[ndctl PATCH v8 4/7] cxl/event_trace: add helpers get_field_[string|data]()

[alison.schofield@intel.com]

From: Alison Schofield <alison.schofield@intel.com>

Add helpers to extract the value of an event record field given the
field name. This is useful when the user knows the name and format
of the field and simply needs to get it. Add signed and unsigned
char* versions to support string and u64 data fields.

This is in preparation for adding a private parser of cxl_poison
events.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
---
 cxl/event_trace.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 cxl/event_trace.h |  5 ++++-
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/cxl/event_trace.c b/cxl/event_trace.c
index fbf7a77235ff..8d04d8d34194 100644
--- a/cxl/event_trace.c
+++ b/cxl/event_trace.c
@@ -15,6 +15,52 @@
 #define _GNU_SOURCE
 #include <string.h>
 
+static struct tep_format_field *__find_field(struct tep_event *event,
+					     const char *name)
+{
+	struct tep_format_field **fields;
+
+	fields = tep_event_fields(event);
+	if (!fields)
+		return NULL;
+
+	for (int i = 0; fields[i]; i++) {
+		struct tep_format_field *f = fields[i];
+
+		if (strcmp(f->name, name) != 0)
+			continue;
+
+		return f;
+	}
+	return NULL;
+}
+
+unsigned char *cxl_get_field_data(struct tep_event *event,
+				  struct tep_record *record, const char *name)
+{
+	struct tep_format_field *f;
+	int len;
+
+	f = __find_field(event, name);
+	if (!f)
+		return NULL;
+
+	return tep_get_field_raw(NULL, event, f->name, record, &len, 0);
+}
+
+char *cxl_get_field_string(struct tep_event *event, struct tep_record *record,
+			   const char *name)
+{
+	struct tep_format_field *f;
+	int len;
+
+	f = __find_field(event, name);
+	if (!f)
+		return NULL;
+
+	return tep_get_field_raw(NULL, event, f->name, record, &len, 0);
+}
+
 static struct json_object *num_to_json(void *num, int elem_size, unsigned long flags)
 {
 	bool sign = flags & TEP_FIELD_IS_SIGNED;
diff --git a/cxl/event_trace.h b/cxl/event_trace.h
index ec61962abbc6..6252f583097a 100644
--- a/cxl/event_trace.h
+++ b/cxl/event_trace.h
@@ -25,5 +25,8 @@ int cxl_parse_events(struct tracefs_instance *inst, struct event_ctx *ectx);
 int cxl_event_tracing_enable(struct tracefs_instance *inst, const char *system,
 		const char *event);
 int cxl_event_tracing_disable(struct tracefs_instance *inst);
-
+char *cxl_get_field_string(struct tep_event *event, struct tep_record *record,
+		const char *name);
+unsigned char *cxl_get_field_data(struct tep_event *event,
+		struct tep_record *record, const char *name);
 #endif
-- 
2.37.3