AUDIO: add support for OPL2LPT

The OPL2LPT is an OPL2 chip plugged on a parallel port. It is
write-only but otherwise acts as a classic AdLib. This commit adds
support for this device.

User is expected to have the right permissions on the parallel
port. By default, the first suitable parallel port is used. It is
possible to override that with the hidden configuration setting
"opl2lpt_parport".

It depends on the presence of the libieee1284 library which abstracts
a bit parallel port handling. An alternative would be to access
directly /dev/parportX on Linux. This would amount of code but it
would be Linux-only.

Tested with Indy 3 and SOMI.

3 files changed, 179 insertions, 1 deletions

diff --git a/audio/fmopl.cpp b/audio/fmopl.cpp
index 3756d98123..3a003c80d9 100644
--- a/audio/fmopl.cpp
+++ b/audio/fmopl.cpp
@@ -43,6 +43,12 @@ namespace ALSA {
 } // End of namespace ALSA
 #endif // USE_ALSA
 
+#ifdef ENABLE_OPL2LPT
+namespace OPL2LPT {
+	OPL *create();
+} // End of namespace OPL2LPT
+#endif // ENABLE_OPL2LPT
+
 // Config implementation
 
 enum OplEmulator {
@@ -50,7 +56,8 @@ enum OplEmulator {
 	kMame = 1,
 	kDOSBox = 2,
 	kALSA = 3,
-	kNuked = 4
+	kNuked = 4,
+	kOPL2LPT = 5
 };
 
 OPL::OPL() {
@@ -71,6 +78,9 @@ const Config::EmulatorDescription Config::_drivers[] = {
 #ifdef USE_ALSA
 	{ "alsa", _s("ALSA Direct FM"), kALSA, kFlagOpl2 | kFlagDualOpl2 | kFlagOpl3 },
 #endif
+#ifdef ENABLE_OPL2LPT
+	{ "opl2lpt", _s("OPL2LPT"), kOPL2LPT, kFlagOpl2 },
+#endif
 	{ 0, 0, 0, 0 }
 };
 
@@ -193,6 +203,15 @@ OPL *Config::create(DriverId driver, OplType type) {
 		return ALSA::create(type);
 #endif
 
+#ifdef ENABLE_OPL2LPT
+	case kOPL2LPT:
+		if (type == kOpl2)
+			return OPL2LPT::create();
+		else
+			warning("OPL2LPT only supports OPL2");
+		return 0;
+#endif
+
 	default:
 		warning("Unsupported OPL emulator %d", driver);
 		// TODO: Maybe we should add some dummy emulator too, which just outputs
diff --git a/audio/module.mk b/audio/module.mk
index 4f296ba0e1..49584aba90 100644
--- a/audio/module.mk
+++ b/audio/module.mk
@@ -72,6 +72,11 @@ MODULE_OBJS += \
 	alsa_opl.o
 endif
 
+ifdef ENABLE_OPL2LPT
+MODULE_OBJS += \
+	opl2lpt.o
+endif
+
 ifndef USE_ARM_SOUND_ASM
 MODULE_OBJS += \
 	rate.o
diff --git a/audio/opl2lpt.cpp b/audio/opl2lpt.cpp
new file mode 100644
index 0000000000..fc5a4ef465
--- /dev/null
+++ b/audio/opl2lpt.cpp
@@ -0,0 +1,154 @@
+/* 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 2
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+/* OPL implementation for OPL2LPT through libieee1284.
+ */
+
+#define FORBIDDEN_SYMBOL_ALLOW_ALL
+#include "common/scummsys.h"
+
+#include "common/config-manager.h"
+#include "common/debug.h"
+#include "common/str.h"
+#include "common/textconsole.h"
+#include "audio/fmopl.h"
+
+#include <unistd.h>
+#include <ieee1284.h>
+
+namespace OPL {
+namespace OPL2LPT {
+
+class OPL : public ::OPL::RealOPL {
+private:
+	struct parport *_pport;
+	int index;
+	static const uint8 ctrlBytes[];
+
+public:
+	OPL();
+	~OPL();
+
+	bool init();
+	void reset();
+
+	void write(int a, int v);
+	byte read(int a);
+
+	void writeReg(int r, int v);
+};
+
+const uint8 OPL::ctrlBytes[] = {
+	(C1284_NSELECTIN | C1284_NSTROBE | C1284_NINIT) ^ C1284_INVERTED,
+	(C1284_NSELECTIN | C1284_NSTROBE) ^ C1284_INVERTED,
+	(C1284_NSELECTIN | C1284_NSTROBE | C1284_NINIT) ^ C1284_INVERTED,
+
+	(C1284_NSELECTIN | C1284_NINIT) ^ C1284_INVERTED,
+	C1284_NSELECTIN ^ C1284_INVERTED,
+	(C1284_NSELECTIN | C1284_NINIT) ^ C1284_INVERTED
+};
+
+OPL::OPL() : _pport(nullptr) {
+}
+
+OPL::~OPL() {
+	if (_pport) {
+		stop();
+		reset();
+		ieee1284_close(_pport);
+	}
+}
+
+bool OPL::init() {
+	struct parport_list parports = {};
+	const Common::String parportName = ConfMan.get("opl2lpt_parport");
+
+	// Look for available parallel ports
+	if (ieee1284_find_ports(&parports, 0) != E1284_OK) {
+		return false;
+	}
+	for (int i = 0; i < parports.portc; i++) {
+		if (parportName == "null" ||
+		    parportName == parports.portv[i]->name) {
+			int caps = CAP1284_RAW;
+			_pport = parports.portv[i];
+			if (ieee1284_open(_pport, F1284_EXCL, &caps) != E1284_OK) {
+				warning("cannot open parallel port %s", _pport->name);
+			}
+			if (ieee1284_claim(_pport) != E1284_OK) {
+				warning("cannot claim parallel port %s", _pport->name);
+				ieee1284_close(_pport);
+				continue;
+			}
+			reset();
+			// Safe to free ports here, opened ports are refcounted.
+			ieee1284_free_ports(&parports);
+			return true;
+		}
+	}
+	_pport = nullptr;
+	ieee1284_free_ports(&parports);
+	return false;
+}
+
+void OPL::reset() {
+	for(int i = 0; i < 256; i ++) {
+		writeReg(i, 0);
+	}
+	index = 0;
+}
+
+void OPL::write(int port, int val) {
+	if (port & 1) {
+		writeReg(index, val);
+	} else {
+		index = val;
+	}
+}
+
+byte OPL::read(int port) {
+	// No read support for the OPL2LPT
+	return 0;
+}
+
+void OPL::writeReg(int r, int v) {
+	r &= 0xff;
+	v &= 0xff;
+	ieee1284_write_data(_pport, r);
+	ieee1284_write_control(_pport, ctrlBytes[0]);
+	ieee1284_write_control(_pport, ctrlBytes[1]);
+	ieee1284_write_control(_pport, ctrlBytes[2]);
+	usleep(4);		// 3.3 us
+
+	ieee1284_write_data(_pport, v);
+	ieee1284_write_control(_pport, ctrlBytes[3]);
+	ieee1284_write_control(_pport, ctrlBytes[4]);
+	ieee1284_write_control(_pport, ctrlBytes[5]);
+	usleep(23);
+}
+
+OPL *create() {
+	return new OPL();
+}
+
+} // End of namespace OPL2LPT
+} // End of namespace OPL