From 526709a1e86d55dd88e2dbdbc471795efce9046b Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Thu, 23 Jul 2026 01:38:56 +0200
Subject: kapi: bootstrap owning device tree

---
 kapi/kapi/devices.hpp         |  4 ++--
 kapi/kapi/devices/bus.hpp     |  8 ++++----
 kapi/kapi/devices/device.hpp  | 11 ++++++++---
 kapi/kapi/devices/manager.hpp |  6 +++---
 4 files changed, 17 insertions(+), 12 deletions(-)

(limited to 'kapi')

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>;
 
   //! @}
 
-- 
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