black_hole: initial support for Usb service

The service is merely announced but trying to request a session always causes a
Service_denied exception. This helps in scenarios where the client is
won't open a session anyway but expects the service to be available. This is
considered a temporary solution.

Ref #4419

repos/os/recipes/pkg/black_hole/runtime

@@ -9,6 +9,7 @@
 		<uplink/>
 		<rom/>
 		<gpu/>
+		<usb/>
 	</provides>
 
 	<config>
@@ -20,6 +21,7 @@
 		<uplink/>
 		<rom/>
 		<gpu/>
+		<usb/>
 	</config>
 
 	<content>

repos/os/recipes/pkg/test-black_hole/runtime

@@ -30,6 +30,7 @@
 		<start name="black_hole" caps="100">
 			<resource name="RAM" quantum="1M"/>
 			<provides>
+				<service name="Usb"/>
 				<service name="Gpu"/>
 				<service name="ROM"/>
 				<service name="Uplink"/>
@@ -40,6 +41,7 @@
 				<service name="Audio_out"/>
 			</provides>
 			<config>
+				<usb/>
 				<gpu/>
 				<rom/>
 				<uplink/>
@@ -61,6 +63,7 @@
 		<start name="test-black_hole" caps="200">
 			<resource name="RAM" quantum="10M"/>
 			<route>
+				<service name="Usb">                   <child name="black_hole"/> </service>
 				<service name="Gpu">                   <child name="black_hole"/> </service>
 				<service name="ROM" label="any_label"> <child name="black_hole"/> </service>
 				<service name="Uplink">                <child name="black_hole"/> </service>

repos/os/recipes/src/black_hole/used_apis

@@ -6,4 +6,5 @@ event_session
 nic_session
 uplink_session
 gpu_session
+usb_session
 os

repos/os/recipes/src/test-black_hole/used_apis

@@ -8,3 +8,4 @@ capture_session
 nic_session
 uplink_session
 gpu_session
+usb_session

repos/os/src/server/black_hole/README

@@ -12,6 +12,7 @@ in the configuration of the component:
 * Uplink
 * ROM
 * Gpu
+* Usb
 
 <config>
 	<audio_in/>
@@ -22,4 +23,9 @@ in the configuration of the component:
 	<uplink/>
 	<rom/>
 	<gpu/>
+	<usb/>
 </config>
+
+Be aware, that the USB service is merely announced but always throws a
+Service_denied exception when trying to request a session. This is considered
+a temporary solution.

repos/os/src/server/black_hole/config.xsd

@@ -4,6 +4,7 @@
 	<xs:element name="config">
 		<xs:complexType>
 			<xs:choice minOccurs="0" maxOccurs="unbounded">
+				<xs:element name="usb"/>
 				<xs:element name="gpu"/>
 				<xs:element name="rom"/>
 				<xs:element name="uplink"/>

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

@@ -29,6 +29,7 @@
 #include "uplink.h"
 #include "rom.h"
 #include "gpu.h"
+#include "usb.h"
 
 
 /***************
@@ -51,6 +52,7 @@ struct Black_hole::Main
 	Genode::Constructible<Uplink_root>     uplink_root    { };
 	Genode::Constructible<Rom_root>        rom_root       { };
 	Genode::Constructible<Gpu_root>        gpu_root       { };
+	Genode::Constructible<Usb_root>        usb_root       { };
 
 	Main(Genode::Env &env) : env(env)
 	{
@@ -88,6 +90,10 @@ struct Black_hole::Main
 			gpu_root.construct(env, heap);
 			env.parent().announce(env.ep().manage(*gpu_root));
 		}
+		if (_config_rom.xml().has_sub_node("usb")) {
+			usb_root.construct(env, heap);
+			env.parent().announce(env.ep().manage(*usb_root));
+		}
 	}
 };
 

