kapi: bootstrap owning device tree

9 files changed, 79 insertions, 51 deletions

diff --git a/arch/x86_64/arch/devices/init.cpp b/arch/x86_64/arch/devices/init.cpp
index 4ac287cf..2c4fb3c3 100644
--- a/arch/x86_64/arch/devices/init.cpp
+++ b/arch/x86_64/arch/devices/init.cpp
@@ -62,13 +62,13 @@ namespace arch::devices
   {
     kstd::println("[x86_64:DEV] Initializing ISA bus...");
 
-    auto isa_bus = kstd::make_unique<arch::bus::isa>();
+    auto isa_bus = kstd::make_shared<arch::bus::isa>();
 
-    auto pit = kstd::make_unique<arch::devices::legacy_pit>(pit_frequency_in_hz);
+    auto pit = kstd::make_shared<arch::devices::legacy_pit>(pit_frequency_in_hz);
     isa_bus->add_child(std::move(pit));
 
-    auto & root_bus = kapi::devices::get_root_bus();
-    root_bus.add_child(std::move(isa_bus));
+    auto root_bus = kapi::devices::get_root_bus();
+    root_bus->add_child(std::move(isa_bus));
   }
 
 }  // namespace arch::devices
diff --git a/arch/x86_64/kapi/cpu.cpp b/arch/x86_64/kapi/cpu.cpp
index bd86f0fa..c45703e5 100644
--- a/arch/x86_64/kapi/cpu.cpp
+++ b/arch/x86_64/kapi/cpu.cpp
@@ -64,19 +64,19 @@ namespace kapi::cpu
     auto bsp_found = false;
     auto core_index = 0uz;
     auto local_apic_address = memory::physical_address{madt->local_interrupt_controller_address()};
-    auto cpu_bus = kstd::make_unique<devices::cpu>();
+    auto cpu_bus = kstd::make_shared<devices::cpu>();
 
     for (auto const & apic : lapic_entries)
     {
       auto is_bsp = !bsp_found;
       bsp_found = true;
-      auto core = kstd::make_unique<devices::cpu::core>(core_index, apic.processor_id(), is_bsp);
-      core->add_child(kstd::make_unique<arch::devices::local_apic>(core_index, apic.id(), local_apic_address, is_bsp));
+      auto core = kstd::make_shared<devices::cpu::core>(core_index, apic.processor_id(), is_bsp);
+      core->add_child(kstd::make_shared<arch::devices::local_apic>(core_index, apic.id(), local_apic_address, is_bsp));
       cpu_bus->add_child(std::move(core));
       ++core_index;
     }
 
-    devices::get_root_bus().add_child(std::move(cpu_bus));
+    devices::get_root_bus()->add_child(std::move(cpu_bus));
 
     kstd::println("[x86_64:PLT] Found {} CPU cores", core_index);
     return core_index > 0;
diff --git a/kapi/kapi/devices.hpp b/kapi/kapi/devices.hpp
index e86e9ee7..5c3d1b63 100644
--- a/kapi/kapi/devices.hpp
+++ b/kapi/kapi/devices.hpp
@@ -29,8 +29,8 @@ namespace kapi::devices
   //!
   //! @warning This function will panic if the root bus has not been initialized.
   //!
-  //! @return a reference to the root bus.
-  auto get_root_bus() -> bus &;
+  //! @return a shared pointer to the root bus.
+  auto get_root_bus() -> kstd::shared_ptr<bus>;
 
   //! Publish the fact that a given device implements a given interface.
   //!
diff --git a/kapi/kapi/devices/bus.hpp b/kapi/kapi/devices/bus.hpp
index 1f433efc..6356e166 100644
--- a/kapi/kapi/devices/bus.hpp
+++ b/kapi/kapi/devices/bus.hpp
@@ -11,6 +11,7 @@
 #include <kstd/vector.hpp>
 
 #include <atomic>
+#include <span>
 
 namespace kapi::devices
 {
@@ -36,9 +37,9 @@ namespace kapi::devices
     //! Whenever a device is attached to a bus, the bus takes sole ownership of the device.
     //!
     //! @param child The child device to attach.
-    auto add_child(kstd::unique_ptr<device> child) -> void;
+    auto add_child(kstd::shared_ptr<device> child) -> void;
 
