From eeffe2ad97710ec7265de5ab020989c5731059c9 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Fri, 24 Jul 2026 10:35:34 +0200
Subject: kapi: generalize device interface resolution

---
 kernel/kapi/devices/device.cpp                   | 15 +++++++++++++++
 kernel/kapi/devices/interface_registry.cpp       | 23 +++++++++++++++++------
 kernel/kapi/devices/interface_registry.tests.cpp | 10 +++++-----
 3 files changed, 37 insertions(+), 11 deletions(-)

(limited to 'kernel/kapi/devices')

diff --git a/kernel/kapi/devices/device.cpp b/kernel/kapi/devices/device.cpp
index 4c63f6a4..3eb9aaac 100644
--- a/kernel/kapi/devices/device.cpp
+++ b/kernel/kapi/devices/device.cpp
@@ -12,6 +12,21 @@ namespace kapi::devices
       : m_name(name)
   {}
 
+  auto device::as(interface interface) noexcept -> void *
+  {
+    return query_interface(interface);
+  }
+
+  auto device::as(interface interface) const noexcept -> void const *
+  {
+    return const_cast<device *>(this)->query_interface(interface);
+  }
+
+  auto device::is_a(interface interface) const noexcept -> bool
+  {
+    return const_cast<device *>(this)->query_interface(interface) != nullptr;
+  }
+
   auto device::name() const -> kstd::string const &
   {
     return m_name;
diff --git a/kernel/kapi/devices/interface_registry.cpp b/kernel/kapi/devices/interface_registry.cpp
index d959c857..2ff42aa3 100644
--- a/kernel/kapi/devices/interface_registry.cpp
+++ b/kernel/kapi/devices/interface_registry.cpp
@@ -85,30 +85,41 @@ namespace kapi::devices
     return filtered;
   }
 
-  auto interface_registry::find(interface interface, std::string_view name) const -> kstd::result<entry>
+  auto interface_registry::resolve(interface interface, std::string_view name) -> void *
   {
     auto found = std::ranges::find_if(
         m_entries, [&](auto e) { return e.interface() == interface && e.name() == name && e.device(); });
+
     if (found == m_entries.cend())
     {
-      return kstd::failure(make_error_code(kstd::errc::no_such_device));
+      return nullptr;
+    }
+    else if (auto device = found->device())
+    {
+      return resolve(interface, *device);
     }
 
-    return *found;
+    return nullptr;
   }
 
-  auto interface_registry::find(interface interface, device const & device) const -> kstd::result<entry>
+  auto interface_registry::resolve(interface interface, device & device) -> void *
   {
+    if (auto by_device = device.as(interface))
+    {
+      return by_device;
+    }
+
     auto found = std::ranges::find_if(m_entries, [&](auto e) {
       auto locked_device = e.device();
       return e.interface() == interface && locked_device && locked_device.get() == &device;
     });
+
     if (found == m_entries.cend())
     {
-      return kstd::failure(make_error_code(kstd::errc::no_such_device));
+      return nullptr;
     }
 
-    return *found;
+    return found->implementation();
   }
 
 }  // namespace kapi::devices
diff --git a/kernel/kapi/devices/interface_registry.tests.cpp b/kernel/kapi/devices/interface_registry.tests.cpp
index 100954ea..f82e867e 100644
--- a/kernel/kapi/devices/interface_registry.tests.cpp
+++ b/kernel/kapi/devices/interface_registry.tests.cpp
@@ -133,23 +133,23 @@ SCENARIO("Publishing and finding a device", "[kapi][devices][interface_registry]
 
       THEN("find finds the published capability by name")
       {
-        REQUIRE(registry.find<probe_device>("probe0"));
+        REQUIRE(registry.resolve<probe_device>("probe0"));
       }
 
       THEN("find for an unpublished capability does not find a device")
       {
-        REQUIRE_FALSE(registry.find<const_device>("probe0"));
+        REQUIRE_FALSE(registry.resolve<const_device>("probe0"));
       }
 
       THEN("find for an unpublished device does not find a device")
       {
-        REQUIRE_FALSE(registry.find<probe_device>("probe1"));
+        REQUIRE_FALSE(registry.resolve<probe_device>("probe1"));
       }
 
       THEN("withdrawing an interface for a device removes it from the registry")
       {
         registry.unpublish(*device, probe_device::id);
-        REQUIRE_FALSE(registry.find<probe_device>("probe0"));
+        REQUIRE_FALSE(registry.resolve<probe_device>("probe0"));
       }
     }
 
@@ -165,7 +165,7 @@ SCENARIO("Publishing and finding a device", "[kapi][devices][interface_registry]
 
       THEN("find() no longer finds it")
       {
-        REQUIRE_FALSE(registry.find<probe_device>("probe0"));
+        REQUIRE_FALSE(registry.resolve<probe_device>("probe0"));
       }
     }
   }
-- 
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