Hi,
In Ubuntu 9.10, support for Video Out devices (bulk-only) has been added. We
noticed that when such a device is disconnected from a non-root hub, the queued
urbs are returned with usb->status == -EPROTO. The video completion callback
cancels the queue, and does not re-submit the urb.
Because the hub driver needs some time to process the disconnect properly,
there is a brief interval in time where queued urbs for the disconnected device
do not result in -ESHUTDOWN, as expected, but with other error codes (such as
EPROTO).
We have found that (in case of status == -EPROTO) resubmitting the urb and not
canceling the queue results in the correct behaviour. Eventually one of the
urbs indeed comes back with status == -ESHUTDOWN and the device is properly
administrated as disconnected. Subsequent QBUF attempts then also result in
correct user-space experience.
We propose the following simple patch:
In uvc_video.c:
static void uvc_video_complete(struct urb *urb)
{
struct uvc_video_device *video = urb->context;
struct uvc_video_queue *queue = &video->queue;
struct uvc_buffer *buf = NULL;
unsigned long flags;
int ret;
switch (urb->status) {
case 0:
break;
default:
uvc_printk(KERN_WARNING, "Non-zero status (%d) in video "
"completion handler.\n", urb->status);
+ break;
case -ENOENT: /* usb_kill_urb() called. */
if (video->frozen)
return;
case -ECONNRESET: /* usb_unlink_urb() called. */
case -ESHUTDOWN: /* The endpoint is being disabled. */
uvc_queue_cancel(queue, urb->status == -ESHUTDOWN);
return;
}
spin_lock_irqsave(&queue->irqlock, flags);
if (!list_empty(&queue->irqqueue))
buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
queue);
spin_unlock_irqrestore(&queue->irqlock, flags);
video->decode(urb, video, buf);
if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",
ret);
}
}
We welcome your comments.
Thanks,
Robert Lukassen
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