USB: EHCI: add pointer to end of async-unlink list

This patch (as1570) adds a pointer for the end of ehci-hcd's
async-unlink list.  The list (which is actually a queue) is singly
linked, so having a pointer to its end makes adding new entries easier
-- there's no longer any need to scan through the whole list.

In principle it could be changed to a standard doubly-linked list.  It
turns out that doing so actually makes the code less clear, so I'm
leaving it as is.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 5 insertions, 7 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index efee426a2465..8b75e4279a47 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -1041,14 +1041,9 @@ static void unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 
         /* defer till later if busy */
         if (ehci->async_unlink) {
-                struct ehci_qh          *last;
-
-                for (last = ehci->async_unlink;
-                                last->unlink_next;
-                                last = last->unlink_next)
-                        continue;
                 qh->qh_state = QH_STATE_UNLINK_WAIT;
-                last->unlink_next = qh;
+                ehci->async_unlink_last->unlink_next = qh;
+                ehci->async_unlink_last = qh;
 
         /* start IAA cycle */
         } else
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 8e80cde8c35e..5193612c96ea 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -1227,6 +1227,8 @@ static void start_unlink_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
 
         qh->qh_state = QH_STATE_UNLINK;
         ehci->async_unlink = qh;
+        if (!qh->unlink_next)
+                ehci->async_unlink_last = qh;
 
         prev = ehci->async;
         while (prev->qh_next.qh != qh)
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 3c6c07c0956a..475f23e10bbf 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -82,6 +82,7 @@ struct ehci_hcd {			/* one per controller */
         struct ehci_qh          *async;
         struct ehci_qh          *dummy;         /* For AMD quirk use */
         struct ehci_qh          *async_unlink;
+        struct ehci_qh          *async_unlink_last;
         struct ehci_qh          *qh_scan_next;
         unsigned                scanning : 1;