meson: use a feature option for gallium-xa

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20409>

docs/drivers/svga3d.rst

@@ -193,7 +193,7 @@ Building the Code
    ::
 
       cd $TOP/mesa
-      meson builddir --prefix=/usr --libdir=${LIBDIR} -Dgallium-drivers=svga -Dgallium-xa=true -Ddri3=disabled
+      meson builddir --prefix=/usr --libdir=${LIBDIR} -Dgallium-drivers=svga -Dgallium-xa=enabled -Ddri3=disabled
       ninja -C builddir
       sudo ninja -C builddir install
         

meson.build

@@ -783,29 +783,11 @@ if va_drivers_path == ''
   va_drivers_path = join_paths(get_option('libdir'), 'dri')
 endif
 
-_xa = get_option('gallium-xa')
-if _xa == 'true'
-  _xa = 'enabled'
-  warning('gallium-xa option "true" deprecated, please use "enabled" instead.')
-elif _xa == 'false'
-  _xa = 'disabled'
-  warning('gallium-xa option "false" deprecated, please use "disabled" instead.')
-endif
-if not system_has_kms_drm
-  if _xa == 'enabled'
-    error('XA state tracker can only be built on unix-like OSes.')
-  else
-    _xa = 'disabled'
-  endif
-elif not (with_gallium_nouveau or with_gallium_freedreno or with_gallium_i915
-          or with_gallium_svga)
-  if _xa == 'enabled'
-    error('XA state tracker requires at least one of the following gallium drivers: nouveau, freedreno, i915, svga.')
-  else
-    _xa = 'disabled'
-  endif
-endif
-with_gallium_xa = _xa != 'disabled'
+with_gallium_xa = get_option('gallium-xa') \
+  .require(system_has_kms_drm, error_message : 'XA state tracker can only be built on unix-like OSes.') \
+  .require(with_gallium_nouveau or with_gallium_freedreno or with_gallium_i915 or with_gallium_svga,
+           error_message : 'XA state tracker requires at least one of the following gallium drivers: nouveau, freedreno, i915, svga.') \
+  .allowed()
 
 d3d_drivers_path = get_option('d3d-drivers-path')
 if d3d_drivers_path == ''

meson_options.txt

@@ -120,9 +120,7 @@ option(
 )
 option(
   'gallium-xa',
-  type : 'combo',
-  value : 'auto',
-  choices : ['auto', 'true', 'false', 'enabled', 'disabled'],
+  type : 'feature',
   description : 'enable gallium xa frontend.',
 )
 option(