-    [[nodiscard]] auto children() const -> kstd::vector<kstd::observer_ptr<device>> const &;
+    [[nodiscard]] auto children() const -> std::span<kstd::shared_ptr<device> const>;
 
   protected:
     //! Enumerate the devices on the bus.
@@ -47,8 +48,7 @@ namespace kapi::devices
     auto virtual enumerate() -> bool;
 
   private:
-    kstd::vector<kstd::unique_ptr<device>> m_devices;
-    kstd::vector<kstd::observer_ptr<device>> m_observers;
+    kstd::vector<kstd::shared_ptr<device>> m_devices;
     std::atomic_flag m_init_was_called{};
     std::atomic_flag m_initialized{};
   };
diff --git a/kapi/kapi/devices/device.hpp b/kapi/kapi/devices/device.hpp
index d72a6bbd..6ffd052d 100644
--- a/kapi/kapi/devices/device.hpp
+++ b/kapi/kapi/devices/device.hpp
@@ -17,7 +17,7 @@ namespace kapi::devices
   /**
    * @brief Base device identified by a name.
    */
-  struct device
+  struct device : kstd::enable_shared_from_this<device>
   {
     /**
      * @brief Create a device identified by @p name.
@@ -60,16 +60,21 @@ namespace kapi::devices
      */
     [[nodiscard]] auto name() const -> kstd::string const &;
 
+    //! Get the parent bus of this device.
+    //!
+    //! @return a shared pointer to the parent bus, or nullptr if this device has no parent.
+    [[nodiscard]] auto parent() const -> kstd::shared_ptr<struct bus>;
+
   protected:
     auto virtual query_interface(interface interface) -> void *;
 
   private:
     friend struct bus;
 
-    auto set_parent(kstd::observer_ptr<struct bus> parent) -> void;
+    auto set_parent(kstd::weak_ptr<struct bus> parent) -> void;
 
     kstd::string m_name;
-    kstd::observer_ptr<bus> m_parent;
+    kstd::weak_ptr<bus> m_parent;
   };
 
   //! @}
diff --git a/kapi/kapi/devices/manager.hpp b/kapi/kapi/devices/manager.hpp
index 25b22510..5b620b27 100644
--- a/kapi/kapi/devices/manager.hpp
+++ b/kapi/kapi/devices/manager.hpp
@@ -19,7 +19,7 @@ namespace kapi::devices
   //!
   //! @param device The device to register.
   //! @return true if the device was registered successfully, false otherwise.
-  auto register_device(device & device) -> bool;
+  auto register_device(kstd::shared_ptr<device> device) -> bool;
 
   //! Unregister a device from the kernel's device manager.
   //!
@@ -30,8 +30,8 @@ namespace kapi::devices
   //! Find a device by its name.
   //!
   //! @param name the name of the device.
-  //! @return a pointer to the device iff. the device was found, nullptr otherwise.
-  auto find_device(std::string_view name) -> kstd::observer_ptr<device>;
+  //! @return a shared pointer to the device iff. the device was found and is still alive, nullptr otherwise.
+  auto find_device(std::string_view name) -> kstd::shared_ptr<device>;
 
   //! @}
 
diff --git a/kernel/kapi/devices.cpp b/kernel/kapi/devices.cpp
index 6da503d9..8f3011fe 100644
--- a/kernel/kapi/devices.cpp
+++ b/kernel/kapi/devices.cpp
@@ -10,7 +10,6 @@
 #include <kstd/print.hpp>
 #include <kstd/string.hpp>
 
-#include <optional>
 #include <string_view>
 #include <utility>
 
@@ -18,37 +17,55 @@ namespace kapi::devices
 {
   namespace
   {
-    auto constinit root_bus = std::optional<kernel::devices::root_bus>{};
-    auto constinit device_tree = kstd::flat_map<kstd::string, kstd::observer_ptr<device>>{};
+    auto constinit root_bus = kstd::shared_ptr<kernel::devices::root_bus>{};
+    auto constinit device_tree = kstd::flat_map<kstd::string, kstd::weak_ptr<device>>{};
   }  // namespace
 
   auto init() -> void
   {
-    if (root_bus.has_value())
+    if (root_bus)
     {
       kapi::system::panic("[OS:DEV] The device subsystem has already been initialized");
     }
 
     interface_registry::init();
 
-    auto & bus = root_bus.emplace();
-    register_device(bus);
-    bus.init();
+    root_bus = kstd::make_shared<kernel::devices::root_bus>();
+    register_device(root_bus);
+    root_bus->init();
   }
 
