[PATCH 1/2] meson: use subproject for internal libfdt

[Paolo Bonzini <pbonzini@redhat.com>]

Recent dtc/libfdt can use both Make and meson as the build system.
By using a subproject, our own meson.build can remove the hard
coded list of source files.

In the future, it may also be possible to use wrap to download
the submodule.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 .gitmodules               |  4 ++--
 configure                 |  2 +-
 meson.build               | 44 +++++++++++++--------------------------
 scripts/archive-source.sh |  2 +-
 dtc => subprojects/dtc    |  0
 5 files changed, 19 insertions(+), 33 deletions(-)
 rename dtc => subprojects/dtc (100%)

diff --git a/.gitmodules b/.gitmodules
index 2a3a12033c4b..3ed5d073d630 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -13,8 +13,8 @@
 [submodule "roms/qemu-palcode"]
 	path = roms/qemu-palcode
 	url = https://gitlab.com/qemu-project/qemu-palcode.git
-[submodule "dtc"]
-	path = dtc
+[submodule "subprojects/dtc"]
+	path = subprojects/dtc
 	url = https://gitlab.com/qemu-project/dtc.git
 [submodule "roms/u-boot"]
 	path = roms/u-boot
diff --git a/configure b/configure
index 31a787153e38..5bbca83d9a31 100755
--- a/configure
+++ b/configure
@@ -1188,7 +1188,7 @@ fi
 case "$fdt" in
   auto | enabled | internal)
     # Simpler to always update submodule, even if not needed.
-    git_submodules="${git_submodules} dtc"
+    git_submodules="${git_submodules} subprojects/dtc"
     ;;
 esac
 
diff --git a/meson.build b/meson.build
index 41c87c441f8e..1e75afdc6844 100644
--- a/meson.build
+++ b/meson.build
@@ -3041,10 +3041,10 @@ if have_system and vfio_user_server_allowed
 endif
 
 fdt = not_found
-if have_system
-  fdt_opt = get_option('fdt')
+fdt_opt = get_option('fdt')
+if fdt_required.length() > 0 or fdt_opt == 'enabled'
+  have_internal = fs.exists(meson.current_source_dir() / 'subprojects/dtc/meson.build')
   if fdt_opt in ['enabled', 'auto', 'system']
-    have_internal = fs.exists(meson.current_source_dir() / 'dtc/libfdt/Makefile.libfdt')
     fdt = cc.find_library('fdt',
                           required: fdt_opt == 'system' or
                                     fdt_opt == 'enabled' and not have_internal)
@@ -3056,41 +3056,27 @@ if have_system
       fdt_opt = 'system'
     elif fdt_opt == 'system'
        error('system libfdt requested, but it is too old (1.5.1 or newer required)')
-    elif have_internal
-      fdt_opt = 'internal'
     else
-      fdt_opt = 'disabled'
+      fdt_opt = 'internal'
       fdt = not_found
     endif
   endif
-  if fdt_opt == 'internal'
-    fdt_files = files(
-      'dtc/libfdt/fdt.c',
-      'dtc/libfdt/fdt_ro.c',
-      'dtc/libfdt/fdt_wip.c',
-      'dtc/libfdt/fdt_sw.c',
-      'dtc/libfdt/fdt_rw.c',
-      'dtc/libfdt/fdt_strerror.c',
-      'dtc/libfdt/fdt_empty_tree.c',
-      'dtc/libfdt/fdt_addresses.c',
-      'dtc/libfdt/fdt_overlay.c',
-      'dtc/libfdt/fdt_check.c',
-    )
 
-    fdt_inc = include_directories('dtc/libfdt')
-    libfdt = static_library('fdt',
-                            build_by_default: false,
-                            sources: fdt_files,
-                            include_directories: fdt_inc)
-    fdt = declare_dependency(link_with: libfdt,
-                             include_directories: fdt_inc)
+  if fdt_opt == 'system'
+    # verified above
+  elif fdt_opt == 'disabled'
+    error('fdt disabled but required by targets ' + ', '.join(fdt_required))
+  elif not have_internal
+    error('libfdt source not found - please pull git submodule')
+  else
+    libfdt_proj = subproject('dtc', required: true,
+                             default_options: ['tools=false',  'yaml=disabled',
+                                               'python=disabled', 'default_library=static'])
+    fdt = libfdt_proj.get_variable('libfdt_dep')
   endif
 else
   fdt_opt = 'disabled'
 endif
-if not fdt.found() and fdt_required.length() > 0
-  error('fdt not available but required by targets ' + ', '.join(fdt_required))
-endif
 
 config_host_data.set('CONFIG_CAPSTONE', capstone.found())
 config_host_data.set('CONFIG_FDT', fdt.found())
diff --git a/scripts/archive-source.sh b/scripts/archive-source.sh
index 23e042dacdb3..b15f6fe6b8fe 100755
--- a/scripts/archive-source.sh
+++ b/scripts/archive-source.sh
@@ -26,7 +26,7 @@ sub_file="${sub_tdir}/submodule.tar"
 # independent of what the developer currently has initialized
 # in their checkout, because the build environment is completely
 # different to the host OS.
-submodules="dtc meson ui/keycodemapdb"
+submodules="subprojects/dtc meson ui/keycodemapdb"
 submodules="$submodules tests/fp/berkeley-softfloat-3 tests/fp/berkeley-testfloat-3"
 sub_deinit=""
 
diff --git a/dtc b/subprojects/dtc
similarity index 100%
rename from dtc
rename to subprojects/dtc
-- 
2.40.1