selftests/resctrl: Refactor get_cbm_mask() and rename to get_full_cbm()

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 indicate what the function does.

Return error from get_full_cbm() if the bitmask is zero for some reason
because it makes the code more robust as the selftests naturally assume
the bitmask has some bits.

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>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 38 insertions, 13 deletions

diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index 81d1e043e17a..a74be17eaa4e 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) {
-		ksft_perror("Failed to open cache level");
-
+		ksft_print_msg("Failed to open bit mask file '%s': %s\n",
+			       filename, strerror(errno));
 		return -1;
 	}
-	if (fscanf(fp, "%s", cbm_mask) <= 0) {
-		ksft_perror("Could not get max cbm_mask");
+
+	if (fscanf(fp, "%lx", mask) <= 0) {
+		ksft_print_msg("Could not read bit mask file '%s': %s\n",
+			       filename, strerror(errno));
 		fclose(fp);
 
 		return -1;
@@ -230,6 +229,32 @@ int get_cbm_mask(char *cache_type, char *cbm_mask)
 }
 
 /*
+ * 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 || !*mask)
+		return -1;
+
+	return 0;
+}
+
+/*
  * get_core_sibling - Get sibling core id from the same socket for given CPU
  * @cpu_no:	CPU number
  *