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

@@ -0,0 +1,96 @@
+/*
+ * \brief  Usb session component and root
+ * \author Martin Stein
+ * \date   2022-02-12
+ */
+
+/*
+ * Copyright (C) 2022 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 _USB_H_
+#define _USB_H_
+
+/* base includes */
+#include <root/component.h>
+
+/* os includes */
+#include <usb_session/rpc_object.h>
+
+namespace Black_hole {
+
+	using namespace Genode;
+	using namespace Usb;
+
+	class Usb_session;
+	class Usb_root;
+}
+
+
+class Black_hole::Usb_session : public Usb::Session_rpc_object
+{
+	public:
+
+		void sigh_state_change(Signal_context_capability /* sigh */) override { }
+
+		bool plugged() override { return false; }
+
+		void config_descriptor(Device_descriptor * /* device_descr */,
+		                       Config_descriptor * /* config_descr */) override { }
+
+		unsigned alt_settings(unsigned /* index */) override { return 0; }
+
+		void interface_descriptor(unsigned               /* index */,
+		                          unsigned               /* alt_setting */,
+		                          Interface_descriptor * /* interface_descr */) override { }
+
+		bool interface_extra(unsigned          /* index */,
+		                     unsigned          /* alt_setting */,
+		                     Interface_extra * /* interface_data */) override { return false; }
+
+		void endpoint_descriptor(unsigned               /* interface_num */,
+		                         unsigned               /* alt_setting */,
+		                         unsigned               /* endpoint_num */,
+		                         Endpoint_descriptor  * /* endpoint_descr */) override { }
+
+		void claim_interface(unsigned /* interface_num */) override { }
+
+		void release_interface(unsigned /* interface_num */) override { }
+};
+
+
+class Black_hole::Usb_root : public Root_component<Usb_session>
+{
+	private:
+
+		Env &_env;
+
+	protected:
+
+		Usb_session *_create_session(char const * /* args */) override
+		{
+			/*
+			 * FIXME
+			 *
+			 * Currently, we're fine with a service that is routable but
+			 * not usable. In the long term, this exception should be removed
+			 * and a session object should be returned that can be used as if
+			 * it was a real USB session.
+			 */
+			throw Service_denied { };
+		}
+
+	public:
+
+		Usb_root(Env       &env,
+		         Allocator &alloc)
+		:
+			Root_component { env.ep(), alloc },
+			_env           { env }
+		{ }
+};
+
+#endif /* _USB_H_ */

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

@@ -25,6 +25,7 @@
 /* os includes */
 #include <gpu_session/connection.h>
 #include <event_session/connection.h>
+#include <usb_session/connection.h>
 #include <capture_session/connection.h>
 #include <audio_in_session/connection.h>
 #include <audio_out_session/connection.h>
@@ -41,6 +42,7 @@ namespace Black_hole_test {
 	class Uplink_test;
 	class Capture_test;
 	class Event_test;
+	class Usb_test;
 	class Rom_test;
 	class Main;
 }
@@ -328,6 +330,41 @@ class Black_hole_test::Rom_test
 };
 
 
+class Black_hole_test::Usb_test
+{
+	private:
+
+		Env           &_env;
+		Allocator_avl  _alloc;
+		bool           _finished  { false };
+
+	public:
+
+		Usb_test(Env  &env,
+		         Heap &heap)
+		:
+			_env   { env },
+			_alloc { &heap }
+		{
+			try {
+				Usb::Connection connection { _env, &_alloc };
+				class Session_request_succeeded { };
+				throw Session_request_succeeded { };
+
+			} catch (Service_denied) {
+
+				_finished = true;
+			}
+		}
+
+		bool finished() const
+		{
+			return _finished;
+		}
+};
+
+
+
 class Black_hole_test::Main
 {
 	private:
@@ -342,6 +379,7 @@ class Black_hole_test::Main
 		Uplink_test            _uplink_test    { _env, _heap, _signal_handler };
 		Capture_test           _capture_test   { _env };
 		Event_test             _event_test     { _env };
+		Usb_test               _usb_test       { _env, _heap };
 		Rom_test               _rom_test       { _env };
 
 		void _handle_signal()
@@ -357,6 +395,7 @@ class Black_hole_test::Main
 			    _uplink_test.finished() &&
 			    _capture_test.finished() &&
 			    _event_test.finished() &&
+			    _usb_test.finished() &&
 			    _rom_test.finished()) {
 
 				log("Finished");