kapi/device: allow removing devices from busses

4 files changed, 140 insertions, 2 deletions

diff --git a/kapi/kapi/devices/bus.hpp b/kapi/kapi/devices/bus.hpp
index 26b46830..13951e46 100644
--- a/kapi/kapi/devices/bus.hpp
+++ b/kapi/kapi/devices/bus.hpp
@@ -37,6 +37,9 @@ namespace kapi::devices
     //! @param protocol The bus protocol to use.
     bus(kstd::string const & name, bus_protocol & protocol);
 
+    //! Tear down this bus recursively.
+    ~bus() override;
+
     //! Attach a child device to this bus.
     //!
     //! Whenever a device is attached to a bus, the bus takes sole ownership of the device.
@@ -44,6 +47,12 @@ namespace kapi::devices
     //! @param child The child device to attach.
     auto add_child(kstd::shared_ptr<device> child) -> void;
 
+    //! Detach a child device from this bus and tear it down.
+    //!
+    //! @param child The device to detach.
+    //! @return true iff. the child was found an removed, false otherwise.
+    auto remove_child(device & child) -> bool;
+
     //! Get the children attached to this bus.
     //!
     //! @return A vector of all children attached to this bus.
@@ -54,6 +63,8 @@ namespace kapi::devices
     auto query_facet(kapi::capabilities::facet_id facet) -> void * override;
 
   private:
+    auto do_remove_child(device & child) -> void;
+
     bus_protocol * m_protocol{};
     kstd::vector<kstd::shared_ptr<device>> m_devices{};
   };
diff --git a/kernel/kapi/devices.cpp b/kernel/kapi/devices.cpp
index 2505779a..f289bbf2 100644
--- a/kernel/kapi/devices.cpp
+++ b/kernel/kapi/devices.cpp
@@ -48,10 +48,10 @@ namespace kapi::test_support::devices
 {
   auto deinit() -> void
   {
+    kapi::devices::root_bus.reset();
+
     deinit_driver_registry();
     deinit_facet_registry();
     deinit_device_registry();
-
-    kapi::devices::root_bus.reset();
   }
 }  // namespace kapi::test_support::devices
\ No newline at end of file
diff --git a/kernel/kapi/devices/bus.cpp b/kernel/kapi/devices/bus.cpp
index dad90a15..d917eb96 100644
--- a/kernel/kapi/devices/bus.cpp
+++ b/kernel/kapi/devices/bus.cpp
@@ -9,6 +9,7 @@
 #include <kstd/string.hpp>
 #include <kstd/vector.hpp>
 
+#include <algorithm>
 #include <span>
 #include <utility>
 
@@ -23,6 +24,15 @@ namespace kapi::devices
       , m_protocol{&protocol}
   {}
 
+  bus::~bus()
+  {
+    auto children = m_devices;
+    for (auto const & child : children)
+    {
+      remove_child(*child);
+    }
+  }
+
   auto bus::add_child(kstd::shared_ptr<device> child) -> void
   {
     child->set_parent(kstd::static_pointer_cast<bus>(shared_from_this()));
@@ -32,12 +42,35 @@ namespace kapi::devices
       kapi::system::panic("[OS:DEV] Failed to register child device {}", child->name());
     }
 
+    // TODO: lock bus
+
     auto & attached = m_devices.emplace_back(std::move(child));
     attached->set_state(state::present);
 
+    // TODO: unlock bus
+
     driver_registry::get().device_attached(attached);
   }
 
+  auto bus::remove_child(device & device) -> bool  // NOLINT(misc-no-recursion)
+  {
+    // TODO: lock bus
+
+    auto found = std::ranges::find_if(m_devices, [&](auto const & d) { return d.get() == &device; });
+    if (!found)
+    {
+      return false;
+    }
+
+    auto lifeline = *found;
+    m_devices.erase(found);
+
+    // TODO: unlock bus
+
+    do_remove_child(*lifeline);
+    return true;
+  }
+
   [[nodiscard]] auto bus::children() const -> std::span<kstd::shared_ptr<device> const>
   {
     return {m_devices.data(), m_devices.size()};
@@ -57,4 +90,37 @@ namespace kapi::devices
     return device::query_facet(facet);
   }
 
