[5.1/ N] set_option/get_option API with {backend_name, backend options} only (#11877)

This PR was created by the merge bot to help merge the original PR into
the main branch.
ghstack PR number: #11865 by
@cccclai
^ Please use this as the source of truth for the PR details, comments,
and reviews
ghstack PR base:
https://github.com/pytorch/executorch/tree/gh/cccclai/31/base
ghstack PR head:
https://github.com/pytorch/executorch/tree/gh/cccclai/31/head
Merge bot PR base:
https://github.com/pytorch/executorch/tree/gh/cccclai/23/orig
Merge bot PR head:
https://github.com/pytorch/executorch/tree/gh/cccclai/31/orig
@diff-train-skip-merge

---------

Co-authored-by: Chen Lai <[email protected]>
Co-authored-by: cccclai <[email protected]>

Author: pytorchbot

runtime/backend/interface.cpp

@@ -66,5 +66,42 @@ Result<const char*> get_backend_name(size_t index) {
   return registered_backends[index].name;
 }
 
+Error set_option(
+    const char* backend_name,
+    const executorch::runtime::Span<executorch::runtime::BackendOption>
+        backend_options) {
+  auto backend_class = get_backend_class(backend_name);
+  if (!backend_class) {
+    return Error::NotFound;
+  }
+
+  BackendOptionContext backend_option_context;
+  Error result =
+      backend_class->set_option(backend_option_context, backend_options);
+  if (result != Error::Ok) {
+    return result;
+  }
+  return Error::Ok;
+}
+
+Error get_option(
+    const char* backend_name,
+    executorch::runtime::Span<executorch::runtime::BackendOption>
+        backend_options) {
+  auto backend_class = get_backend_class(backend_name);
+  if (!backend_class) {
+    return Error::NotFound;
+  }
+  BackendOptionContext backend_option_context;
+  executorch::runtime::Span<BackendOption> backend_options_ref(
+      backend_options.data(), backend_options.size());
+  auto result =
+      backend_class->get_option(backend_option_context, backend_options_ref);
+  if (result != Error::Ok) {
+    return result;
+  }
+  return Error::Ok;
+}
+
 } // namespace ET_RUNTIME_NAMESPACE
 } // namespace executorch

runtime/backend/interface.h

@@ -183,6 +183,34 @@ size_t get_num_registered_backends();
  */
 Result<const char*> get_backend_name(size_t index);
 
+/**
+ * Sets backend options for a specific backend.
+ *
+ * @param backend_name The name of the backend to set options for
+ * @param backend_options The backend option list containing the options
+ * to set
+ * @return Error::Ok on success, Error::NotFound if backend is not found, or
+ * other error codes on failure
+ */
+Error set_option(
+    const char* backend_name,
+    const executorch::runtime::Span<executorch::runtime::BackendOption>
+        backend_options);
+
+/**
+ * Retrieves backend options for a specific backend.
+ *
+ * @param backend_name The name of the backend to get options from
+ * @param backend_options The backend option objects that will be filled with
+ * the populated values from the backend
+ * @return Error::Ok on success, Error::NotFound if backend is not found, or
+ * other error codes on failure
+ */
+Error get_option(
+    const char* backend_name,
+    executorch::runtime::Span<executorch::runtime::BackendOption>
+        backend_options);
+
 } // namespace ET_RUNTIME_NAMESPACE
 } // namespace executorch
 

runtime/backend/test/backend_interface_update_test.cpp

@@ -7,9 +7,11 @@
  */
 
 #include <executorch/runtime/backend/interface.h>
+#include <executorch/runtime/backend/options.h>
 #include <executorch/runtime/platform/runtime.h>
 
