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>

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([
+])