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.

1 files changed, 154 insertions, 0 deletions

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