kapi: introduce the "bus" facet

2 files changed, 21 insertions, 0 deletions

diff --git a/kapi/kapi/devices/bus.hpp b/kapi/kapi/devices/bus.hpp
index af9f2c33..2a306031 100644
--- a/kapi/kapi/devices/bus.hpp
+++ b/kapi/kapi/devices/bus.hpp
@@ -4,6 +4,7 @@
 // IWYU pragma: private, include <kapi/devices.hpp>
 
 #include <kapi/devices/device.hpp>
+#include <kapi/devices/interface_id.hpp>
 
 #include <kstd/memory.hpp>
 #include <kstd/print.hpp>
@@ -21,6 +22,9 @@ namespace kapi::devices
   //! A bus device that represents a logical/physical tree of devices and busses.
   struct bus : device
   {
+    //! The id of the bus facet.
+    constexpr auto static id = interface_id{"bus"};
+
     //! Construct a bus with the given name.
     //!
     //! @param name The name of the bus.
@@ -33,6 +37,9 @@ namespace kapi::devices
     //! @param child The child device to attach.
     auto add_child(kstd::shared_ptr<device> child) -> void;
 
+    //! Get the children attached to this bus.
+    //!
+    //! @return A vector of all children attached to this bus.
     [[nodiscard]] auto children() const -> std::span<kstd::shared_ptr<device> const>;
 
     //! Get this bus's protocol facet, if present.
@@ -40,6 +47,10 @@ namespace kapi::devices
     //! @return this bus's protocol facet if it has one, nullptr otherwise.
     [[nodiscard]] virtual auto protocol() -> struct bus_protocol *;
 
+  protected:
+    //! All busses have the "bus" facet.
+    auto query_interface(interface_id interface) -> void * override;
+
   private:
     kstd::vector<kstd::shared_ptr<device>> m_devices;
   };
diff --git a/kernel/kapi/devices/bus.cpp b/kernel/kapi/devices/bus.cpp
index 1b3ad4bf..a9bba4fb 100644
--- a/kernel/kapi/devices/bus.cpp
+++ b/kernel/kapi/devices/bus.cpp
@@ -42,4 +42,14 @@ namespace kapi::devices
     return nullptr;
   }
 
+  auto bus::query_interface(interface_id interface) -> void *
+  {
+    if (interface == bus::id)
+    {
+      return this;
+    }
+
+    return device::query_interface(interface);
+  }
+
 }  // namespace kapi::devices
\ No newline at end of file