black_hole: provide Event service

Fixes #4419

repos/os/recipes/pkg/black_hole/runtime

@@ -4,12 +4,14 @@
 		<audio_in/>
 		<audio_out/>
 		<capture/>
+		<event/>
 	</provides>
 
 	<config>
 		<audio_in/>
 		<audio_out/>
 		<capture/>
+		<event/>
 	</config>
 
 	<content>

repos/os/recipes/src/black_hole/used_apis

@@ -2,4 +2,5 @@ base
 audio_in_session
 audio_out_session
 capture_session
+event_session
 os

repos/os/src/server/black_hole/README

@@ -7,9 +7,11 @@ in the configuration of the component:
 * Audio_in
 * Audio_out
 * Capture
+* Event
 
 <config>
 	<audio_in/>
 	<audio_out/>
 	<capture/>
+	<event/>
 </config>

repos/os/src/server/black_hole/event.h

@@ -0,0 +1,102 @@
+/*
+ * \brief  Event session component and root
+ * \author Martin Stein
+ * \date   2021-12-20
+ */
+
+/*
+ * Copyright (C) 2021 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _EVENT_H_
+#define _EVENT_H_
+
+/* Genode includes */
+#include <base/session_object.h>
+#include <event_session/event_session.h>
+
+namespace Black_hole {
+
+	using namespace Genode;
+
+	class Event_session;
+	class Event_root;
+}
+
+
+class Black_hole::Event_session
+:
+public Session_object<Event::Session, Event_session>
+{
+	private:
+
+		Constrained_ram_allocator _ram;
+
+		Attached_ram_dataspace _ds;
+
+	public:
+
+		Event_session(Env              &env,
+		              Resources  const &resources,
+		              Label      const &label,
+		              Diag       const &diag)
+		:
+			Session_object(env.ep(), resources, label, diag),
+			_ram(env.ram(), _ram_quota_guard(), _cap_quota_guard()),
+			_ds(_ram, env.rm(), 4096)
+		{ }
+
+		~Event_session() { }
+
+
+		/*****************************
+		 ** Event session interface **
+		 *****************************/
+
+		Dataspace_capability dataspace() { return _ds.cap(); }
+
+		void submit_batch(unsigned const /* count */) { }
+};
+
+
+class Black_hole::Event_root : public Root_component<Event_session>
+{
+	private:
+
+		Env &_env;
+
+	protected:
+
+		Event_session *_create_session(const char *args) override
+		{
+			return new (md_alloc())
+				Event_session(_env,
+				              session_resources_from_args(args),
+				              session_label_from_args(args),
+				              session_diag_from_args(args));
+		}
+
+		void _upgrade_session(Event_session *s, const char *args) override
+		{
+			s->upgrade(ram_quota_from_args(args));
+			s->upgrade(cap_quota_from_args(args));
+		}
+
+		void _destroy_session(Event_session *session) override
+		{
+			Genode::destroy(md_alloc(), session);
+		}
+
+	public:
+
+		Event_root(Env &env, Allocator &md_alloc)
+		:
+			Root_component<Event_session>(&env.ep().rpc_ep(), &md_alloc),
+			_env(env)
+		{ }
+};
+
+#endif /* _EVENT_H_ */

repos/os/src/server/black_hole/main.cc

@@ -24,6 +24,7 @@
 #include "audio_in.h"
 #include "audio_out.h"
 #include "capture.h"
+#include "event.h"
 
 
 /***************
@@ -41,6 +42,7 @@ struct Black_hole::Main
 	Genode::Constructible<Audio_in::Root>  audio_in_root  { };
 	Genode::Constructible<Audio_out::Root> audio_out_root { };
 	Genode::Constructible<Capture::Root>   capture_root   { };
+	Genode::Constructible<Event_root>      event_root     { };
 
 	Main(Genode::Env &env) : env(env)
 	{
@@ -60,6 +62,10 @@ struct Black_hole::Main
 			capture_root.construct(env, heap);
 			env.parent().announce(env.ep().manage(*capture_root));
 		}
+		if (_config_rom.xml().has_sub_node("event")) {
+			event_root.construct(env, heap);
+			env.parent().announce(env.ep().manage(*event_root));
+		}
 	}
 };