-  auto get_root_bus() -> bus &
+  auto get_root_bus() -> kstd::shared_ptr<bus>
   {
-    if (!root_bus.has_value())
+    if (!root_bus)
     {
       kapi::system::panic("[OS:DEV] Root bus not initialized!");
     }
-    return *root_bus;
+    return root_bus;
   }
 
-  auto register_device(device & device) -> bool
+  auto register_device(kstd::shared_ptr<device> device) -> bool
   {
-    kstd::println("[OS:DEV] Registering device {}", device.name());
-    return device_tree.emplace(device.name(), &device).second;
+    if (!device)
+    {
+      return false;
+    }
+
+    kstd::println("[OS:DEV] Registering device {}", device->name());
+
+    auto found = device_tree.find(device->name());
+    if (found != device_tree.end())
+    {
+      if (!found->second.expired())
+      {
+        return false;
+      }
+
+      found->second = device;
+      return true;
+    }
+
+    return device_tree.emplace(device->name(), device).second;
   }
 
   auto unregister_device(device &) -> bool
@@ -57,16 +74,15 @@ namespace kapi::devices
     return false;
   }
 
-  auto find_device(std::string_view name) -> kstd::observer_ptr<device>
+  auto find_device(std::string_view name) -> kstd::shared_ptr<device>
   {
-    for (auto const & [key, value] : device_tree)
+    auto found = device_tree.find(kstd::string{name});
+    if (found == device_tree.end())
     {
-      if (value->name() == name)
-      {
-        return value;
-      }
+      return nullptr;
     }
-    return nullptr;
+
+    return found->second.lock();
   }
 
 }  // namespace kapi::devices
diff --git a/kernel/kapi/devices/bus.cpp b/kernel/kapi/devices/bus.cpp
index d9f3f991..179a04a8 100644
--- a/kernel/kapi/devices/bus.cpp
+++ b/kernel/kapi/devices/bus.cpp
@@ -9,6 +9,7 @@
 #include <kstd/vector.hpp>
 
 #include <algorithm>
+#include <span>
 #include <utility>
 
 namespace kapi::devices
@@ -41,29 +42,30 @@ namespace kapi::devices
     return child_status;
   }
 
-  auto bus::add_child(kstd::unique_ptr<device> child) -> void
+  auto bus::add_child(kstd::shared_ptr<device> child) -> void
   {
-    auto observer = m_observers.emplace_back(child.get());
-    child->set_parent(kstd::make_observer(this));
-    m_devices.push_back(std::move(child));
-    if (!kapi::devices::register_device(*observer))
+    child->set_parent(kstd::static_pointer_cast<bus>(shared_from_this()));
+
+    if (!kapi::devices::register_device(child))
     {
       kapi::system::panic("[OS:DEV] Failed to register child device");
     }
 
+    auto & attached = m_devices.emplace_back(std::move(child));
+
     if (m_initialized.test())
     {
-      kstd::println("[OS:DEV] Initializing child device {}@{}", observer->name(), name());
-      if (!observer->init())
+      kstd::println("[OS:DEV] Initializing child device {}@{}", attached->name(), name());
+      if (!attached->init())
       {
         kapi::system::panic("[OS:DEV] Failed to initialize child device");
       }
     }
   }
 
-  [[nodiscard]] auto bus::children() const -> kstd::vector<kstd::observer_ptr<device>> const &
+  [[nodiscard]] auto bus::children() const -> std::span<kstd::shared_ptr<device> const>
   {
-    return m_observers;
+    return {m_devices.data(), m_devices.size()};
   }
 
   auto bus::enumerate() -> bool
diff --git a/kernel/kapi/devices/device.cpp b/kernel/kapi/devices/device.cpp
index 0d00d8fd..540d37b7 100644
--- a/kernel/kapi/devices/device.cpp
+++ b/kernel/kapi/devices/device.cpp
@@ -12,12 +12,17 @@ namespace kapi::devices
       : m_name(name)
   {}
 
-  [[nodiscard]] auto device::name() const -> kstd::string const &
+  auto device::name() const -> kstd::string const &
   {
     return m_name;
   }
 
-  auto device::set_parent(kstd::observer_ptr<bus> parent) -> void
+  auto device::parent() const -> kstd::shared_ptr<bus>
+  {
+    return m_parent.lock();
+  }
+
+  auto device::set_parent(kstd::weak_ptr<bus> parent) -> void
   {
     m_parent = parent;
   }