egl: Improve driver selection.
The idea is to be able to match a driver using the following order
try egl_gallium with hw renderer
try egl_dri2
try egl_gallium with sw renderer
try egl_glx
given the module list
egl_gallium
egl_dri2
egl_glx
For that, UseFallback initialization option is added. The module list
is matched twice: with the option unset and with the option set. In the
first pass, egl_gallium skips its sw renderer and egl_glx rejects to
initialize since UseFallback is not set. In the second pass,
egl_gallium skips its hw renderer and egl_dri2 rejects to initialize
since UseFallback is set. The process stops at the first driver that
initializes the display.
diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
index 2e827f4..6fc1e49 100644
--- a/src/egl/drivers/dri2/egl_dri2.c
+++ b/src/egl/drivers/dri2/egl_dri2.c
@@ -1470,6 +1470,10 @@
static EGLBoolean
dri2_initialize(_EGLDriver *drv, _EGLDisplay *disp)
{
+ /* not until swrast_dri is supported */
+ if (disp->Options.UseFallback)
+ return EGL_FALSE;
+
switch (disp->Platform) {
case _EGL_PLATFORM_X11:
if (disp->Options.TestOnly)