[PATCH 4/4] libtracefs: New API for applying filter on event.

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

There is no API for applying a filter string on event. Existing APIs
only constructs and verifies the filter string. Even though the actual
applying is just writing into the event's filter file, it is good to
have a dedicated API for that:
	tracefs_event_apply_filter()

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 Documentation/libtracefs-filter.txt | 11 ++++++++++-
 include/tracefs.h                   |  3 +++
 src/tracefs-filter.c                | 19 +++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/Documentation/libtracefs-filter.txt b/Documentation/libtracefs-filter.txt
index 7e167bc..7532c96 100644
--- a/Documentation/libtracefs-filter.txt
+++ b/Documentation/libtracefs-filter.txt
@@ -3,7 +3,8 @@ libtracefs(3)
 
 NAME
 ----
-tracefs_event_append_filter, tracefs_event_verify_filter - Add and verify event filters
+tracefs_event_append_filter, tracefs_event_verify_filter tracefs_event_apply_filter -
+Add, verify and apply event filters
 
 SYNOPSIS
 --------
@@ -15,6 +16,7 @@ int tracefs_event_append_filter(struct tep_event pass:[*]event, char pass:[**] f
 				 struct tracefs_filter type, const char pass:[*]field,
 				 enum tracefs_synth_compare compare, const char pass:[*]val);
 int tracefs_event_verify_filter(struct tep_event pass:[*]event, const char pass:[*]filter, char pass:[**]err);
+int tracefs_event_apply_filter(struct tracefs_instance pass:[*]instance, struct tep_event pass:[*]event, const char pass:[*]filter);
 
 --
 
@@ -66,6 +68,8 @@ error in the syntax, and _err_ is not NULL, then it will be allocated with an
 error message stating what was found wrong with the filter. _err_ must be freed
 with *free*().
 
+*tracefs_event_apply_filter*() applies given _filter_ string on _event_ in given _instance_.
+
 RETURN VALUE
 ------------
 *tracefs_event_append_filter*() returns 0 on success and -1 on error.
@@ -75,6 +79,8 @@ is an error, and _errno_ is not *ENOMEM*, then _err_ is allocated and will
 contain a string describing what was found wrong with _filter_. _err_ must be
 freed with *free*().
 
+*tracefs_event_apply_filter*() returns 0 on success and -1 on error.
+
 EXAMPLE
 -------
 [source,c]
@@ -269,6 +275,9 @@ int main (int argc, char **argv)
 		}
 	}
 
+	if (tracefs_event_apply_filter(NULL, event, new_filter))
+		fprintf(stderr, "Failed to apply filter on event");
+
 	tep_free(tep);
 
 	printf("Created new filter: '%s'\n", new_filter);
diff --git a/include/tracefs.h b/include/tracefs.h
index fbd7d31..8ac9694 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -475,6 +475,9 @@ int tracefs_event_append_filter(struct tep_event *event, char **filter,
 				const char *val);
 int tracefs_event_verify_filter(struct tep_event *event, const char *filter,
 				char **err);
+int tracefs_event_apply_filter(struct tracefs_instance *instance,
+			       struct tep_event *event, const char *filter);
+
 
 #define TRACEFS_TIMESTAMP "common_timestamp"
 #define TRACEFS_TIMESTAMP_USECS "common_timestamp.usecs"
diff --git a/src/tracefs-filter.c b/src/tracefs-filter.c
index def8f68..43683d0 100644
--- a/src/tracefs-filter.c
+++ b/src/tracefs-filter.c
@@ -745,3 +745,22 @@ int tracefs_event_verify_filter(struct tep_event *event, const char *filter,
 	free(str);
 	return 0;
 }
+
+/**
+ * tracefs_event_apply_filter - apply given filter on event in given instance
+ * @instance: The instance in which the filter will be applied (NULL for toplevel).
+ * @event: The event to apply the filter on.
+ * @filter: The filter to apply.
+ *
+ * Apply the @filter to given @event in givem @instance. The @filter string
+ * should be created with tracefs_event_append_filter().
+ *
+ * Returns 0 on succes and -1 on error.
+ */
+int tracefs_event_apply_filter(struct tracefs_instance *instance,
+			       struct tep_event *event, const char *filter)
+{
+	return tracefs_event_file_append(instance, event->system, event->name,
+					 "filter", filter);
+}
+
-- 
2.33.1