rename to get_full_cbm()

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

Callers of get_cbm_mask() are required to pass a string into which the
capacity bitmask (CBM) is read. Neither CAT nor CMT tests need the
bitmask as string but just convert it into an unsigned long value.

Another limitation is that the bit mask reader can only read
.../cbm_mask files.

Generalize the bit mask reading function into get_bit_mask() such that
it can be used to handle other files besides the .../cbm_mask and
handles the unsigned long conversion within get_bit_mask() using
fscanf(). Change get_cbm_mask() to use get_bit_mask() and rename it to
get_full_cbm() to better indicates what the function does.

Also mark cache_type const while at it and remove useless comments that
are related to processing of CBM bits.

Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 tools/testing/selftests/resctrl/cat_test.c  |  7 +--
 tools/testing/selftests/resctrl/cmt_test.c  |  5 +-
 tools/testing/selftests/resctrl/resctrl.h   |  2 +-
 tools/testing/selftests/resctrl/resctrlfs.c | 51 +++++++++++++++------
 4 files changed, 41 insertions(+), 24 deletions(-)

diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
index 224ba8544d8a..92f0f3ce90e5 100644
--- a/tools/testing/selftests/resctrl/cat_test.c
+++ b/tools/testing/selftests/resctrl/cat_test.c
@@ -93,25 +93,20 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
 	int ret, pipefd[2], sibling_cpu_no;
 	unsigned long cache_size = 0;
 	unsigned long long_mask;
-	char cbm_mask[256];
 	int count_of_bits;
 	char pipe_message;
 	size_t span;
 
-	/* Get default cbm mask for L3/L2 cache */
-	ret = get_cbm_mask(cache_type, cbm_mask);
+	ret = get_full_cbm(cache_type, &long_mask);
 	if (ret)
 		return ret;
 
-	long_mask = strtoul(cbm_mask, NULL, 16);
-
 	/* Get L3/L2 cache size */
 	ret = get_cache_size(cpu_no, cache_type, &cache_size);
 	if (ret)
 		return ret;
 	ksft_print_msg("Cache size :%lu\n", cache_size);
 
-	/* Get max number of bits from default-cabm mask */
 	count_of_bits = count_bits(long_mask);
 
 	if (!n)
diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c
index 50bdbce9fba9..d6ddacfb4416 100644
--- a/tools/testing/selftests/resctrl/cmt_test.c
+++ b/tools/testing/selftests/resctrl/cmt_test.c
@@ -75,17 +75,14 @@ int cmt_resctrl_val(int cpu_no, int n, const char * const *benchmark_cmd)
 	unsigned long cache_size = 0;
 	unsigned long long_mask;
 	char *span_str = NULL;
-	char cbm_mask[256];
 	int count_of_bits;
 	size_t span;
 	int ret, i;
 
-	ret = get_cbm_mask("L3", cbm_mask);
+	ret = get_full_cbm("L3", &long_mask);
 	if (ret)
 		return ret;
 
-	long_mask = strtoul(cbm_mask, NULL, 16);
-
 	ret = get_cache_size(cpu_no, "L3", &cache_size);
 	if (ret)
 		return ret;
diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
index 08b95b5a4949..7a2b4da684ed 100644
--- a/tools/testing/selftests/resctrl/resctrl.h
+++ b/tools/testing/selftests/resctrl/resctrl.h
@@ -99,7 +99,7 @@ void tests_cleanup(void);
 void mbm_test_cleanup(void);
 int mba_schemata_change(int cpu_no, const char * const *benchmark_cmd);
 void mba_test_cleanup(void);
-int get_cbm_mask(char *cache_type, char *cbm_mask);
+int get_full_cbm(const char *cache_type, unsigned long *mask);
 int get_cache_size(int cpu_no, char *cache_type, unsigned long *cache_size);
 void ctrlc_handler(int signum, siginfo_t *info, void *ptr);
 int signal_handler_register(void);
diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index 5ebd43683876..211fc7647659 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -196,30 +196,29 @@ int get_cache_size(int cpu_no, char *cache_type, unsigned long *cache_size)
 #define CORE_SIBLINGS_PATH	"/sys/bus/cpu/devices/cpu"
 
 /*
- * get_cbm_mask - Get cbm mask for given cache
- * @cache_type:	Cache level L2/L3
- * @cbm_mask:	cbm_mask returned as a string
+ * get_bit_mask - Get bit mask from given file
+ * @filename:	File containing the mask
+ * @mask:	The bit mask returned as unsigned long
  *
  * Return: = 0 on success, < 0 on failure.
  */
-int get_cbm_mask(char *cache_type, char *cbm_mask)
+static int get_bit_mask(const char *filename, unsigned long *mask)
 {
-	char cbm_mask_path[1024];
 	FILE *fp;
 
-	if (!cbm_mask)
+	if (!filename || !mask)
 		return -1;
 
-	sprintf(cbm_mask_path, "%s/%s/cbm_mask", INFO_PATH, cache_type);
-
-	fp = fopen(cbm_mask_path, "r");
+	fp = fopen(filename, "r");
 	if (!fp) {
-		perror("Failed to open cache level");
-
+		fprintf(stderr, "Failed to open bit mask file '%s': %s\n",
+			filename, strerror(errno));
 		return -1;
 	}
-	if (fscanf(fp, "%s", cbm_mask) <= 0) {
-		perror("Could not get max cbm_mask");
+
+	if (fscanf(fp, "%lx", mask) <= 0) {
+		fprintf(stderr, "Could not read bit mask file '%s': %s\n",
+			filename, strerror(errno));
 		fclose(fp);
 
 		return -1;
@@ -229,6 +228,32 @@ int get_cbm_mask(char *cache_type, char *cbm_mask)
 	return 0;
 }
 
+/*
+ * get_full_cbm - Get full Cache Bit Mask (CBM)
+ * @cache_type:	Cache type as "L2" or "L3"
+ * @mask:	Full cache bit mask representing the maximal portion of cache
+ *		available for allocation, returned as unsigned long.
+ *
+ * Return: = 0 on success, < 0 on failure.
+ */
+int get_full_cbm(const char *cache_type, unsigned long *mask)
+{
+	char cbm_path[PATH_MAX];
+	int ret;
+
+	if (!cache_type)
+		return -1;
+
+	snprintf(cbm_path, sizeof(cbm_path), "%s/%s/cbm_mask",
+		 INFO_PATH, cache_type);
+
+	ret = get_bit_mask(cbm_path, mask);
+	if (ret)
+		return -1;
+
+	return 0;
+}
+
 /*
  * get_core_sibling - Get sibling core id from the same socket for given CPU
  * @cpu_no:	CPU number
-- 
2.30.2