don't time out prolific i/o.  (should do for all serial types?)

when rts/cts are used, i/o can hang forever.  this is not a problem.
this is expected.

Reference: /n/atom/patch/applied/usbprolificnotmout
Date: Sat Apr 19 16:05:59 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/usb/serial/prolific.c	Sat Apr 19 16:05:01 2014
+++ /sys/src/cmd/usb/serial/prolific.c	Sat Apr 19 16:05:01 2014
@@ -348,32 +348,28 @@
 static int
 plreadstatus(Serialport *p)
 {
-	int nr, dfd;
+	int nr;
 	char err[ERRMAX];
 	uchar buf[VendorReqSz];
 	Serial *ser;
 
 	ser = p->s;
+	nr = read(p->epintr->dfd, buf, sizeof buf);
 
 	qlock(ser);
-	dsprint(2, "serial: reading from interrupt\n");
-	dfd = p->epintr->dfd;
+	dsprint(2, "serial: interrupt read %d\n", nr);
 
-	qunlock(ser);
-	nr = read(dfd, buf, sizeof buf);
-	qlock(ser);
-	snprint(err, sizeof err, "%r");
-	dsprint(2, "serial: interrupt read %d %r\n", nr);
-
-	if(nr < 0 && strstr(err, "timed out") == nil){
-		dsprint(2, "serial: need to recover, status read %d %r\n", nr);
-		if(serialrecover(ser, nil, nil, err) < 0){
-			qunlock(ser);
-			return -1;
+	if(nr < 0){
+		snprint(err, sizeof err, "%r");
+		dsprint(2, "serial: reading status: %s", err);
+		if(nr < 0 && strstr(err, "timed out") == nil){
+			dsprint(2, "serial: need to recover, status read %d %s\n", nr, err);
+			if(serialrecover(ser, nil, nil, err) < 0){
+				qunlock(ser);
+				return -1;
+			}
 		}
 	}
-	if(nr < 0)
-		dsprint(2, "serial: reading status: %r");
 	else if(nr >= sizeof buf - 1){
 		p->dcd = buf[8] & DcdStatus;
 		p->dsr = buf[8] & DsrStatus;
@@ -387,8 +383,7 @@
 		if(buf[8] & OvererrStatus)
 			p->novererr++;
 	} else
-		dsprint(2, "serial: bad status read %d\n", nr);
-	dsprint(2, "serial: finished read %d from interrupt\n", nr);
+		dsprint(2, "serial: bad status read %d bytes\n", nr);
 	qunlock(ser);
 	return 0;
 }
@@ -416,6 +411,14 @@
 static int
 plseteps(Serialport *p)
 {
+	if(devctl(p->epin, "timeout 0") < 0){
+		fprint(2, "can't set timeout on %s: %r\n", p->epin->dir);
+		return -1;
+	}
+	if(devctl(p->epout, "timeout 0") < 0){
+		fprint(2, "can't set timeout on %s: %r\n", p->epin->dir);
+		return -1;
+	}
 	devctl(p->epin,  "maxpkt 256");
 	devctl(p->epout, "maxpkt 256");
 	return 0;
--- /sys/src/cmd/usb/serial/serial.c	Sat Apr 19 16:05:01 2014
+++ /sys/src/cmd/usb/serial/serial.c	Sat Apr 19 16:05:01 2014
@@ -525,13 +525,9 @@
 				dsprint(2, "serial: read: %s %ld\n", err, rcount);
 		} while(rcount < 0 && strstr(err, "timed out") != nil);
 
-		dsprint(2, "serial: read %ld bytes from bulk, %10.10s\n", rcount, err);
-		if(rcount < 0){
-			dsprint(2, "serial: need to recover, data read %ld %r\n",
-				count);
+		dsprint(2, "serial: read from bulk %ld, %10.10s\n", rcount, err);
+		if(rcount < 0)
 			serialrecover(ser, p, p->epin, err);
-		}
-		dsprint(2, "serial: read %ld bytes from bulk\n", rcount);
 		count = rcount;
 		break;
 	case Qctl: