CHROMIUM: egl/android: Add fallback to kms_swrast driver

If no hardware driver is present, it is possible to fall back to
the kms_swrast driver with any DRI node that supports dumb GEM create
and mmap IOCTLs with softpipe/llvmpipe drivers. This patch makes the
Android EGL platform code retry probe with kms_swrast if hardware-only
probe fails.

BUG=b:28803368
TEST=Boot cyan-cheets in qemu and see the container working

Upstreaming effort tracked by:
BUG=b:32077881

Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/374309


Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
(reapplied manually from commit c652588e1b2cbe53ddb7adc25ea8a5817f0f023e)

BUG=b:33533853
TEST=No CTS regressions on cyan and reef

Change-Id: Ida864d90a715d563090c0eb5caa8557684a8cb26
Reviewed-on: https://chromium-review.googlesource.com/558136


Tested-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Chad Versace <chadversary@chromium.org>
Commit-Queue: Tomasz Figa <tfiga@chromium.org>

src/egl/drivers/dri2/platform_android.c

@@ -1048,6 +1048,37 @@ static const __DRIextension *droid_image_loader_extensions[] = {
    NULL,
 };
 
+static bool
+droid_load_driver(_EGLDisplay *dpy, bool swrast, bool dri3)
+{
+   struct dri2_egl_display *dri2_dpy = dpy->DriverData;
+   bool loaded;
+
+   if (swrast)
+      dri2_dpy->driver_name = strdup("kms_swrast");
+   else
+      dri2_dpy->driver_name = loader_get_driver_for_fd(dri2_dpy->fd);
+
+   if (dri2_dpy->driver_name == NULL) {
+      _eglLog(_EGL_WARNING, "DRI2: failed to get driver name");
+      return false;
+   }
+
+   if (dri3)
+      loaded = dri2_load_driver_dri3(dpy);
+   else
+	   loaded = dri2_load_driver(dpy);
+
+   if (!loaded) {
+      _eglLog(_EGL_WARNING, "DRI2: failed to load driver");
+      free(dri2_dpy->driver_name);
+      dri2_dpy->driver_name = NULL;
+      return false;
+   }
+
+   return true;
+}
+
 EGLBoolean
 dri2_initialize_android(_EGLDriver *drv, _EGLDisplay *dpy)
 {
@@ -1077,26 +1108,19 @@ dri2_initialize_android(_EGLDriver *drv, _EGLDisplay *dpy)
       goto cleanup;
    }
 
-   dri2_dpy->driver_name = loader_get_driver_for_fd(dri2_dpy->fd);
-   if (dri2_dpy->driver_name == NULL) {
-      err = "DRI2: failed to get driver name";
-      goto cleanup;
-   }
-
    dri2_dpy->is_render_node = drmGetNodeTypeFromFd(dri2_dpy->fd) == DRM_NODE_RENDER;
 
    /* render nodes cannot use Gem names, and thus do not support
     * the __DRI_DRI2_LOADER extension */
-   if (!dri2_dpy->is_render_node) {
+   if (!dri2_dpy->is_render_node)
       dri2_dpy->loader_extensions = droid_dri2_loader_extensions;
-      if (!dri2_load_driver(dpy)) {
-         err = "DRI2: failed to load driver";
-         goto cleanup;
-      }
-   } else {
+   else
       dri2_dpy->loader_extensions = droid_image_loader_extensions;
-      if (!dri2_load_driver_dri3(dpy)) {
-         err = "DRI3: failed to load driver";
+
+   if (!droid_load_driver(dpy, false, dri2_dpy->is_render_node)) {
+      _eglLog(_EGL_WARNING, "DRI2: Failed to load hardware driver, trying software...");
+      if (!droid_load_driver(dpy, true, dri2_dpy->is_render_node)) {
+         err = "DRI2: failed to load driver";
          goto cleanup;
       }
    }