libvulkan: Use a stub HAL when no real Vulkan HAL is present

This stub HAL enumerates zero VkPhysicalDevices. This allows a
VkInstane to be created and queried for physical devices successfully
even on devices without a Vulkan driver. Handling this with a stub HAL
avoids the need for NULL HAL and NULL driver function pointer checks
in many places throughout the loader, which would be more error-prone.

Fixes bug: 28100673
Change-Id: I76bea975929a85eda354730d6c815567b412b160

1 files changed, 30 insertions, 0 deletions

diff --git a/vulkan/libvulkan/stubhal.h b/vulkan/libvulkan/stubhal.h
new file mode 100644
index 0000000000..9ba7d04067
--- /dev/null
+++ b/vulkan/libvulkan/stubhal.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LIBVULKAN_STUBHAL_H
+#define LIBVULKAN_STUBHAL_H 1
+
+struct hwvulkan_device_t;
+
+namespace vulkan {
+namespace stubhal {
+
+extern const hwvulkan_device_t kDevice;
+
+}  // namespace stubhal
+}  // namespace vulkan
+
+#endif  // LIBVULKAN_STUBHAL_H