[ 3.8.y.z extended stable ] Patch "USB: UHCI: accept very late isochronous URBs" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    USB: UHCI: accept very late isochronous URBs

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.11.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From e52b175ec7e444b0f50cac3c12b44522e4d4cc16 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern at rowland.harvard.edu>
Date: Tue, 24 Sep 2013 15:47:20 -0400
Subject: USB: UHCI: accept very late isochronous URBs

commit bef073b067a7b1874a6b381e0035bb0516d71a77 upstream.

Commit 24f531371de1 (USB: EHCI: accept very late isochronous URBs)
changed the isochronous API provided by ehci-hcd.  URBs submitted too
late, so that the time slots for all their packets have already
expired, are no longer rejected outright.  Instead the submission is
accepted, and the URB completes normally with a -EXDEV error for each
packet.  This is what client drivers expect.

This patch implements the same policy in uhci-hcd.  It should be
applied to all kernels containing commit c44b225077bb (UHCI: implement
new semantics for URB_ISO_ASAP).

Signed-off-by: Alan Stern <stern at rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/usb/host/uhci-q.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/uhci-q.c b/drivers/usb/host/uhci-q.c
index 3b08519..3232578 100644
--- a/drivers/usb/host/uhci-q.c
+++ b/drivers/usb/host/uhci-q.c
@@ -1303,7 +1303,7 @@ static int uhci_submit_isochronous(struct uhci_hcd *uhci, struct urb *urb,
 		}

 		/* Fell behind? */
-		if (uhci_frame_before_eq(frame, next)) {
+		if (!uhci_frame_before_eq(next, frame)) {

 			/* USB_ISO_ASAP: Round up to the first available slot */
 			if (urb->transfer_flags & URB_ISO_ASAP)
@@ -1311,13 +1311,17 @@ static int uhci_submit_isochronous(struct uhci_hcd *uhci, struct urb *urb,
 						-qh->period;

 			/*
-			 * Not ASAP: Use the next slot in the stream.  If
-			 * the entire URB falls before the threshold, fail.
+			 * Not ASAP: Use the next slot in the stream,
+			 * no matter what.
 			 */
 			else if (!uhci_frame_before_eq(next,
 					frame + (urb->number_of_packets - 1) *
 						qh->period))
-				return -EXDEV;
+				dev_dbg(uhci_dev(uhci), "iso underrun %p (%u+%u < %u)\n",
+						urb, frame,
+						(urb->number_of_packets - 1) *
+							qh->period,
+						next);
 		}
 	}

--
1.8.1.2