USB: see if URB comes from a completion handler (c7ccde6e) · Commits · 戴 / test

Now that URBs can be completed inside tasklets, we need a way of determining whether a completion handler for a given endpoint is currently running. Otherwise it's not possible to maintain the API guarantee about keeping isochronous streams synchronous when an underrun occurs. This patch adds a field and a routine to check whether a completion handler for a periodic endpoint is running. At the moment no analogous routine appears to be necessary for async endpoints, but one can always be added. Signed-off-by:

Alan Stern <stern@rowland.harvard.edu> CC: Ming Lei <tom.leiming@gmail.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1703,7 +1703,9 @@ static void usb_giveback_urb_bh(unsigned long param)

		urb = list_entry(local_list.next, struct urb, urb_list);
		list_del_init(&urb->urb_list);
		bh->completing_ep = urb->ep;
		__usb_hcd_giveback_urb(urb);
		bh->completing_ep = NULL;
		}

		/* check if there are new URBs to giveback */

include/linux/usb/hcd.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -73,6 +73,7 @@ struct giveback_urb_bh {
		spinlock_t lock;
		struct list_head head;
		struct tasklet_struct bh;
		struct usb_host_endpoint *completing_ep;
		};

		struct usb_hcd {
		@@ -378,6 +379,12 @@ static inline int hcd_giveback_urb_in_bh(struct usb_hcd *hcd)
		return hcd->driver->flags & HCD_BH;
		}

		static inline bool hcd_periodic_completion_in_progress(struct usb_hcd *hcd,
		struct usb_host_endpoint *ep)
		{
		return hcd->high_prio_bh.completing_ep == ep;
		}

		extern int usb_hcd_link_urb_to_ep(struct usb_hcd hcd, struct urb urb);
		extern int usb_hcd_check_unlink_urb(struct usb_hcd hcd, struct urb urb,
		int status);

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