Re: [Linux-usb-users] USB: Non zero status

On Thu, 23 Aug 2007, Martin Bachem wrote:

> Martin Bachem wrote:
> > Meanwhile I received another peace of information:
> > It might happen that at a tx iso completetion with -EXDEV error,
> > resubmitting the URB fails with -EFBIG (too much ISO frames requested).
> > I suppose this is an effect of the same problem. Anyway, as soon I got
> > the messagelog of the start_frames when getting -EXDEV, I tell you.
> 
> Supplement:
> This situation a bit different. Here all ISO packets failed with -EXDEV
> within that URB. I treat this this like no Error by resubmitting the
> URB, but this leads to a complete -EXDEV again and again. When finally a
> submit_urb() failed with -EFBIG, the endpoints is no longer served by
> the driver.
> 
> At all of my previous reports I got the -EXDEV only partially in 3 of 8
> packets within a single URB and no problem with resubmitting...

I think there's no choice but to change the way uhci-hcd allocates Iso 
URBs to frames.  Try this patch, and make sure you always set the 
URB_ISO_ASAP flag on all your URBs.

Alan Stern



Index: usb-2.6/drivers/usb/host/uhci-q.c
===================================================================
--- usb-2.6.orig/drivers/usb/host/uhci-q.c
+++ usb-2.6/drivers/usb/host/uhci-q.c
@@ -1271,7 +1271,8 @@ static int uhci_submit_isochronous(struc
 	} else if (qh->period != urb->interval) {
 		return -EINVAL;		/* Can't change the period */
 
-	} else {	/* Pick up where the last URB leaves off */
+	} else {
+		/* Find the next unused frame */
 		if (list_empty(&qh->queue)) {
 			frame = qh->iso_frame;
 		} else {
@@ -1283,10 +1284,18 @@ static int uhci_submit_isochronous(struc
 					lurb->number_of_packets *
 					lurb->interval;
 		}
-		if (urb->transfer_flags & URB_ISO_ASAP)
-			urb->start_frame = frame;
-		else if (urb->start_frame != frame)
-			return -EINVAL;
+		if (urb->transfer_flags & URB_ISO_ASAP) {
+			/* Skip some frames if necessary to insure
+			 * the start frame is in the future.
+			 */
+			uhci_get_current_frame_number(uhci);
+			if (uhci_frame_before_eq(frame, uhci->frame_number)) {
+				frame = uhci->frame_number + 1;
+				frame += ((qh->phase - frame) &
+					(qh->period - 1));
+			}
+		}	/* Otherwise pick up where the last URB leaves off */
+		urb->start_frame = frame;
 	}
 
 	/* Make sure we won't have to go too far into the future */


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