[PATCH 1/2] libtracefs: Document new instance APIs

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

Added documentation for these new APIs:
 tracefs_instance_alloc()
 tracefs_instance_get_trace_dir()

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 Documentation/libtracefs-instances-manage.txt | 34 +++++++++++++++----
 Documentation/libtracefs-instances-utils.txt  | 16 +++++++--
 2 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/Documentation/libtracefs-instances-manage.txt b/Documentation/libtracefs-instances-manage.txt
index a831ef2..e7dc393 100644
--- a/Documentation/libtracefs-instances-manage.txt
+++ b/Documentation/libtracefs-instances-manage.txt
@@ -3,7 +3,7 @@ libtracefs(3)
 
 NAME
 ----
-tracefs_instance_create, tracefs_instance_destroy, tracefs_instance_free,
+tracefs_instance_create, tracefs_instance_destroy, tracefs_instance_alloc, tracefs_instance_free,
 tracefs_instance_is_new - Manage trace instances.
 
 SYNOPSIS
@@ -14,6 +14,7 @@ SYNOPSIS
 
 struct tracefs_instance pass:[*]*tracefs_instance_create*(const char pass:[*]_name_);
 int *tracefs_instance_destroy*(struct tracefs_instance pass:[*]_instance_);
+struct tracefs_instance pass:[*]*tracefs_instance_alloc*(const char pass:[*]_tracing_dir_, const char pass:[*]_name_);
 void *tracefs_instance_free*(struct tracefs_instance pass:[*]_instance_);
 bool *tracefs_instance_is_new*(struct tracefs_instance pass:[*]_instance_);
 
@@ -28,12 +29,22 @@ system, nor other instances, as events enabled in the main tracing system
 or other instances do not affect the given instance.
 
 The _tracefs_instance_create()_ function allocates and initializes a new
-tracefs_instance structure and returns it. If the instance does not yet
-exist in the system, it will be created.
+tracefs_instance structure and returns it. If the instance with _name_ does
+not yet exist in the system, it will be created. The _name_ could be NULL,
+then the new tracefs_instance structure is initialised for the top instance.
+Note that the top instance cannot be created in the system, if it does not
+exist.
 
 The _tracefs_instance_destroy()_ frees the _instance_ structure, and will
 also remove the trace instance from the system.
 
+The _tracefs_instance_alloc()_ function allocates a new tracefs_instance structure
+for existing trace instance. If the instance does not exist in the system, the function
+fails. The _tracing_dir_ parameter points to the system trace directory. It can be
+NULL, then default system trace directory is used. This parameter is useful to allocate
+instances to trace directories, copied from another machine. The _name_ is the name of
+the instance, or NULL for the top instance in the given _tracing_dir_.
+
 The _tracefs_instance_free()_ function frees the tracefs_instance structure,
 without removing the trace instance from the system.
 
@@ -43,8 +54,8 @@ before that.
 
 RETURN VALUE
 ------------
-The _tracefs_instance_create()_ function returns a pointer to a newly allocated
-tracefs_instance structure. It must be freed with _tracefs_instance_destroy()_ or
+The _tracefs_instance_create()_ and _tracefs_instance_alloc()_ functions return a pointer to
+a newly allocated tracefs_instance structure. It must be freed with _tracefs_instance_destroy()_ or
 _tracefs_instance_free()_.
 
 The _tracefs_instance_destroy()_ function returns -1 in case of an error,
@@ -54,7 +65,7 @@ The _tracefs_instance_is_new()_ function returns true if the
 _tracefs_instance_create()_ that allocated _instance_ also created the
 trace instance in the system, or false if the trace instance already
 existed in the system when _instance_ was allocated by
-_tracefs_instance_create()_.
+_tracefs_instance_create()_ or _tracefs_instance_alloc()_.
 
 EXAMPLE
 -------
@@ -74,6 +85,17 @@ struct tracefs_instance *inst = tracefs_instance_create("foo");
 		tracefs_instance_destroy(inst);
 	else
 		tracefs_instance_free(inst);
+...
+
+struct tracefs_instance *inst = tracefs_instance_alloc(NULL, "bar");
+	if (!inst) {
+		/* Error allocating 'bar' trace instance */
+		...
+	}
+
+	...
+
+	tracefs_instance_free(inst);
 --
 FILES
 -----
diff --git a/Documentation/libtracefs-instances-utils.txt b/Documentation/libtracefs-instances-utils.txt
index 3bd54a5..f559406 100644
--- a/Documentation/libtracefs-instances-utils.txt
+++ b/Documentation/libtracefs-instances-utils.txt
@@ -3,7 +3,8 @@ libtracefs(3)
 
 NAME
 ----
-tracefs_instance_get_name, tracefs_instances_walk, tracefs_instance_exists -
+tracefs_instance_get_name, tracefs_instance_get_trace_dir,
+tracefs_instances_walk, tracefs_instance_exists -
 Helper functions for working with tracing instances.
 
 SYNOPSIS
@@ -13,6 +14,7 @@ SYNOPSIS
 *#include <tracefs.h>*
 
 const char pass:[*]*tracefs_instance_get_name*(struct tracefs_instance pass:[*]_instance_);
+const char pass:[*]*tracefs_instance_get_trace_dir*(struct tracefs_instance pass:[*]_instance_);
 int *tracefs_instances_walk*(int (pass:[*]_callback_)(const char pass:[*], void pass:[*]), void pass:[*]_context)_;
 bool *tracefs_instance_exists*(const char pass:[*]_name_);
 
@@ -25,6 +27,9 @@ Helper functions for working with trace instances.
 The _tracefs_instance_get_name()_ function returns the name of the given _instance_.
 Note that the top instance has no name, the function returns NULL for it.
 
+The _tracefs_instance_get_trace_dir()_ function returns the tracing directory, where
+the given _instance_ is configured.
+
 The _tracefs_instances_walk()_ function walks through all configured tracing
 instances in the system and calls _callback_ for each one of them. The _context_
 argument is passed to the _callback_, together with the instance name. If the
@@ -39,6 +44,9 @@ RETURN VALUE
 The _tracefs_instance_get_name()_ returns a string or NULL in case of the top
 instance. The returned string must _not_ be freed.
 
+The _tracefs_instance_get_trace_dir()_ returns a string or NULL in case of an error.
+The returned string must _not_ be freed.
+
 The _tracefs_instances_walk()_ function returns 0, if all instances were iterated, 1
 if the iteration was stopped by the _callback_, or -1 in case of an error.
 
@@ -54,11 +62,13 @@ EXAMPLE
 struct tracefs_instance *inst;
 ....
 char *name = tracefs_instance_get_name(inst);
-
 	if(name) {
 		/* Got name of the instance */
 	}
-
+char *dir = tracefs_instance_get_trace_dir(inst);
+	if(dir) {
+		/* Got tracing directory of the instance */
+	}
 ...
 static int instance_walk(char *name, void *context)
 {
-- 
2.29.2