+  auto bus::do_remove_child(device & device) -> void  // NOLINT(misc-no-recursion)
+  {
+    if (device.state() == state::removed)
+    {
+      return;
+    }
+
+    if (auto child_bus = device.facet<bus>())
+    {
+      auto grandchildren = kstd::vector<kstd::shared_ptr<kapi::devices::device>>{};
+      // TODO: lock child bus
+      // NOTE: this could be more efficient one vector::assign is implemented.
+      grandchildren = kstd::vector(child_bus->m_devices.begin(), child_bus->m_devices.end());
+      // TODO: unlock child bus
+
+      for (auto & grandchild : grandchildren)
+      {
+        child_bus->remove_child(*grandchild);
+      }
+    }
+
+    device.set_state(state::removed);
+
+    if (auto bound_driver = device.bound_driver())
+    {
+      bound_driver->unbind(device);
+    }
+
+    facet_registry::get().withdraw_all_for(device);
+    device_registry::get().remove(device);
+    device.set_parent(kstd::weak_ptr<bus>{});
+  }
+
 }  // namespace kapi::devices
\ No newline at end of file
diff --git a/kernel/kapi/devices/bus.tests.cpp b/kernel/kapi/devices/bus.tests.cpp
index 9f95513b..0a33df1a 100644
--- a/kernel/kapi/devices/bus.tests.cpp
+++ b/kernel/kapi/devices/bus.tests.cpp
@@ -92,3 +92,64 @@ SCENARIO("A bus shares ownership of its children, holding a weak link to its par
     }
   }
 }
+
+SCENARIO("Removing a child from a bus tears down the while subtree", "[devices][bus]")
+{
+  GIVEN("A bus with a child bus")
+  {
+    auto root = kstd::make_shared<test_bus>("bus_removal_root");
+    auto middle = kstd::make_shared<test_bus>("bus_removal_middle");
+    auto leaf_destroyed = false;
+    auto leaf = kstd::make_shared<flagging_device>("bus_removal_leaf", leaf_destroyed);
+
+    root->add_child(middle);
+    middle->add_child(leaf);
+
+    REQUIRE(root->children().size() == 1);
+    REQUIRE(middle->children().size() == 1);
+
+    WHEN("the middle bus is removed from the root")
+    {
+      REQUIRE(root->remove_child(*middle));
+
+      THEN("the middle bus's own subtree was torn down")
+      {
+        REQUIRE(middle->children().empty());
+      }
+
+      THEN("the leaf is marked as removed but not destroyed")
+      {
+        REQUIRE(leaf->state() == kapi::devices::state::removed);
+        REQUIRE(leaf->parent() == nullptr);
+        REQUIRE_FALSE(leaf_destroyed);
+      }
+
+      AND_WHEN("dropping the outside leaf reference")
+      {
+        leaf.reset();
+
+        THEN("the leaf is destroyed")
+        {
+          REQUIRE(leaf_destroyed);
+        }
+      }
+
+      THEN("the root no longer considers the middle its child")
+      {
+        REQUIRE(root->children().empty());
+        REQUIRE(middle->state() == kapi::devices::state::removed);
+      }
+    }
+  }
+
+  GIVEN("A bus and a device that was never actually attached to it")
+  {
+    auto bus = kstd::make_shared<test_bus>("bus_removal_unrelated_bus");
+    auto unrelated = kstd::make_shared<test_device>("bus_removal_unrelated_device");
+
+    THEN("removing the child fails")
+    {
+      REQUIRE_FALSE(bus->remove_child(*unrelated));
+    }
+  }
+}