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
diff --git a/vulkan/libvulkan/stubhal.cpp b/vulkan/libvulkan/stubhal.cpp
new file mode 100644
index 0000000..89fcebb
--- /dev/null
+++ b/vulkan/libvulkan/stubhal.cpp
@@ -0,0 +1,134 @@
+/*
+ * 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.
+ */
+
+/* NOTE:
+ * This stub HAL is only used internally by the loader when a real HAL
+ * implementation is not present, in order to avoid needing "null HAL" checks
+ * throughout the loader. It does not enumerate any physical devices, and is
+ * only as conformant to the Vulkan and Android HAL interfaces as the loader
+ * needs it to be. Do not use it as an example of a correct implementation; the
+ * code in ../null_driver is better for that.
+ */
+
+#undef LOG_TAG
+#define LOG_TAG "vkstub"
+
+#include <array>
+#include <bitset>
+#include <mutex>
+#include <hardware/hwvulkan.h>
+#include <log/log.h>
+#include "stubhal.h"
+
+namespace vulkan {
+namespace stubhal {
+
+namespace {
+
+const size_t kMaxInstances = 32;
+static std::mutex g_instance_mutex;
+static std::bitset<kMaxInstances> g_instance_used(false);
+static std::array<hwvulkan_dispatch_t, kMaxInstances> g_instances;
+
+[[noreturn]] void NoOp() {
+ LOG_ALWAYS_FATAL("invalid stub function called");
+}
+
+VKAPI_ATTR VkResult
+EnumerateInstanceExtensionProperties(const char* /*layer_name*/,
+ uint32_t* count,
+ VkExtensionProperties* /*properties*/) {
+ *count = 0;
+ return VK_SUCCESS;
+}
+
+VKAPI_ATTR VkResult
+EnumerateInstanceLayerProperties(uint32_t* count,
+ VkLayerProperties* /*properties*/) {
+ *count = 0;
+ return VK_SUCCESS;
+}
+
+VKAPI_ATTR VkResult CreateInstance(const VkInstanceCreateInfo* /*create_info*/,
+ const VkAllocationCallbacks* /*allocator*/,
+ VkInstance* instance) {
+ std::lock_guard<std::mutex> lock(g_instance_mutex);
+ for (size_t i = 0; i < kMaxInstances; i++) {
+ if (!g_instance_used[i]) {
+ g_instance_used[i] = true;
+ g_instances[i].magic = HWVULKAN_DISPATCH_MAGIC;
+ *instance = reinterpret_cast<VkInstance>(&g_instances[i]);
+ return VK_SUCCESS;
+ }
+ }
+ ALOGE("no more instances available (max=%zu)", kMaxInstances);
+ return VK_ERROR_INITIALIZATION_FAILED;
+}
+
+VKAPI_ATTR void DestroyInstance(VkInstance instance,
+ const VkAllocationCallbacks* /*allocator*/) {
+ std::lock_guard<std::mutex> lock(g_instance_mutex);
+ ssize_t idx =
+ reinterpret_cast<hwvulkan_dispatch_t*>(instance) - &g_instances[0];
+ ALOG_ASSERT(idx >= 0 && idx < g_instance_used.size(),
+ "DestroyInstance: invalid instance handle");
+ g_instance_used[static_cast<size_t>(idx)] = false;
+}
+
+VKAPI_ATTR VkResult EnumeratePhysicalDevices(VkInstance /*instance*/,
+ uint32_t* count,
+ VkPhysicalDevice* /*gpus*/) {
+ *count = 0;
+ return VK_SUCCESS;
+}
+
+VKAPI_ATTR PFN_vkVoidFunction GetInstanceProcAddr(VkInstance /*instance*/,
+ const char* name) {
+ if (strcmp(name, "vkCreateInstance") == 0)
+ return reinterpret_cast<PFN_vkVoidFunction>(CreateInstance);
+ if (strcmp(name, "vkDestroyInstance") == 0)
+ return reinterpret_cast<PFN_vkVoidFunction>(DestroyInstance);
+ if (strcmp(name, "vkEnumerateInstanceExtensionProperties") == 0)
+ return reinterpret_cast<PFN_vkVoidFunction>(
+ EnumerateInstanceExtensionProperties);
+ if (strcmp(name, "vkEnumeratePhysicalDevices") == 0)
+ return reinterpret_cast<PFN_vkVoidFunction>(EnumeratePhysicalDevices);
+ if (strcmp(name, "vkGetInstanceProcAddr") == 0)
+ return reinterpret_cast<PFN_vkVoidFunction>(GetInstanceProcAddr);
+
+ // None of the other Vulkan functions should ever be called, as they all
+ // take a VkPhysicalDevice or other object obtained from a physical device.
+ return reinterpret_cast<PFN_vkVoidFunction>(NoOp);
+}
+
+} // anonymous namespace
+
+const hwvulkan_device_t kDevice = {
+ .common =
+ {
+ .tag = HARDWARE_DEVICE_TAG,
+ .version = HWVULKAN_DEVICE_API_VERSION_0_1,
+ .module = nullptr,
+ .close = nullptr,
+ },
+ .EnumerateInstanceExtensionProperties =
+ EnumerateInstanceExtensionProperties,
+ .CreateInstance = CreateInstance,
+ .GetInstanceProcAddr = GetInstanceProcAddr,
+};
+
+} // namespace stubhal
+} // namespace vulkan