Permit multiple opens of #m/mousein.  Simplifies debugging, and allows for possibilities
like bluetooth mice or trackpads without disabling usb mouse.

Reference: /n/sources/patch/applied/mousein-non-excl
Date: Tue Dec 11 15:40:09 CET 2012
Signed-off-by: miller@hamnavoe.com

--- /sys/src/9/port/devmouse.c	Tue Dec 11 15:35:56 2012
+++ /sys/src/9/port/devmouse.c	Tue Dec 11 15:35:53 2012
@@ -44,7 +44,6 @@
 	Ref;
 	QLock;
 	int	open;
-	int	inopen;
 	int	acceleration;
 	int	maxacc;
 	Mousestate	queue[16];	/* circular buffer of click events */
@@ -202,13 +201,6 @@
 	case Qmousein:
 		if(!iseve())
 			error(Eperm);
-		lock(&mouse);
-		if(mouse.inopen){
-			unlock(&mouse);
-			error(Einuse);
-		}
-		mouse.inopen = 1;
-		unlock(&mouse);
 		break;
 	default:
 		incref(&mouse);
@@ -231,14 +223,11 @@
 mouseclose(Chan *c)
 {
 	if((c->qid.type&QTDIR)==0 && (c->flag&COPEN)){
+		if(c->qid.path == Qmousein)
+			return;
 		lock(&mouse);
 		if(c->qid.path == Qmouse)
 			mouse.open = 0;
-		else if(c->qid.path == Qmousein){
-			mouse.inopen = 0;
-			unlock(&mouse);
-			return;
-		}
 		if(--mouse.ref == 0){
 			cursoroff(1);
 			curs = arrow;
--- /sys/man/3/mouse	Tue Dec 11 15:35:59 2012
+++ /sys/man/3/mouse	Tue Dec 11 15:35:57 2012
@@ -62,7 +62,7 @@
 file.
 The
 .B mousein
-file, which is exclusive-use and may be opened
+file, which may be opened
 only by the host owner, is intended for controlling devices, such as USB mice,
 that are managed by user-level software.
 Each event should consist of