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Subject[PATCH 16/23 v3] tools lib traceevent: Document tep_load_plugins_hook()
From: "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>

Add description of tep_load_plugins_hook() traceevent API. Updated
library man pages with description of the tep_load_plugins_hook() API.

Link: https://lore.kernel.org/r/CAM9d7cgLBWCrEHwz+Lhv5x5EXGcNWB0QQoeGh3OKh2JfR=dV9Q@mail.gmail.com
Link: https://lore.kernel.org/linux-trace-devel/20200714103027.2477584-2-tz.stoyanov@gmail.com
Link: https://lore.kernel.org/linux-trace-devel/20200716092014.2613403-2-tz.stoyanov@gmail.com

Suggested-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
.../Documentation/libtraceevent-plugins.txt | 25 ++++++++++++++++++-
tools/lib/traceevent/event-plugin.c | 16 ++++++++++++
2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/Documentation/libtraceevent-plugins.txt b/tools/lib/traceevent/Documentation/libtraceevent-plugins.txt
index 596032ade31f..4d6394397d92 100644
--- a/tools/lib/traceevent/Documentation/libtraceevent-plugins.txt
+++ b/tools/lib/traceevent/Documentation/libtraceevent-plugins.txt
@@ -3,7 +3,7 @@ libtraceevent(3)

NAME
----
-tep_load_plugins, tep_unload_plugins - Load / unload traceevent plugins.
+tep_load_plugins, tep_unload_plugins, tep_load_plugins_hook - Load / unload traceevent plugins.

SYNOPSIS
--------
@@ -13,6 +13,12 @@ SYNOPSIS

struct tep_plugin_list pass:[*]*tep_load_plugins*(struct tep_handle pass:[*]_tep_);
void *tep_unload_plugins*(struct tep_plugin_list pass:[*]_plugin_list_, struct tep_handle pass:[*]_tep_);
+void *tep_load_plugins_hook*(struct tep_handle pass:[*]_tep_, const char pass:[*]_suffix_,
+ void (pass:[*]_load_plugin_)(struct tep_handle pass:[*]tep,
+ const char pass:[*]path,
+ const char pass:[*]name,
+ void pass:[*]data),
+ void pass:[*]_data_);
--

DESCRIPTION
@@ -22,11 +28,13 @@ directories. The _tep_ argument is trace event parser context.
The plugin directories are :
[verse]
--
+ - Directories, specified in _tep_->plugins_dir with priority TEP_PLUGIN_FIRST
- System's plugin directory, defined at the library compile time. It
depends on the library installation prefix and usually is
_(install_preffix)/lib/traceevent/plugins_
- Directory, defined by the environment variable _TRACEEVENT_PLUGIN_DIR_
- User's plugin directory, located at _~/.local/lib/traceevent/plugins_
+ - Directories, specified in _tep_->plugins_dir with priority TEP_PLUGIN_LAST
--
Loading of plugins can be controlled by the _tep_flags_, using the
_tep_set_flag()_ API:
@@ -44,6 +52,12 @@ _tep_load_plugins()_. The _tep_ argument is trace event parser context. The
_plugin_list_ is the list of loaded plugins, returned by
the _tep_load_plugins()_ function.

+The _tep_load_plugins_hook_ function walks through all directories with plugins
+and calls user specified _load_plugin()_ hook for each plugin file. Only files
+with given _suffix_ are considered to be plugins. The _data_ is a user specified
+context, passed to _load_plugin()_. Directories and the walk order are the same
+as in _tep_load_plugins()_ API.
+
RETURN VALUE
------------
The _tep_load_plugins()_ function returns a list of successfully loaded plugins,
@@ -63,6 +77,15 @@ if (plugins == NULL) {
}
...
tep_unload_plugins(plugins, tep);
+...
+void print_plugin(struct tep_handle *tep, const char *path,
+ const char *name, void *data)
+{
+ pritnf("Found libtraceevent plugin %s/%s\n", path, name);
+}
+...
+tep_load_plugins_hook(tep, ".so", print_plugin, NULL);
+...
--

FILES
diff --git a/tools/lib/traceevent/event-plugin.c b/tools/lib/traceevent/event-plugin.c
index 1d4f1809cf17..aa6f43290cd3 100644
--- a/tools/lib/traceevent/event-plugin.c
+++ b/tools/lib/traceevent/event-plugin.c
@@ -543,6 +543,22 @@ load_plugins_dir(struct tep_handle *tep, const char *suffix,
closedir(dir);
}

+/**
+ * tep_load_plugins_hook - call a user specified callback to load a plugin
+ * @tep: handler to traceevent context
+ * @suffix: filter only plugin files with given suffix
+ * @load_plugin: user specified callback, called for each plugin file
+ * @data: custom context, passed to @load_plugin
+ *
+ * Searches for traceevent plugin files and calls @load_plugin for each
+ * The order of plugins search is:
+ * - Directories, specified in @tep->plugins_dir and priority TEP_PLUGIN_FIRST
+ * - Directory, specified at compile time with PLUGIN_TRACEEVENT_DIR
+ * - Directory, specified by environment variable TRACEEVENT_PLUGIN_DIR
+ * - In user's home: ~/.local/lib/traceevent/plugins/
+ * - Directories, specified in @tep->plugins_dir and priority TEP_PLUGIN_LAST
+ *
+ */
void tep_load_plugins_hook(struct tep_handle *tep, const char *suffix,
void (*load_plugin)(struct tep_handle *tep,
const char *path,
--
2.26.2

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