From cdc9c5bf0932e07ed1a19bd7315bad79a2a41b4c Mon Sep 17 00:00:00 2001
From: michael <michael>
Date: Mon, 2 Apr 2007 08:22:08 +0000
Subject: [PATCH] Add hack to force the detection of a parallel cable by Stefan
 Ziegenbalg. This hack is activated by preloading libusb-driver-trenz.so.

---
 Makefile     | 15 ++++++++++-----
 README       |  5 +++++
 usb-driver.c | 11 ++++++++++-
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 4ef6aba..3325a89 100644
--- a/Makefile
+++ b/Makefile
@@ -1,14 +1,19 @@
-CFLAGS=-Wall
+CFLAGS=-Wall -fPIC
 
-all: libusb-driver.so libusb-driver-DEBUG.so
+SOBJECTS=libusb-driver.so libusb-driver-DEBUG.so libusb-driver-trenz.so
+
+all: $(SOBJECTS)
 
 libusb-driver.so: usb-driver.c usb-driver.h
-	gcc -fPIC $(CFLAGS) $< -o $@ -ldl -lusb -lpthread -shared
+	gcc $(CFLAGS) $< -o $@ -ldl -lusb -lpthread -shared
+
+libusb-driver-trenz.so: usb-driver.c usb-driver.h
+	gcc -DTRENZ $(CFLAGS) $< -o $@ -ldl -lusb -lpthread -shared
 
 libusb-driver-DEBUG.so: usb-driver.c usb-driver.h
-	gcc -fPIC -DDEBUG $(CFLAGS) $< -o $@ -ldl -lusb -lpthread -shared
+	gcc -DDEBUG $(CFLAGS) $< -o $@ -ldl -lusb -lpthread -shared
 
 clean:
-	rm -f libusb-driver.so libusb-driver-DEBUG.so
+	rm -f $(SOBJECTS)
 
 .PHONY: clean all
diff --git a/README b/README
index 13737b5..fcf211a 100644
--- a/README
+++ b/README
@@ -72,6 +72,11 @@ ppdev
 To use the device as an ordinary user, put the user in the group 'lp'
 
 
+If you have an almost compatible cable which works with other software but not
+with Impact, try preloading libusb-driver-trenz.so instead of libusb-driver.so.
+It includes a hack by Stefan Ziegenbalg to force detection of a parallel cable.
+
+
 Parallel Cable IV is currently only supported in 'compatibility mode', as no
 attempt to configure the ECP registers is done by this library.
 
diff --git a/usb-driver.c b/usb-driver.c
index fa2611e..c497b50 100644
--- a/usb-driver.c
+++ b/usb-driver.c
@@ -241,6 +241,7 @@ int pp_transfer(WD_TRANSFER *tr, int fd, unsigned int request, unsigned char *wd
 	int ret = 0;
 	unsigned long port = (unsigned long)tr->dwPort;
 	unsigned char val;
+	static int last_pp_write = 0;
 
 	DPRINTF("dwPort: 0x%lx, cmdTrans: %lu, dwbytes: %ld, fautoinc: %ld, dwoptions: %ld\n",
 			(unsigned long)tr->dwPort, tr->cmdTrans, tr->dwBytes,
@@ -268,6 +269,7 @@ int pp_transfer(WD_TRANSFER *tr, int fd, unsigned int request, unsigned char *wd
 
 			case PP_WRITE:
 				ret = ioctl(parportfd, PPWDATA, &val);
+				last_pp_write = val;
 				break;
 
 			default:
@@ -276,10 +278,17 @@ int pp_transfer(WD_TRANSFER *tr, int fd, unsigned int request, unsigned char *wd
 				break;
 		}
 	} else if (port == ppbase + PP_STATUS) {
-		DPRINTF("status port\n");
+		DPRINTF("status port (last write: %d)\n", last_pp_write);
 		switch(tr->cmdTrans) {
 			case PP_READ:
 				ret = ioctl(parportfd, PPRSTATUS, &val);
+#ifdef TRENZ
+				val &= 95;
+				if (last_pp_write & 64)
+					val |= 32;
+				else
+					val |= 128;
+#endif
 				break;
 
 			case PP_WRITE:
-- 
2.39.2