RISCOS: Add a native MIDI driver

backends/midi/riscos.cpp

@@ -0,0 +1,174 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+// Disable symbol overrides so that we can use system headers.
+#define FORBIDDEN_SYMBOL_ALLOW_ALL
+
+#include "common/scummsys.h"
+
+#ifdef RISCOS
+
+#include "common/error.h"
+#include "common/textconsole.h"
+#include "audio/musicplugin.h"
+#include "audio/mpu401.h"
+
+#include <kernel.h>
+#include <swis.h>
+
+#ifndef MIDI_TxByte
+#define MIDI_TxByte 0x404C9
+#endif
+#ifndef MIDI_TxCommand
+#define MIDI_TxCommand 0x404CA
+#endif
+
+
+class MidiDriver_RISCOS final : public MidiDriver_MPU401 {
+public:
+	MidiDriver_RISCOS(int port = 0) : _isOpen(false), _port(port) {}
+	~MidiDriver_RISCOS() {}
+
+	int open() override;
+	bool isOpen() const override { return _isOpen; }
+	void close() override;
+	void send(uint32 b) override;
+	void sysEx(const byte *msg, uint16 length) override;
+
+private:
+	_kernel_oserror *txByte(int r0);
+	_kernel_oserror *txCommand(int r0, int r1);
+
+	bool _isOpen;
+	int _port;
+};
+
+int MidiDriver_RISCOS::open() {
+	if (isOpen())
+		return MERR_ALREADY_OPEN;
+
+	_isOpen = true;
+	return 0;
+}
+
+void MidiDriver_RISCOS::close() {
+	MidiDriver_MPU401::close();
+	_isOpen = false;
+}
+
+void MidiDriver_RISCOS::send(uint32 b) {
+	assert(isOpen());
+
+	midiDriverCommonSend(b);
+
+	// Extract the MIDI data
+	byte status_byte = (b & 0x000000FF);
+	// byte first_byte = (b & 0x0000FF00) >> 8;
+	// byte second_byte = (b & 0x00FF0000) >> 16;
+
+	// Compute the correct length of the MIDI command. This is important,
+	// else things may screw up badly...
+	byte length;
+	switch (status_byte & 0xF0) {
+	case 0x80:	// Note Off
+	case 0x90:	// Note On
+	case 0xA0:	// Polyphonic Aftertouch
+	case 0xB0:	// Controller Change
+	case 0xE0:	// Pitch Bending
+		length = 3;
+		break;
+	case 0xC0:	// Programm Change
+	case 0xD0:	// Monophonic Aftertouch
+		length = 2;
+		break;
+	default:
+		warning("RISC OS driver encountered unsupported status byte: 0x%02x", status_byte);
+		length = 3;
+		break;
+	}
+
+	// Finally send it out to the synthesizer.
+	txCommand(b | (length << 24) | (_port << 28), 0);
+}
+
+void MidiDriver_RISCOS::sysEx(const byte *msg, uint16 length) {
+	assert(isOpen());
+
+	int port = (_port << 28);
+
+	txByte(0xF0 | port);
+	for (; length; --length, ++msg) {
+		txByte(*msg | port);
+	}
+	txByte(0xF7 | port);
+}
+
+_kernel_oserror *MidiDriver_RISCOS::txByte(int r0) {
+	_kernel_swi_regs regs;
+	regs.r[0] = r0;
+	return _kernel_swi(MIDI_TxByte, &regs, &regs);
+}
+
+_kernel_oserror *MidiDriver_RISCOS::txCommand(int r0, int r1) {
+	_kernel_swi_regs regs;
+	regs.r[0] = r0;
+	regs.r[1] = r1;
+	return _kernel_swi(MIDI_TxCommand, &regs, &regs);
+}
+
+
+// Plugin interface
+
+class RISCOSMusicPlugin : public MusicPluginObject {
+public:
+	const char *getName() const {
+		return "RISC OS MIDI";
+	}
+
+	const char *getId() const {
+		return "riscos";
+	}
+
+	MusicDevices getDevices() const;
+	Common::Error createInstance(MidiDriver **mididriver, MidiDriver::DeviceHandle = 0) const;
+};
+
+MusicDevices RISCOSMusicPlugin::getDevices() const {
+	MusicDevices devices;
+	// TODO: Return a different music type depending on the configuration
+	// TODO: List the available devices
+	devices.push_back(MusicDevice(this, "", MT_GM));
+	return devices;
+}
+
+Common::Error RISCOSMusicPlugin::createInstance(MidiDriver **mididriver, MidiDriver::DeviceHandle device) const {
+	*mididriver = new MidiDriver_RISCOS();
+
+	return Common::kNoError;
+}
+
+//#if PLUGIN_ENABLED_DYNAMIC(RISCOS)
+	//REGISTER_PLUGIN_DYNAMIC(RISCOS, PLUGIN_TYPE_MUSIC, RISCOSMusicPlugin);
+//#else
+	REGISTER_PLUGIN_STATIC(RISCOS, PLUGIN_TYPE_MUSIC, RISCOSMusicPlugin);
+//#endif
+
+#endif // RISCOS

backends/module.mk

@@ -275,6 +275,7 @@ MODULE_OBJS += \
 	events/riscossdl/riscossdl-events.o \
 	fs/riscos/riscos-fs.o \
 	fs/riscos/riscos-fs-factory.o \
+	midi/riscos.o \
 	plugins/riscos/riscos-provider.o
 ifndef SDL_BACKEND
 # This is needed for null backend but already included in SDL backend

base/plugins.cpp

@@ -130,6 +130,9 @@ public:
 		#if defined(__amigaos4__) || defined(__MORPHOS__)
 		LINK_PLUGIN(CAMD)
 		#endif
+		#if defined(RISCOS)
+		LINK_PLUGIN(RISCOS)
+		#endif
 		#if defined(MACOSX)
 		LINK_PLUGIN(COREAUDIO)
 		LINK_PLUGIN(COREMIDI)