buildman: Support #include files in defconfigs

This is used by some boards in U-Boot and is a convenient way to deal
with common settings where using a Kconfig files is not desirable.

Detect #include files and process them as if they were part of the
original file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Fixes: https://source.denx.de/u-boot/custodians/u-boot-dm/-/issues/30

tools/buildman/boards.py

@@ -19,7 +19,10 @@ import time
 from buildman import board
 from buildman import kconfiglib
 
+from u_boot_pylib import command
 from u_boot_pylib.terminal import print_clear, tprint
+from u_boot_pylib import tools
+from u_boot_pylib import tout
 
 ### constant variables ###
 OUTPUT_FILE = 'boards.cfg'
@@ -202,6 +205,7 @@ class KconfigScanner:
         os.environ['KCONFIG_OBJDIR'] = ''
         self._tmpfile = None
         self._conf = kconfiglib.Kconfig(warn=False)
+        self._srctree = srctree
 
     def __del__(self):
         """Delete a leftover temporary file before exit.
@@ -239,7 +243,26 @@ class KconfigScanner:
         expect_target, match, rear = leaf.partition('_defconfig')
         assert match and not rear, f'{leaf} : invalid defconfig'
 
-        self._conf.load_config(defconfig)
+        temp = None
+        if b'#include' in tools.read_file(defconfig):
+            cmd = [
+                os.getenv('CPP', 'cpp'),
+                '-nostdinc', '-P',
+                '-I', self._srctree,
+                '-undef',
+                '-x', 'assembler-with-cpp',
+                defconfig]
+            result = command.run_pipe([cmd], capture=True, capture_stderr=True)
+            temp = tempfile.NamedTemporaryFile(prefix='buildman-')
+            tools.write_file(temp.name, result.stdout, False)
+            fname = temp.name
+            tout.info(f'Processing #include to produce {defconfig}')
+        else:
+            fname = defconfig
+
+        self._conf.load_config(fname)
+        if temp:
+            del temp
         self._tmpfile = None
 
         params = {}

tools/buildman/buildman.rst

@@ -1112,6 +1112,30 @@ The -U option uses the u-boot.env files which are produced by a build.
 Internally, buildman writes out an out-env file into the build directory for
 later comparison.
 
+defconfig fragments
+-------------------
+
+Buildman provides some initial support for configuration fragments. It can scan
+these when present in defconfig files and handle the resuiting Kconfig
+correctly. Thus it is possible to build a board which has a ``#include`` in the
+defconfig file.
+
+For now, Buildman simply includes the files to produce a single output file,
+using the C preprocessor. It does not call the ``merge_config.sh`` script. The
+redefined/redundant logic in that script could fairly easily be repeated in
+Buildman, to detect potential problems. For now it is not clear that this is
+useful.
+
+To specify the C preprocessor to use, set the ``CPP`` environment variable. The
+default is ``cpp``.
+
+Note that Buildman does not support adding fragments to existing boards, e.g.
+like::
+
+    make qemu_riscv64_defconfig acpi.config
+
+This is partly because there is no way for Buildman to know which fragments are
+valid on which boards.
 
 Building with clang
 -------------------

tools/buildman/func_test.py

@@ -2,8 +2,10 @@
 # Copyright (c) 2014 Google, Inc
 #
 
+import io
 import os
 from pathlib import Path
+import re
 import shutil
 import sys
 import tempfile
@@ -373,6 +375,22 @@ class TestFunctional(unittest.TestCase):
     def _HandleCommandSize(self, args):
         return command.CommandResult(return_code=0)
 
+    def _HandleCommandCpp(self, args):
+        # args ['-nostdinc', '-P', '-I', '/tmp/tmp7f17xk_o/src', '-undef',
+        # '-x', 'assembler-with-cpp', fname]
+        fname = args[7]
+        buf = io.StringIO()
+        for line in tools.read_file(fname, False).splitlines():
+            if line.startswith('#include'):
+                # Example: #include <configs/renesas_rcar2.config>
+                m_incfname = re.match('#include <(.*)>', line)
+                data = tools.read_file(m_incfname.group(1), False)
+                for line in data.splitlines():
+                    print(line, file=buf)
+            else:
+                print(line, file=buf)
+        return command.CommandResult(stdout=buf.getvalue(), return_code=0)
+
     def _HandleCommand(self, **kwargs):
         """Handle a command execution.
 
@@ -406,6 +424,8 @@ class TestFunctional(unittest.TestCase):
             return self._HandleCommandObjcopy(args)
         elif cmd.endswith( 'size'):
             return self._HandleCommandSize(args)
+        elif cmd.endswith( 'cpp'):
+            return self._HandleCommandCpp(args)
 
         if not result:
             # Not handled, so abort
@@ -1118,3 +1138,17 @@ CONFIG_SOC="fred"
             'config': '-',
             'target': 'board0'},
             ['WARNING: board0_defconfig: No TARGET_BOARD0 enabled']), res)
+
+        # check handling of #include files; see _HandleCommandCpp()
+        inc = os.path.join(src, 'common')
+        tools.write_file(inc, b'CONFIG_TARGET_BOARD0=y\n')
+        tools.write_file(norm, f'#include <{inc}>', False)
+        res = scanner.scan(norm, True)
+        self.assertEqual(({
+            'arch': 'arm',
+            'cpu': 'armv7',
+            'soc': '-',
+            'vendor': 'Tester',
+            'board': 'ARM Board 0',
+            'config': 'config0',
+            'target': 'board0'}, []), res)