meson: support building with system libgbm

This is the next step towards making libgbm just a loader.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33890>

meson.build

@@ -2365,7 +2365,7 @@ summary(egl_summary, section: 'EGL', bool_yn: true, list_sep: ' ')
 
 gbm_summary = {'Enabled': with_gbm}
 if with_gbm
-  gbm_summary += {'Backends path': gbm_backends_path}
+  gbm_summary += {'External libgbm': get_option('libgbm-external'), 'Backends path': gbm_backends_path}
 endif
 summary(gbm_summary, section: 'GBM', bool_yn: true, list_sep: ' ')
 

meson.options

@@ -330,6 +330,13 @@ option(
   description : 'Build support for gbm platform'
 )
 
+option(
+  'libgbm-external',
+  type: 'boolean',
+  value: false,
+  description: 'Whether to use external libgbm (default: use in-tree copy)'
+)
+
 option(
   'gbm-backends-path',
   type : 'string',

src/egl/meson.build

@@ -108,9 +108,8 @@ if with_dri
   endif
   if with_gbm and not with_platform_android
     files_egl += files('drivers/dri2/platform_drm.c')
-    link_for_egl += libgbm
-    incs_for_egl += [inc_gbm, include_directories('../gbm/main')]
-    deps_for_egl += dep_libdrm
+    incs_for_egl += [include_directories('../gbm/backends/dri')]
+    deps_for_egl += [dep_libdrm, dep_gbm]
   endif
   if with_platform_wayland
     deps_for_egl += [dep_wayland_client, dep_wayland_server, dep_wayland_egl_headers]

src/gallium/targets/dril/dril_target.c

@@ -25,7 +25,7 @@
 #include <dlfcn.h>
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
-#include "gbm/main/gbm.h"
+#include <gbm.h>
 #include "drm-uapi/drm_fourcc.h"
 
 #define EGL_PLATFORM_GBM_MESA             0x31D7

src/gallium/targets/dril/meson.build

@@ -51,10 +51,10 @@ dril_dri = shared_library(
   link_depends : dril_link_depends,
   link_with : [
     libgallium,
-    libgbm,
   ],
   dependencies : [
     idep_mesautil,
+    dep_gbm,
   ],
   # Will be deleted during installation, see install_megadrivers.py
   install : true,

src/gbm/backends/dri/gbm_dri.c

@@ -43,7 +43,7 @@
 
 #include "mesa_interface.h"
 #include "gbm_driint.h"
-#include "gbmint.h"
+#include <gbm_backend_abi.h>
 #include "loader_dri_helper.h"
 #include "kopper_interface.h"
 #include "loader.h"

src/gbm/backends/dri/gbm_driint.h

@@ -31,7 +31,7 @@
 #include <xf86drm.h>
 #include <string.h>
 #include <sys/mman.h>
-#include "gbmint.h"
+#include <gbm_backend_abi.h>
 #include "c11/threads.h"
 
 #include <GL/gl.h> /* mesa_interface needs GL types */

src/gbm/backends/dri/meson.build

@@ -11,10 +11,10 @@ endif
 shared_library(
   'dri_gbm',
   files('gbm_dri.c', 'gbm_driint.h'),
-  include_directories : [incs_gbm, incs_gbm_dri, inc_st_dri, inc_gallium_aux],
+  include_directories : [inc_gallium, incs_gbm_dri, inc_loader, inc_st_dri, inc_gallium_aux],
   link_args : [ld_args_gc_sections],
   link_with : [libloader, libgallium_dri],
-  dependencies : [deps_gbm_dri, dep_dl, dep_libdrm, idep_mesautil, idep_xmlconfig],
+  dependencies : [deps_gbm_dri, dep_dl, dep_gbm, dep_libdrm, idep_mesautil, idep_xmlconfig],
   gnu_symbol_visibility : 'hidden',
   install : true,
   install_dir: join_paths(get_option('libdir'), 'gbm'),

src/gbm/meson.build

@@ -15,10 +15,6 @@ args_gbm = [
 ]
 incs_gbm = [include_directories('main'), inc_loader, inc_gallium]
 
-if with_dri2
-  subdir('backends/dri')
-endif
-
 libgbm_name = 'gbm'
 
 if with_platform_android and get_option('platform-sdk-version') >= 30
@@ -43,7 +39,7 @@ if with_tests
   test('gbm-abi-check', abi_check, suite : ['gbm'])
 endif
 
-install_headers('main/gbm.h')
+install_headers('main/gbm.h', 'main/gbm_backend_abi.h')
 
 pkg.generate(
   name : 'gbm',
@@ -67,3 +63,8 @@ if with_symbols_check
     suite : ['gbm'],
   )
 endif
+
+dep_gbm = declare_dependency(
+  link_with : libgbm,
+  include_directories : inc_gbm,
+)

src/meson.build

@@ -127,11 +127,17 @@ endif
 if with_glx == 'dri'
   subdir('glx')
 endif
+
 if with_gbm
-  subdir('gbm')
+  if get_option('libgbm-external')
+    dep_gbm = dependency('gbm')
+  else
+    subdir('gbm')
+  endif
 else
-  inc_gbm = []
+  dep_gbm = null_dep
 endif
+
 if with_egl
   subdir('egl')
 endif
@@ -141,6 +147,10 @@ if with_gallium and with_gbm
   endif
 endif
 
+if with_gbm and with_dri2
+  subdir('gbm/backends/dri')
+endif
+
 # This must be after at least mesa, glx, and gallium, since libgl will be
 # defined in one of those subdirs depending on the glx provider.
 if with_glx != 'disabled' and not with_glvnd