[PATCH] parport: daisy chain end detection fix

Daisy chain end detection failed at least with older daisy chain devices that
do not implement the last device signal.
Signed-off-by: Marko Kohtala <marko.kohtala@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/parport/daisy.c

@@ -436,7 +436,7 @@ static int select_port (struct parport *port)
 
 static int assign_addrs (struct parport *port)
 {
-	unsigned char s, last_dev;
+	unsigned char s;
 	unsigned char daisy;
 	int thisdev = numdevs;
 	int detected;
@@ -472,10 +472,13 @@ static int assign_addrs (struct parport *port)
 	}
 
 	parport_write_data (port, 0x78); udelay (2);
-	last_dev = 0; /* We've just been speaking to a device, so we
-			 know there must be at least _one_ out there. */
+	s = parport_read_status (port);
 
-	for (daisy = 0; daisy < 4; daisy++) {
+	for (daisy = 0;
+	     (s & (PARPORT_STATUS_PAPEROUT|PARPORT_STATUS_SELECT))
+		     == (PARPORT_STATUS_PAPEROUT|PARPORT_STATUS_SELECT)
+		     && daisy < 4;
+	     ++daisy) {
 		parport_write_data (port, daisy);
 		udelay (2);
 		parport_frob_control (port,
@@ -485,14 +488,18 @@ static int assign_addrs (struct parport *port)
 		parport_frob_control (port, PARPORT_CONTROL_STROBE, 0);
 		udelay (1);
 
-		if (last_dev)
-			/* No more devices. */
-			break;
+		add_dev (numdevs++, port, daisy);
 
-		last_dev = !(parport_read_status (port)
-			     & PARPORT_STATUS_BUSY);
+		/* See if this device thought it was the last in the
+		 * chain. */
+		if (!(s & PARPORT_STATUS_BUSY))
+			break;
 
-		add_dev (numdevs++, port, daisy);
+		/* We are seeing pass through status now. We see
+		   last_dev from next device or if last_dev does not
+		   work status lines from some non-daisy chain
+		   device. */
+		s = parport_read_status (port);
 	}
 
 	parport_write_data (port, 0xff); udelay (2);