From d2d4fa3330a09f421b8658c077166cc493532b9e Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Tue, 2 Jun 2026 10:54:17 +0200
Subject: kernel/vfs: extract fs type registry

---
 kernel/src/filesystem/devfs/filesystem.cpp |  6 +--
 kernel/src/filesystem/ext2/filesystem.cpp  |  6 +--
 kernel/src/filesystem/type_registry.cpp    | 67 ++++++++++++++++++++++++++++++
 kernel/src/filesystem/vfs.cpp              | 17 --------
 kernel/src/main.cpp                        |  2 +
 5 files changed, 75 insertions(+), 23 deletions(-)
 create mode 100644 kernel/src/filesystem/type_registry.cpp

(limited to 'kernel/src')

diff --git a/kernel/src/filesystem/devfs/filesystem.cpp b/kernel/src/filesystem/devfs/filesystem.cpp
index 1aaa0d1..ce887ff 100644
--- a/kernel/src/filesystem/devfs/filesystem.cpp
+++ b/kernel/src/filesystem/devfs/filesystem.cpp
@@ -32,10 +32,10 @@ namespace kernel::filesystem::devfs
     {
       return kstd::make_shared<filesystem>();
     }
-  } const constinit type_instance{};
+  };
 
-  [[gnu::section("vfs_type_descriptors"), gnu::used]]
-  auto const * const type_descriptor_pointer = static_cast<kernel::filesystem::type const *>(&type_instance);
+  [[gnu::used]]
+  constexpr auto registration = type_registration<type>{};
 
   auto filesystem::mount(kstd::shared_ptr<kernel::filesystem::inode> const &) -> operation_result
   {
diff --git a/kernel/src/filesystem/ext2/filesystem.cpp b/kernel/src/filesystem/ext2/filesystem.cpp
index 7b5d2d7..3180a19 100644
--- a/kernel/src/filesystem/ext2/filesystem.cpp
+++ b/kernel/src/filesystem/ext2/filesystem.cpp
@@ -36,10 +36,10 @@ namespace kernel::filesystem::ext2
     {
       return kstd::make_shared<filesystem>();
     }
-  } const constinit type_instance{};
+  };
 
-  [[gnu::section("vfs_type_descriptors"), gnu::used]]
-  auto const * const type_descriptor_pointer = static_cast<kernel::filesystem::type const *>(&type_instance);
+  [[gnu::used]]
+  constexpr auto registration = type_registration<type>{};
 
   auto filesystem::mount(kstd::shared_ptr<kernel::filesystem::inode> const & backing_inode) -> operation_result
   {
diff --git a/kernel/src/filesystem/type_registry.cpp b/kernel/src/filesystem/type_registry.cpp
new file mode 100644
index 0000000..033b879
--- /dev/null
+++ b/kernel/src/filesystem/type_registry.cpp
@@ -0,0 +1,67 @@
+#include <kernel/filesystem/type_registry.hpp>
+
+#include <kapi/system.hpp>
+
+#include <kstd/memory>
+#include <kstd/print>
+
+#include <algorithm>
+#include <optional>
+#include <ranges>
+#include <span>
+
+namespace kernel::filesystem
+{
+
+  extern "C"
+  {
+    extern type_registry::pointer const __start_fs_types;
+    extern type_registry::pointer const __stop_fs_types;
+  }
+
+  namespace
+  {
+    auto constinit instance = std::optional<type_registry>{};
+  }
+
+  auto type_registry::init() -> void
+  {
+    if (instance)
+    {
+      kapi::system::panic("[FILESYSTEM] tried to initialize type registry more than once!");
+    }
+
+    instance.emplace();
+
+    auto type_descriptors = std::span{&__start_fs_types, &__stop_fs_types} |  //
+                            std::views::filter([](auto p) { return p != nullptr; });
+
+    std::ranges::for_each(type_descriptors, [](auto descriptor) {
+      kstd::println("[FILESYSTEM] registering '{}'", descriptor->name());
+      instance->add(descriptor);
+    });
+  }
+
+  auto type_registry::get() -> type_registry &
+  {
+    if (!instance)
+    {
+      kapi::system::panic("[FILESYSTEM] type registry has not been initialized!");
+    }
+
+    return *instance;
+  }
+
+  auto type_registry::add(pointer descriptor) -> bool
+  {
+    auto result = m_descriptors.emplace(descriptor->name(), descriptor);
+    return result.second;
+  }
+
+  [[nodiscard]] auto type_registry::all() const noexcept -> std::span<pointer>
+  {
+    // TODO: implement value accessor for flat_map
+    return {};
+  }
+
+}  // namespace kernel::filesystem
diff --git a/kernel/src/filesystem/vfs.cpp b/kernel/src/filesystem/vfs.cpp
index 8dcae2c..8d1fd23 100644
--- a/kernel/src/filesystem/vfs.cpp
+++ b/kernel/src/filesystem/vfs.cpp
@@ -8,29 +8,20 @@
 #include <kernel/filesystem/mount_table.hpp>
 #include <kernel/filesystem/path.hpp>
 #include <kernel/filesystem/rootfs/filesystem.hpp>
-#include <kernel/filesystem/type.hpp>
 
 #include <kapi/system.hpp>
 
 #include <kstd/memory>
 #include <kstd/print>
-#include <kstd/string>
 #include <kstd/vector>
 
 #include <algorithm>
 #include <cstdint>
 #include <optional>
 #include <ranges>
-#include <span>
 #include <string_view>
 #include <utility>
 
-extern "C"
-{
-  extern kernel::filesystem::type const * const __start_vfs_type_descriptors;
-  extern kernel::filesystem::type const * const __stop_vfs_type_descriptors;
-}
-
 namespace
 {
   constinit auto static active_vfs = std::optional<kernel::filesystem::vfs>{};
@@ -50,14 +41,6 @@ namespace kernel::filesystem
 
   vfs::vfs()
   {
-    // Register all compiled-in filesystems
-    auto type_descriptors = std::span{&__start_vfs_type_descriptors, &__stop_vfs_type_descriptors} |
-                            std::views::filter([](auto p) { return p != nullptr; });
-    std::ranges::for_each(type_descriptors, [this](auto descriptor) {
-      kstd::println("[FILESYSTEM] registering '{}'", descriptor->name());
-      m_filesystems.emplace(descriptor->name(), descriptor);
-    });
-
     // mount rootfs at /
     auto root_fs = kstd::make_shared<rootfs::filesystem>();
     root_fs->mount(nullptr);
diff --git a/kernel/src/main.cpp b/kernel/src/main.cpp
index 6985e94..5063d18 100644
--- a/kernel/src/main.cpp
+++ b/kernel/src/main.cpp
@@ -1,3 +1,4 @@
+#include "kernel/filesystem/type_registry.hpp"
 #include <kernel/devices/storage/management.hpp>
 #include <kernel/filesystem/open_file_table.hpp>
 #include <kernel/filesystem/vfs.hpp>
@@ -138,6 +139,7 @@ auto main() -> int
   kernel::filesystem::open_file_table::init();
   kstd::println("[OS] Global open file table initialized.");
 
+  kernel::filesystem::type_registry::init();
   kernel::filesystem::vfs::init();
   kstd::println("[OS] Virtual filesystem initialized.");
 
-- 
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