 #include <gtest/gtest.h>
+#include <memory>
 
 using namespace ::testing;
 using executorch::runtime::ArrayRef;
@@ -61,7 +63,8 @@ class MockBackend : public BackendInterface {
     int success_update = 0;
     for (const auto& backend_option : backend_options) {
       if (strcmp(backend_option.key, "Backend") == 0) {
-        if (std::holds_alternative<std::array<char, 256>>(
+        if (std::holds_alternative<
+                std::array<char, executorch::runtime::kMaxOptionValueLength>>(
                 backend_option.value)) {
           // Store the value in our member variable
           const auto& arr =
@@ -285,3 +288,114 @@ TEST_F(BackendInterfaceUpdateTest, UpdateBetweenExecutes) {
   ASSERT_TRUE(mock_backend->target_backend.has_value());
   EXPECT_STREQ(mock_backend->target_backend.value().c_str(), "NPU");
 }
+
+// Mock backend for testing
+class StubBackend : public BackendInterface {
+ public:
+  ~StubBackend() override = default;
+
+  bool is_available() const override {
+    return true;
+  }
+
+  Result<DelegateHandle*> init(
+      BackendInitContext& context,
+      FreeableBuffer* processed,
+      ArrayRef<CompileSpec> compile_specs) const override {
+    return nullptr;
+  }
+
+  Error execute(
+      BackendExecutionContext& context,
+      DelegateHandle* handle,
+      EValue** args) const override {
+    return Error::Ok;
+  }
+
+  Error get_option(
+      BackendOptionContext& context,
+      executorch::runtime::Span<executorch::runtime::BackendOption>&
+          backend_options) override {
+    // For testing purposes, just record that get_option was called
+    // and verify the input parameters
+    get_option_called = true;
+    get_option_call_count++;
+    last_get_option_size = backend_options.size();
+
+    // Verify that the expected option key is present and modify the value
+    for (size_t i = 0; i < backend_options.size(); ++i) {
+      if (strcmp(backend_options[i].key, "NumberOfThreads") == 0) {
+        // Set the value to what was stored by set_option
+        backend_options[i].value = last_num_threads;
+        found_expected_key = true;
+        break;
+      }
+    }
+
+    return Error::Ok;
+  }
+
+  Error set_option(
+      BackendOptionContext& context,
+      const executorch::runtime::Span<executorch::runtime::BackendOption>&
+          backend_options) override {
+    // Store the options for verification
+    last_options_size = backend_options.size();
+    if (backend_options.size() > 0) {
+      for (const auto& option : backend_options) {
+        if (strcmp(option.key, "NumberOfThreads") == 0) {
+          if (auto* val = std::get_if<int>(&option.value)) {
+            last_num_threads = *val;
+          }
+        }
+      }
+    }
+    return Error::Ok;
+  }
+
+  // Mutable for testing verification
+  size_t last_options_size = 0;
+  int last_num_threads = 0;
+  bool get_option_called = false;
+  int get_option_call_count = 0;
+  size_t last_get_option_size = 0;
+  bool found_expected_key = false;
+};
+
+class BackendUpdateTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    // Since these tests cause ET_LOG to be called, the PAL must be initialized
+    // first.
+    executorch::runtime::runtime_init();
+
+    // Register the stub backend
+    stub_backend = std::make_unique<StubBackend>();
+    Backend backend_config{"StubBackend", stub_backend.get()};
+    auto register_result = register_backend(backend_config);
+    ASSERT_EQ(register_result, Error::Ok);
+  }
+
+  std::unique_ptr<StubBackend> stub_backend;
+};
+
+// Test basic string functionality
+TEST_F(BackendUpdateTest, TestSetGetOption) {
+  BackendOptions<1> backend_options;
+  int new_num_threads = 4;
+  backend_options.set_option("NumberOfThreads", new_num_threads);
+
+  auto status = set_option("StubBackend", backend_options.view());
+  ASSERT_EQ(status, Error::Ok);
+
+  // Set up the default option, which will be populuated by the get_option call
+  BackendOption ref_backend_option{"NumberOfThreads", 0};
+  status = get_option("StubBackend", ref_backend_option);
+
+  // Verify that the backend actually received the options
+  ASSERT_TRUE(std::get<int>(ref_backend_option.value) == new_num_threads);
+
+  // Verify that the backend actually update the options
+  ASSERT_EQ(stub_backend->last_options_size, 1);
+  ASSERT_EQ(stub_backend->last_num_threads, new_num_threads);
+}