kapi: add basic device subsystem

1 files changed, 63 insertions, 0 deletions

diff --git a/kernel/kapi/devices.cpp b/kernel/kapi/devices.cpp
new file mode 100644
index 0000000..dc19ab4
--- /dev/null
+++ b/kernel/kapi/devices.cpp
@@ -0,0 +1,63 @@
+#include "kapi/devices.hpp"
+
+#include "kapi/system.hpp"
+
+#include "kernel/devices/root_bus.hpp"
+
+#include <kstd/flat_map>
+#include <kstd/memory>
+#include <kstd/print>
+
+#include <atomic>
+#include <cstddef>
+#include <optional>
+#include <utility>
+
+namespace kapi::devices
+{
+
+  namespace
+  {
+    auto constinit next_major_number = std::atomic_size_t{0};
+    auto constinit root_bus = std::optional<kernel::devices::root_bus>{};
+    auto constinit device_tree = kstd::flat_map<std::pair<std::size_t, std::size_t>, kstd::observer_ptr<device>>{};
+  }  // namespace
+
+  auto init() -> void
+  {
+    auto static is_initialized = std::atomic_flag{};
+    if (is_initialized.test_and_set())
+    {
+      return;
+    }
+
+    root_bus.emplace();
+    root_bus->init();
+  }
+
+  auto get_root_bus() -> bus &
+  {
+    if (!root_bus.has_value())
+    {
+      kapi::system::panic("[kernel:devices] Root bus not initialized!");
+    }
+    return *root_bus;
+  }
+
+  auto allocate_major_number() -> std::size_t
+  {
+    return next_major_number++;
+  }
+
+  auto register_device(device & device) -> bool
+  {
+    return device_tree.emplace(std::pair{device.major(), device.minor()}, &device).second;
+  }
+
+  auto unregister_device(device &) -> bool
+  {
+    kstd::println("[kernel:devices] TODO: implement device deregistration");
+    return false;
+  }
+
+}  // namespace kapi::devices
\ No newline at end of file