egl: Native Display autodetection

EGL doesnt define howto manage different native platforms.
So mesa has a builtime configurable default platform,
whith non-standard envvar (EGL_PLATFORM) overwrites.
This caused unneeded bugreports, when EGL_PLATFORM was forgotten.

Detection is grouped into basic types of NativeDisplays (which itself
needs to be detected).  The final decision is based on characteristcs
of these basic types:

  File Desciptor based platforms (fbdev):
    - fstat(2) to check for being a fd that belongs to a character device
    - check kernel subsystem (todo)

  Pointer to structuctures (x11, wayland, drm/gbm):
    - mincore(2) to check whether its valid pointer to some memory.
    - magic elements (e.g. pointers to exported symbols):
      o wayland display stores interface type pointer (first elm.)
      o gbm stores pointer to its constructor (first elm.)
      o x11 as a fallback (FIXME?)

Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 1b1823a211..9195da9b3a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1370,6 +1370,8 @@ if test "x$enable_egl" = xyes; then
     EGL_LIB_DEPS="$DLOPEN_LIBS $SELINUX_LIBS -lpthread"
     EGL_DRIVERS_DIRS=""
 
+    AC_CHECK_FUNC(mincore, [DEFINES="$DEFINES -DHAVE_MINCORE"])
+
     if test "$enable_static" != yes; then
         # build egl_glx when libGL is built
         if test "x$enable_glx" = xyes; then