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>

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')