Hi,
On Tuesday 15 September 2009 10:01:03 Bo Liu wrote:
> Hi,
>
> I found a problem when using my webcam. First, it's ok, but after I unplug
> it. Systerm call poll() will not return.
>
> I looked at the src code, and found that uvc_queue_poll() always return 0,
> it didn't know the webcam have unpluged at that time.
>
> And I saw in funtion uvc_video_complete(), if urb->status is
> -ESHUTDOWN,uvc_queue_cancel(queue, urb->status == -ESHUTDOWN); will be
> called.
That's right, and then uvc_queue_poll() should return POLLERR, making poll()
return.
> But, if just when in uvc_video_complete()> usb_submit_urb() , the webcam is
> unpluged, the usb_submit_urb() will failed, but just with a printk. Won't
> call uvc_queue_cancel(). So, uvc_queue_poll() will always return 0. And, I
> add uvc_queue_cancel() after usb_submit_urb() failed,erverything is ok.
>
> Is this a bug ?
This is weird. The uvcvideo driver submits several URBs, so even if the device
is disconnected during the completion handler, the next URBs should get a -
ESHUTDOWN status (at least with EHCI USB controllers).
Are you using the latest driver ? What status do you get when the completion
handler is called for the next URB after usb_submit_urb() returns -ESHUTDOWN ?
What USB controller are you using ?
> Funtions uvc_video_complete():
>
> 716 if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
> 717 uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",
> 718 ret);
> 719 }
--
Regards,
Laurent Pinchart
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