libcamera: tracing: Implement tracing infrastructure

Implement tracing infrastructure in libcamera. It takes .tp files, as
required by lttng, and generates a tracepoint header and C file, as lttng
requires. meson is updated accordingly to get it to compile with the
rest of libcamera. Update the documentation accordingly.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Documentation/Doxyfile.in

@@ -840,7 +840,9 @@ EXCLUDE                = @TOP_SRCDIR@/include/libcamera/span.h \
 			 @TOP_SRCDIR@/src/libcamera/device_enumerator_sysfs.cpp \
 			 @TOP_SRCDIR@/src/libcamera/device_enumerator_udev.cpp \
 			 @TOP_SRCDIR@/src/libcamera/pipeline/ \
-			 @TOP_SRCDIR@/src/libcamera/proxy/
+			 @TOP_SRCDIR@/src/libcamera/proxy/ \
+			 @TOP_SRCDIR@/src/libcamera/tracepoints.cpp \
+			 @TOP_BUILDDIR@/include/libcamera/internal/tracepoints.h
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
 # directories that are symbolic links (a Unix file system feature) are excluded

README.rst

@@ -81,6 +81,9 @@ for gstreamer: [optional]
 for qcam: [optional]
 	qtbase5-dev libqt5core5a libqt5gui5 libqt5widgets5 qttools5-dev-tools libtiff-dev
 
+for tracing with lttng: [optional]
+        lttng-ust-dev python3-jinja2
+
 Using GStreamer plugin
 ~~~~~~~~~~~~~~~~~~~~~~
 

include/libcamera/internal/meson.build

@@ -1,5 +1,14 @@
 # SPDX-License-Identifier: CC0-1.0
 
+subdir('tracepoints')
+
+libcamera_tracepoint_header = custom_target(
+    'tp_header',
+    input: [ 'tracepoints.h.in', tracepoint_files ],
+    output: 'tracepoints.h',
+    command: [ gen_tracepoints_header, '@OUTPUT@', '@INPUT@' ],
+)
+
 libcamera_internal_headers = files([
     'byte_stream_buffer.h',
     'camera_controls.h',

include/libcamera/internal/tracepoints.h.in

@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) {{year}}, Google Inc.
+ *
+ * tracepoints.h - Tracepoints with lttng
+ *
+ * This file is auto-generated. Do not edit.
+ */
+#ifndef __LIBCAMERA_INTERNAL_TRACEPOINTS_H__
+#define __LIBCAMERA_INTERNAL_TRACEPOINTS_H__
+
+#if HAVE_TRACING
+#define LIBCAMERA_TRACEPOINT(...) tracepoint(libcamera, __VA_ARGS__)
+
+#define LIBCAMERA_TRACEPOINT_IPA_BEGIN(pipe, func) \
+tracepoint(libcamera, ipa_call_begin, #pipe, #func)
+
+#define LIBCAMERA_TRACEPOINT_IPA_END(pipe, func) \
+tracepoint(libcamera, ipa_call_end, #pipe, #func)
+
+#else
+
+namespace {
+
+template <typename ...Args>
+inline void unused([[maybe_unused]] Args&& ...args)
+{
+}
+
+} /* namespace */
+
+#define LIBCAMERA_TRACEPOINT(category, ...) unused(__VA_ARGS__)
+
+#define LIBCAMERA_TRACEPOINT_IPA_BEGIN(pipe, func)
+#define LIBCAMERA_TRACEPOINT_IPA_END(pipe, func)
+
+#endif /* HAVE_TRACING */
+
+#endif /* __LIBCAMERA_INTERNAL_TRACEPOINTS_H__ */
+
+
+#if HAVE_TRACING
+
+#undef TRACEPOINT_PROVIDER
+#define TRACEPOINT_PROVIDER libcamera
+
+#undef TRACEPOINT_INCLUDE
+#define TRACEPOINT_INCLUDE "{{path}}"
+
+#if !defined(INCLUDE_LIBCAMERA_INTERNAL_TRACEPOINTS_TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ)
+#define INCLUDE_LIBCAMERA_INTERNAL_TRACEPOINTS_TP_H
+
+#include <lttng/tracepoint.h>
+
+{{source}}
+
+#endif /* INCLUDE_LIBCAMERA_INTERNAL_TRACEPOINTS_TP_H */
+
+#include <lttng/tracepoint-event.h>
+
+#endif /* HAVE_TRACING */

include/libcamera/internal/tracepoints/meson.build

@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: CC0-1.0
+
+tracepoint_files = files([
+])

meson.build

@@ -108,6 +108,9 @@ libcamera_includes = include_directories('include')
 # Sub-directories fill py_modules with their dependencies.
 py_modules = []
 
+# Libraries used by multiple components
+liblttng = cc.find_library('lttng-ust', required : get_option('tracing'))
+
 # Utilities are parsed first to provide support for other components.
 subdir('utils')
 

meson_options.txt

@@ -28,6 +28,11 @@ option('test',
         type : 'boolean',
         description: 'Compile and include the tests')
 
+option('tracing',
+        type : 'feature',
+        value : 'auto',
+        description: 'Enable tracing (based on lttng)')
+
 option('v4l2',
         type : 'boolean',
         value : false,

src/libcamera/meson.build

@@ -55,6 +55,7 @@ libcamera_sources = files([
 ])
 
 libcamera_sources += libcamera_public_headers
+libcamera_sources += libcamera_tracepoint_header
 
 includes = [
     libcamera_includes,
@@ -72,6 +73,11 @@ if libgnutls.found()
     config_h.set('HAVE_GNUTLS', 1)
 endif
 
+if liblttng.found()
+    config_h.set('HAVE_TRACING', 1)
+    libcamera_sources += files(['tracepoints.cpp'])
+endif
+
 if libudev.found()
     config_h.set('HAVE_LIBUDEV', 1)
     libcamera_sources += files([
@@ -114,6 +120,7 @@ libcamera_deps = [
     libatomic,
     libdl,
     libgnutls,
+    liblttng,
     libudev,
     dependency('threads'),
 ]

src/libcamera/tracepoints.cpp

@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2020, Google Inc.
+ *
+ * tracepoints.cpp - Tracepoints with lttng
+ */
+#define TRACEPOINT_CREATE_PROBES
+#define TRACEPOINT_DEFINE
+
+#include "libcamera/internal/tracepoints.h"

utils/meson.build

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: CC0-1.0
 
 subdir('ipu3')
+subdir('tracepoints')
 
 ## Code generation
 py_modules += ['yaml']

utils/tracepoints/gen-tp-header.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Copyright (C) 2020, Google Inc.
+#
+# Author: Paul Elder <paul.elder@ideasonboard.com>
+#
+# gen-tp-header.py - Generate header file to contain lttng tracepoints
+
+import datetime
+import jinja2
+import os
+import sys
+
+def main(argv):
+    if len(argv) < 3:
+        print(f'Usage: {argv[0]} output template tp_files...')
+        return 1
+
+    output = argv[1]
+    template = argv[2]
+
+    year = datetime.datetime.now().year
+    path = output.replace('include/', '', 1)
+
+    source = ''
+    for fname in argv[3:]:
+        source += open(fname, 'r', encoding='utf-8').read() + '\n\n'
+
+    template = jinja2.Template(open(template, 'r', encoding='utf-8').read())
+    string = template.render(year=year, path=path, source=source)
+
+    f = open(output, 'w', encoding='utf-8').write(string)
+
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv))

utils/tracepoints/meson.build

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: CC0-1.0
+
+py_modules += ['jinja2']
+
+gen_tracepoints_header = find_program('./gen-tp-header.py')